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MYC promotes tumor growth through multiple mechanisms. Here, we show that, in human glioblastomas, the variant MYC transcript encodes a 114–amino acid peptide, MYC pre-mRNA encoded protein (MPEP), from the upstream open reading frame (uORF) MPEP. Secreted MPEP promotes patient-derived xenograft tumor growth in vivo, independent of MYC through direct binding, and activation of tropomyosin receptor kinase B (TRKB), which induces downstream AKT-mTOR signaling. Targeting MPEP through genetic ablation reduced growth of patient-derived 4121 and 3691 glioblastoma stem cells. Administration of an MPEP-neutralizing antibody in combination with a small-molecule TRKB inhibitor reduced glioblastoma growth in patient-derived xenograft tumor–bearing mice. The overexpression of MPEP in surgical glioblastoma specimens predicted a poor prognosis, supporting its clinical relevance. In summary, our results demonstrate that tumor-specific translation of a MYC-associated uORF promotes glioblastoma growth, suggesting a new therapeutic strategy for glioblastoma. Editor's summary: Upstream open reading frames (uORFs) are RNA sequences encoding short peptides that mainly function as translational represssors. Here, Li et al. show that the uORF of the oncogene MYC is translated into a peptide (MPEP) that is secreted from glioblastoma stem cells (GSCs). MPEP expression promoted proliferation of GSCs in vitro and accelerated tumorigenesis in a mouse model. MPEP acted through canonical activation of tropomyosin receptor kinase B, which was corroborated by the increase in survival rates of glioblastoma mice undergoing combination treatment with an MPEP antibody and the TRK inhibitor entrecitinib. —Daniela Neuhofer [ABSTRACT FROM AUTHOR]

Dilated cardiomyopathy (DCM) is an inherited disorder often leading to severe heart failure. Linkage studies in affected families have revealed hundreds of different mutations that can cause DCM, with most occurring in genes associated with the cardiac sarcomere. We have developed an investigational pipeline for discovering mechanistic genotype-phenotype relationships in DCM and here apply it to the DCM-linked tropomyosin mutation TPM1 M8R. Atomistic simulations predict that M8R increases flexibility of the tropomyosin chain and enhances affinity for the blocked or inactive state of tropomyosin on actin. Applying these molecular effects to a Markov model of the cardiac thin filament reproduced the shifts in Ca2+sensitivity, maximum force, and a qualitative drop in cooperativity that were observed in an in vitro system containing TPM1 M8R. The model was then used to simulate the impact of M8R expression on twitch contractions of intact cardiac muscle, predicting that M8R would reduce peak force and duration of contraction in a dose-dependent manner. To evaluate this prediction, TPM1 M8R was expressed via adenovirus in human engineered heart tissues and isometric twitch force was observed. The mutant tissues manifested depressed contractility and twitch duration that agreed in detail with model predictions. Additional exploratory simulations suggest that M8R-mediated alterations in tropomyosin-actin interactions contribute more potently than tropomyosin chain stiffness to cardiac twitch dysfunction, and presumably to the ultimate manifestation of DCM. This study is an example of the growing potential for successful in silico prediction of mutation pathogenicity for inherited cardiac muscle disorders. [ABSTRACT FROM AUTHOR]

Aberrant activation of tropomyosin receptor kinases (TRKs) is a well-defined oncogenic driver for neurotrophic tropomyosin receptor kinase (NTRK)-fusion cancers, and acquired resistant mutations have emerged with clinical use of the first-generation TRK inhibitors. Here we present BPI-28592, a novel second-generation TRK inhibitor with efficacy against TRK fusion-positive cancers, including those with resistant mutations. Docking simulations indicated no steric hindrance between BPI-28592 and TRK mutants, suggesting its potential to overcome drug resistance. Biochemical assays showed strong inhibition and high selectivity against TRKA, TRKB, and TRKC. The inhibitor significantly reduced cell proliferation and blocked TRK signaling. In vivo studies demonstrated effective tumor suppression in xenograft models harboring TRK fusions with or without resistant mutations. Clinically, BPI-28592 achieved a complete response in a patient with malignant melanoma carrying an AP3S2-NTRK3 fusion (Clinicaltrials. gov identifier: NCT05302843). [ABSTRACT FROM AUTHOR]

Background Objective Animals Materials and Methods Results Conclusions and Clinical Relevance Immunoglobulin (Ig)E cross‐reactivity has been shown between Dermatophagoides farinae (Df; house dust mite) and the nematode Toxocara canis (Tc), yet its allergen basis is unknown.To identify the Df allergens IgE‐cross‐reactive with those of Tc.Archived sera from 73 dogs with suspected allergy sensitised to Df.We performed a combination of Pet Allergy Xplorer (PAX) and enzyme‐linked immunosorbent assay (ELISA) inhibitions with excretory–secretory and somatic (i.e. nematode body) extracts of Tc or recombinant Tc tropomyosin on coats of Df, Der f 15 and Zen‐1 (ELISA) or PAX allergens.The ELISA and PAX inhibitions established that there is mutual yet variable cross‐reactivity between the Tc excretory–secretory extract, purified Der f 15 and purified Zen‐1. This cross‐reactivity is likely to involve cross‐reactive glycans, as there is no inhibition between the Tc excretory–secretory extract and recombinant Der f 15 without its predicted natural O‐glycans. We also confirmed a heterogeneous cross‐reactivity between the somatic Tc extract and Der p 11 (paramyosin), as well as between the recombinant Toxo c 3 and Der p 10 tropomyosins. The cross‐reactivity among tropomyosins and paramyosins is likely to involve peptidic epitopes, as these recombinant allergens are not glycosylated.In dogs with suspected allergies, the cross‐reactivity between Tc and Df for dogs is complex and heterogeneous. Some of the cross‐reactive IgE recognises shared glycans on Der f 15 and Zen‐1, while some targets peptidic epitopes on shared paramyosins and tropomyosins. We do not exclude that additional cross‐reactive allergens between Df and Tc also might exist. [ABSTRACT FROM AUTHOR]

Introduction: Ox-LDL (oxidized low-density lipoprotein)-induced endothelial cell injury and dysfunction of vascular smooth muscle cells play critical roles in the development of atherosclerosis (AS). Tropomyosin 2 (TPM2) has been implicated in cardiac diseases, but its critical role and regulatory mechanism in AS progression have not yet been elucidated. Material and methods: The expression of TPM2 was investigated in AS tissues. Ox-LDL was used to construct an AS in vitro model based on endothelial and vascular smooth muscle cells (HAECs and VSMCs). An overexpression assay was performed to evaluate the role of TPM2 in AS. Meanwhile, the involvement of the RhoA pathway in TPM2-mediated AS progression was evaluated using narciclasine. Results: Tropomyosin 2 was dramatically upregulated in both AS tissues and ox-LDL-induced HAECs. Overexpression of TPM2 attenuated ox-LDL-stimulated cell growth depression, inflammatory and adhesive responses in HAECs, as well as oxidative stress and mitochondrial dysfunction. Additionally, VSMCs, impacted by TPM2-overexpressed HAECs, showed alleviated cellular processes which were abnormally activated by ox-LDL. Furthermore, depressed activation of the RhoA pathway was found in TPM2-overexpressed HAECs and activating the signaling rescued these effects of TPM2 exerted on ox-LDL-stimulated HAECs and VSMCs. Conclusions: TPM2 had an advantageous impact on ox-LDL-induced AS progression in vitro by mediating the RhoA pathway. This evidence might contribute to the therapy of AS. [ABSTRACT FROM AUTHOR]

Force generation and motility by actomyosin in nonmuscle cells are spatially regulated by (40 tropomyosin (Tpm) isoforms. The means by which Tpms are targeted to specific cellular regions and the mechanisms that result in differential activity of myosin paralogs are unknown. We show that Tpm3.1 and Tpm1.7 inhibit Myosin-IC (Myo1C), with Tpm1.7 more effectively reducing the number of gliding filaments than Tpm3.1. Strikingly, cosedimentation and fluorescence microscopy assays revealed that Tpm3.1 is displaced from actin by Myo1C and not by myosin-II. In contrast, Tpm1.7 is only weakly displaced by Myo1C. Unlike other characterized myosins, Myo1C motility is inhibited by Tpm when the Tpm-actin filament is activated by myosin-II. These results point to a mechanism for the exclusion of myosin-I paralogs from cellular Tpm-decorated actin filaments that are activated by other myosins. Additionally, our results suggest a potential mechanism for myosin-induced Tpm sorting in cells. [ABSTRACT FROM AUTHOR]

Tropomyosin receptor kinases (Trks) are transmembrane receptor tyrosine kinases named TrkA, TrkB, and TrkC and encoded by the NTRK1, NTRK2, and NTRK3 genes, respectively. These kinases have attracted significant attention and represent a promising therapeutic target for solid tumor treatment due to their vital role in cellular signaling pathways. First-generation TRK inhibitors, i.e., Larotrectinib sulfate and Entrectinib, received clinical approval in 2018 and 2019, respectively. However, the use of these inhibitors was significantly limited because of the development of resistance due to mutations. Fortunately, the second-generation Trk inhibitor Repotrectinib (TPX-0005) was approved by the FDA in November 2023, while Selitrectinib (Loxo-195) has provided an effective solution to this issue. Another macrocycle-based analog, along with many other TRK inhibitors, is currently in clinical trials. Two of the three marketed drugs for NTRK fusion cancers feature a pyrazolo[1,5-a] pyrimidine nucleus, prompting medicinal chemists to develop numerous novel pyrazolopyrimidine-based molecules to enhance clinical applications. This article focuses on a comprehensive review of chronological synthetic developments and the structure–activity relationships (SAR) of pyrazolo[1,5-a]pyrimidine derivatives as Trk inhibitors. This article will also provide comprehensive knowledge and future directions to the researchers working in the field of medicinal chemistry by facilitating the structural modification of pyrazolo [1,5-a]pyrimidine derivatives to synthesize more effective novel chemotherapeutics as TRK inhibitors. [ABSTRACT FROM AUTHOR]

This article explores the effects of the Yizhi Qingxin formula (YQF) extract on cognitive impairment in aged rats. The study found that oral treatment with YQF extract improved spatial learning and memory abilities in aged rats. The extract also had positive effects on histopathological and morphological characteristics in the rats. Additionally, the YQF extract activated the brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB) pathway, which is involved in cognitive impairment. However, it is important to note that this article has been retracted, so further research is needed to confirm these findings. [Extracted from the article]

Background: Members of the neurotrophic tropomyosin receptor kinase (NTRK) gene family, NTRK1, NTRK2, and NTRK3 encode TRK receptor tyrosine kinases. Intra‐ or inter‐chromosomal gene rearrangements produce NTRK gene fusions encoding fusion proteins which are oncogenic drivers in various solid tumors. Methods: This study investigated the prevalence of NTRK fusion genes and identified fusion partners in Japanese patients with solid tumors recorded in the Center for Cancer Genomics and Advanced Therapeutics database of comprehensive genomic profiling test. Results: In the analysis population (n = 46,621), NTRK fusion genes were detected in 91 patients (0.20%). The rate was higher in pediatric cases (<18 years; 1.69%) than in adults (0.16%). NTRK gene fusions were identified in 21 different solid tumor types involving 38 different partner genes including 22 (57.9%) previously unreported NTRK gene fusions. The highest frequency of NTRK gene fusions was head and neck cancer (1.31%) and thyroid cancer (1.31%), followed by soft tissue sarcoma (STS; 0.91%). A total of 97 NTRK fusion gene partners were analyzed involving mainly NTRK1 (49.5%) or NTRK3 (44.2%) gene fusions. The only fusion gene detected in head and neck cancer was ETV6::NTRK3 (n = 22); in STS, ETV6::NTRK3 (n = 7) and LMNA::NTRK1 (n = 5) were common. Statistically significant mutual exclusivity of NTRK fusions with alterations was confirmed in TP53, KRAS, and APC. NTRK gene fusion was detected from 11 STS cases: seven unclassified sarcoma, three sarcoma NOS, and one Ewing sarcoma. Conclusions: NTRK gene fusion identification in solid tumors enables accurate diagnosis and potential TRK inhibitor therapy. [ABSTRACT FROM AUTHOR]

Dynamic interactions between the myosin motor head on thick filaments and the actin molecular track on thin filaments drive the myosin-crossbridge cycle that powers muscle contraction. The process is initiated by Ca2+ and the opening of troponin--tropomyosin--blocked myosin-binding sites on actin. The ensuing recruitment of myosin heads and their transformation from pre-powerstroke to post-powerstroke conformation on actin produce the force required for contraction. Cryo-EM-based atomic models confirm that during this process, tropomyosin occupies three different average positions on actin. Tropomyosin pivoting on actin away from a TnI-imposed myosin-blocking position accounts for part of the Ca2+ activation observed. However, the structure of tropomyosin on thin filaments that follows pre-powerstroke myosin binding and its translocation during myosin's pre-powerstroke to post-powerstroke transition remains unresolved. Here, we approach this transition computationally in silico. We used the myosin helix-loop-helix motif as an anchor to dock models of pre- powerstroke cardiac myosin to the cleft between neighboring actin subunits along cardiac thin filaments.We then performed targeted molecular dynamics simulations of the transition between pre- and post-powerstroke conformations on actin in the presence of cardiac troponin--tropomyosin. These simulations show Arg 369 and Glu 370 on the tip of myosin Loop-4 encountering identically charged residues on tropomyosin. The charge repulsion between residues causes tropomyosin translocation across actin, thus accounting for the final regulatory step in the activation of the thin filament, and, in turn, facilitating myosin movement along the filament. We suggest that during muscle activity, myosin-induced tropomyosin movement is likely to result in unencumbered myosin head interactions on actin at low-energy cost. [ABSTRACT FROM AUTHOR]

Background: Tropomyosins (TM) from vertebrates are generally non-allergenic, while invertebrate homologs are potent pan-allergens. This study aims to compare the risk of sensitization between chicken TM and shrimp TM through affecting the intestinal epithelial barrier integrity and type 2 mucosal immune activation. Methods: Epithelial activation and/or barrier effects upon exposure to 2–50 μg/mL chicken TM, shrimp TM or ovalbumin (OVA) as a control allergen, were studied using Caco-2, HT-29MTX, or HT-29 intestinal epithelial cells. Monocyte-derived dendritic cells (moDC), cocultured with HT-29 cells or moDC alone, were exposed to 50 μg/mL chicken TM or shrimp TM. Primed moDC were cocultured with naïve Th cells. Intestinal barrier integrity (TEER), gene expression, cytokine secretion and immune cell phenotypes were determined in these human in vitro models. Results: Shrimp TM, but not chicken TM or OVA exposure, profoundly disrupted intestinal barrier integrity and increased alarmin genes expression in Caco-2 cells. Proinflammatory cytokine secretion in HT-29 cells was only enhanced upon shrimp TM or OVA, but not chicken TM, exposure. Shrimp TM enhanced the maturation of moDC and chemokine secretion in the presence or absence of HT-29 cells, while only in the absence of epithelial cells chicken TM activated moDC. Direct exposure of moDC to shrimp TM increased IL13 and TNFα secretion by Th cells cocultured with these primed moDC, while shrimp TM exposure via HT-29 cells cocultured with moDC sequentially increased IL13 expression and IL4 secretion in Th cells. Conclusions: Shrimp TM, but not chicken TM, disrupted the epithelial barrier while triggering type 2 mucosal immune activation, both of which are key events in allergic sensitization. [ABSTRACT FROM AUTHOR]

Antarctic krill tropomyosin (AkTM) has been shown in mice to cause IgE-mediated food allergy. The objective of this work was to investigate the role of Notch signaling in AkTM-sensitized mice, as well as to determine the changes in gut microbiota composition and short-chain fatty acids (SCFAs) in the allergic mice. An AkTM-induced food allergy mouse model was built and N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT) was used as an γ-secretase inhibitor to inhibit the activation of Notch signaling. Food allergy indices, some key transcription factors, histologic alterations in the small intestine, and changes in gut microbiota composition were examined. The results showed that DAPT inhibited Notch signaling, which reduced AkTM-specific IgE, suppressed mast cell degranulation, decreased IL-4 but increased IFN-γ production, and alleviated allergic symptoms. Quantitative real-time PCR and Western blotting analyses revealed that expressions of Hes-1, Gata3, and IL-4 were down-regulated after DAPT treatment, accompanied by increases in T-bet and IFN-γ, indicating that Notch signaling was active in AkTM-sensitized mice and blocking it could reverse the Th1/Th2 imbalance. Expressions of key transcription factors revealed that Notch signaling could promote Th2 cell differentiation in sensitized mice. Furthermore, 16S rRNA sequencing results revealed that AkTM could alter the diversity and composition of gut microbiota in mice, leading to increases in inflammation-inducing bacteria such as Enterococcus and Escherichia-Shigella. Correlation analysis indicated that reduced SCFA concentrations in AkTM-allergic mice may be related to decreases in certain SCFA-producing bacteria, such as Clostridia_UCG-014. The changes in gut microbiota and SCFAs could be partially restored by DAPT treatment. Our findings showed that inhibiting Notch signaling could alleviate AkTM-induced food allergy by correcting Th1/Th2 imbalance and modulating the gut microbiota. [ABSTRACT FROM AUTHOR]

The starting compound 3-amino-1,7-dihydro-4H-pyrazolo[4,3-c]pyridine-4,6(5H)-dione (1) is reacted with each of diketone and β-ketoester, forming pyridopyrazolo[1,5-a]pyrimidines 4a,b and 14a,b, respectively. The compounds 4 and 14 reacted with each of aromatic aldehyde and arenediazonium salt to give the respective arylidenes and arylhydrazo derivatives, respectively. The structure of the new products was established using spectroscopic techniques. The cytotoxic activity of selected targets was tested in vitro against three cancer cell lines MCF7, HepG2 and HCT116. The data obtained from enzymatic assays of TrKA indicated that compounds 7b and 16c have the strongest inhibitory effects on TrKA with IC50 = 0.064 ± 0.0037 μg/ml and IC50 = 0.047 ± 0.0027 μg/ml, respectively, compared to the standard drug Larotrectinib with IC50 = 0.034 ± 0.0021 μg/ml for the HepG2 cancer cell line. In cell cycle analysis, compounds 7b, 15b, 16a and 16c caused the greatest arrest in cell cycle at the G2/M phase. In addition, compound 15b has a higher apoptosis-inducing effect (36.72%) than compounds 7b (34.70%), 16a (21.14) and 16c (26.54%). Compounds 7b, 16a and 16c were shown fit tightly into the active site of the TrKA kinase crystal structure (PDB: 5H3Q). Also, ADME study was performed on some selected potent anticancer compounds described in this study. Highlights: A series of new pyrido[4ʹ,3ʹ:3,4]pyrazolo[1,5-a]pyrimidine derivatives were synthesized. The anticancer activity of the new compounds were tested in vitro. Compounds 7b and 16c showed broad spectrum potent anticancer activity. Compound 15b induced cell cycle arrest at G2/M phase in HepG-2 cell line. Compound 7c, the most promising agent, can be absorbed very easily by the gastrointestinal tract with potential BBB permeability. [ABSTRACT FROM AUTHOR]

This article discusses the development of a potential treatment for shrimp allergy using hypoallergenic chimeric virus-like particles (VLPs). The VLPs were designed to display the major shrimp allergen, Pen m 1, and were shown to elicit blocking IgG antibody responses. The VLPs exhibited reduced allergenicity compared to the soluble form of Pen m 1 and induced a Th1-biased immune response in mice. Further research is needed to investigate the reactogenicity and therapeutic capacity of the VLPs in animal models of shrimp allergy. The study was funded by various organizations and the authors declare no conflict of interest. [Extracted from the article]

Tropomyosin (TM) is a pan-allergen with cross-reactivity to arthropods, insects, and nematodes in tropical regions. While IgE epitopes of TM contribute to sensitization, T-cell (MHC-II) epitopes polarize the Th2 immune response. This study aimed to identify linear B and T consensus epitopes among house dust mites, cockroaches, Ascaris lumbricoides, shrimp, and mosquitoes, exploring the molecular basis of cross-reactivity in allergic diseases. Amino acid sequences of Der p 10, Der f 10, Blo t 10, Lit v 1, Pen a 1, Pen m 1, rAsc l 3, Per a 7, Bla g 7, and Aed a 10 were collected from Allergen Nomenclature and UniProt. B epitopes were predicted using AlgPred 2.0 and BepiPred 3.0. T epitopes were predicted with NetMHCIIpan 4.1 against 10 HLA-II alleles. Consensus epitopes were obtained through analysis and Epitope Cluster Analysis in the Immune Epitope Database. We found 7 B-cell epitopes and 28 linear T-cell epitopes binding to MHC II. A unique peptide (residues 160–174) exhibited overlap between linear B-cell and T-cell epitopes, highly conserved across tropomyosin sequences. These findings shed light on IgE cross-reactivity among the tested species. The described immuno-informatics pipeline and epitopes can inform in vitro research and guide synthetic multi-epitope proteins' design for potential allergology immunotherapies. Further in silico studies are warranted to confirm epitope accuracy and guide future experimental protocols. [ABSTRACT FROM AUTHOR]

Tropomyosin is a muscle contraction protein documented across all animal life. Despite its ubiquity, its unique structure in invertebrates leads to allergic responses in humans that vertebrate tropomyosin does not. High degrees of homology can explain cross-reactivity between tropomyosin derived from distantly-related arthropod species and establishes tropomyosin as a panallergen. Given this cross-reactivity and that they are commonly found in high numbers indoors, research on the potential of the common bed bug (Cimex lectularius L.) to contribute tropomyosin to the indoor environment is needed. Therefore, we investigated tropomyosin homology between bed bugs and known tropomyosin allergens from other taxa, tropomyosin in bed bug bodies, feces, and exuviae (cast skins), tropomyosin persistence over time, and impacts of common bed bug treatment strategies on detectable tropomyosin. Tropomyosin was detected in mechanically fractured bed bug cadavers and was detectable in bed bugs cadavers aged for 18 months. Additionally, a survey of pest management professionals showed dead bed bugs are not cleaned up following treatment. As such, dead bed bugs could act as tropomyosin reservoirs following bed bug treatment and exposure to tropomyosin from bed bugs could sensitize individuals and lead to increased responses to other arthropod tropomyosin. [ABSTRACT FROM AUTHOR]

The cardiac thin filament proteins troponin and tropomyosin control actomyosin formation and thus cardiac contractility. Calcium binding to troponin changes tropomyosin position along the thin filament, allowing myosin head binding to actin required for heart muscle contraction. The thin filament regulatory proteins are hot spots for genetic mutations causing heart muscle dysfunction. While much of the thin filament structure has been characterized, critical regions of troponin and tropomyosin involved in triggering conformational changes remain unresolved. A poorly resolved region, helix-4 (H 4) of troponin I, is thought to stabilize tropomyosin in a position on actin that blocks actomyosin interactions at low calcium concentrations during muscle relaxation. We have proposed that contact between glutamate 139 on tropomyosin and positively charged residues on H 4 leads to blocking-state stabilization. In this study, we attempted to disrupt these interactions by replacing E139 with lysine (E139K) to define the importance of this residue in thin filament regulation. Comparison of mutant and wild-type tropomyosin was carried out using in-vitro motility assays, actin co-sedimentation, and molecular dynamics simulations to determine perturbations in troponin-tropomyosin function caused by the tropomyosin mutation. Motility assays revealed that mutant thin filaments moved at higher velocity at low calcium with increased calcium sensitivity demonstrating that tropomyosin residue 139 is vital for proper tropomyosin-mediated inhibition during relaxation. Similarly, molecular dynamic simulations revealed a mutation-induced decrease in interaction energy between tropomyosin-E139K and troponin I (R170 and K174). These results suggest that salt-bridge stabilization of tropomyosin position by troponin I H 4 is essential to prevent actomyosin interactions during cardiac muscle relaxation. [Display omitted] • Electrostatic interactions between Tpm and TnI contribute to B-state stability during thin filament regulation. • Interactions between TnI helix 4 and the central region of Tpm anchor Tpm in place during relaxation. • Glutamate 139 of Tpm interacts with two residues on TnI (R170 and K174). • Residue-specific interactions involved in blocked-state stabilization inform targeted cardiomyopathy treatments. [ABSTRACT FROM AUTHOR]

At low free Ca[sup 2]+, the actin binding proteins tropomyosin, troponin I, troponin T and troponin C inhibit contraction in striated muscles. Ca[sup 2]+ activation alters the position of tropomyosin on actin to uncover binding sites for high affinity forms of myosin (i.e., myosin-ADP). Inhibition of contraction is commonly thought to result from steric blocking of myosin binding to actin by tropomyosin. However, myosin-ADP binding to actin is energetically more favorable than localization of tropomyosin in the blocking position. Tropomyosin is an effective inhibitor of binding only at low levels of myosin-ADP. At low free Ca[sup 2]+, troponin-tropomyosin also inhibits the rate of a step associated with Pi release to about 1% of the maximum rate. This results in accumulation of myosin with bound ATP and ADP- Pi. Such myosin binds weakly to actin. Ca[sup 2]+ activation increases the rate of Pi release, but not to the maximum value, and increases the population of myosin- ADP. The high affinity binding of myosin-ADP to actin can displace tropomyosin into the fully active position in relation to the amount of myosin-ADP bound. It seems likely that an important outcome of the steric clash between myosin-ADP and tropomyosin is the dual activation by Ca[sup 2]+ and myosin-ADP. The C-terminal region of troponin T (TnT) contributes to the incomplete activation by Ca[sup 2]+ alone. Because this region of TnT is highly conserved, the ability of myosin-ADP to move tropomyosin may be more important than any restriction that tropomyosin may place on myosin binding. [ABSTRACT FROM AUTHOR]

• Novel clinical finding of muscle hypertonia in tropomyosin-caused congenital myopathy. • Unusual symptom of trismus. • Unspecific histological findings. Patients with myopathies caused by pathogenic variants in tropomyosin genes TPM2 and TPM3 usually have muscle hypotonia and weakness, their muscle biopsies often showing fibre size disproportion and nemaline bodies. Here, we describe a series of patients with hypercontractile molecular phenotypes, high muscle tone, and mostly non-specific myopathic biopsy findings without nemaline bodies. Three of the patients had trismus, whilst in one patient, the distal joints of her fingers flexed on extension of the wrists. In one biopsy from a patient with a rare TPM3 pathogenic variant, cores and minicores were observed, an unusual finding in TPM3 -caused myopathy. The variants alter conserved contact sites between tropomyosin and actin. [ABSTRACT FROM AUTHOR]

Neurotrophic receptor kinase (NTRK) fusions are actionable oncogenic drivers of multiple pediatric and adult solid tumors, and tropomyosin receptor kinase (TRK) has been considered as an attractive therapeutic target for "pan-cancer" harboring these fusions. Currently, two generations TRK inhibitors have been developed. The representative second-generation inhibitors selitrectinib and repotrectinib were designed to overcome clinic acquired resistance of the first-generation inhibitors larotrectinib or entrectinib resulted from solvent-front and gatekeeper on-target mutations. However, xDFG (TRKAG667C/A/S, homologous TRKCG696C/A/S) and some double mutations still confer resistance to selitrectinib and repotrectinib, and overcoming these resistances represents a major unmet clinical need. In this review, we summarize the acquired resistance mechanism of the first- and second-generation TRK inhibitors, and firstly put forward the emerging selective type II TRK inhibitors to overcome xDFG mutations mediated resistance. Additionally, we concluded our perspectives on new challenges and future directions in this field. This review mainly summarizes the acquired resistance mechanisms of the first- and second-generation TRK inhibitors and firstly update the emerging selective type II TRK inhibitors to overcome the xDFG mutations mediated resistance. [Display omitted] [ABSTRACT FROM AUTHOR]

Especially in higher eukaryotes, the N termini of proteins are subject to enzymatic modifications, with the acetylation of the alpha‐amino group of nascent polypeptides being a prominent one. In recent years, the specificities and substrates of the enzymes responsible for this modification, the Nα‐terminal acetyltransferases, have been mapped in several proteomic studies. Aberrant expression of, and mutations in these enzymes were found to be associated with several human diseases, explaining the growing interest in protein Nα‐terminal acetylation. With some enzymes, such as the Nα‐terminal acetyltransferase A complex having thousands of possible substrates, researchers are now trying to decipher the functional outcome of Nα‐terminal protein acetylation. In this review, we zoom in on one possible functional consequence of Nα‐terminal protein acetylation; its effect on protein folding. Using selected examples of proteins associated with human diseases such as alpha‐synuclein and huntingtin, here, we discuss the sometimes contradictory findings of the effects of Nα‐terminal protein acetylation on protein (mis)folding and aggregation. [ABSTRACT FROM AUTHOR]

Aberrant brain‐derived neurotrophic factor (BDNF) signaling has been proposed to contribute to the pathophysiology of depression and other neurological disorders such as Angelman syndrome. We have previously shown that targeting the tropomyosin receptor kinase B/postsynaptic density protein‐95 (PSD‐95) nexus in the BDNF signaling pathway by peptidomimetic inhibitors is a promising approach for therapeutic intervention. Here, we used structure‐based knowledge to develop a new Syn3 peptidomimetic compound series that fuses peptides derived from the PSD‐95‐binding protein SynGAP to our prototype compound CN2097. The new compounds target the PSD‐95 PDZ3 domain and adjoining αC helix to achieve bivalent binding that results in up to 7‐fold stronger affinity compared to CN2097. These compounds were designed to improve CN2097 specificity for the PSD‐95 PDZ3 domain, and structure–activity relationship studies were performed to improve their resistance to proteolysis. [ABSTRACT FROM AUTHOR]

TRK, as a type of cell surface protein, plays a critical role in various biological processes, particularly as a key target for cancer treatment. We explored the correlation between the structure and activity of indole‐2‐one derivatives through investigations involving 3D‐QSAR molecular modelling, molecular docking, molecular dynamics, and ADMET property research. The statistical data from the CoMFA and CoMSIA models exhibit excellent internal stability (CoMFA: q2=0.622, r2=0.992; CoMSIA: q2=0.740, r2=0.972). Further molecular docking unveiled the interaction mechanism between small molecules and receptor proteins, demonstrating that the hydrogen bonding between amino acids Met590 and Glu592 and small molecules could enhance the ligand‐receptor binding affinity. Based on the 3D‐QSAR model and molecular docking, we designed and predicted the activity of eight new molecules, which displayed high expected activity. Subsequently, through 100 ns MD simulations and binding free energy calculations, we affirmed the stability of the molecular docking results. Finally, we employed ADMET to predict the pharmacokinetic properties of the newly designed molecules, validating their commendable drug‐like characteristics. These research findings provide valuable references for the design and development of novel TRK inhibitors, offering fresh perspectives for subsequent drug design. [ABSTRACT FROM AUTHOR]

Background: House dust mite (HDM) allergy is a prevalent global health concern, with varying sensitization profiles observed across populations. We aimed to provide a comprehensive assessment of molecular allergen sensitization patterns in the Lithuanian population, with a focus on Dermatophagoides pteronyssinus (Der p), and investigate patterns of concomitant reactivity among different allergens to enhance the accuracy of HDM allergy diagnostics. Methods: A comprehensive analysis of 1520 patient test results in Lithuania from 2020 to 2022 was performed. Sensitization patterns to major (Der p 1, Der p 2, and Der p 23) and minor (Der p 5, Der p 7, and Der p 21) Der p allergen components were described using molecular‐based diagnostics. Additionally, we investigated sensitization to allergen components from other allergen sources, including tropomyosins (Der p 10, Per a 7, Pen m 1, Ani s 3, Blo t 10) and arginine kinases (Pen m 2, Bla g 9, Der p 20). Results: This study reveals a high prevalence of HDM sensitization in Lithuania ‐ 481 individuals (45.38% of the sensitized group) exhibited sensitization to at least one Der p allergen component. Importantly, within the sensitized group, 37.21% of patients were sensitized to Der p 5, Der p 7, or Der p 21 in addition to major allergenic components. Distinct sensitization patterns were observed across different age groups, indicating the influence of age‐related factors. Furthermore, we confirmed cross‐reactivity between Der p 5 and Blo t 5 as well as between Der p 21 and Blo t 21, emphasizing the clinical relevance of these associations. We also highlighted the complexity of sensitization patterns among tropomyosins and arginine kinases. Conclusion: This study provides valuable insights into HDM allergy sensitization profiles in Lithuania, emphasizing the importance of considering major and minor HDM allergen components for accurate diagnosis and management of HDM‐related allergic diseases. Differences between populations and age‐related factors impact sensitization patterns. Understanding concomitant reactivity among allergens, such as Der p 5 and Blo t 5, Der p 21 and Blo t 21, tropomyosins, and arginine kinases, is crucial for improving diagnostic strategies and developing targeted interventions for allergic individuals. [ABSTRACT FROM AUTHOR]

Background and Objective: VC004 is a novel next-generation tropomyosin receptor kinase (TRK) inhibitor that is approved for the treatment of advanced or metastatic NTRK fusion-positive solid tumors and abrogated the drug resistance of the first-generation TRK inhibitors. The objective of the present study was to evaluate the effect of food on the pharmacokinetics and safety of VC004. Methods: The study was a randomized, open-label, two-period crossover, single-dose, phase I clinical trial. A total of 16 healthy subjects participated the trial. Subjects fasted for 10 h before drug administration in both fasting and fed states. Subjects received VC004 50 mg orally in the fasting state and after a high caloric food in the fed state. Blood samples at the designated time points were collected to determine the plasma concentration of VC004. Safety evaluation in both the fasted and fed periods were assessed via vital sign monitoring and clinical laboratory tests. Results: The maximum plasma concentration (Cmax) of VC004 in fed group decreased by 32.8%, corresponding with the slower absorption rate (time to Cmax (Tmax) delayed by almost 3 h) compared with the fasting group. Ratios of geometric means (GMRs) and 90% confidence intervals (90% CIs) of Cmax, the area under the curve of plasma concentration-time from zero to the last measurable concentration (AUC0–t), and AUC from zero to infinity (AUC0–∞) for VC004 between the two states were 67.18 (58.16–77.60), 103.59 (95.04–112.92) and 103.55 (95.63–112.11), respectively. No serious adverse events (AEs) occurred; only three grade 1 or grade 2 adverse events occurred in the fasted group, who recovered by the end of the study. Conclusions: The intake of high calorie food decreased the absorption rate and increased the Tmax of VC004, while the AUC values were similar in both groups. No serious adverse event was reported. In conclusion, food does not alter the pharmacokinetics and safety profile of VC004 in a clinically meaningful manner. Trial Registration: ClinicalTrials.gov ID: NCT055528120. [ABSTRACT FROM AUTHOR]

Background: This study aimed to investigate the effect of four weeks of selected endurance training on neurotrophin-3 (NT-3) and tropomyosin receptor kinase C (TrkC) gene expression in hippocampal areas of rats with spinal cord injury (SCI). Methods: In this experimental study, the rats were separated into six equal groups. First, the animals were put under general anesthesia and had their SCI. Then, for four weeks, they were subjected to two kinds of endurance training programs. However, the control injury group received no intervention or training. Following the completion of the training regimes, molecular tests were done using the qRT-PCR technique to evaluate changes in the gene expression of NT-3 and TrkC from the animals' hippocampus. Results: The expression of NT-3 and TrkC genes were significantly reduced in the SCI model compared to the healthy control group, but it was increased in the SCI + exercise 1 and SCI + exercise 2 groups compared to the SCI group. NT-3 levels did not vary significantly between the SCI + exercise 1 and SCI + exercise 2 groups, although alterations in TrkC levels altered. Conclusion: In addition to enhancing locomotion in animals with SCI, the endurance training regimens in this research were effective on the expression of NT-3 and TrkC genes and may play a role in axonal development and neuronal survival in SCI recovery. [ABSTRACT FROM AUTHOR]

Background: Tropomyosins (TM) from vertebrates are generally non-allergenic, while invertebrate homologs are potent pan-allergens. This study aims to compare the risk of sensitization between chicken TM and shrimp TM through affecting the intestinal epithelial barrier integrity and type 2 mucosal immune activation. Methods: Epithelial activation and/or barrier effects upon exposure to 2–50 μg/mL chicken TM, shrimp TM or ovalbumin (OVA) as a control allergen, were studied using Caco-2, HT-29MTX, or HT-29 intestinal epithelial cells. Monocyte-derived dendritic cells (moDC), cocultured with HT-29 cells or moDC alone, were exposed to 50 μg/mL chicken TM or shrimp TM. Primed moDC were cocultured with naïve Th cells. Intestinal barrier integrity (TEER), gene expression, cytokine secretion and immune cell phenotypes were determined in these human in vitro models. Results: Shrimp TM, but not chicken TM or OVA exposure, profoundly disrupted intestinal barrier integrity and increased alarmin genes expression in Caco-2 cells. Proinflammatory cytokine secretion in HT-29 cells was only enhanced upon shrimp TM or OVA, but not chicken TM, exposure. Shrimp TM enhanced the maturation of moDC and chemokine secretion in the presence or absence of HT-29 cells, while only in the absence of epithelial cells chicken TM activated moDC. Direct exposure of moDC to shrimp TM increased IL13 and TNFα secretion by Th cells cocultured with these primed moDC, while shrimp TM exposure via HT-29 cells cocultured with moDC sequentially increased IL13 expression and IL4 secretion in Th cells. Conclusions: Shrimp TM, but not chicken TM, disrupted the epithelial barrier while triggering type 2 mucosal immune activation, both of which are key events in allergic sensitization.

The allergenic potential of four digestion-resistant linear epitopes (EADRKYDE, ERAEERAEAG, RSVQKLQKEVDR, and VNEKEKYKGI) in Antarctic krill tropomyosin was investigated through in vivo and in vitro experiments. Mice induced by the four epitopes exhibited obvious clinical allergic symptoms, with significant increases in serum specific antibody levels and blood lymphocytes, neutrophils, and eosinophils (p < 0.05). Additionally, mast cells exhibited pronounced degranulation, as well as increased release of histamine and mMCP-1, and enhanced vascular permeability. Mice challenged with the four epitopes further displayed severe pathological damage. In contrast to the antagonistic effect of interleukin-4 and interferon-γ in the plasma of mice in previous studies, stimulation of the epitopes resulted in immune system dysregulation in mice, with significant increases in the levels of interleukin-4 and interferon-γ to 110.03 pg/mL and 103.59 pg/mL, respectively. The enhanced binding ability of the four epitopes to IgE was also indicated in vitro. The four digestion-resistant epitopes are the major factors to the allergenicity of tropomyosin and have strong sensitizing abilities. This study provides a theoretical basis for using site directed mutagenesis to reduce the allergenicity of tropomyosin in Antarctic krill. [Display omitted] • Four digestion-resistant epitopes from tropomyosin have strong sensitizing abilities. • The immune system was dysregulated with significantly elevated IL-4 and IFN-γ levels. • The enhanced binding ability of the four epitopes to IgE was indicated in vitro. • The four epitopes are the major factors to the allergenicity of tropomyosin. • To provide a scientific basis for further targeted mutation of tropomyosin epitopes. [ABSTRACT FROM AUTHOR]

• Tumour-agnostic authorisations shifted the indication-setting paradigm. • European decision-makers diverged in identified uncertainties and recommendations. • Early multi-stakeholder dialogues should discuss the minimum evidence requirements. • Clinicians should be involved earlier and more systematically. • The parallel EMA-HTA scientific consultations should adopt these lessons. The tumour-agnostic authorisations of larotrectinib and entrectinib shifted the paradigm for indication setting. European healthcare decision-makers agreed on their therapeutic potential but diverged primarily in identified uncertainties concerning basket trial designs and endpoints, prognostic value of neurotrophic tropomyosin receptor kinase (NTRK) gene fusions, and resistance mechanisms. In addition, assessments of relevant comparators, unmet medical needs (UMNs), and implementation of NTRK-testing strategies diverged. In particular, the tumour-specific reimbursement recommendations and guidelines do not reflect tumour-agnostic thinking. These differences indicate difficulties experienced in these assessments and provide valuable lessons for future disruptive therapies. As we discuss here, early multistakeholder dialogues concerning minimum evidence requirements and involving clinicians are essential. [ABSTRACT FROM AUTHOR]

• We focused on the relationship between macrophage polarization and food allergy. • Cellular and murine models were used to investigate the macrophage polarization. • mBMDMs polarized toward to M2 phenotypes induced by TM in vitro. • M2 phenotypes participated in allergic responses in TM-sensitized mice. Macrophages are one of the important immune cells, which play important roles in innate and adaptive immune. However, the roles of macrophages in food allergy are not thoroughly understood. To investigate the roles of macrophages during food allergy, we focused on the relationship between macrophage polarization and allergic responses induced by tropomyosin (TM) in the present study. Arg 1 and CD206 expressions in the TM group were significantly higher than those of the PBS group, while iNOS and TNF-α expressions were no obvious difference, moreover, the morphology of macrophages stimulated by TM was similar to that of M2 macrophages. These results indicated macrophages were mainly polarized toward M2 phenotypes in vitro. The antibodies, mMCP-1, histamine and cytokines, revealed that macrophages could participate in food allergy, and macrophage polarization was associated with changes in allergic-related factors. The cytokine levels of M2 phenotypes were significantly higher than those of M1 phenotypes in peripheral blood. The mRNA expressions and protein levels of Arg1 and iNOS in the jejunum and peritoneal cells indicated that M2 phenotypes were the major macrophage in these tissues compared with M1 phenotypes. Hence, macrophage polarization plays an important role in food allergy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Chlorogenic acid treatment reduced the allergenicity of crayfish tropomyosin. • Chlorogenic acid altered structure and masked allergenic epitopes of tropomyosin. • Chlorogenic acid reduced allergic response by up-regulating toll-like receptor 8. • Toll-like receptor 8 agonist suppressed Th2 response and allergy symptoms. Studies have shown that high hydrostatic pressure (HHP) processing and chlorogenic acid (CA) treatment can effectively reduce food allergenicity. We hypothesize that these novel processing techniques can help tackle crayfish allergy and examined the impact and mechanism of HHP (300 MPa, 15 min) and CA (CA:tropomyosin = 1:4000, 15 min) on the allergenicity of crayfish tropomyosin. Our results revealed that CA, rather than HHP, effectively reduced tropomyosin's allergenicity, as evident in the alleviation of allergic symptoms in a food allergy mouse model. Spectroscopy and molecular docking analyses demonstrated that CA could reduce the allergenicity of tropomyosin by covalent or non-covalent binding, altering its secondary structure (2.1 % decrease in α-helix; 1.9 % increase in β-fold) and masking tropomyosin's linear epitopes. Moreover, CA-treated tropomyosin potentially induced milder allergic reactions by up-regulating TLR8. While our results supported the efficacy of CA in alleviating crayfish allergy, further exploration is needed to determine clinical effectiveness. [ABSTRACT FROM AUTHOR]

[Display omitted] • The spines of Heliocidaris crassispina was composed of calcite containing magnesium (approximately 4.8%). • The crude extract from spines converted amorphous calcium carbonate to calcite in the presence of high concentrations of magnesium. • HC tropomyosin contributing to calcite formation was determined from spines of Heliocidaris crassispina. • Magnesium-containing calcite was synthesized by recombinant recombinant HC tropomyosin. Calcium carbonate is present in many biominerals, including in the exoskeletons of crustaceans and shells of mollusks. High Mg-containing calcium carbonate was synthesized by high temperatures, high pressures or high molecular organic matter. For example, biogenic high Mg-containing calcite is synthesized under strictly controlled Mg concentration at ambient temperature and pressure. The spines of sea urchins consist of calcite, which contain a high percentage of magnesium. In this study, we investigated the factors that increase the magnesium content in calcite from the spines of the sea urchin, Heliocidaris crassispina. X-ray diffraction and inductively coupled plasma mass spectrometry analyses showed that sea urchin spines contain about 4.8% Mg. The organic matrix extracted from the H. crassispina spines induced the crystallization of amorphous phase and synthesis of magnesium-containing calcite, while amorphous was synthesized without SUE (sea urchin extract). In addition, aragonite was synthesized by SUE treated with protease-K. HC tropomyosin was specifically incorporated into Mg precipitates. Recombinant HC-tropomyosin induced calcite contained 0.1–2.5% Mg synthesis. Western blotting of sea urchin spine extracts confirmed that HC tropomyosin was present in the purple sea urchin spines at a protein weight ratio of 1.5%. These results show that HC tropomyosin is one factor that increases the magnesium concentration in the calcite of H. crassispina spines. [ABSTRACT FROM AUTHOR]

While it is well-established that F-actin networks with specific organizations and dynamics are tightly regulated by distinct sets of associated actin-binding proteins (ABPs), how ABPs self-sort to particular F-actin networks remains largely unclear. We report that actin assembly factors Arp2/3 complex and formin Cdc12 tune the association of ABPs fimbrin Fim1 and tropomyosin Cdc8 to different F-actin networks in fission yeast. Genetic and pharmacological disruption of F-actin networks revealed that Fim1 is preferentially directed to Arp2/3-complex mediated actin patches, whereas Cdc8 is preferentially targeted to formin Cdc12-mediated filaments in the contractile ring. To investigate the role of Arp2/3 complex- and formin Cdc12-mediated actin assembly, we used four-color TIRF microscopy to observe the in vitro reconstitution of ABP sorting with purified proteins. Fim1 or Cdc8 alone bind similarly well to filaments assembled by either assembly factor. However, in 'competition' reactions containing both actin assembly factors and both ABPs, ∼2.0-fold more Fim1 and ∼3.5-fold more Cdc8 accumulates on Arp2/3 complex branch points and formin Cdc12-assembled actin filaments, respectively. These findings indicate that F-actin assembly factors Arp2/3 complex and formin Cdc12 help facilitate the recruitment of specific ABPs, thereby tuning ABP sorting and subsequently establishing the identity of F-actin networks in fission yeast. • In vitro reconstitution of actin-binding protein sorting to distinct F-actin networks. • Fimbrin Fim1 and tropomyosin Cdc8 are preferentially recruited to different F-actin networks in fission yeast cells. • Competition between Fim1 and Cdc8 is essential for maximal ABP sorting to different F-actin networks. • F-actin assembly factors Arp2/3 complex and formin Cdc12 differentially facilitate recruitment of Fim1 and Cdc8, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ready-to-eat clam meat processed at 121 °C and 0.14 MPa for 15 min had better sensory acceptability. • High temperature–pressure (HTP) processing led to a significant increase in VOCs. • The increased esters and aldehydes content imparted good flavor to clam meat. • Ready-to-eat clam meat obtained through HTP processing offered high-protein nutritional value. • Increased time of HTP had the potential to reduce the tropomyosin allergenicity of clam. Investigating technologies to control the allergenicity of seafood is particularly important to safeguard consumer health, but there is currently a dearth of research focused on reducing the allergenicity of clam meat. This study aimed to investigate the effects of high temperature–pressure (HTP) processing times (121 °C, 0.14 MPa; 5, 10, 15, 20 min) on the sensory quality, nutrition, and allergenicity of ready-to-eat clam meat. With the extension of HTP time, the hardness of clam meat gradually decreased, the chewiness decreased initially and then increased, and the meat became tender. HTP processing endowed clam meat with abundant esters and aldehydes. Among all the processing groups, the umami and saltiness were better at 15 min, correlating with the highest overall acceptability. Ready-to-eat clam meat contained high-protein nutritional value. Compared with raw clam meat, the tropomyosin allergenicity of clam meat treated with HTP for 15 and 20 min was significantly reduced by 51.9 % and 56.5 %, respectively (P < 0.05). However, there was no significant difference between these two groups. Appropriate HTP processing time might be an efficient condition to reduce the tropomyosin allergenicity of ready-to-eat clam meat and improve its quality, particularly for the time of 15 min. The results of this study could provide a reliable theoretical basis for the development of hypoallergenic clam foods. [ABSTRACT FROM AUTHOR]

[Display omitted] • Simultaneous detection of crustacean and egg allergens using one strip is achieved. • The mutual interference of different T lines weakens by the optimum flow system. • The strip is the first detection method of sarcoplasmic calcium binding protein. • Target allergen in matrices and commercial food could be detected effectively. A quantum dot (QD) based multiplexed lateral flow immunoassay (xLFIA) for the simultaneous detection of egg allergen ovalbumin, crustacean allergen tropomyosin (TM) and sarcoplasmic calcium binding protein (SCP) was developed in this study. QD-labeled rabbit anti-ovalbumin, SCP and TM antibodies were applied as fluorescent detection probes. The chromatography system was optimized to reduce the mutual interference of different test lines. Visual and instrumental detection limits of the xLFIA were 0.1 and 0.05 μg/mL for SCP, both 0.05 μg/mL for ovalbumin and both 0.5 μg/mL for TM. As low as 0.10 % crab powder, 0.01 % egg white powder and 0.05 % shrimp powder could be detected in all three model foods using xLFIA. Besides, the xLFIA detection results of 23 of 28 commercial foods were consistent with ingredient labels. These findings indicate that the developed xLFIA is a practical tool for point-of-care detection of egg and crustacean allergens in processed and commercial foods. [ABSTRACT FROM AUTHOR]

[Display omitted] • A recombinant full-length isotope-labelled tropomyosin was expressed with high purity and isotope labeling ratio. • An absolute LC-MS/MS quantification assay was developed for shrimp tropomyosin in complex food matrices. • The limits of quantification for tropomyosin were 1–10 μg/g. • This method was successfully applied to the accurate quantification of tropomyosin in real samples. The carryover of trace allergens in complex food matrices poses challenges for detection techniques. Here, we demonstrate an accurate UPLC-MS/MS quantification assay for the shrimp allergen tropomyosin with a full-length isotope-labelled recombinant tropomyosin (TM-I) internal standard in complex food matrices. The TM-I, expressed based on the SILAC technique, exhibited a high isotope labelling ratio (>99%), purity, and alignment with the natural sequence. This method determined the tropomyosin ranging from 0.2 to 100 ng/mL. Mean recoveries ranged from 89 to 116%, with intra- and inter-day RSDs below 12%, for three signature peptides across three types of commercially processed food matrices. The limits of quantitation were 1 μg/g in pop food and sauce, and 10 μg/g in surimi product, respectively. This study supports the use of recombinant full-length isotope-labelled proteins rather than stable-isotope labelling peptides as internal standards to achieve more accurate quantitation of food allergens as the digestion error is corrected. [ABSTRACT FROM AUTHOR]

Tropomyosin (TM) is the primary allergenic protein responsible for crustacean food allergies, and thus sensitive and rapid methods are required for the screening of crustacean TM in food. In this study, using the phage-displayed shark nanobody (PSN) as a multifunctional biomaterial, we developed a colorimetric and surface-enhanced Raman scattering dual-mode lateral flow immunosensor (CM/SERS-LFI) for competitive detection of crustacean TM. The SERS tag AuMBA@AgNPs with the Raman signal molecule 4-mercaptobenzoic acid (4-MBA) was prepared and immobilized on the PSN to construct the immunoprobe AuMBA@Ag-PSN. The probe can identify free TM that competes with TM on the T-line, and the optimized CM/SERS-LFI enables quantitative analysis of TM using the probe with a limit of detection (LOD) of 0.0026 μg/mL (SERS mode) and 0.0057 μg/mL (colorimetric mode), respectively. Additionally, it can implement a qualitative analysis by the naked eye with a visual LOD of 0.01 μg/mL. The CM/SERS-LFI exhibited excellent performance in the tests of selectivity, accuracy, precision, and stability. Moreover, the method's effectiveness in the analysis of real samples was confirmed by a commercial ELISA kit. Therefore, the developed CM/SERS-LFI was demonstrated to be a powerful and reliable tool for the rapid and sensitive detection of crustacean TM in food. [Display omitted] • Colorimetric/SERS dual-mode lateral flow immunosensor for crustacean tropomyosin. • The phage that displays shark nanobody serves as a multifunctional biomaterial. • The phage loading the AuMBA@AgNPs SERS tag to construct the immunoprobe. • The immunosensor enables quantitative and qualitative detection of tropomyosin. • The immunosensor is reliable for the detection of tropomyosin in food samples. [ABSTRACT FROM AUTHOR]

• IgE of patients allergic to shrimp or mites cross-react with TPM of H. illucens. • The main structure in solution of both TPM variants is a α-helices tetramer. • In vitro gastrointestinal digestion reduces the number of potential epitopes. Insect consumption could address the increasing protein demand in compliance with environmental sustainability. Hermetia illucens (black soldier fly, BSF) is a promising insect for human diet and it is essential to assess the related allergenic risk, meant as primary sensitization or cross-reactivity with known allergens. In this work, we investigate the allergenicity of two tropomyosin variants identified in the BSF genome and produced as recombinant proteins. Immunoblot experiments showed that both proteins were recognized by sera of patients allergic to shrimp or mites highlighting the cross-reactivity risk. CD spectroscopy, cross-linking assays and size-exclusion chromatography showed a structure composed of alpha-helices oligomers for both variants. These proteins were quite stable to pH but sensitive to increasing temperatures. In vitro simulated digestion associated to mass-spectrometry allowed the identification of peptides resistant to gastrointestinal conditions which were compared with epitopes of Arthropoda and Mollusca allergens to predict the persistence of allergenicity upon digestion. [ABSTRACT FROM AUTHOR]

The study aimed to assay the allergenicity of shrimp tropomyosin (TM) following covalent conjugation with quercetin (QR) and chlorogenic acid (CA). The structure of the TM-polyphenol covalent conjugates was examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), circular dichroism (CD), fluorescence, differential scanning calorimetry (DSC), and Fourier Transform infrared spectroscopy (FTIR). Potential allergenicity was evaluated using in vitro and in vivo methods. The results showed that QR and CA induced structural changes in TM through aggregation. RBL-2H3 cell results showed that TM-QR and TM-CA covalent conjugates reduced the release of β-hexosaminidase and histamine, respectively. In the mice model, TM-QR and TM-CA covalent conjugates reduced the level of IgE, IgG, IgG1, histamine, and mMCP-1 in sera. Furthermore, the allergenicity was reduced by suppressing Th2-related cytokines (IL-4, IL-5, IL-13) and promoting Th1-related cytokines (IFN-γ). These research findings demonstrate that the covalent binding of TM with QR and CA, modifies the allergenic epitopes of shrimp TM, thereby reducing its potential allergenicity. This approach holds practical applications in the production of low-allergenicity food within the food industry. [ABSTRACT FROM AUTHOR]

Cod proteins (CPs) have potential applications in designing desirable gel-based products, and this study aimed to unravel their heat-induced aggregation pattern and further probe the roles in protein gels. SDS-PAGE analysis indicated that high-precipitation-coefficient aggregates (HPCAs) of CPs aggregates were composed of considerable polymers of myosin heavy chains and actin, and their low-precipitation-coefficient aggregates (LPCAs) contained myosin light chains and tropomyosin. Studies from correlation analysis between the structure and aggregation kinetics revealed that the generation of β-sheet and S S bonds were responsible for their spontaneous thermal aggregation induced by heating temperature and protein concentration, respectively. Additionally, as protein denaturation ratio increased, more and larger HPCAs were formed, which was evidenced driving the network formation of protein gels and resulting in higher storage modulus (G') values. These novel findings may be applicable to other animal proteins for better tailoring the manufacturing of muscle gel-based products. [Display omitted] • β-sheet structure favored the aggregation of water-soluble cod proteins. • High-precipitation-coefficient aggregates led to stronger cod protein gels. • Myosin heavy chains and actin mainly contributed to gel network formation. [ABSTRACT FROM AUTHOR]

• Backslopping , improvement method in Terasi's' manufacture. • Isazaami (N. awatchensis) Terasi contained tropomyosin with high IgE-binding ability. • Starter improves the productivity of microorganisms during fermentation. • The IgE-binding ability of TM in Terasi was diminished in all the C-ELISA. • Backslopping effectively promoted the degradation of TM contained in Terasi. The backslopping method was applied to the manufacture of Terasi (fermented shrimp paste) as countermeasures against the technical issue depending on the raw material, and its contribution to reduction of the potential allergenicity of Terasi was examined. Three kinds of starters, the low allergenic Indonesian commercial Terasi (CT), Akiami (Acetes japonicus) Terasi produced in laboratory scale (AT) and heated AT (HAT) were added to the manufacturing process of the Isazaami (Neomysis awatchensis) Terasi which contained tropomyosin (TM) with high IgE-binding ability. Addition of the starter effectively promoting the degradation of the shrimp protein and the reduction of the IgE-binding ability of TM. Interestingly, Terasi added as a starter would have acted primarily as a nutrient source to promote microbial fermentation rather than as a source of fermenting microorganisms and endogenous proteases. The backslopping method is one of the improving methods for reduction of potential allergenicity of Terasi product. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effect of LA on in vitro digestibility and immunodetection of TM was evaluated. • Structure changes were accessed by spectroscopic and molecular modeling techniques. • Immunodetection reliability was adversely impacted by LA matrix interferences. • The binding of LA to TM would mask the related epitopes and cleavage sites of TM. • Complex matrixes immunodetection results should be interpreted with outmost care. The effect of linoleic acid (LA) on the IgG/IgE recognition, in vitro digestibility and immunodetection of shrimp tropomyosin (TM) was investigated. Subsequently, the simultaneous binding of LA-TM was explored using multi-spectroscopic and molecular modeling techniques. Our findings reveled that the addition of LA significantly reduced TM's IgG/IgE immunoreactivity, digestibility, and immunodetection. Further analysis using multi-spectroscopic and molecular modeling techniques indicated that while TM's secondary structure remained largely unchanged, its 3-D structure showed significant alterations such as increased particle size and hydrophobic surface area, and a higher number of buried hydrophobic residues exposed due to the binding of LA to TM. These structural changes rendered it difficult for target antibodies and digestive enzymes to interact with related epitopes and cleavage sites buried inside the molecule. The results obtained in this study provide valuable insights into the molecular mechanism of poor immunodetection caused by food matrix interference. [ABSTRACT FROM AUTHOR]