Substrate-specific adapter of a BCR (BTB-CUL3-RBX1) E3 ubiquitin ligase complex that acts as a regulator of the insulin signaling pathway, modulating insulin sensitivity by limiting PIK3R1/p85alpha abundance in adipocytes. Targets PIK3R1, the regulatory subunit of phosphatidylinositol 3-kinase (PI3K), for ‘Lys-48’-linked polyubiquitination and proteasome-mediated degradation.