The canonical transient receptor potential channel 1 is an essential structural component of the mechanosensitive calcium permeable channel in vertebrate cells

O.P. Hamill¹, R. Maroto¹, A. Kurosky², T.G. Wood², A. Raso³ and B. Martinac³, ¹Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, Texas, U.S.A., ²Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston, Texas, U.S.A. and ³Department of Pharmacology, University of Western Australia, Crawley, WA, Australia.

The mechanosensitive cation channel (MscCa) transduces membrane stretch into cation (Na⁺, K⁺, Ca²⁺ and Mg²⁺) flux across the cell membrane, and is implicated in cell volume regulation, cell locomotion, muscle dystrophy and cardiac arrhythmias (Hamill & Martinac, 2001). However, the membrane protein(s) forming the MscCa in vertebrates remains unknown. Here we use an identification strategy based on detergent-solubilizing of frog oocyte membrane proteins followed by liposome reconstitution and evaluation by patch-clamp (Sukharev et al., 1993; Maroto et al., 2005). The oocyte was chosen because it expresses the prototypical MscCa (≥10⁷ MscCa/oocyte) that is preserved in cytoskeleton-deficient membrane vesicles (Zhang et al., 2000). We identified a membrane protein fraction that reconstituted high MscCa activity and showed an abundance of an 80 kDa protein identified immunologically as the canonical transient receptor potential channel 1 (TRPC1) (Wes et al., 1995; Brereton et al., 2000). Heterologous expression of the human TRPC1 resulted in a > 1000% increase in MscCa patch density, whereas injection of a TRPC1-specific antisense RNA abolished endogenous MscCa activity. hTRPC1 transfection of CHO-K1 cells also significantly increased MscCa expression. These observations indicate that TRPC1 is a component of the vertebrate MscCa, which like various prokaryotic Ms channels (Martinac & Kloda, 2004), is gated by tension developed in the lipid bilayer.

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