title: TRPC3 channels colocalize with Na+/Ca2+ exchanger and Na+ pump in axial component of transverse-axial tubular system of rat ventricle.
abstract: Transient receptor potential canonical (TRPC) proteins form Ca(2+)-permeable, nonselective cation channels activated after stimulation of G protein-coupled membrane receptors linked to phospholipase C (PLC). Although the PLC/inositol phosphate signaling pathway is known to exist in heart, expression and subcellular distribution of TRPC channel proteins in ventricular myocardium have not been evaluated. Of the six members of the TRPC channel family examined here, only TRPC3 was found by Western blot analysis of membrane proteins from rodent or canine ventricle. Likewise, only TRPC3 was observed in immunofluorescence analysis of thin sections from rat ventricle. TRPC3 was also the only family member observed in neonatal rat ventricular myocytes in culture. In longitudinal sections of rat ventricle, TRPC3 was predominantly localized to the intercalated disk region of the myocyte. However, transverse sections through heart muscle or single isolated adult myocytes revealed TRPC3-specific labeling in a vast network of intracellular membranes, where it colocalized with the Na(+)-K(+)-ATPase (NKA) pump and the Na(+)/Ca(2+) exchanger (NCX) but not with the ryanodine receptor or the sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) pump. Reciprocal immunoprecipitation assays from rat or canine ventricle showed that TRPC3 associates with NKA and NCX but not with the plasmalemmal Ca(2+)-ATPase pump. Immunoprecipitations from Sf9 insect cells heterologously expressing TRPC3, NKA, and NCX in various combinations revealed that NKA and NCX interact and that TRPC3 and NCX interact, but that TRPC3 does not directly associate with NKA. Together, these results suggest that TRPC3 is localized in the ventricular myocyte to the axial component of the transverse-axial tubular system, where it exists in a signaling complex that includes NCX and NKA.
authors.affiliation: Rammelkamp Center for Education and Research, Rm. R-322, MetroHealth Medical Center, 2500 MetroHealth Dr., Cleveland OH 44109-1998, USA.
authors.forename: Monu
authors.initials: M
authors.lastname: Goel
authors.forename: Cheng-Di
authors.initials: CD
authors.lastname: Zuo
authors.forename: William G
authors.initials: WG
authors.lastname: Sinkins
authors.forename: William P
authors.initials: WP
authors.lastname: Schilling
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry; D002478:Cells, Cultured; D004285:Dogs; D005455:Fluorescent Antibody Technique; D006352:Heart Ventricles / Q000737:chemistry; D047468:Immunoprecipitation; D007313:Insecta; D046912:Multiprotein Complexes / Q000737:chemistry; D009206:Myocardium / Q000737:chemistry*; D032383:Myocytes, Cardiac / Q000737:chemistry*; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000032:analysis; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D019837:Ryanodine Receptor Calcium Release Channel / Q000032:analysis; D012519:Sarcoplasmic Reticulum / Q000737:chemistry*; D019831:Sodium-Calcium Exchanger / Q000032:analysis* / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis* / Q000378:metabolism; D050052:TRPC Cation Channels / Q000032:analysis* / Q000378:metabolism
chemical_list: D046912:Multiprotein Complexes; D019837:Ryanodine Receptor Calcium Release Channel; D019831:Sodium-Calcium Exchanger; D050052:TRPC Cation Channels; C104603:TRPC3 cation channel; D053499:Plasma Membrane Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase