The present invention provides methods, compositions, and kits useful for modulating insulin/glucose homeostasis in a subject by modulating CAP/SORBS1. In addition, the invention provides a variety of prescreening and screening methods aimed at identifying agents that modulate insulin/glucose homeostasis. Methods of the invention can involve assaying test agent binding to CAP/SORBS1 polypeptides or polynucleotides. Alternatively, test agents can be screened for their ability to alter the level of CAP/SORBS1 polypeptides, polynucleotides, or action.