Fig. 6.

CADM1 interacts with components of the insulin exocytic assembly and the actin-binding protein DAL-1. Immunoprecipitates were prepared from INS-1 cell lysates using an anti-CADM1 antibody or nonimmune rabbit IgG (control). Immunoprecipitated proteins were analyzed by Western blotting, with probing for the proteins indicated to the right of each row. CASK, Munc18, and syntaxin-1 are constituents of the subplasmalemmal insulin secretory machinery. The F-actin-binding protein DAL-1, also known as EPB41L3 and protein 4.1B, is known to bind to CADM1 in other cell types. Synaptophysin, unlike the other proteins, is a vesicle-associated protein, not a component of the submembrane secretory apparatus, and no corresponding band was detected, even after adjusting the fluorescent imaging system for maximal sensitivity, during immunoblot analysis of precipitated proteins (results are representative of 3 separate experiments).