Pore residues of TRPC1/4 heteromer determine channel properties.

TRPC1 and TRPC4 are proteins belonging in the same TRPC channel family and the two are known to form a heterotetrameric channel. TRPC4 can form a homotetrameric, non-selective cation channel by itself, but the involvement of TRPC1 subunit changes several major characteristics of the channel. In this study, we focused on the pore region (selectivity filter, pore helix, and S6 helix) of TRPC1 and TRPC4 as a determinant of the identity and characteristics of a heteromeric TRPC1/4 channel: decreased calcium permeability of the channel and outward-rectifying I-V curve. Mutants and chimeras of the pore residues were created and their currents were recorded using whole-cell patch clamp. The lower gate mutants of TRPC4 exhibited diminished calcium permeability as measured by GCaMP6s fluorescence. Also, chimeric channels substituting the pore region of TRPC1 to TRPC4 were made to locate the pore region that is critical in production of an outward-rectifying I-V curve characteristic to TRPC1/4 heteromeric channels.