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OSCA/TMEM63 is a newly identified family of mechanically activated (MA) ion channels in plants and animals, respectively, which convert physical forces into electrical signals or trigger intracellular cascades and are essential for eukaryotic physiology. OSCAs and related TMEM16s and transmembrane channel‐like (TMC) proteins form homodimers with two pores. However, the molecular architecture of the mammalian TMEM63 proteins remains unclear. Here we elucidate the structure of human TMEM63A in the presence of calcium by single particle cryo‐EM, revealing a distinct monomeric architecture containing eleven transmembrane helices. It has structural similarity to the single subunit of the Arabidopsis thaliana OSCA proteins. We locate the ion permeation pathway within the monomeric configuration and observe a nonprotein density resembling lipid. These results lay a foundation for understanding the structural organization of OSCA/TMEM63A family proteins. [ABSTRACT FROM AUTHOR]

Post-amputation pain causes great suffering to amputees, but still no effective drugs are available due to its elusive mechanisms. Our previous clinical studies found that surgical removal or radiofrequency treatment of the neuroma at the axotomized nerve stump effectively relieves the phantom pain afflicting patients after amputation. This indicated an essential role of the residual nerve stump in the formation of chronic post-amputation pain (CPAP). However, the molecular mechanism by which the residual nerve stump or neuroma is involved and regulates CPAP is still a mystery. In this study, we found that nociceptors expressed the mechanosensitive ion channel TMEM63A and macrophages infiltrated into the dorsal root ganglion (DRG) neurons worked synergistically to promote CPAP. Histology and qRT-PCR showed that TMEM63A was mainly expressed in mechanical pain-producing non-peptidergic nociceptors in the DRG, and the expression of TMEM63A increased significantly both in the neuroma from amputated patients and the DRG in a mouse model of tibial nerve transfer (TNT). Behavioral tests showed that the mechanical, heat, and cold sensitivity were not affected in the Tmem63a-/- mice in the naïve state, suggesting the basal pain was not affected. In the inflammatory and post-amputation state, the mechanical allodynia but not the heat hyperalgesia or cold allodynia was significantly decreased in Tmem63a-/- mice. Further study showed that there was severe neuronal injury and macrophage infiltration in the DRG, tibial nerve, residual stump, and the neuroma-like structure of the TNT mouse model, Consistent with this, expression of the pro-inflammatory cytokines TNF-α, IL-6, and IL-1β all increased dramatically in the DRG. Interestingly, the deletion of Tmem63a significantly reduced the macrophage infiltration in the DRG but not in the tibial nerve stump. Furthermore, the ablation of macrophages significantly reduced both the expression of Tmem63a and the mechanical allodynia in the TNT mouse model, indicating an interaction between nociceptors and macrophages, and that these two factors gang up together to regulate the formation of CPAP. This provides a new insight into the mechanisms underlying CPAP and potential drug targets its treatment. [ABSTRACT FROM AUTHOR]

Background: Diffuse large B-cell lymphoma (DLBCL) is a genetically heterogeneous disease with a complicated prognosis. Even though various prognostic evaluations have been applied currently, they usually only use the clinical factors that overlook the molecular underlying DLBCL progression. Therefore, more accurate prognostic assessment needs further exploration. In the present study, we constructed a novel prognostic model based on microtubule associated genes (MAGs). Methods: A total of 33 normal controls and 1360 DLBCL samples containing geneexpression from the Gene Expression Omnibus (GEO) database were included. Subsequently, the univariate Cox, the least absolute shrinkage and selection operator (LASSO), and multivariate Cox regression analysis were used to select the best prognosis related genes into the MAGs model. To validate the model, Kaplan-Meier curve, and nomogram were analyzed. Results: A risk score model based on fourteen candidate MAGs (CCDC78, CD300LG, CTAG2, DYNLL2, MAPKAPK2, MREG, NME8, PGK2, RALBP1, SIGLEC1, SLC1A1, SLC39A12, TMEM63A, and WRAP73) was established. The K-M curve presented that the high-risk patients had a significantly inferior overall survival (OS) time compared to low-risk patients in training and validation datasets. Furthermore, knocking-out TMEM63A, a key gene belonging to the MAGs model, inhibited cell proliferation noticeably. Conclusion: The novel MAGs prognostic model has a well predictive capability, which may as a supplement for the current assessments. Furthermore, candidate TMEM63A gene has therapeutic target potentially in DLBCL. [ABSTRACT FROM AUTHOR]

Heterozygous variants in TMEM63A have been recently identified as the cause of infantile-onset transient hypomyelination. To date, four TMEM63A variants have been reported in five patients. These patients exhibited favorable clinical course, developmental progress, and completion of myelination. The patient was a 5-year-old girl with severe global developmental delay, absent speech, no turning over, no gazing, hypotonia, and daily episodes of autonomic seizures. Brain MRI showed hypomyelination of deep and subcortical white matter that appeared hyperintense in T2-weighted imaging from 2 months of age and that showed no change at 4 years of age. Exome sequencing of the patient and her parents revealed a novel de novo missense variant, NM_014698.3:c.1658G>T, p.(Gly553Val), in the TMEM63A gene, which was confirmed by Sanger sequencing. The variant has not been registered in public databases, and it substitutes a highly conserved glycine residue located in a pore-lining transmembrane helix. No other candidate variants were identified. Although TMEM63A variants are generally thought to cause transient hypomyelination with favorable developmental progress, identification of a de novo TMEM63A variant in our patient suggests that the TMEM63A -related clinical spectrum is broad and includes severe developmental delay with seizures. [ABSTRACT FROM AUTHOR]

Summary: Hypotonic stress causes the activation of swelling-activated nonselective cation channels (NSCCs), which leads to Ca2+-dependent regulatory volume decrease (RVD) and adaptive maintenance of the cell volume; however, the molecular identities of the osmosensitive NSCCs remain unclear. Here, we identified TMEM63B as an osmosensitive NSCC activated by hypotonic stress. TMEM63B is enriched in the inner ear sensory hair cells. Genetic deletion of TMEM63B results in necroptosis of outer hair cells (OHCs) and progressive hearing loss. Mechanistically, the TMEM63B channel mediates hypo-osmolarity-induced Ca2+ influx, which activates Ca2+-dependent K+ channels required for the maintenance of OHC morphology. These findings demonstrate that TMEM63B is an osmosensor of the mammalian inner ear and the long-sought cation channel mediating Ca2+-dependent RVD.

Mechanically activated (MA) ion channels convert physical forces into electrical signals. Despite the importance of this function, the involvement of mechanosensitive ion channels in human disease is poorly understood. Here we report heterozygous missense mutations in the gene encoding the MA ion channel TMEM63A that result in an infantile disorder resembling a hypomyelinating leukodystrophy. Four unrelated individuals presented with congenital nystagmus, motor delay, and deficient myelination on serial scans in infancy, prompting the diagnosis of Pelizaeus-Merzbacher (like) disease. Genomic sequencing revealed that all four individuals carry heterozygous missense variants in the pore-forming domain of TMEM63A. These variants were confirmed to have arisen de novo in three of the four individuals. While the physiological role of TMEM63A is incompletely understood, it is highly expressed in oligodendrocytes and it has recently been shown to be a MA ion channel. Using patch clamp electrophysiology, we demonstrated that each of the modeled variants result in strongly attenuated stretch-activated currents when expressed in naive cells. Unexpectedly, the clinical evolution of all four individuals has been surprisingly favorable, with substantial improvements in neurological signs and developmental progression. In the three individuals with follow-up scans after 4 years of age, the myelin deficit had almost completely resolved. Our results suggest a previously unappreciated role for mechanosensitive ion channels in myelin development. [ABSTRACT FROM AUTHOR]

Abstract Background Hco-gal-m and -f were two isoforms of galectin cloned from male and female Haemonchus contortus, respectively, and it was demonstrated that recombinant Hco-gal-m and -f could act as immune suppressors. However, little is known about the receptors or binding partners of these galectins in the host. The research of the molecular mechanisms that govern the interactions between these galectins and host molecules will fill a gap in our understanding how parasite galectins interact with host cells. Methods A yeast two-hybrid system was used to identify the binding partners of Hco-gal-m and -f in this research. The interaction between rHco-gal-m and candidate binding protein was validated by co-immunoprecipitation. The localization of transmembrane protein 63A (TMEM63A) in peripheral blood mononuclear cells (PBMCs) was detected by immunofluorescence. The distribution of TMEM63A in T cells, B cells and monocytes in PBMCs was detected by flow cytometry. The immunomodulatory effects of Hco-gal-m and TMEM63A on cell proliferation, migration, apoptosis, nitric oxide production and cytokine secretion were observed by co-incubation of rHco-gal-m and TMEM63A-siRNA with goat PBMCs and monocytes. Results We found that TMEM63A, a functionally unknown protein, from goat PBMCs could bind to Hco-gal-m and -f. Immunofluorescence showed that TMEM63A was localized to the cell membrane. Flow cytometric analysis revealed that TMEM63A was expressed in the majority of goat PBMCs. After using RNA interference to knockdown expression of TMEM63A, the PBMC proliferation and migration were significantly increased, while the influence of rHco-gal-m on monocyte phagocytosis, PBMC nitric oxide production and migration were potently blocked. In addition, the production of IL-10, IFN-γ and TGF-β induced by rHco-gal-m were also altered. Conclusions Our results show that TMEM63A is a binding partner of Hco-gal-m/f, and involved in the immune responses of host PBMCs induced by Hco-gal-m for the first time.

Osmoreception is essential for systemic osmoregulation, a process to stabilize the tonicity and volume of the extracellular fluid through regulating the ingestive behaviour, sympathetic outflow and renal function. The sensation of osmotic changes by osmoreceptor neurons is mediated by ion channels that detect the change of osmolarity in extracellular fluid. However, the molecular identity of these channels remains mysterious. AtCSC1and OSCA1,two closely related paralogues from Arabidopsis, have been demonstrated to form hyperosmolarity activated ion channels, which makes their mammalian orthologues-the members of TMEM63 proteins, possible candidates for osmoreceptor transduction channel. To test this possibility, we cloned the cDNAs of all the three members of the mouse TMEM63 family, TMEM63A, TMEM63B and TMEM63C from the mRNA from mouse brain. When all of the three subtypes of TMEM63 proteins were co-expressed in HEK293 cells, we recorded membrane currents evoked by hypertonic stimulation in these cells. However, the cells expressing the combinations of any two subtypes of TMEM63 proteins could not exhibit any hyperosmolarity evoked currents. Thus, all the three members of TMEM63 proteins are required to constitute a hyperosmolarity activated ion channel. We propose that the TMEM63 proteins may serve as an osmolarity sensitive ion channel for the osmoreception. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Background: Diffuse large B-cell lymphoma (DLBCL) is a genetically heterogeneous disease with a complicated prognosis. Even though various prognostic evaluations have been applied currently, they usually only use the clinical factors that overlook the molecular underlying DLBCL progression. Therefore, more accurate prognostic assessment needs further exploration. In the present study, we constructed a novel prognostic model based on microtubule associated genes (MAGs). Methods: A total of 33 normal controls and 1360 DLBCL samples containing gene-expression from the Gene Expression Omnibus (GEO) database were included. Subsequently, the univariate Cox, the least absolute shrinkage and selection operator (LASSO), and multivariate Cox regression analysis were used to select the best prognosis related genes into the MAGs model. To validate the model, Kaplan-Meier curve, and nomogram were analyzed. Results: A risk score model based on fourteen candidate MAGs ( CCDC78, CD300LG, CTAG2, DYNLL2, MAPKAPK2, MREG, NME8, PGK2, RALBP1, SIGLEC1, SLC1A1, SLC39A12, TMEM63A, and WRAP73 ) was established. The K-M curve presented that the high-risk patients had a significantly inferior overall survival (OS) time compared to low-risk patients in training and validation datasets. Furthermore, knocking-out TMEM63A , a key gene belonging to the MAGs model, inhibited cell proliferation noticeably. Conclusion: The novel MAGs prognostic model has a well predictive capability, which may as a supplement for the current assessments. Furthermore, candidate TMEM63A gene has therapeutic target potentially in DLBCL., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Wu, Liu, Tian, Li, Jiang, Wang, Lv, Guo, Xing, Zhai, Sun, Li, Zhang, He, Luo, Zhan and Zhao.)

Hypotonic stress causes the activation of swelling-activated nonselective cation channels (NSCCs), which leads to Ca 2+ -dependent regulatory volume decrease (RVD) and adaptive maintenance of the cell volume; however, the molecular identities of the osmosensitive NSCCs remain unclear. Here, we identified TMEM63B as an osmosensitive NSCC activated by hypotonic stress. TMEM63B is enriched in the inner ear sensory hair cells. Genetic deletion of TMEM63B results in necroptosis of outer hair cells (OHCs) and progressive hearing loss. Mechanistically, the TMEM63B channel mediates hypo-osmolarity-induced Ca 2+ influx, which activates Ca 2+ -dependent K + channels required for the maintenance of OHC morphology. These findings demonstrate that TMEM63B is an osmosensor of the mammalian inner ear and the long-sought cation channel mediating Ca 2+ -dependent RVD., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)