Cryo-EM structure of the cytoplasmic domain of murine transient receptor potential cation channel subfamily C member 6 (TRPC6)

• Published in: The Journal of biological chemistry Vol. 293; no. 26; pp. 10381 - 10391
• Main Authors: Azumaya, Caleigh M., Sierra-Valdez, Francisco, Cordero-Morales, Julio F., Nakagawa, Terunaga
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 29.06.2018; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; calcium channel; cryo-electron microscopy; Cryoelectron Microscopy; Cytoplasm - metabolism; electrophysiology; glomerulosclerosis; HEK293 Cells; Humans; ion channel; kidney; membrane protein; Mice; Mutation; Protein Domains; Protein Structure and Folding; purification; transient receptor potential channels (TRP channels); TRPC6; TRPC6 Cation Channel - chemistry; TRPC6 Cation Channel - genetics; TRPC6 Cation Channel - metabolism; vasoconstriction; calcium channel; transient receptor potential channels (TRP channels); kidney; TRPC6; electrophysiology; glomerulosclerosis; ion channel; purification; membrane protein; vasoconstriction; cryo-electron microscopy
• ISSN: 0021-9258; 1083-351X; 1083-351X
• DOI: 10.1074/jbc.RA118.003183

The kidney maintains the internal milieu by regulating the retention and excretion of proteins, ions, and small molecules. The glomerular podocyte forms the slit diaphragm of the ultrafiltration filter, whose damage leads to progressive kidney failure and focal segmental glomerulosclerosis (FSGS). The canonical transient receptor potential 6 (TRPC6) ion channel is expressed in the podocyte, and mutations in its cytoplasmic domain cause FSGS in humans. In vitro evaluation of disease-causing mutations in TRPC6 has revealed that these genetic alterations result in abnormal ion channel gating. However, the mechanism whereby the cytoplasmic domain modulates TRPC6 function is largely unknown. Here, we report a cryo-EM structure of the cytoplasmic domain of murine TRPC6 at 3.8 Å resolution. The cytoplasmic fold of TRPC6 is characterized by an inverted dome-like chamber pierced by four radial horizontal helices that converge into a vertical coiled-coil at the central axis. Unlike other TRP channels, TRPC6 displays a unique domain swap that occurs at the junction of the horizontal helices and coiled-coil. Multiple FSGS mutations converge at the buried interface between the vertical coiled-coil and the ankyrin repeats, which form the dome, suggesting these regions are critical for allosteric gating modulation. This functionally critical interface is a potential target for drug design. Importantly, dysfunction in other family members leads to learning deficits (TRPC1/4/5) and ataxia (TRPC3). Our data provide a structural framework for the mechanistic investigation of the TRPC family.