TMC6 Is a Novel Therapeutic Target for Pathogenic Cardiac Hypertrophy.

BACKGROUND

Pathogenic cardiac hypertrophy, often driven by mechanical stress, is a leading cause of heart failure. However, effective therapeutic targets remain limited. TMC6 (transmembrane channel-like protein 6) is abundant in healthy myocardium but downregulated in hypertrophic hearts; its role in cardiac hypertrophy remains undefined.

METHODS

We combined cardiac-specific Tmc6 knockout mice subjected to transverse aortic constriction surgery, neonatal rat ventricular myocytes, and CRISPR/Cas9-edited human pluripotent stem cell-derived cardiomyocytes to assess hypertrophy and signaling readouts. Subcellular localization, protein-protein interaction, and competitive peptide assays were used to dissect the mechanism. Adeno-associated virus serotype 9 (AAV9)-cTnT (cardiac troponin T)-TMC6 was used for in vivo rescue.

RESULTS

TMC6 deficiency increased cardiomyocyte size, fetal gene expression, and adverse remodeling in vivo and in vitro, whereas TMC6 overexpression blunted hypertrophic responses. Full-length TMC6 localized to the endoplasmic reticulum and bound CIB1 (calcium and integrin-binding protein 1) to sequester it in the endoplasmic reticulum, limiting CIB1 access to sarcolemmal Ca2+ microdomains required to scaffold calcineurin and activate NFAT (nuclear factor of activated T cells). A cell-permeable TMC6161-180 peptide competitively displaced CIB1 from TMC6 and augmented hypertrophy in wild-type but not Tmc6 knockout cardiomyocytes, indicating a dominant-negative mechanism. Therapeutically, AAV9-cTnT-TMC6 restored TMC6-CIB1 engagement, suppressed calcineurin/NFAT readouts, and improved function after pressure overload.

CONCLUSIONS

TMC6 is an endogenous brake on pathological hypertrophy that restrains CIB1-calcineurin/NFAT signaling via endoplasmic reticulum sequestration of CIB1. Restoring full-length TMC6 mitigates pressure-overload remodeling, nominating the TMC6-CIB1 axis as a therapeutic target.