Figure 2.

Coupling of Sig-1R, ankyrin B, and IP₃R-3 as a trimeric complex. (A) Coimmunoprecipitation (IP) followed by Western blotting of the Sig-1R/ankyrin B/IP₃R-3 complex by respective cognate antibodies. (B) Percentages of IP₃R-3 and ankyrin B, respectively, coimmunoprecipitated with Sig-1R. IP₃R-3 were immunoprecipitated with anti-IP₃R-3 antibodies or anti-Sig-1R antibodies. Ankyrin B isoforms were coimmunoprecipitated with either anti-ankyrin B antibodies or anti-Sig-1R antibodies. Immunoblots were digitally scanned and densitometrically quantified by a Macintosh computer-based image analysis program (image, National Institutes of Health). Note: Anti-IP₃R-3 antibodies and anti-ankyrin B antibodies also immunoprecipitated proteolytic products of IP₃R-3 and ankyrin B, respectively (see lanes 1 and 3, from left).