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Porcine reproductive and respiratory syndrome virus (PRRSV) is a major swine pathogen, which can survive host antiviral immunity with various mechanisms. PRRSV infection induces macroautophagy/autophagy, facilitating virus replication. MALT1, a central immune regulator, was manipulated by PRRSV to optimize viral infection at different stages of the virus cycle. In this study, the key role of MALT1 in autophagy regulation during PRRSV infection was characterized, enlightening the role of autophagy flux in favor of virus spread and persistent infection. PRRSV-induced autophagy was confirmed to facilitate virus proliferation. Furthermore, autophagic fusion was dynamically regulated during PRRSV infection. Importantly, PRRSV-induced MALT1 facilitated autophagosome-lysosome fusion and autolysosome formation, thus contributing to autophagy flux and virus proliferation. Mechanically, MALT1 regulated autophagy via mediating MTOR-ULK1 and -TFEB signaling and affecting lysosomal homeostasis. MALT1 inhibition by inhibitor Mi-2 or RNAi induced lysosomal membrane permeabilization (LMP), leading to the block of autophagic fusion. Further, MALT1 overexpression alleviated PRRSV-induced LMP via inhibiting ROS generation. In addition, blocking autophagy flux suppressed virus release significantly, indicating that MALT1-maintained complete autophagy flux during PRRSV infection favors successful virus spread and its proliferation. In contrast, autophagosome accumulation upon MALT1 inhibition promoted PRRSV reserve for future virus proliferation once the autophagy flux recovers. Taken together, for the first time, these findings elucidate that MALT1 was utilized by PRRSV to regulate host autophagy flux, to determine the fate of virus for either proliferation or reserve.Abbreviations: 3-MA: 3-methyladenine; BafA1: bafilomycin A1; BFP/mBFP: monomeric blue fluorescent protein; CQ: chloroquine; DMSO: dimethyl sulfoxide; dsRNA: double-stranded RNA; GFP: green fluorescent protein; hpi: hours post infection; IFA: indirect immunofluorescence assay; LAMP1: lysosomal associated membrane protein 1; LGALS3: galectin 3; LLOMe: L-leucyl-L-leucine-methyl ester; LMP: lysosomal membrane permeabilization; mAb: monoclonal antibody; MALT1: MALT1 paracaspase; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MOI: multiplicity of infection; MTOR: mechanistic target of rapamycin kinase; NFKB/NF-κB: nuclear factor kappa B; nsp: nonstructural protein; ORF: open reading frame; pAb: polyclonal antibody; PRRSV: porcine reproductive and respiratory syndrome virus; PRRSV-N: PRRSV nucleocapsid protein; Rapa: rapamycin; RFP: red fluorescent protein; ROS: reactive oxygen species; SBI: SBI-0206965; siRNA: small interfering RNA; SQSTM1/p62: sequestosome 1; TCID50: 50% tissue culture infective dose; TFEB: transcription factor EB; ULK1: unc-51 like autophagy activating kinase 1. [ABSTRACT FROM AUTHOR]

CARD-BCL10-MALT1 (CBM) signalosomes connect distal signaling of innate and adaptive immune receptors to proximal signaling pathways and immune activation. Four CARD scaffold proteins (CARD9, 10, 11, 14) can form seeds that nucleate the assembly of BCL10-MALT1 filaments in a cell- and stimulus-specific manner. MALT1 (also known as PCASP1) serves a dual function within the assembled CBM complexes. By recruiting TRAF6, MALT1 acts as a molecular scaffold that initiates IkB kinase (IKK)/NF-kB and c-Jun N-terminal kinase (JNK)/AP-1 signaling. In parallel, proximity-induced dimerization of the paracaspase domain activates the MALT1 protease which exerts its function by cleaving a set of specific substrates. While complete MALT1 ablation leads to immune deficiency, selective destruction of either scaffolding or protease function provokes autoimmune inflammation. Thus, balanced MALT1-TRAF6 recruitment and MALT1 substrate cleavage are critical to maintain immune homeostasis and to promote optimal immune activation. Further, MALT1 protease activity drives the survival of aggressive lymphomas and other nonhematologic solid cancers. However, little is known about the relevance of the cleavage of individual substrates for the pathophysiological functions of MALT1. Unbiased serendipity, screening and computational predictions have identified and validated ~20 substrates, indicating that MALT1 targets a quite distinct set of proteins. Known substrates are involved in CBM auto-regulation (MALT1, BCL10 and CARD10), regulation of signaling and adhesion (A20, CYLD, HOIL-1 and Tensin-3), or transcription (RelB) and mRNA stability/translation (Regnase-1, Roquin-1/2 and N4BP1), indicating that MALT1 often targets multiple proteins involved in similar cellular processes. Here, we will summarize what is known about the fate and functions of individual MALT1 substrates and how their cleavage contributes to the biological functions of the MALT1 protease. We will outline what is needed to better connect critical pathophysiological roles of the MALT1 protease with the cleavage of distinct substrates. [ABSTRACT FROM AUTHOR]

MALT1 has been implicated as an upstream regulator of NF-κB signaling in immune cells and tumors. This study determined the regulatory mechanisms and biological functions of MALT1 in non-small cell lung cancer (NSCLC). In cell culture and orthotopic xenograft models, MALT1 suppression via gene expression interference or protein activity inhibition significantly impaired malignant phenotypes and enhanced radiation sensitivity of NSCLC cells. CSN5, the core subunit of COP9 signalosome, was firstly verified to stabilize MALT1 via disturbing the interaction with E3 ligase FBXO3. Loss of FBXO3 in NSCLC cells reduced MALT1 ubiquitination and promoted its accumulation, which was reversed by CSN5 interference. An association between CSN5/FBXO3/MALT1 regulatory axis and poor prognosis in NSCLC patients was identified. Our findings revealed the detail mechanism of continuous MALT1 activation in NF-κB signaling, highlighting its significance as predictor and potential therapeutic target in NSCLC. [ABSTRACT FROM AUTHOR]

Abstract The proinflammatory cytokines and arachidonic acid (AA)-derived eicosanoids play a key role in cartilage degeneration in osteoarthritis (OA). The lysophosphatidylcholine acyltransferase 3 (LPCAT3) preferentially incorporates AA into the membranes. Our recent studies showed that MALT1 [mucosa-associated lymphoid tissue lymphoma translocation protein 1]) plays a crucial role in propagating inflammatory signaling triggered by IL-1β and other inflammatory mediators in endothelial cells. The present study shows that LPCAT3 expression was up-regulated in both human and mice articular cartilage of OA, and correlated with severity of OA. The IL-1β-induces cell death via upregulation of LPCAT3, MMP3, ADAMTS5, and eicosanoids via MALT1. Gene silencing or pharmacological inhibition of LPCAT3 or MALT1 in chondrocytes and human cartilage explants notably suppressed the IL-1β-induced cartilage catabolism through inhibition of expression of MMP3, ADAMTS5, and also secretion of cytokines and eicosanoids. Mechanistically, overexpression of MALT1 in chondrocytes significantly upregulated the expression of LPCAT3 along with MMP3 and ADAMTS5 via c-Myc. Inhibition of c-Myc suppressed the IL-1β-MALT1-dependent upregulation of LPCAT3, MMP3 and ADAMTS5. Consistent with the in vitro data, pharmacological inhibition of MALT1 or gene silencing of LPCAT3 using siRNA-lipid nanoparticles suppressed the synovial articular cartilage erosion, pro-inflammatory cytokines, and eicosanoids such as PGE2, LTB4, and attenuated osteoarthritis induced by the destabilization of the medial meniscus in mice. Overall, our data reveal a previously unrecognized role of the MALT1-LPCAT3 axis in osteoarthritis. Targeting the MALT1-LPCAT3 pathway with MALT1 inhibitors or siRNA-liposomes of LPCAT3 may become an effective strategy to treat OA by suppressing eicosanoids, matrix-degrading enzymes, and proinflammatory cytokines. Graphical Abstract

The proinflammatory cytokines and arachidonic acid (AA)-derived eicosanoids play a key role in cartilage degeneration in osteoarthritis (OA). The lysophosphatidylcholine acyltransferase 3 (LPCAT3) preferentially incorporates AA into the membranes. Our recent studies showed that MALT1 [mucosa-associated lymphoid tissue lymphoma translocation protein 1]) plays a crucial role in propagating inflammatory signaling triggered by IL-1β and other inflammatory mediators in endothelial cells. The present study shows that LPCAT3 expression was up-regulated in both human and mice articular cartilage of OA, and correlated with severity of OA. The IL-1β-induces cell death via upregulation of LPCAT3, MMP3, ADAMTS5, and eicosanoids via MALT1. Gene silencing or pharmacological inhibition of LPCAT3 or MALT1 in chondrocytes and human cartilage explants notably suppressed the IL-1β-induced cartilage catabolism through inhibition of expression of MMP3, ADAMTS5, and also secretion of cytokines and eicosanoids. Mechanistically, overexpression of MALT1 in chondrocytes significantly upregulated the expression of LPCAT3 along with MMP3 and ADAMTS5 via c-Myc. Inhibition of c-Myc suppressed the IL-1β-MALT1-dependent upregulation of LPCAT3, MMP3 and ADAMTS5. Consistent with the in vitro data, pharmacological inhibition of MALT1 or gene silencing of LPCAT3 using siRNA-lipid nanoparticles suppressed the synovial articular cartilage erosion, pro-inflammatory cytokines, and eicosanoids such as PGE2, LTB4, and attenuated osteoarthritis induced by the destabilization of the medial meniscus in mice. Overall, our data reveal a previously unrecognized role of the MALT1-LPCAT3 axis in osteoarthritis. Targeting the MALT1-LPCAT3 pathway with MALT1 inhibitors or siRNA-liposomes of LPCAT3 may become an effective strategy to treat OA by suppressing eicosanoids, matrix-degrading enzymes, and proinflammatory cytokines. [ABSTRACT FROM AUTHOR]

Non-Hodgkin lymphoma (NHL) is one of the most common cancer types. Deregulated signaling pathways can trigger certain NHL subtypes, including Diffuse Large B-cell lymphoma. NF-ĸB signaling pathway, which is responsible for the proliferation, growth, and survival of cells, has an essential role in lymphoma development. Although different signals control NF-ĸB activation in various lymphoid malignancies, the characteristic one is the CARD11-BCL10-MALT1 (CBM) complex. The CBM complex is responsible for the initiation of adaptive immune response. Our study is focused on the molecular docking of ten polyphenols as potential CARD11-BCL10-MALT1 complex inhibitors, essentially through MALT1 inhibition. Molecular docking was performed by Auto Dock Tools and AutoDock Vina tool, while SwissADME was used for drug-likeness and absorption, distribution, metabolism, excretion, and toxicity (ADMET) analysis of the ligands. Out of 66 ligands that were used in this study, we selected and visualized five. Selection criteria were based on the binding energy score and position of the ligands on the used protein. 2D and 3D visualizations showed interactions of ligands with the protein. Five ligands are considered potential inhibitors of MALT1, thus affecting NF-ĸB signaling pathway. However, additional in vivo and in vitro studies are required to confirm their mechanism of inhibition. [ABSTRACT FROM AUTHOR]

CARD-BCL10-MALT1 (CBM) signalosomes connect distal signaling of innate and adaptive immune receptors to proximal signaling pathways and immune activation. Four CARD scaffold proteins (CARD9, 10, 11, 14) can form seeds that nucleate the assembly of BCL10-MALT1 filaments in a cell- and stimulus-specific manner. MALT1 (also known as PCASP1) serves a dual function within the assembled CBM complexes. By recruiting TRAF6, MALT1 acts as a molecular scaffold that initiates IκB kinase (IKK)/NF-κB and c-Jun N-terminal kinase (JNK)/AP-1 signaling. In parallel, proximity-induced dimerization of the paracaspase domain activates the MALT1 protease which exerts its function by cleaving a set of specific substrates. While complete MALT1 ablation leads to immune deficiency, selective destruction of either scaffolding or protease function provokes autoimmune inflammation. Thus, balanced MALT1-TRAF6 recruitment and MALT1 substrate cleavage are critical to maintain immune homeostasis and to promote optimal immune activation. Further, MALT1 protease activity drives the survival of aggressive lymphomas and other non-hematologic solid cancers. However, little is known about the relevance of the cleavage of individual substrates for the pathophysiological functions of MALT1. Unbiased serendipity, screening and computational predictions have identified and validated ~20 substrates, indicating that MALT1 targets a quite distinct set of proteins. Known substrates are involved in CBM auto-regulation (MALT1, BCL10 and CARD10), regulation of signaling and adhesion (A20, CYLD, HOIL-1 and Tensin-3), or transcription (RelB) and mRNA stability/translation (Regnase-1, Roquin-1/2 and N4BP1), indicating that MALT1 often targets multiple proteins involved in similar cellular processes. Here, we will summarize what is known about the fate and functions of individual MALT1 substrates and how their cleavage contributes to the biological functions of the MALT1 protease. We will outline what is needed to better connect critical pathophysiological roles of the MALT1 protease with the cleavage of distinct substrates.

MALT1 (mucosa-associated lymphoid tissue lymphoma translocation protein 1) serves as a pivotal mediator for NF-κB activation in response to a wide spectrum of transmembrane receptor stimuli. In the present study, a homolog of MALT1, named LvMALT1, is cloned from the Pacific white shrimp (Litopenaeus vannamei) and its potential function in shrimp innate immunity is explored. The open reading frame of LvMALT1 is 2364 bp that encodes 787 amino acids. The predicted LvMALT1 protein structure comprises a death domain, three immunoglobulin domains, and a caspase-like domain, exhibiting remarkable similarity to other homologs. LvMALT1 is a cytoplasmic-localized protein and could interact with LvTRAF6. Overexpression of LvMALT1 induces the activation of promoter elements governing the expression of several key antimicrobial peptides (AMPs), including penaeidins (PENs) and crustins (CRUs). Conversely, silencing of LvMALT1 leads to a reduction in the phosphorylation levels of Dorsal and Relish, along with a concomitant decline in the in vivo expression levels of multiple AMPs. Furthermore, LvMALT1 is prominently upregulated in response to a challenge by the white spot syndrome virus (WSSV), facilitating the NF-κB-mediated expression of AMPs as a defense against viral infection. Taken together, we identified a MALT1 homolog from the shrimp L. vannamei, which plays a positive role in the TRAF6/NF-κB/AMPs axis-mediated innate immunity. [ABSTRACT FROM AUTHOR]

ABSTRACT: Heat stress (HS) in poultry has deleterious effects on intestinal development and barrier function, along with inflammatory outbursts. In the present study, chronic HS reduced body weight of broilers and activated mucosa-associated lymphoid tissue lymphoma translocation protein 1 (Malt1) /nuclear factor kappa B (NF-κB) signaling pathways to elicit the inflammatory cytokine response in jejunum. Subsequently, this study investigated the protective effects of the Malt1 inhibitor on the intestine of broilers under HS conditions. The 21-day-old male broilers were allocated to 8 pens housed in HS room (34°C for 7 h/d) until 28 d of age. During this period, 4 birds were selected from each heat-stressed pen and received intraperitoneal injection of 20 mg/kg body weight Mepazine (a Malt1 inhibitor) or the equivalent volume of phosphate buffer saline (PBS) every other day. When compared to PBS broilers, birds received Mepazine injection exhibited increased relative weight and higher villus height in jejunum (both P < 0.05). Mepazine treatment also increased (P < 0.05) the mRNA of zonula occludens-1 (ZO-1), claudin-1, and cadherin 1 of jejunum, which was companied by the reduced caspase-3 transcription under HS condition. Meanwhile, the gene expression levels of toll-like receptor 4 (TLR4), Malt1, NF-κB, interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α) in the jejunum were significantly downregulated by Mepazine administration (P < 0.05). Although there were no significant differences in the relative weight of the thymus and bursa, the transcription levels of T helper 1 (Th1)- and Th17-related cytokines were lower in thymus of birds injected with Mepazine. The cytokines of Treg cytokine transforming growth factor beta (TGF-β) and forkhead box protein P3 (Foxp3) in both the thymus and bursa were not influenced. These results suggest that inhibition of Malt1 protease activity can protect intestinal integrity by promoting the production of tight junction proteins and attenuating NF-κB-mediated intestinal inflammation response under HS conditions.

Introduction: Regulatory T cells (Tregs) play a critical role in the maintenance of immune homeostasis but also protect tumors from immune-mediated growth control or rejection and pose a significant barrier to effective immunotherapy. Inhibition of MALT1 paracaspase activity can selectively reprogram immune-suppressive Tregs in the tumor microenvironment to adopt a proinflammatory fragile state, which offers an opportunity to impede tumor growth and enhance the efficacy of immune checkpoint therapy (ICT). Methods: We performed preclinical studies with the orally available allosteric MALT1 inhibitor (S)-mepazine as a single-agent and in combination with anti-programmed cell death protein 1 (PD-1) ICT to investigate its pharmacokinetic properties and antitumor effects in several murine tumor models as well as patient-derived organotypic tumor spheroids (PDOTS). Results: (S)-mepazine demonstrated significant antitumor effects and was synergistic with anti-PD-1 therapy in vivo and ex vivo but did not affect circulating Treg frequencies in healthy rats at effective doses. Pharmacokinetic profiling revealed favorable drug accumulation in tumors to concentrations that effectively blocked MALT1 activity, potentially explaining preferential effects on tumor-infiltrating over systemic Tregs. Conclusions: The MALT1 inhibitor (S)-mepazine showed single-agent anticancer activity and presents a promising opportunity for combination with PD-1 pathway-targeted ICT. Activity in syngeneic tumor models and human PDOTS was likely mediated by induction of tumor-associated Treg fragility. This translational study supports ongoing clinical investigations (ClinicalTrials.gov Identifier: NCT04859777) of MPT-0118, (S)-mepazine succinate, in patients with advanced or metastatic treatment-refractory solid tumors.

Macrophages are the major primary immune cells that mediate the inflammatory response. In this process, long non-coding RNAs (lncRNAs) play an important, yet largely unknown role. Therefore, utilizing several publicly available RNA sequencing datasets, we predicted and selected lncRNAs that are differentially expressed in M1 or M2 macrophages and involved in the inflammatory response. We identified SUGCT-AS1, which is a human macrophage-specific lncRNA whose expression is increased upon M1 macrophage stimulation. Conditioned media of SUGCT-AS1-depleted M1 macrophages induced an inflammatory phenotype of vascular smooth muscle cells, which included increased expression of inflammatory genes (IL1B and IL6), decreased contractile marker proteins (ACTA2 and SM22α), and increased cell migration. Depletion of SUGCT-AS1 promoted the expression and secretion of proinflammatory cytokines, such as TNF, IL1B, and IL6, in M1 macrophages, and transcriptomic analysis showed that SUGCT-AS1 has functions related to inflammatory responses and cytokines. Furthermore, we found that SUGCT-AS1 directly binds to hnRNPU and regulates its nuclear–cytoplasmic translocation. This translocation of hnRNPU altered the proportion of the MALT1 isoforms by regulating the alternative splicing of MALT1, a mediator of NF-κB signaling. Overall, our findings suggest that lncRNAs can be used for future studies on macrophage regulation. Moreover, they establish the SUGCT-AS1/hnRNPU/MALT1 axis, which is a novel inflammatory regulatory mechanism in macrophages. [ABSTRACT FROM AUTHOR]

Mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) modulates colorectal cancer (CRC) malignant behaviors and tumor immune escape. The present study aimed to explore the association of MALT1 with treatment response and survival time among patients with metastatic CRC (mCRC) after programmed cell death protein-1 (PD-1) inhibitor-based treatment. MALT1 from the blood samples of 75 patients with unresectable mCRC receiving PD-1 inhibitor-based treatment at baseline and after 2-cycle treatment, as well as 20 healthy controls (HCs), was detected by reverse transcription-quantitative PCR. In the patients with mCRC, the objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS) and overall survival (OS) were calculated. MALT1 expression was elevated in patients with mCRC compared with that in HCs (P<0.001). In patients with mCRC, MALT1 expression was positively correlated with multiple (vs. single) metastasis (P=0.032) and peritoneum metastasis (P=0.029). MALT1 levels before treatment were decreased in ORR patients vs. non-ORR patients (P=0.043) and in DCR patients vs. non-DCR patients (P=0.007). Additionally, MALT1 expression was reduced after treatment compared with that before treatment (P<0.001). Meanwhile, MALT1 expression after treatment was notably decreased in ORR patients vs. non-ORR patients (P<0.001) and in DCR patients vs. non-DCR patients (P<0.001). Furthermore, a low MALT1 level before treatment was associated with longer PFS (P=0.030) and OS (P=0.025) times. Decreased MALT1 expression after treatment and a decline in MALT1 expression of >30% after treatment (ratio to MALT1 before treatment) (both P=0.001) presented more significant associations with prolonged PFS and OS times. In conclusion, early low levels of blood MALT1 during therapy may predict an improved response to PD-1 inhibitor-based treatment and survival time in patients with mCRC. [ABSTRACT FROM AUTHOR]

G-coupled protein receptors (GPCRs) comprise the largest class of druggable targets. Signaling by GPCRs is initiated from subcellular hot spots including the plasma membrane, signalosomes, and endosomes to contribute to vascular inflammation. GPCR-G protein signaling at the plasma membrane causes endothelial barrier disruption and also cross-talks with growth factor receptors to promote proinflammatory signaling. A second surge of GPCR signaling is initiated by cytoplasmic NFκB activation mediated by β-arrestins and CARMA-BCL10-MALT1 signalosomes. Once internalized, ubiquitinated GPCRs initiate signaling from endosomes via assembly of the transforming growth factor-β-activated kinase binding protein-1 (TAB1)-TAB2-p38 MAPK complex to promote vascular inflammation. Understanding the complexities of GPCR signaling is critical for development of new strategies to treat vascular inflammation such as that associated with COVID-19.

Mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) is involved in neural injury, neuroinflammation, microglia activation, and polarization, while its function in spinal cord injury (SCI) remains unclear. Thus, this study aimed to evaluate the role of MALT1 modification on SCI recovery and its underlying mechanism. SCI surgery or sham surgery was performed in Sprague–Dawley rats. Then, MALT1 knockdown or negative control lentivirus was injected into SCI rats. Subsequently, MALT1 expression, locomotor capability, neural injury, markers for microglia activation and polarization, inflammatory cytokine expressions, and nuclear factor (NF)-κB pathway were detected. SCI rats exhibited higher MALT1 expression, microglia activation and M1 polarization, neuroinflammation, and NF-κB pathway activation, while worse locomotor capacity compared to sham rats (all P < 0.05). In SCI rats, MALT1 knockdown alleviated Basso, Beattie, and Bresnahan score from 10 to 28 days and attenuated HE staining reflected neural injury (all P < 0.05). Besides, MALT1 knockdown declined the number of IBA1+ cells, IBA1+ iNOS+ cells, and IBA1+ CD86+ cells, while enhanced the number of IBA1+ Arg1+ cells and IBA1+ CD206+ cells in SCI rats (all P < 0.05). Meanwhile, MALT1 knockdown declined the expressions of IL-1β, IL-6, and TNF-α in SCI (all P < 0.05), but did not affect IL-10 expression (P > 0.05). Furthermore, MALT1 knockdown suppressed NF-κB pathway activation validated by immunofluorescence staining and western blot assays (all P < 0.05). MALT1 knockdown improves functional recovery, attenuates microglia activation, M1 polarization, and neuroinflammation via inhibiting NF-κB pathway in SCI. [ABSTRACT FROM AUTHOR]

The androgen-dependent or -independent pathways are regarded as primary therapeutic targets for the neoplasm of the prostate. Mucosa-associated lymphoid tissue 1 (MALT1) acting as a paracaspase in the regulation of nuclear factor κB (NF-κB) signal transduction plays a central role in inflammation and oncogenesis in cancers. This study confirmed the potential linkages between androgen and NF-κB activation by inducing MALT1 in the androgen receptor-full length (ARFL)-positive LNCaP and 22Rv1 prostate cancer cells. Although androgen did not stimulate MALT1 expression in AR-null or ectopic ARFL-overexpressed PC-3 cells, the ectopic overexpression of the AR splicing variant 7 (ARv7) upregulated MALT1 to activate NF-κB activities in 22Rv1 and PC-3 cells. Since the nuclear translocation of p50 and p65 was facilitated by ARv7 to motivate NF-κB activity, the expressions of MALT1, prostate-specific antigen (PSA), and N-myc downstream regulated 1 (NDRG1) were therefore induced in ectopic ARv7-overexpressed prostate cancer cells. Ectopic ARv7 overexpression not only enhanced 22Rv1 or PC-3 cell growth and invasion in vitro but also the tumor growth of PC-3 cells in vivo. These results indicate that an androgen receptor induces MALT1 expression androgen-dependently and -independently in ARFL- or ARv7-overexpressed prostate cancer cells, suggesting a novel ARv7/MALT1/NF-κB-signaling pathway may exist in the cells of prostate cancer. [ABSTRACT FROM AUTHOR]

Examining the genetics of peanut allergy (PA) in the context of clinical trial interventions and outcomes provides an opportunity to not only understand gene-environment interactions for PA risk but to also understand the benefit of allergen immunotherapy. A consistent theme in the genetics of food allergy is that in keeping with the dual allergen exposure hypothesis, barrier- and immune-related genes are most commonly implicated in food allergy and tolerance. With a focus on PA, we review how genetic risk factors across 3 genes (FLG , MALT1 , and HLA-DQA1) have helped delineate distinct allergic characteristics and outcomes in the context of environmental interventions in the Learning Early about Peanut Allergy (LEAP) study and other clinical trials. We specifically consider and present a framework for genetic risk prediction for the development of PA and discuss how genetics, age, and oral consumption intertwine to predict PA outcome. Although there is some promise in this proposed framework, a better understanding of the mechanistic pathways by which PA develops and persists is needed to develop targeted therapeutics for established disease. Only by understanding the mechanisms by which PA develops, persists, and resolves can we identify adjuvants to oral immunotherapy to make older children and adults immunologically similar to their younger, more malleable counterparts and thus more likely to achieve long-term tolerance. [ABSTRACT FROM AUTHOR]

In the present paper, a set of 42 derivatives for 5-oxo-1-thioxo-4,5-dihydro-1H-thiazolo[3,4-a]quinazoline are investigated in silico combining 3D-QSAR study, drug-likeness, ADMET properties, and molecular docking. The study is carried out to elaborate the reliable 3D-QSAR models using the CoMFA and CoMSIA techniques. CoMFA (Q2 = 0.637, R2 = 0.978, SEE = 0.058) and CoMSIA (Q2 = 0.544, R2 = 0.949, SEE = 0.091) models show the two elaborated models have been reliable and statistically significant. The reliability of the obtained models was validated using validation methods such as internal, external, and Y-randomization validation. Based on the contour maps of the CoMFA and CoMSIA models, we obtained information that allows us to propose five new molecules with higher MALT1 inhibitory activity than the 40 compounds. The five compounds were then examined for their drug-like and ADMET properties. Based on the results, two compounds T1 and T2 have very good ADMET properties. The two molecules selected by their ADMET properties T1 and T2 were submitted to the molecular docking test to examine the bindings established between the two newly designed molecules and the MALT1 protein. The obtained results show that the new molecules T1 and T2 have high stability in the active site of MALT1 and more efficient binding affinity compared to the reference compound 26. The two new molecules T1 and T2 may be an interesting proposition for in vitro studies in the treatment of diffuse large B cell lymphoma. [ABSTRACT FROM AUTHOR]

Glutamate receptor ionotropic NMDA 2B (GluN2B) plays an essential role in calcium overload during excitotoxicity. Reverse-phase nano-liquid chromatography-tandem mass spectrometry has revealed an interaction between GluN2B and HECT domain E3 ubiquitin protein ligase 4 (HECTD4), an E3 ubiquitin ligase highly expressed in the brain. As a potential substrate for HECTD4, mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) acts as a scaffold with hydrolysis activity. This study explores the relationship between HECTD4, GluN2B, and MALT1, focusing on their role in brain injury in ischemic stroke. Rats were subjected to 2 h-ischemia followed by 24-h reperfusion to establish an ischemic stroke model. We observed the downregulation of HECTD4 and the upregulation of MALT1. Additionally, an increased GluN2B phosphorylation was concomitant with weakened interactions between HECTD4 and GluN2B, followed by decreased striatal-enriched protein phosphatase (STEP61). Knockdown of HECTD4 exacerbated hypoxia- or NMDA-induced injury in nerve cells coincident with a decrease in GluN2B and MALT1 ubiquitination, and an increase in GluN2B phosphorylation as well as an increase in intracellular calcium level, which were counteracted by MALT1 siRNA. Blockage of MALT1 with its inhibitor or siRNA reduced STEP61 degradation, accompanied by a decrease in GluN2B phosphorylation, intracellular calcium concentration, and brain cell injury, which were reversed by overexpression of MALT1. Based on these observations, we conclude that the downregulation of HECTD4 in ischemic stroke rat brain accounts for calcium overload and brain injury due to activating GluN2B directly and indirectly through a mechanism involving the reduced ubiquitination of GluN2B and MALT1, respectively. [ABSTRACT FROM AUTHOR]

MALT1 (mucosa-associated lymphoid tissue lymphoma translocation protein 1) serves as a pivotal mediator for NF-κB activation in response to a wide spectrum of transmembrane receptor stimuli. In the present study, a homolog of MALT1, named LvMALT1, is cloned from the Pacific white shrimp (Litopenaeus vannamei) and its potential function in shrimp innate immunity is explored. The open reading frame of LvMALT1 is 2364 bp that encodes 787 amino acids. The predicted LvMALT1 protein structure comprises a death domain, three immunoglobulin domains, and a caspase-like domain, exhibiting remarkable similarity to other homologs. LvMALT1 is a cytoplasmic-localized protein and could interact with LvTRAF6. Overexpression of LvMALT1 induces the activation of promoter elements governing the expression of several key antimicrobial peptides (AMPs), including penaeidins (PENs) and crustins (CRUs). Conversely, silencing of LvMALT1 leads to a reduction in the phosphorylation levels of Dorsal and Relish, along with a concomitant decline in the in vivo expression levels of multiple AMPs. Furthermore, LvMALT1 is prominently upregulated in response to a challenge by the white spot syndrome virus (WSSV), facilitating the NF-κB-mediated expression of AMPs as a defense against viral infection. Taken together, we identified a MALT1 homolog from the shrimp L. vannamei, which plays a positive role in the TRAF6/NF-κB/AMPs axis-mediated innate immunity.

The caspase activation and recruitment domain-coiled-coil (CARD-CC) family of proteins—CARD9, CARD10, CARD11, and CARD14—is collectively expressed across nearly all tissues of the body and is a crucial mediator of immunologic signaling as part of the CARD–B-cell lymphoma/leukemia 10–mucosa-associated lymphoid tissue lymphoma translocation protein 1 (CBM) complex. Dysfunction or dysregulation of CBM proteins has been linked to numerous clinical manifestations known as "CBM-opathies." The CBM-opathy spectrum encompasses diseases ranging from mucocutaneous fungal infections and psoriasis to combined immunodeficiency and lymphoproliferative diseases; however, there is accumulating evidence that the CARD-CC family members also contribute to the pathogenesis and progression of allergic inflammation and allergic diseases. Here, we review the 4 CARD-CC paralogs, as well as B-cell lymphoma/leukemia 10 and mucosa-associated lymphoid tissue lymphoma translocation protein 1, and their individual and collective roles in the pathogenesis and progression of allergic inflammation and 4 major allergic diseases (allergic asthma, atopic dermatitis, food allergy, and allergic rhinitis). [ABSTRACT FROM AUTHOR]

Mucosa-associated lymphoid tissue protein 1 (MALT1) plays a key role in adaptive immune responses by modulating specific intracellular signalling pathways that control the development and proliferation of both T and B cells. Dysfunction of these pathways is coupled to the progress of highly aggressive lymphoma as well as to potential development of an array of different immune disorders. In contrast to other signalling mediators, MALT1 is not only activated through the formation of the CBM complex together with the proteins CARMA1 and Bcl10, but also by acting as a protease that cleaves multiple substrates to promote lymphocyte proliferation and survival via the NF-κB signalling pathway. Herein, we present the partial 1H, 13C Ile/Val/Leu-Methyl resonance assignment of the monomeric apo form of the paracaspase-IgL3 domain of human MALT1. Our results provide a solid ground for future elucidation of both the three-dimensional structure and the dynamics of MALT1, key for adequate development of inhibitors, and a thorough molecular understanding of its function(s). [ABSTRACT FROM AUTHOR]

We developed a bioinformatics-led substrate discovery workflow to expand the known substrate repertoire of MALT1. Our approach, termed GO-2-Substrates, integrates protein function information, including GO terms from known substrates, with protein sequences to rank substrate candidates by similarity. We applied GO-2-Substrates to MALT1, a paracaspase and master regulator of NF-κB signalling in adaptive immune responses. With only 12 known substrates, the evolutionarily conserved paracaspase functions and phenotypes of Malt1 –/– mice strongly implicate the existence of undiscovered substrates. We tested the ranked predictions from GO-2-Substrates of new MALT1 human substrates by co-expression of candidates transfected with the oncogenic constitutively active cIAP2-MALT1 fusion protein or CARD11/BCL10/MALT1 active signalosome. We identified seven new MALT1 substrates by the co-transfection screen: TANK, TAB3, CASP10, ZC3H12D, ZC3H12B, CILK1 and ILDR2. Using catalytically inactive cIAP2-MALT1 (Cys464Ala), a MALT1 inhibitor, MLT-748, and noncleavable P1-Arg to Ala mutant versions of each substrate in dual transfections, we validated the seven new substrates in vitro. We confirmed the cleavage of endogenous TANK and the RNase ZC3H12D in B cells by Western blotting and mining TAILS N-terminomics datasets, where we also uncovered evidence for these and 12 other candidate substrates by endogenous MALT1. Thus, protein function information improves substrate predictions. The new substrates and other high-ranked MALT1 candidate substrates should open new biological frontiers for further validation and exploration of the function of MALT1 within and beyond NF-κB regulation.

Oxidative stress contributes greatly to doxorubicin (DOX)-induced cardiotoxicity. Down-regulation of nuclear factor erythroid 2-related factor 2 (Nrf2) is a key factor in DOX-induced myocardial oxidative injury. Recently, we found that mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1)-dependent k48-linked ubiquitination was responsible for down-regulation of myocardial Nrf2 in DOX-treated mice. Micafungin, an antifungal drug, was identified as a potential MALT1 inhibitor. This study aims to explore whether micafungin can reduce DOX-induced myocardial oxidative injury and if its anti-oxidative effect involves a suppression of MALT1-dependent k48-linked ubiquitination of Nrf2. To establish the cardiotoxicity models in vivo and in vitro, mice were treated with a single dose of DOX (15 mg/kg, i.p.) and cardiomyocytes were incubated with DOX (1 μM) for 24 h, respectively. Using mouse model of DOX-induced cardiotoxicity, micafungin (10 or 20 mg/kg) was shown to improve cardiac function, concomitant with suppression of oxidative stress, mitochondrial dysfunction, and cell death in a dose-dependent manner. Similar protective roles of micafungin (1 or 5 μM) were observed in DOX-treated cardiomyocytes. Mechanistically, micafungin weakened the interaction between MALT1 and Nrf2, decreased the k48-linked ubiquitination of Nrf2 while elevated the protein levels of Nrf2 in both DOX-treated mice and cardiomyocytes. Furthermore, MALT1 overexpression counteracted the cardioprotective effects of micafungin. In conclusion, micafungin reduces DOX-induced myocardial oxidative injury via suppression of MALT1, which decreases the k48-linked ubiquitination of Nrf2 and elevates Nrf2 protein levels. Thus, micafungin may be repurposed for treating DOX-induced cardiotoxicity. • Micafungin protected the mouse heart against DOX-induced oxidative injury. • Micafungin suppressed the E3 ubiquitin ligase activity of MALT1. • Micafungin reduced the k48-linked ubiquitination of Nrf2 and alleviated oxidative injury via inhibition of MALT1. [ABSTRACT FROM AUTHOR]

Macrophages are the major primary immune cells that mediate the inflammatory response. In this process, long non-coding RNAs (lncRNAs) play an important, yet largely unknown role. Therefore, utilizing several publicly available RNA sequencing datasets, we predicted and selected lncRNAs that are differentially expressed in M1 or M2 macrophages and involved in the inflammatory response. We identified SUGCT-AS1, which is a human macrophage-specific lncRNA whose expression is increased upon M1 macrophage stimulation. Conditioned media of SUGCT-AS1-depleted M1 macrophages induced an inflammatory phenotype of vascular smooth muscle cells, which included increased expression of inflammatory genes (IL1B and IL6), decreased contractile marker proteins (ACTA2 and SM22α), and increased cell migration. Depletion of SUGCT-AS1 promoted the expression and secretion of proinflammatory cytokines, such as TNF, IL1B, and IL6, in M1 macrophages, and transcriptomic analysis showed that SUGCT-AS1 has functions related to inflammatory responses and cytokines. Furthermore, we found that SUGCT-AS1 directly binds to hnRNPU and regulates its nuclear–cytoplasmic translocation. This translocation of hnRNPU altered the proportion of the MALT1 isoforms by regulating the alternative splicing of MALT1, a mediator of NF-κB signaling. Overall, our findings suggest that lncRNAs can be used for future studies on macrophage regulation. Moreover, they establish the SUGCT-AS1/hnRNPU/MALT1 axis, which is a novel inflammatory regulatory mechanism in macrophages.

Caspase recruitment domain and membrane-associated guanylate kinase-like protein 3 (CARMA3) is a scaffold protein widely expressed in non-hematopoietic cells. It is encoded by the caspase recruitment domain protein 10 (CARD10) gene. CARMA3 can form a CARMA3-BCL10-MALT1 complex by recruiting B cell lymphoma 10 (BCL10) and mucosa-​associated lymphoid tissue lymphoma translocation protein 1 (MALT1), thereby activating nuclear factor-​κB (NF-κB), a key transcription factor that involves in various biological responses. CARMA3 mediates different receptors-dependent signaling pathways, including G protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs). Inappropriate expression and activation of GPCRs and/or RTKs/CARMA3 signaling lead to the pathogenesis of human diseases. Emerging studies have reported that CARMA3 mediates the development of various types of cancers. Moreover, CARMA3 and its partners participate in human non-cancer diseases, including atherogenesis, abdominal aortic aneurysm, asthma, pulmonary fibrosis, liver fibrosis, insulin resistance, inflammatory bowel disease, and psoriasis. Here we provide a review on its structure, regulation, and molecular function, and further highlight recent findings in human non-cancerous diseases, which will provide a novel therapeutic target.

Prostate cancer (PCa) is one of the most common cancer types in men and represents an increasing global problem due to the modern Western lifestyle. The signalling adapter protein CARD14 is specifically expressed in epithelial cells, where it has been shown to mediate NF-κB signalling, but a role for CARD14 in carcinoma has not yet been described. By analysing existing cancer databases, we found that CARD14 overexpression strongly correlates with aggressive PCa in human patients. Moreover, we showed that CARD14 is overexpressed in the LNCaP PCa cell line and that knockdown of CARD14 severely reduces LNCaP cell survival. Similarly, knockdown of BCL10 and MALT1, which are known to form a signalling complex with CARD14, also induced LNCaP cell death. MALT1 is a paracaspase that mediates downstream signalling by acting as a scaffold, as well as a protease. Recent studies have already indicated a role for the scaffold function of MALT1 in PCa cell growth. Here, we also demonstrated constitutive MALT1 proteolytic activity in several PCa cell lines, leading to cleavage of A20 and CYLD. Inhibition of MALT1 protease activity did not affect PCa cell survival nor activation of NF-κB and JNK signalling, but reduced expression of cancer-associated genes, including the cytokine IL-6. Taken together, our results revealed a novel role for CARD14-induced signalling in regulating PCa cell survival and gene expression. The epithelial cell type-specific expression of CARD14 may offer novel opportunities for more specific therapeutic targeting approaches in PCa. [ABSTRACT FROM AUTHOR]

Objective: MALT1 regulates immunity and inflammation in multiple ways, while its role in rheumatoid arthritis (RA) is obscure. This study aimed to investigate the relationship of MALT1 with disease features, treatment outcome, as well as its effect on Th1/2/17 cell differentiation and underlying molecule mechanism in RA. Methods: Totally 147 RA patients were enrolled. Then their blood Th1, Th2, and Th17 cells were detected by flow cytometry. Besides, PBMC MALT1 expression was detected before treatment (baseline), at week (W) 6, W12, and W24. PBMC MALT1 in 30 osteoarthritis patients and 30 health controls were also detected. Then, blood CD4+ T cells were isolated from RA patients, followed by MALT1 overexpression or knockdown lentivirus transfection and Th1/2/17 polarization assay. In addition, IMD 0354 (NF-kB antagonist) and SP600125 (JNK antagonist) were also added to treat CD4+ T cells. Results: MALT1 was increased in RA patients compared to osteoarthritis patients and healthy controls. Meanwhile, MALT1 positively related to CRP, ESR, DAS28 score, Th17 cells, negatively linked with Th2 cells, but did not link with other features or Th1 cells in RA patients. Notably, MALT1 decreased longitudinally during treatment, whose decrement correlated with RA treatment outcome (treatment response, low disease activity, or disease remission). In addition, MALT1 overexpression promoted Th17 differentiation, inhibited Th2 differentiation, less affected Th1 differentiation, activated NF-kB and JNK pathways in RA CD4+ T cells; while MALT1 knockdown exhibited the opposite effect. Besides, IMD 0354 and SP600125 addition attenuated MALT1's effect on Th2 and Th17 differentiation. Conclusion: MALT1 regulates Th2 and Th17 differentiation via NF-kB and JNK pathways, as well as correlates with disease activity and treatment outcome in RA. [ABSTRACT FROM AUTHOR]

Shutian Zhang,1,2,&ast; Yufeng Yan,3,&ast; Yongze Wang,1,2 Zhaodong Sun,1,2 Chengzhi Han,1,2 Xinyi Qian,1,2 Xiaorong Ren,1,2 Yi Feng,4 Jian Cai,5 Chunmei Xia1 1Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Fudan University, Shanghai, 200032, People’s Republic of China; 2Department of Clinical Medicine, Shanghai Medical College, Fudan University, Shanghai, 200032, People’s Republic of China; 3Experimental Teaching Center of Basic Medicine, School of Basic Medical Sciences, Fudan University, Shanghai, 200032, People’s Republic of China; 4Department of Integrative Medicine and Neurobiology, School of Basic Medical Sciences, Fudan University, Shanghai, 200032, People’s Republic of China; 5Department of Neurology, Renji Hospital, School of Medicine, Shanghai Jiaotong University, Shanghai, 200240, People’s Republic of China&ast;These authors contributed equally to this workCorrespondence: Chunmei XiaDepartment of Physiology and Pathophysiology, School of Basic Medical Sciences, Fudan University, Shanghai, 200032, People’s Republic of ChinaTel +86 21 54237612-805Email cmxia@fudan.edu.cnJian CaiDepartment of Neurology, Renji Hospital, School of Medicine, Shanghai Jiaotong University, Shanghai, 200240, People’s Republic of ChinaEmail feele@sina.comPurpose: Glial activation and the disorders of cytokine secretion induced by endoplasmic reticulum stress (ERS) are crucial pathogenic processes in establishing ischemia/reperfusion (I/R) injury of the brain and spinal cord. This present study aimed to investigate the effects of mucous-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) on spinal cord ischemia/reperfusion (SCI/R) injury via regulating glial ERS.Methods: SCI/R was induced by thoracic aorta occlusion-reperfusion in rats. The MALT1-specific inhibitor MI-2 or human recombinant MALT1 protein (hrMALT1) was administrated for three consecutive days after the surgery. Immunofluorescent staining was used to detect the localization of MALT1 and ERS profiles in activated astrocyte and microglia of spinal cord. The ultrastructure of endoplasmic reticulum (ER) was examined by transmission electron microscopy. Blood-spinal cord barrier (BSCB) disruption and noninflammatory status were assessed. The neuron loss and demyelination in the spinal cord were monitored, and the hindlimb motor function was evaluated in SCI/R rats.Results: Intraperitoneally postoperative MI-2 treatment down-regulated phos-NF-κB (p65) and Bip (ERS marker protein) expression in the spinal cord after SCI/R in rats. Intraperitoneal injection MI-2 attenuated the swelling/dilation of ER of the glia in SCI/R rats. Furthermore, MI-2 attenuated I/R-induced Evans blue (EB) leakage and microglia M1 polarization in spinal cord, implying a role for MALT1 in the BSCB destruction and neuroinflammation after SCI/R in rats. Furthermore, intrathecal injection of hrMALT1 aggravated the fragmentation of neuron, loss of neurofibrils and demyelination caused by I/R, while 4-PBA, an ERS inhibitor, co-treatment with hrMALT1 reversed these effects in SCI/R rats. hrMALT1 administration aggravated the motor deficit index (MDI) scoring, while 4-PBA co-treatment improved SCI/R-induced motor deficits in rats.Conclusion: Inhibition of MALT1 alleviates SCI/R injury-induced neuroinflammation by modulating glial endoplasmic reticulum stress in rats.Keywords: MALT1, blood-spinal cord barrier, astrocytes, microglia, endoplasmic reticulum stress, spinal cord ischemia/reperfusion injury

ObjectiveMALT1 regulates immunity and inflammation in multiple ways, while its role in rheumatoid arthritis (RA) is obscure. This study aimed to investigate the relationship of MALT1 with disease features, treatment outcome, as well as its effect on Th1/2/17 cell differentiation and underlying molecule mechanism in RA.MethodsTotally 147 RA patients were enrolled. Then their blood Th1, Th2, and Th17 cells were detected by flow cytometry. Besides, PBMC MALT1 expression was detected before treatment (baseline), at week (W) 6, W12, and W24. PBMC MALT1 in 30 osteoarthritis patients and 30 health controls were also detected. Then, blood CD4+ T cells were isolated from RA patients, followed by MALT1 overexpression or knockdown lentivirus transfection and Th1/2/17 polarization assay. In addition, IMD 0354 (NF-κB antagonist) and SP600125 (JNK antagonist) were also added to treat CD4+ T cells.ResultsMALT1 was increased in RA patients compared to osteoarthritis patients and healthy controls. Meanwhile, MALT1 positively related to CRP, ESR, DAS28 score, Th17 cells, negatively linked with Th2 cells, but did not link with other features or Th1 cells in RA patients. Notably, MALT1 decreased longitudinally during treatment, whose decrement correlated with RA treatment outcome (treatment response, low disease activity, or disease remission). In addition, MALT1 overexpression promoted Th17 differentiation, inhibited Th2 differentiation, less affected Th1 differentiation, activated NF-κB and JNK pathways in RA CD4+ T cells; while MALT1 knockdown exhibited the opposite effect. Besides, IMD 0354 and SP600125 addition attenuated MALT1’s effect on Th2 and Th17 differentiation.ConclusionMALT1 regulates Th2 and Th17 differentiation via NF-κB and JNK pathways, as well as correlates with disease activity and treatment outcome in RA.

Purpose: MALT1 deficiency is a combined immune deficiency characterized by recurrent infections, eczema, chronic diarrhea, and failure to thrive. Clinical and immunological characterizations of the disease have not been previously reported in large cohorts. We sought to determine the clinical, immunological, genetic features, and the natural history of MALT-1 deficiency. Methods: The clinical findings and treatment outcomes were evaluated in nine new MALT1-deficient patients. Peripheral lymphocyte subset analyses, cytokine secretion, and proliferation assays were performed. We also analyzed ten previously reported patients to comprehensively evaluate genotype/phenotype correlation. Results: The mean age of patients and disease onset were 33 ± 17 and 1.6 ± 0.7 months, respectively. The main clinical findings of the disease were recurrent infections (100%), skin involvement (100%), failure to thrive (100%), oral lesions (67%), chronic diarrhea (56%), and autoimmunity (44%). Eosinophilia and high IgE were observed in six (67%) and two (22%) patients, respectively. The majority of patients had normal T and NK cells, while eight (89%) exhibited reduced B cells. Immunoglobulin replacement and antibiotics prophylaxis were mostly ineffective in reducing the frequency of infections and other complications. One patient received hematopoietic stem cell transplantation (HSCT) and five patients died as a complication of life-threatening infections. Analyzing this cohort with reported patients revealed overall survival in 58% (11/19), which was higher in patients who underwent HSCT (P = 0.03). Conclusion: This cohort provides the largest analysis for clinical and immunological features of MALT1 deficiency. HSCT should be offered as a curative therapeutic option for all patients at the early stage of life. [ABSTRACT FROM AUTHOR]

ABSTRACT To fulfill virus replication and persistent infection in hosts, viruses have to find ways to compromise innate immunity, including timely impedance on antiviral RNases and inflammatory responses. Porcine reproductive and respiratory syndrome virus (PRRSV) is a major swine pathogen causing immune suppression. MALT1 is a central immune regulator in both innate and adaptive immunity. In this study, MALT1 was confirmed to be induced rapidly upon PRRSV infection and mediate the degradation of two anti-PRRSV RNases, MCPIP1 and N4BP1, relying on its proteolytic activity, consequently facilitating PRRSV replication. Multiple PRRSV nsps, including nsp11, nsp7β, and nsp4, contributed to MALT1 elicitation. Interestingly, the elevated expression of MALT1 began to decrease once intracellular viral expression reached a high enough level. Higher infection dose brought earlier MALT1 inflection. Further, PRRSV nsp6 mediated significant MALT1 degradation via ubiquitination-proteasome pathway. Downregulation of MALT1 suppressed NF-κB signals, leading to the decrease in proinflammatory cytokine expression. In conclusion, MALT1 expression was manipulated by PRRSV in an elaborate manner to antagonize precisely the antiviral effects of host RNases without excessive and continuous activation of inflammatory responses. These findings throw light on the machinery of PRRSV to build homeostasis in infected immune system for viral settlement. IMPORTANCE PRRSV is a major swine pathogen, suppresses innate immunity, and causes persistent infection and coinfection with other pathogens. As a central immune mediator, MALT1 plays essential roles in regulating immunity and inflammation. Here, PRRSV was confirmed to manipulate MALT1 expression in an accurate way to moderate the antiviral immunity. Briefly, multiple PRRSV nsps induced MALT1 protease to antagonize anti-PRRSV RNases N4BP1 and MCPIP1 upon infection, thereby facilitating viral replication. In contrast, PRRSV nsp6 downregulated MALT1 expression via ubiquitination-proteasome pathway to suppress the inflammatory responses upon infection aggravation, contributing to immune defense alleviation and virus survival. These findings revealed the precise expression control on MALT1 by PRRSV for antagonizing antiviral RNases, along with recovering immune homeostasis. For the first time, this study enlightens a new mechanism of PRRSV adapting antiviral innate immunity by modulating MALT1 expression.

The androgen-dependent or -independent pathways are regarded as primary therapeutic targets for the neoplasm of the prostate. Mucosa-associated lymphoid tissue 1 (MALT1) acting as a paracaspase in the regulation of nuclear factor κB (NF-κB) signal transduction plays a central role in inflammation and oncogenesis in cancers. This study confirmed the potential linkages between androgen and NF-κB activation by inducing MALT1 in the androgen receptor-full length (ARFL)-positive LNCaP and 22Rv1 prostate cancer cells. Although androgen did not stimulate MALT1 expression in AR-null or ectopic ARFL-overexpressed PC-3 cells, the ectopic overexpression of the AR splicing variant 7 (ARv7) upregulated MALT1 to activate NF-κB activities in 22Rv1 and PC-3 cells. Since the nuclear translocation of p50 and p65 was facilitated by ARv7 to motivate NF-κB activity, the expressions of MALT1, prostate-specific antigen (PSA), and N-myc downstream regulated 1 (NDRG1) were therefore induced in ectopic ARv7-overexpressed prostate cancer cells. Ectopic ARv7 overexpression not only enhanced 22Rv1 or PC-3 cell growth and invasion in vitro but also the tumor growth of PC-3 cells in vivo. These results indicate that an androgen receptor induces MALT1 expression androgen-dependently and -independently in ARFL- or ARv7-overexpressed prostate cancer cells, suggesting a novel ARv7/MALT1/NF-κB-signaling pathway may exist in the cells of prostate cancer.

Regulatory T cells (Tregs) are capable of inhibiting the proliferation, activation and function of T cells and play an important role in impeding the immune response to cancer. In chronic lymphocytic leukemia (CLL) a dysfunctional immune response and elevated percentage of effector-like phenotype Tregs have been described. In this study, using the Eµ-TCL1 mouse model of CLL, we evaluated the changes in the Tregs phenotype and their expansion at different stages of leukemia progression. Importantly, we show that Tregs depletion in DEREG mice triggered the expansion of new anti-leukemic cytotoxic T cell clones leading to leukemia eradication. In TCL1 leukemia-bearing mice we identified and characterized a specific Tregs subpopulation, the phenotype of which suggests its role in the formation of an immunosuppressive microenvironment, supportive for leukemia survival and proliferation. This observation was also confirmed by the gene expression profile analysis of these TCL1-specific Tregs. The obtained data on Tregs are consistent with those described so far, however, above all show that the changes in the Tregs phenotype described in CLL result from the formation of a specific, described in this study Tregs subpopulation. In addition, functional tests revealed the ability of Tregs to inhibit T cells that recognize model antigens expressed by leukemic cells. Moreover, inhibition of Tregs with a MALT1 inhibitor provided a therapeutic benefit, both as monotherapy and also when combined with an immune checkpoint inhibitor. Altogether, activation of Tregs appears to be crucial for CLL progression. [ABSTRACT FROM AUTHOR]

Background: CARD9 deficiency is an autosomal recessive primary immunodeficiency underlying increased susceptibility to fungal infection primarily presenting as invasive CNS Candida and/or cutaneous/invasive dermatophyte infections. More recently, a rare heterozygous dominant negative CARD9 variant c.1434 + 1G > C was reported to be protective from inflammatory bowel disease. Objective: We studied two siblings carrying homozygous CARD9 variants (c.1434 + 1G > C) and born to heterozygous asymptomatic parents. One sibling was asymptomatic and the other presented with candida esophagitis, upper respiratory infections, hypogammaglobulinemia, and low class-switched memory B cells. Methods and Results: The CARD9 c.1434 + 1G > C variant generated two mutant transcripts confirmed by mRNA and protein expression: an out-of-frame c.1358–1434 deletion/ ~ 55 kDa protein (CARD9Δex.11) and an in-frame c.1417–1434 deletion/ ~ 61 kDa protein (CARD9Δ18 nt.). Neither transcript was able to form a complete/functional CBM complex, which includes TRIM62. Based on the index patient's CVID-like phenotype, CARD9 expression was tested and detected in lymphocytes and monocytes from humans and mice. The functional impact of different CARD9 mutations and gene dosage conditions was evaluated in heterozygous and homozygous c.1434 + 1 G > C members of the index family, and in WT (two WT alleles), haploinsufficiency (one WT, one null allele), and null (two null alleles) individuals. CARD9 gene dosage impacted lymphocyte and monocyte functions including cytokine generation, MAPK activation, T-helper commitment, transcription, plasmablast differentiation, and immunoglobulin production in a differential manner. Conclusions: CARD9 exon 11 integrity is critical to CBM complex function. CARD9 is expressed and affects particular T and B cell functions in a gene dosage-dependent manner, which in turn may contribute to the phenotype of CARD9 deficiency. [ABSTRACT FROM AUTHOR]

Colorectal cancer (CRC) is a malignant tumor with the second highest morbidity and the third highest mortality in the world, while the therapeutic options of targeted agents remain limited. Here, mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1), known as the upstream of the NF-κB signaling pathway, was identified to be highly upregulated in CRC tumors and cell lines. Furthermore, the downregulation of MALT1 or inhibition of its proteolytic function by MI-2 suppressed the cell proliferation and migration of CRC cells. In vivo, suppressing the MALT1 expression or its proteasome activity effectively reduced the size of the subcutaneous tumor in nude mice. Mechanistically, miR-375 and miR-365a-3p were identified to inhibit NF-κB activation via targeting MALT1. Overall, our results highlight that a novel regulatory axis, miRNA-MALT1-NF-κB, plays a vital role in the progression of CRC and provides novel and hopeful therapeutic targets for clinical treatment.

Regulatory T cells (Tregs) are capable of inhibiting the proliferation, activation and function of T cells and play an important role in impeding the immune response to cancer. In chronic lymphocytic leukemia (CLL) a dysfunctional immune response and elevated percentage of effector-like phenotype Tregs have been described. In this study, using the Eµ-TCL1 mouse model of CLL, we evaluated the changes in the Tregs phenotype and their expansion at different stages of leukemia progression. Importantly, we show that Tregs depletion in DEREG mice triggered the expansion of new anti-leukemic cytotoxic T cell clones leading to leukemia eradication. In TCL1 leukemia-bearing mice we identified and characterized a specific Tregs subpopulation, the phenotype of which suggests its role in the formation of an immunosuppressive microenvironment, supportive for leukemia survival and proliferation. This observation was also confirmed by the gene expression profile analysis of these TCL1-specific Tregs. The obtained data on Tregs are consistent with those described so far, however, above all show that the changes in the Tregs phenotype described in CLL result from the formation of a specific, described in this study Tregs subpopulation. In addition, functional tests revealed the ability of Tregs to inhibit T cells that recognize model antigens expressed by leukemic cells. Moreover, inhibition of Tregs with a MALT1 inhibitor provided a therapeutic benefit, both as monotherapy and also when combined with an immune checkpoint inhibitor. Altogether, activation of Tregs appears to be crucial for CLL progression.

Nuclear factor kappa B (NF-κB) is a critical transcription factor involved in regulating cell activation, inflammation, and survival. The linear ubiquitin chain assembly complex (LUBAC) which consists of HOIL1, HOIP, and SHARPIN, catalyzes the linear ubiquitination of target proteins—a post-translational modification that is essential for NF-κB activation. Human germline pathogenic variants that dysregulate linear ubiquitination and NF-κB signaling are associated with immunodeficiency and/or autoinflammation including dermatitis, recurrent fevers, systemic inflammation and enteropathy. We previously identified MALT1 paracaspase as a novel negative regulator of LUBAC by proteolytic cleavage of HOIL1. To directly investigate the impact of HOIL1 cleavage activity on the inflammatory response, we employed a stable transduction system to express and directly compare non-cleavable HOIL1 with wild-type HOIL1 in primary HOIL1-deficient patient skin fibroblasts. We discovered that non-cleavable HOIL1 resulted in enhanced NF-κB signaling in response to innate stimuli. Transcriptomics revealed enrichment of inflammation and proinflammatory cytokine-related pathways after stimulation. Multiplexed cytokine assays confirmed a 'hyperinflammatory' phenotype in these cells. This work highlights the physiological importance of MALT1-dependent cleavage and modulation of HOIL1 on NF-κB signaling and inflammation, provides a mechanism for the autoinflammation observed in MALT1-deficient patients, and will inform the development of therapeutics that target MALT1 paracaspase and LUBAC function in treating autoinflammatory skin diseases. [ABSTRACT FROM AUTHOR]

Background: Mucosa-associated lymphoma antigen 1 (MALT1) is an oncogene in subsets of diffuse large B cell lymphoma (DLBCL) and mucosa-associated lymphoid tissue type (MALT) lymphoma. However, the role of MALT1 across cancers, especially in prostate cancer is still poorly understood.Methods: Here, we used several public datasets to evaluate MALT1 expression. Then, PCa cell lines and nude mice were used to investigate the cellular functions in vitro and in vivo. Microarray data were downloaded from The Cancer Genome Atlas and MALT1 was subjected to gene set enrichment analysis (GSEA) and Gene Ontology (GO) analysis to identify the biological functions and relevant pathways. Additionally, the correlations between MALT1 expression and mismatch repair (MMR) gene mutation, immune checkpoint gene expression, tumor mutational burden (TMB), and microsatellite instability (MSI) were investigated by Pearson correlation analysis. Moreover, the correlation between MALT1 expression and tumor immune infiltration was analyzed by the Tumor Immune Evaluation Resource (TIMER) database.Results: MALT1 overexpression was significantly correlated with MMR gene mutation levels and crucially promoted proliferation and colony genesis while reducing PCa cell apoptosis levels in vivo and in vitro. MALT1 expression showed strong correlations with immune checkpoint genes, TMB, and MSI in most cancers. The GO analysis indicated that MALT1-coexpressed genes were involved in heterotypic cell-cell adhesion, actin filament-based movement regulation, and action potential regulation. GSEA revealed that MALT1 expression was associated with several signaling pathways, including the NF-κB signaling, Wnt/β-catenin and TGF-β signaling pathways, in PCa. Additionally, MALT1 expression was significantly correlated with the infiltration of immune cells, including B cells, CD8+ T cells, dendritic cells and macrophages, and negatively correlated with CD4+ cell infiltration in PCa.Conclusion: MALT1 expression is higher in pancancer samples than in normal tissues. MALT1 promoted proliferation and colony genesis while reducing PCa cell apoptosis levels, and MALT1 suppression could inhibit xenograft tumor establishment in nude mice. Furthermore, MALT1 expression is closely related to the occurrence and development of multiple tumors in multiple ways. Therefore, MALT1 may be an emerging therapeutic target for a variety of cancers especially PCa.

Nuclear factor kappa B (NF-κB) is a critical transcription factor involved in regulating cell activation, inflammation, and survival. The linear ubiquitin chain assembly complex (LUBAC) which consists of HOIL1, HOIP, and SHARPIN, catalyzes the linear ubiquitination of target proteins—a post-translational modification that is essential for NF-κB activation. Human germline pathogenic variants that dysregulate linear ubiquitination and NF-κB signaling are associated with immunodeficiency and/or autoinflammation including dermatitis, recurrent fevers, systemic inflammation and enteropathy. We previously identified MALT1 paracaspase as a novel negative regulator of LUBAC by proteolytic cleavage of HOIL1. To directly investigate the impact of HOIL1 cleavage activity on the inflammatory response, we employed a stable transduction system to express and directly compare non-cleavable HOIL1 with wild-type HOIL1 in primary HOIL1-deficient patient skin fibroblasts. We discovered that non-cleavable HOIL1 resulted in enhanced NF-κB signaling in response to innate stimuli. Transcriptomics revealed enrichment of inflammation and proinflammatory cytokine-related pathways after stimulation. Multiplexed cytokine assays confirmed a ‘hyperinflammatory’ phenotype in these cells. This work highlights the physiological importance of MALT1-dependent cleavage and modulation of HOIL1 on NF-κB signaling and inflammation, provides a mechanism for the autoinflammation observed in MALT1-deficient patients, and will inform the development of therapeutics that target MALT1 paracaspase and LUBAC function in treating autoinflammatory skin diseases.

Mucosa‐associated lymphoid tissue lymphoma translocation protein 1 (MALT1) is a key adaptor protein that regulates the NF‐κB pathway, in which MALT1 functions as a scaffold protein and protease to trigger downstream signals. The abnormal expression of MALT1 is closely associated with lymphomagenesis and other diseases, including solid tumors and autoimmune diseases. MALT1 is the only protease in the underlying pathogenesis of these diseases, and its proteolytic activity can be pharmacologically regulated. Therefore, MALT1 is a potential and promising target for anti‐lymphoma and other MALT1‐related disease treatments. Currently, the development of MALT1 inhibitors is still in its early stages. This review presents an overview of MALT1, particularly its X‐ray structures and biological functions, and elaborates on the pathogenesis of diseases associated with its dysregulation. We then summarize previously reported MALT1 inhibitors, focusing on their molecular structure, biological activity, structure–activity relationship, and limitations. Finally, we propose future research directions to accelerate the discovery of novel MALT1 inhibitors with clinical applications. Overall, this review provides a comprehensive and systematic overview of MALT1‐related research advances and serves as a theoretical basis for drug discovery and research. [ABSTRACT FROM AUTHOR]

Prostate cancer (PCa) is one of the most common cancer types in men and represents an increasing global problem due to the modern Western lifestyle. The signalling adapter protein CARD14 is specifically expressed in epithelial cells, where it has been shown to mediate NF-κB signalling, but a role for CARD14 in carcinoma has not yet been described. By analysing existing cancer databases, we found that CARD14 overexpression strongly correlates with aggressive PCa in human patients. Moreover, we showed that CARD14 is overexpressed in the LNCaP PCa cell line and that knockdown of CARD14 severely reduces LNCaP cell survival. Similarly, knockdown of BCL10 and MALT1, which are known to form a signalling complex with CARD14, also induced LNCaP cell death. MALT1 is a paracaspase that mediates downstream signalling by acting as a scaffold, as well as a protease. Recent studies have already indicated a role for the scaffold function of MALT1 in PCa cell growth. Here, we also demonstrated constitutive MALT1 proteolytic activity in several PCa cell lines, leading to cleavage of A20 and CYLD. Inhibition of MALT1 protease activity did not affect PCa cell survival nor activation of NF-κB and JNK signalling, but reduced expression of cancer-associated genes, including the cytokine IL-6. Taken together, our results revealed a novel role for CARD14-induced signalling in regulating PCa cell survival and gene expression. The epithelial cell type-specific expression of CARD14 may offer novel opportunities for more specific therapeutic targeting approaches in PCa.

Heat stress (HS) in poultry has deleterious effects on intestinal development and barrier function, along with inflammatory outbursts. In the present study, chronic HS reduced body weight of broilers and activated mucosa-associated lymphoid tissue lymphoma translocation protein 1 (Malt1) /nuclear factor kappa B (NF-κB) signaling pathways to elicit the inflammatory cytokine response in jejunum. Subsequently, this study investigated the protective effects of the Malt1 inhibitor on the intestine of broilers under HS conditions. The 21-day-old male broilers were allocated to 8 pens housed in HS room (34°C for 7 h/d) until 28 d of age. During this period, 4 birds were selected from each heat-stressed pen and received intraperitoneal injection of 20 mg/kg body weight Mepazine (a Malt1 inhibitor) or the equivalent volume of phosphate buffer saline (PBS) every other day. When compared to PBS broilers, birds received Mepazine injection exhibited increased relative weight and higher villus height in jejunum (both P < 0.05). Mepazine treatment also increased (P < 0.05) the mRNA of zonula occludens-1 ( ZO-1 ), claudin-1 , and cadherin 1 of jejunum, which was companied by the reduced caspase-3 transcription under HS condition. Meanwhile, the gene expression levels of toll-like receptor 4 ( TLR4 ), Malt1, NF-κB , interleukin-6 ( IL-6 ), and tumor necrosis factor alpha ( TNF-α ) in the jejunum were significantly downregulated by Mepazine administration (P < 0.05). Although there were no significant differences in the relative weight of the thymus and bursa, the transcription levels of T helper 1 (Th1)- and Th17-related cytokines were lower in thymus of birds injected with Mepazine. The cytokines of Treg cytokine transforming growth factor beta ( TGF-β ) and forkhead box protein P3 ( Foxp3 ) in both the thymus and bursa were not influenced. These results suggest that inhibition of Malt1 protease activity can protect intestinal integrity by promoting the production of tight junction proteins and attenuating NF-κB-mediated intestinal inflammation response under HS conditions. [ABSTRACT FROM AUTHOR]

Xu Wang,1,2,* Shuai Lu,1,2,* Yankai Xiao,1,2 Ling Xu,2,3 Lingling Zhou,1,2 Junyan Hu,2 Bo Li,1,2 Chengwu Zeng,1,2 Yangqiu Li1–3 1Key Laboratory for Regenerative Medicine of Ministry of Education, Jinan University, Guangzhou, 510632, People’s Republic of China; 2Institute of Hematology, Jinan University, Guangzhou, 510632, People’s Republic of China; 3Department of Hematology, First Affiliated Hospital, Jinan University, Guangzhou, 510632, People’s Republic of China *These authors contributed equally to this work Background: T cell immunodeficiency is a common feature in patients with different kinds of hematological disease such as T cell non-Hodgkin lymphoma (T-NHL), B cells NHL (B-NHL), NK/T cell NHL (NK/T-CL) and acute myeloid leukemia (AML). In our recent research, we found that significantly lower expression levels in MALT1 and NF-κB were related to suppression of T cell activation. Therefore, this study was conducted to further investigate the role of downregulating MALT1 in the development of immunodeficiency in T cells.Methods: We induced activation inhibition in CD3+ T cells by MALT1 knockdown. Then we characterized the gene expression profile after MALT1 suppression by microarray analysis.Result: The differentially expressed genes were ZAP-70, p65, MDM2, ATM, NFATC2 which participate in the NF-κB, p53, and NFAT pathways in CD3+ T cells after MALT1 downregulation.Conclusion: MALT1 suppression may contribute to immunodeficiency in T cells via suppression of T cell activation and proliferation pathways. These data may help to explain some of the characteristics of immunodeficiency of T cells. Keywords: CD3+ T-cells, MALT1, immunodeficiency, T-cell activation, microarray

Signal transduction typically displays a so‐called bow‐tie topology: Multiple receptors lead to multiple cellular responses but the signals all pass through a narrow waist of central signaling nodes. One such signaling node for several inflammatory and oncogenic signaling pathways is the CARD‐CC/BCL10/MALT1 (CBM) complexes, which get activated by protein kinase C (PKC)‐mediated phosphorylation of the caspase activation and recruitment domain (CARD)‐coiled‐coil domain (CC) component. In humans, there are four CARD‐CC family proteins (CARD9, CARD10, CARD11, and CARD14) and 9 true PKC isozymes (α to ι). At this moment, less than a handful of PKC::CARD‐CC relationships are known. In order to explore the biologically relevant combinatorial space out of all 36 potential permutations in this two‐component signaling event, we made use of CARD10‐deficient human embryonic kidney 293T cells for subsequent pairwise cotransfections of all CARD‐CC family members and all activated PKCs. Upon analysis of NF‐κB‐dependent reporter gene expression, we could define specific PKC::CARD‐CC relationships. Surprisingly, as many as 21 PKC::CARD‐CC functional combinations were identified. CARD10 was responsive to most PKCs, while CARD14 was mainly activated by PKCδ. The CARD11 activation profile was most similar to that of CARD9. We also discovered the existence of mixed protein complexes between different CARD‐CC proteins, which was shown to influence their PKC response profile. Finally, multiple PKCs were found to use a common phosphorylation site to activate CARD9, while additional phosphorylation sites contribute to CARD14 activation. Together, these data reveal the combinatorial space of PKC::CARD‐CC signal transduction nodes, which will be valuable for future studies on the regulation of CBM signaling. [ABSTRACT FROM AUTHOR]

Mantle cell lymphoma (MCL) is an aggressive B cell lymphoma and characterized by the t(11;14)(q13;q32)/CCND1+. MALT1 amplification is the most common genetic event in MALT lymphomas. Identification of CCND1 and MALT1 gene over expression plays a key role in the diagnosis of MCL and some MALT lymphomas. Several unusual variants of MCL have been described with variable morphological, immunophenotypic and genetic characteristics. Here, we report an unusual nasopharyngeal B cell lymphoma with both CCND1 rearrangement and MALT1 amplification. The patient was a 60 year old gentleman admitted for further evaluation of “unspecified lymphoma”. PET oncology study revealed intense FDG avidity in the nasopharyngeal region, highly suspicious for malignancy. A biopsy of nasopharyngeal lesion was performed. Histological examination showed focal expansion of mantle zone surrounding residual germinal centers. Flow cytometry demonstrated one population of monoclonal B cells, negative for CD23 with variable CD5 expression. Lymphocytes in mantle zone were positive for CD20, BCL1 and weakly CD5 by immunohistochemistry. Interestingly, FISH studies were positive for standard and variant IGH/CCND1 rearrangement (85%) and MALT1 gene amplification (60%). Staging evaluations showed minimal bone marrow lymphoma involvement and increased FDG avidity in bilateral tonsillar regions and regional nodes of the neck, indicative of systemic disease. The overall findings were consistent with primary nasopharyngeal mantle cell lymphoma, which harbored both CCND1 and MALT1, with systemic involvement. The patient responded well with chemotherapy. To our knowledge, this is the first such case reported in the literature. Recent studies have shown that MALT1 gene may involve in the MYC pathway regulation in MCL, which represents a promising target for future therapies in MCL patients.

Almost twenty years ago, the importance of the paracaspase MALT1 in antigen receptor-induced NF-κB activation was first described. Since then, several other immune receptors, G-protein-coupled receptors, and receptor tyrosine kinases were identified as relying on MALT1 to induce NF-κB activation. In various hematological malignancies and solid tumors, MALT1 is constitutively activated and drives chronic NF-κB target gene expression. Deregulated MALT1 activity in cancer thus promotes tumor cell survival, proliferation, and metastasis. Since the molecular function of MALT1 partially requires its protease activity, pharmacological targeting of MALT1 may represent a promising anti-cancer strategy. Here, we review the molecular features of MALT1 activation and function as well as the therapeutic potential of MALT1 inhibition in hematological malignancies and solid tumors.