C2CD6 associates with subunits of the CatSper channel complex. (A-F) HEK293T cells were transfected with the indicated expression constructs and protein extracts were used for immunoprecipitation (IP) and western blotting (WB) analyses. Input is 1% of the protein extracts used for IP. The antibodies used for IP and WB are shown in each panel. Co-immunoprecipitation of C2CD6 with CatSper1 (A), CatSper2 (B), CatSper3 (C), CatSper4 (D) and EFCAB9 (E) was demonstrated. Asterisk in D indicates Ig heavy chain. (F) C2CD6 is not associated with CatSperz. Asterisk indicates Ig light chain. (G) A working model of the CatSper channel complex. Eleven known subunits of the CatSper channel, including C2CD6, are shown. C2CD6 is associated with CatSper 1-4 and EFCAB9.