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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: Larotrectinib, a first‐in‐class, highly selective tropomyosin receptor kinase (TRK) inhibitor, has demonstrated efficacy in adult and pediatric patients with various solid tumors harboring NTRK gene fusions. This subset analysis focuses on the efficacy and safety of larotrectinib in an expanded cohort of adult patients with TRK fusion sarcomas. Methods: Patients (≥18 years old) with sarcomas harboring NTRK gene fusions were identified from three clinical trials. Patients received larotrectinib 100 mg orally twice daily. Response was investigator‐assessed per RECIST v1.1. Data cutoff was July 20, 2021. Results: At the data cutoff, 36 adult patients with TRK fusion sarcomas had initiated larotrectinib therapy: two (6%) patients had bone sarcomas, four (11%) had gastrointestinal stromal tumors, and 30 (83%) had soft tissue sarcomas. All patients were evaluable for response and demonstrated an objective response rate of 58% (95% confidence interval, 41–74). Patients responded well to larotrectinib regardless of number of prior lines of therapy. Adverse events (AEs) were mostly grade 1/2. Grade 3 treatment‐emergent AEs (TEAEs) occurred in 15 (42%) patients. There were no grade 4 TEAEs. Two grade 5 TEAEs were reported, neither of which were considered related to larotrectinib. Four (11%) patients permanently discontinued treatment due to TEAEs. Conclusions: Larotrectinib demonstrated robust and durable responses, extended survival benefit, and a favorable safety profile in adult patients with TRK fusion sarcomas with longer follow‐up. These results continue to demonstrate that testing for NTRK gene fusions should be incorporated into the clinical management of adult patients with various types of sarcomas. Plain Language Summary: Tropomyosin receptor kinase (TRK) fusion proteins result from translocations involving the NTRK gene and cause cancer in a range of tumor types.Larotrectinib is an agent that specifically targets TRK fusion proteins and is approved for the treatment of patients with TRK fusion cancer.This study looked at how well larotrectinib worked in adult patients with sarcomas caused by TRK fusion proteins.Over half of patients had a durable response to larotrectinib, with no unexpected side effects.These results show that larotrectinib is safe and effective in adult patients with TRK fusion sarcomas. Larotrectinib, a first‐in‐class tropomyosin receptor kinase (TRK) inhibitor, demonstrated robust and durable responses, extended survival benefit, and a favorable safety profile in adult patients with TRK fusion sarcomas. Testing for NTRK gene fusions should be incorporated into the clinical management of adult patients with various types of sarcomas to identify those suitable for targeted therapy. [ABSTRACT FROM AUTHOR]

The aim of this study was evaluated the effect of selected bioactive substances and nanoparticles on the immunoreactivity of edible packages based on chitosan using the ELISA. The analysed protein was the tropomyosin. The results confirmed the presence of the tropomyosin (3.77 ± 0.79-5.75 ± 0.01 µg/g) in control samples. This study demonstrated that the bioactive substances in the form of grape (0.61 ± 0.34-0.43 ± 0.16 µg/g), blueberry (0.58 ± 0.32-0.39 ± 0.27 µg/g), and parsley extracts (2.09 ± 1.28-0.79 ± 0.40 µg/g) reduces immunoreactivity (p < 0.05) of the tropomyosin. The elder pollen had no significant effect (p > 0.05) on immunoreactivity. ZnO and TiO2 nanoparticles also demonstrated immunoreactivity reduction (p < 0.05). The exception was silver nanoparticles, where the immunoreactivity increased with increasing concentration of grape extract (1.29 ± 0.01-5.47 ± 0.25 µg/g). The results confirmed the inhibitory effect of bioactive substances on the immunoreactivity of the used ELISA and also showed the need to consider immunoreactive substances when interpreting ELISA results. [ABSTRACT FROM AUTHOR]

Contraction of striated muscles is initiated by an increase in cytosolic Ca2+ concentration, which is regulated by tropomyosin and troponin acting on actin filaments at the sarcomere level. Namely, Ca2+-binding to troponin C shifts the "on--off" equilibrium of the thin filament state toward the "on" state, promoting actomyosin interaction; likewise, an increase in temperature to within the body temperature range shifts the equilibrium to the on state, even in the absence of Ca2+. Here, we investigated the temperature dependence of sarcomere shortening along isolated fast skeletal myofibrils using optical heating microscopy. Rapid heating (25 to 41.5°C) within 2 s induced reversible sarcomere shortening in relaxing solution. Further, we investigated the temperature-dependence of the sliding velocity of reconstituted fast skeletal or cardiac thin filaments on fast skeletal or β-cardiac myosin in an in vitro motility assay within the body temperature range.We found that (a) with fast skeletal thin filaments on fast skeletal myosin, the temperature dependence was comparable to that obtained for sarcomere shortening in fast skeletal myofibrils (Q10 -8), (b) both types of thin filaments started to slide at lower temperatures on fast skeletal myosin than on β-cardiac myosin, and (c) cardiac thin filaments slid at lower temperatures compared with fast skeletal thin filaments on either type of myosin. Therefore, the mammalian striated muscle may be finetuned to contract efficiently via complementary regulation of myosin and tropomyosin--troponin within the body temperature range, depending on the physiological demands of various circumstances. [ABSTRACT FROM AUTHOR]

The tropomyosin genes (TPM1-4) contribute to the functional diversity of skeletal muscle fibers. Since its discovery in 1988, the TPM3 gene has been recognized as an indispensable regulator of muscle contraction in slow muscle fibers. Recent advances suggest that TPM3 isoforms hold more extensive functions during skeletal muscle development and in postnatal muscle. Additionally, mutations in the TPM3 gene have been associated with the features of congenital myopathies. The use of different in vitro and in vivo model systems has leveraged the discovery of several disease mechanisms associated with TPM3-related myopathy. Yet, the precise mechanisms by which TPM3 mutations lead to muscle dysfunction remain unclear. This review consolidates over three decades of research about the role of TPM3 in skeletal muscle. Overall, the progress made has led to a better understanding of the phenotypic spectrum in patients affected by mutations in this gene. The comprehensive body of work generated over these decades has also laid robust groundwork for capturing the multiple functions this protein plays in muscle fibers. [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: Reduced expression or impaired signalling of tropomyosin receptor kinases (Trk receptors) are found in a vast spectrum of CNS disorders. [18F]TRACK is the first PET radioligand for TrkB/C with proven in vivo brain penetration and on-target specific signal. Here we report dosimetry data for [18F]TRACK in healthy humans. 6 healthy participants (age 22–61 y, 3 female) were scanned on a General Electric Discovery PET/CT 690 scanner. [18F]TRACK was synthesized with high molar activities (Am = 250 ± 75 GBq/µmol), and a dynamic series of 12 whole-body scans were acquired after injection of 129 to 147 MBq of the tracer. Images were reconstructed with standard corrections using the manufacturer's OSEM algorithm. Tracer concentration time-activity curves (TACs) were obtained using CT-derived volumes-of-interest. Organ-specific doses and the total effective dose were estimated using the Committee on Medical Internal Radiation Dose equation for adults and tabulated Source tissue values (S values). Results: Average organ absorbed dose was highest for liver and gall bladder with 6.1E−2 (± 1.06E−2) mGy/MBq and 4.6 (± 1.18E−2) mGy/MBq, respectively. Total detriment weighted effective dose EDW was 1.63E−2 ± 1.68E−3 mSv/MBq. Organ-specific TACs indicated predominantly hepatic tracer elimination. Conclusion: Total and organ-specific effective doses for [18F]TRACK are low and the dosimetry profile is similar to other 18F-labelled radio tracers currently used in clinical settings. [ABSTRACT FROM AUTHOR]

NTRK (neurotrophic tyrosine receptor kinase) gene fusions that encode chimeric proteins exhibiting constitutive activity of tropomyosin receptor kinases (TRK), are oncogenic drivers in multiple cancer types. However, the underlying mechanisms in oncogenesis that involve various N-terminal fusion partners of NTRK fusions remain elusive. Here, we show that NTRK fusion proteins form liquid-like condensates driven by their N-terminal fusion partners. The kinase reactions are accelerated in these condensates where the complexes for downstream signaling activation are also concentrated. Our work demonstrates that the phase separation driven by NTRK fusions is not only critical for TRK activation, but the condensates formed through phase separation serve as organizational hubs for oncogenic signaling. [ABSTRACT FROM AUTHOR]

Tropomyosin is the major and predominant allergen among shellfish. This study developed an ultrasensitive immuno-PCR method for the quantification of crustacean tropomyosin in foods. The method couples sandwich ELISA with the real-time PCR (rtPCR) amplification of marker DNAs. Monoclonal anti-TPM antibody was the capture antibody, polyclonal rabbit anti-shrimp tropomyosin antibody was the detection antibody, while natural shrimp tropomyosin served as the standard. A double-stranded amino-DNA was covalently conjugated to a secondary anti-rabbit antibody and subsequently amplified and quantified via rtPCR. The quantification sensitivity of immuno-PCR was 20-fold higher than analogous ELISA, with LOQ 19.8 pg/mL. The developed immuno-PCR method is highly specific for the detection of crustacean tropomyosin and is highly precise in a broad concentration range. Tropomyosin recovery in the spiked vegetable soup was 87.7–115.6%. Crustacean tropomyosin was also quantified in commercial food products. The reported immuno-PCR assay is the most sensitive method for the quantification of crustacean tropomyosin and is the first immuno-PCR-based assay for the quantification of food allergen and food protein in general. The described method could be easily adapted for the specific and ultrasensitive immuno-PCR-based detection of traces of any food allergen that is currently being quantified with ELISA, which is of critical importance for people with food allergies. [ABSTRACT FROM AUTHOR]

Despite the success in identifying new crustacean allergens other than tropomyosin, many potential allergens remain unidentified. At present, there are no diagnostic and treatment crustacean allergens on the Russian market, including tropomyosin of invertebrates. The aim of the research was to explore allergenic properties of tropomyosin and other proteins in water-salt extract from tiger shrimp (Penaeus monodon). Raw and boiled meat of giant tiger shrimp was used to prepare allergenic extracts. To identify the specific activity of experimental allergens, sera from patients allergic to crustaceans with an established degree of activity (class 3) were used. The levels of specific IgE were from 3.5 to 17.5 IU/mL. ELISA was performed with the allergen samples. Polyacrylamide gel electrophoresis of raw and boiled shrimp allergen preparations was followed by western blotting with the most allergen-specific serum. It has been shown that the extracts from raw and boiled shrimp have allergenic activity (bind IgE). The heat treatment of shrimp had no effect on allergenic activity except for one sample, where a strong reaction with the antigens was found. It is proved that the selected extraction conditions make it possible to reveal the multifractional nature of the protein profile of raw and boiled shrimp extracts. In western blotting experiments, the raw shrimp extract showed a weak reaction; tropomyosin was not detected. At the same time, five protein fractions were identified in the boiled shrimp samples which reacted with IgE antibodies of a patient allergic to crustaceans. The data obtained will allow us to expand the knowledge about crustacean allergy and continue our research to determine the optimal conditions for cleaning shrimp allergens. [ABSTRACT FROM AUTHOR]

Background: Recently, we have developed a method to identify IgE cross-reactive allergens. However, the mechanism by which IgE cross-reactive allergens cause food allergy is not yet fully understood how. In this study, we aimed to understand the underlying pathogenesis by identifying food allergens that cross-react with house dust mite allergens in a murine model. Material and methods: Allergenic protein microarray analysis was conducted using serum from mice intraperitoneally injected with Dermatophagoides pteronyssinus (Der p) extract plus alum or alum alone as controls. Der p, Dermatophagoides farinae (Der f), coho salmon extract-sensitized and control mice were analyzed. Serum levels of IgE against Der p, Der f, coho salmon extract, protein fractions of coho salmon extract separated by ammonium sulfate precipitation and anion exchange chromatography, and recombinant coho salmon tropomyosin or actin were measured by an enzyme-linked immunosorbent assay. A murine model of cutaneous anaphylaxis or oral allergy syndrome (OAS) was established in Der p extract-sensitized mice stimulated with coho salmon extract, tropomyosin, or actin. Results: Protein microarray analysis showed that coho salmon-derived proteins were highly bound to serum IgE in Der p extract-sensitized mice. Serum IgE from Der p or Der f extract-sensitized mice was bound to coho salmon extract, whereas serum IgE from coho salmon extract-sensitized mice was bound to Der p or Der f extract. Analysis of the murine model showed that cutaneous anaphylaxis and oral allergic reaction were evident in Der p extract-sensitized mice stimulated by coho salmon extract. Serum IgE from Der p or Der f extractsensitized mice was bound strongly to protein fractions separated by anion exchange chromatography of coho salmon proteins precipitated with 50% ammonium sulfate, which massively contained the approximately 38 kDa protein. We found that serum IgE from Der p extract-sensitized mice was bound to recombinant coho salmon tropomyosin. Der p extract-sensitized mice exhibited cutaneous anaphylaxis in response to coho salmon tropomyosin. Conclusion: Our results showed IgE cross-reactivity of tropomyosin between Dermatophagoides and coho salmon which illustrates salmon allergy following sensitization with the house dust mite Dermatophagoides. Our method for identifying IgE cross-reactive allergens will help understand the underlying mechanisms of food allergies. [ABSTRACT FROM AUTHOR]

Tropomyosin (TM) is a heat-stable protein that plays a crucial role as a major pan-allergen in crustacean shellfish. Despite the high thermal stability of the TM structure, its IgG/IgE binding ability, immunodetection, and in vitro digestibility can be negatively influenced by glycation during food processing, and the underlying mechanism remains unclear. In this study, TM was subjected to glycosylation using various sugars and temperatures. The resulting effects on IgG/IgE-binding capacity, immunodetection, and in vitro digestibility were analyzed, meanwhile, the structural alterations and modifications using spectroscopic and LC-MS/MS analysis were determined. Obtained results suggested that the IgG/IgE binding capacity of glycosylated TM, immunodetection recovery, and in vitro digestibility were significantly reduced depending on the degree of glycosylation, with the greatest reduction occurring in Rib-TM. These changes may be attributable to structural alterations and modifications that occur during glycosylation processing, which could mask or shield antigenic epitopes of TM (E3: 61–81, E5b: 142–162, and E5c: 157–183), subsequently reducing the immunodetection recognition and digestive enzyme degradation. Overall, these findings shed light on the detrimental impact of glycation on TMs potential allergenicity and digestibility immunodetection and provide insights into the structural changes and modifications induced by thermal processing. [ABSTRACT FROM AUTHOR]

We characterized a novel genetic variant c.292G > A (p.E98K) in the TPM1 gene encoding cardiac tropomyosin 1.1 isoform (Tpm1.1), found in a proband with a phenotype of complex cardiomyopathy with conduction dysfunction and slow progressive neuromuscular involvement. To understand the molecular mechanism by which this mutation impairs cardiac function, we produced recombinant Tpm1.1 carrying an E98K substitution and studied how this substitution affects the structure of the Tpm1.1 molecule and its functional properties. The results showed that the E98K substitution in the N-terminal part of the Tpm molecule significantly destabilizes the C-terminal part of Tpm, thus indicating a long-distance destabilizing effect of the substitution on the Tpm coiled-coil structure. The E98K substitution did not noticeably affect Tpm's affinity for F-actin but significantly impaired Tpm's regulatory properties. It increased the Ca2+ sensitivity of the sliding velocity of regulated thin filaments over cardiac myosin in an in vitro motility assay and caused an incomplete block of the thin filament sliding at low Ca2+ concentrations. The incomplete motility block in the absence of Ca2+ can be explained by the loosening of the Tpm interaction with troponin I (TnI), thus increasing Tpm mobility on the surface of an actin filament that partially unlocks the myosin binding sites. This hypothesis is supported by the molecular dynamics (MD) simulation that showed that the E98 Tpm residue is involved in hydrogen bonding with the C-terminal part of TnI. Thus, the results allowed us to explain the mechanism by which the E98K Tpm mutation impairs sarcomeric function and myocardial relaxation. [ABSTRACT FROM AUTHOR]

NTRK gene fusions have been identified in various tumors; some requiring aggressive therapy and sometimes new TRK inhibitors (TRKi). We aimed to describe a national, unselected, retrospective, multicenter cohort. Patients were identified through the French sarcoma diagnostic laboratory at Institut Curie through samples analyzed by RT-qPCR or whole-transcriptome sequencing. From 2001 to 2019, 65 NTRK fusion tumors were identified within 2120 analyses (3.1%): 58 by RNA sequencing (including 20 after RT-qPCR analysis) and 7 exclusively by RT-qPCR. Of the 61 patients identified, 37 patients had infantile soft tissue or kidney fibrosarcomas (IFS), 15 other mesenchymal (Other-MT) and nine central nervous system (CNS) tumors. They encompassed 14 different tumor types with variable behaviors. Overall, 53 patients had surgery (3 mutilating), 38 chemotherapy (20 alkylating agents/anthracycline), 11 radiotherapy, two 'observation strategy' and 13 received TRKi. After a median follow-up of 61.0 months [range, 2.5–226.0], 10 patients died. Five-year overall survival is, respectively, 91.9% [95%CI, 83.5–100.0], 61.1% [95%CI, 34.2–100.0] and 64.8% [95%CI, 39.3–100.0] for IFS, Other-MT, and CNS groups. NTRK-fusion positive tumors are rare but detection is improved through RNA sequencing. TRKi could be considered at diagnosis for CNS NTRK-fusion positive tumors, some IFS, and Other-MT. Not adapted. [ABSTRACT FROM AUTHOR]

Recent decades see a steady increase in the number of patients suffering from food allergies worldwide. Children have a variety of clinical symptoms of food allergy. Some patients have local allergic reaction in the oral cavity, other — atopic dermatitis or gastrointestinal allergy, and sometimes there is the food anaphylaxis that put child’s life in danger. Atopic dermatitis is among the most common food allergy symptom. We all know that atopic dermatitis is a multifactorial chronic disease characterized by skin itching and inflammation. Allergens in children food intake are considered to be the main factors to provoke atopic dermatitis at an early age, but sometimes not only oral allergens are the main triggers of the disease. Nowadays we get more data about inhalation and transdermal ways of sensitization with atopic dermatitis.Resent global scientific discoveries in molecular allergology changed the awareness of allergen structure and new ways to detect allergy. Scientists proved the direct connection between recurrent and difficult to treat signs of atopic dermatitis and IgE-dependent allergic reactions. That forces doctors to choose ISAC-112 ImmunoCAP test to treat patients with severe skin lesions to clarify the spectrum of sensitization.Objective: to describe a clinical case and to stress the importance of clarifying all possible allergens that can sensitize a patient with symptoms of atopic dermatitis, detected by ISAC-112 ImmunoCAP test.

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.

Parkinson's disease is a complex age-related progressive dopaminergic neurodegenerative disease consistently viewed as a disorder of movement and is characterized by its cardinal motor symptoms. While the motor symptoms and its clinical manifestations are attributed to the nigral dopaminergic neuronal death and basal ganglia dysfunction, studies have subsequently proven that the non-dopaminergic neurons in various brain regions are also additionally involved with the disease progression. Thus, it is now well accepted that the involvement of various neurotransmitters and other ligands accounts for the non-motor symptoms (NMS) associated with the Parkinson's disease. Consequently, this has demonstrated to possess remarkable clinical concerns to the patients in terms of various disability, such impaired to compromised quality of life and increased risk of morbidity and mortality. Currently, available pharmacological, non-pharmacological, and surgical therapeutic strategies neither prevent, arrest, nor reverse the nigral dopaminergic neurodegeneration. Thus, there is an imminent medical necessity to increase patient's quality of life and survival, which in turn decreases the incidence and prevalence of the NMS. The current research article reviews the potential direct involvement of neurotrophin and its mimetics to target and modulate neurotrophin-mediated signal transduction pathways to enlighten a new and novel therapeutic strategy along with the pre-existing treatments for Parkinson's disease and other neurological/neurodegenerative disorders which are associated with the downregulation of neurotrophins. [ABSTRACT FROM AUTHOR]

Regulation of the crossbridge cycle that drives muscle contraction involves a reconfiguration of the troponin--tropomyosin complex on actin filaments. By comparing atomic models of troponin--tropomyosin fitted to cryo-EM structures of inhibited and Ca2+-activated thin filaments, we find that tropomyosin pivots rather than rolls or slides across actin as generally thought. We propose that pivoting can account for the Ca2+ activation that initiates muscle contraction and then relaxation influenced by troponin-I (TnI). Tropomyosin is well-known to occupy either of three meta-stable configurations on actin, regulating access of myosin motorheads to their actin-binding sites and thus the crossbridge cycle. At low Ca2+ concentrations, tropomyosin is trapped by TnI in an inhibitory B-state that sterically blocks myosin binding to actin, leading to muscle relaxation. Ca2+ binding to TnC draws TnI away from tropomyosin, while tropomyosin moves to a C-state location over actin. This partially relieves the steric inhibition and allows weak binding of myosin heads to actin, which then transition to strong actin-bound configurations, fully activating the thin filament. Nevertheless, the reconfiguration that accompanies the initial Ca2+-sensitive B-state/C-state shift in troponin--tropomyosin on actin remains uncertain and at best is described by moderate-resolution cryo- EM reconstructions. Our recent computational studies indicate that intermolecular residue-to-residue salt-bridge linkage between actin and tropomyosin is indistinguishable in B- and C-state thin filament configurations. We show here that tropomyosin can pivot about relatively fixed points on actin to accompany B-state/C-state structural transitions. We argue that at low Ca2+ concentrations C-terminal TnI domains attract tropomyosin, causing it to bend and then pivot toward the TnI, thus blocking myosin binding and contraction. [ABSTRACT FROM AUTHOR]

Background: Clinical trials have reported the efficacy of tropomyosin receptor kinase (TRK) inhibitors against neurotrophic receptor tyrosine kinase (NTRK) fusion gene-positive advanced solid tumors. The accumulated evidence of tumor-agnostic agent has made since TRK inhibitors were approved and used in clinical practice. Therefore, we have revised the 'Japan Society of Clinical Oncology (JSCO)/Japanese Society of Medical Oncology (JSMO)-led clinical recommendations on the diagnosis and use of tropomyosin receptor kinase inhibitors in adult and pediatric patients with neurotrophic receptor tyrosine kinase fusion-positive advanced solid tumors, cooperated by the Japanese Society of Pediatric Hematology/Oncology (JSPHO)'. Methods: Clinical questions regarding medical care were formulated for patients with NTRK fusion-positive advanced solid tumors. Relevant publications were searched by PubMed and Cochrane Database. Critical publications and conference reports were added manually. Systematic reviews were performed for each clinical question for the purpose of developing clinical recommendations. The committee members identified by JSCO, JSMO, and JSPHO voted to determine the level of each recommendation considering the strength of evidence, expected risks and benefits to patients, and other related factors. Thereafter, a peer review by experts nominated from JSCO, JSMO, and JSPHO, and the public comments among all societies' members was done. Results: The current guideline describes 3 clinical questions and 14 recommendations for whom, when, and how NTRK fusion should be tested, and what is recommended for patients with NTRK fusion-positive advanced solid tumors. Conclusion: The committee proposed 14 recommendations for performing NTRK testing properly to select patients who are likely to benefit from TRK inhibitors. [ABSTRACT FROM AUTHOR]

The dynamically growing incidence of food allergies forces the scientific community to develop new methods for their diagnosis, differentiation, and effective treatment. Parasitoses appear much less frequently in the scientific literature, as well as among the presumed causes of numerous conditions. The similarity of inflammatory mechanisms in allergies and parasitosis necessitates a revision of current diagnostic standards. A lack of specificity and the coincidence of symptoms at an early stage of disease can lead to misdiagnosis. In this paper, we attempted to perform a comparative analysis of the similarities and differences in symptoms for these two types of diseases. We described the molecular mechanisms and metabolic pathways of food allergy and parasitosis. We presented the available research methods and directions of ongoing studies aimed at implementing precise medical techniques for differential diagnosis. We discussed the allergenic properties of certain parasite proteins, using the example of myofibrillar tropomyosins from the nematode Anisakis simplex. The literature in the fields of allergology and parasitology leads to the conclusion that it is reasonable to run parallel allergological and parasitological diagnostics in patients with non-specific symptoms. This approach will facilitate accurate and early diagnosis and implementation of effective therapy. [ABSTRACT FROM AUTHOR]

Background. Allergy toward the dust mite is steadily increasing on the European continent. This sensitization may be a risk factor for developing sensitization to other mite molecules such as tropomyosin Der p 10. This molecule often correlates with food allergy and the risk of anaphylaxis after ingesting mollusks and shrimps. Materials and Methods. We analyzed the sensitization profiles by ImmunoCAP ISAC of pediatric patients from 2017 to 2021. The patients under investigation were being followed for atopic disorders such as allergic asthma and food allergies. The study aimed to analyze the prevalence of sensitization toward Der p 10 in our pediatric population and assess the related clinical symptoms and reactions after ingestion of foods containing tropomyosins. Results. This study included 253 patients; 53% were sensitized toward Der p 1 and Der p 2; 10.4% were also sensitized to Der p 10. Assessing patients sensitized to Der p 1 or Der p 2, and Der p 10, we observed that 78.6% were affected by asthma (p < 0.005) and had a history of prior anaphylaxis after ingestion of shrimp or shellfish (p < 0.0001). Conclusion. The component-resolved diagnosis gave us a deeper understanding of patients' molecular sensitization profiles. Our study showed that a fair proportion of children sensitive to Der p 1 or Der p 2 are also sensitive to Der p 10. However, many patients sensitized to all three molecules had a high risk of asthma and anaphylaxis. Therefore, the assessment of Der p 10 sensitization should be considered in atopic patients with sensitization to Der p 1 and Der p 2 to avoid encountering possible adverse reactions after ingesting foods containing tropomyosins. [ABSTRACT FROM AUTHOR]

Tropomyosin (Tpm) is one of the most important partners of actin filament that largely determines its properties. In animal organisms, there are different isoforms of Tpm, which are believed to be involved in the regulation of various cellular functions. However, molecular mechanisms by which various Tpm cytoplasmic regulate of the functioning of actin filaments are still poorly understood. Here, we investigated the properties of Tpm2.1 and Tpm4.1 isoforms and compared them to each other and to more extensively studied Tpm isoforms. Tpm2.1 and Tpm4.1 were very similar in their affinity to F-actin, thermal stability, and resistance to limited proteolysis by trypsin, but differed markedly in the viscosity of their solutions and thermal stability of their complexes with F-actin. The main difference of Tpm2.1 and Tpm4.1 from other Tpm isoforms (e.g., Tpm1.6 and Tpm1.7) was their extremely low thermal stability as measured by the CD and DSC methods. We suggested the possible causes of this instability based on comparing the amino acid sequences of Tpm4.1 and Tpm2.1 with the sequences of Tpm1.6 and Tpm1.7 isoforms, respectively, that have similar exon structure. [ABSTRACT FROM AUTHOR]

Background: This paper aims to establish a light-controlled phosphorylation detection method at the Y785 site of tropomyosin receptor kinase A (TrkA) receptor in mammalian cells by using genetic code expansion technology and detecting the effects of optical activation of this site on the downstream MAPK/ERK pathway. The study is based on the current situation that the regulatory mechanism of TrkA phosphorylation has not been fully elucidated. Methods: Two photosensitive unnatural amino acids, p-azido-L-phenylalanine (AzF) and photo-caged tyrosine (ONB) were introduced into the TrkA-Y785 site by genetic code expansion technology and site-directed mutagenesis. Western blotting and laser confocal imaging were conducted to analyze the effects of this site on activating the MAPK/ERK pathway and nerve cell differentiation before and after photostimulation. Results: Our results supplemented the light-controlled results of the TrkA-Y785 site based on our previous research and verified that Y785 also makes important contributions in regulating the MAPK/ERK pathway. Conclusion: This study demonstrated the significant contributions of the TrkAY785 site in regulating the ERK pathway by precisely controlling the phosphorylation state of a single tyrosine site. [ABSTRACT FROM AUTHOR]

NTRK fusions are validated oncogenic drivers of various adult and pediatric tumor types, including thyroid cancer, and serve as a therapeutic target. Recently, tropomyosin receptor kinase (TRK) inhibitors, such as entrectinib and larotrectinib, display promising therapeutic efficacy in NTRK-positive solid tumors. Although some NTRK fusion partners have been identified in thyroid cancer, the spectrum of NTRK fusion is not fully characterized. In this study, a dual NTRK3 fusion was identified by targeted RNA-Seq in a 47-year-old female patient with papillary thyroid carcinoma. The patient harbors a novel in-frame fusion between NTRK3 exon 13 and AJUBA exon 2, co-existing with a known inframe fusion between ETV6 exon 4 and NTRK3 exon 14. The dual NTRK3 fusion was validated by Sanger sequencing and fluorescence in situ hybridization (FISH) but lack TRK protein expression as defined by pan-TRK immunohistochemistry (IHC). We supposed the pan-TRK IHC result to be falsely negative. In conclusion, we present the first case of a novel NTRK3-AJUBA fusion co-existing with a known ETV6-NTRK3 fusion in thyroid cancer. These findings extend the spectrum of translocation partners in NTRK3 fusion, and the effect of dual NTRK3 fusion on TRK inhibitor therapy and prognosis needs long-term follow-up. [ABSTRACT FROM AUTHOR]

Background: We report a patient with a novel c.737 C > T variant (p.Ser246Leu) of the TPM3 gene presenting with adult-onset distal myopathy. Case presentation: A 35-year-old Chinese male patient presented with a history of progressive finger weakness. Physical examination revealed differential finger extension weakness, together with predominant finger abduction, elbow flexion, ankle dorsiflexion and toe extension weakness. Muscle MRI showed disproportionate fatty infiltration of the glutei, sartorius and extensor digitorum longus muscles without significant wasting. Muscle biopsy and ultrastructural examination showed a non-specific myopathic pattern without nemaline or cap inclusions. Genetic sequencing revealed a novel heterozygous p.Ser246Leu variant (c.737C>T) of the TPM3 gene which is predicted to be pathogenic. This variant is located in the area of the TPM3 gene where the protein product interacts with actin at position Asp25 of actin. Mutations of TPM3 in these loci have been shown to alter the sensitivity of thin filaments to the influx of calcium ions. Conclusion: This report further expands the phenotypic spectrum of myopathies associated with TPM3 mutations, as mutations in TPM3 had not previously been reported with adult-onset distal myopathy. We also discuss the interpretation of variants of unknown significance in patients with TPM3 mutations and summarise the typical muscle MRI findings of patients with TPM3 mutations. [ABSTRACT FROM AUTHOR]

In the myocardium, the TPM1 gene expresses two isoforms of tropomyosin (Tpm), alpha (αTpm; Tpm 1.1) and kappa (κTpm; Tpm 1.2). κTpm is the result of alternative splicing of the TPM1 gene. We studied the structural features of κTpm and its regulatory function in the atrial and ventricular myocardium using an in vitro motility assay. We tested the possibility of Tpm heterodimer formation from α- and κ-chains. Our result shows that the formation of ακTpm heterodimer is thermodynamically favorable, and in the myocardium, κTpm most likely exists as ακTpm heterodimer. Using circular dichroism, we compared the thermal unfolding of ααTpm, ακTpm, and κκTpm. κκTpm had the lowest stability, while the ακTpm was more stable than ααTpm. The differential scanning calorimetry results indicated that the thermal stability of the N-terminal part of κκTpm is much lower than that of ααTpm. The affinity of ααTpm and κκTpm to F-actin did not differ, and ακTpm interacted with F-actin significantly worse. The troponin T1 fragment enhanced the κκTpm and ακTpm affinity to F-actin. κκTpm differently affected the calcium regulation of the interaction of pig and rat ventricular myosin with the thin filament. With rat myosin, calcium sensitivity of thin filaments containing κκTpm was significantly lower than that with ααTpm and with pig myosin, and the sensitivity did not differ. Thin filaments containing κκTpm and ακTpm were better activated by pig atrial myosin than those containing ααTpm. [ABSTRACT FROM AUTHOR]