FKBP52 regulates TRPC3-dependent Ca2+ signals and the hypertrophic growth of cardiomyocyte cultures

The Transient receptor potential (TRP; C-classical; TRPC) channel TRPC3 permeates a cation (Na+/Ca2+) influx that is favoured by the stimulation of Gq protein-coupled receptors (GPCRs). An enhanced TRPC3 activity is related to adverse effects including pathological hypertrophy in chronic cardiac disease states. In the present study we identified FK506 binding protein 52 (FKBP52) as a novel interaction partner of TRPC3 in the heart. FKBP52 was recovered from a cardiac cDNA library by a C-terminal TRPC3 fragment (amino acids 742-848) in a yeast two-hybrid screen. Downregulation of FKBP52 promoted a TRPC3-dependent hypertrophic response in neonatal rat cardiomyocytes (NRC). A similar effect was achieved by overexpressing PPIase-deficient FKBP52 mutants. Mechanistically, FKBP52 truncated mutants elevated TRPC3-mediated currents and Ca2+ fluxes, the activation of calcineurin and the nuclear factor of activated T-cells in NRCs. Our data demonstrate that FKBP52 associates with TRPC3 via an as yet undescribed binding site in the C-terminus of TRPC3 and modulates TRPC3-dependent Ca2+ signals in a PPIase-dependent manner. This functional interaction might be crucial for limiting TRPC3-dependent signaling during chronic hypertrophic stimulation.