This gene belongs to the signal induced proliferation associated 1 family of genes, which encode GTPase-activating proteins specific for the GTP-binding protein Rap1. Rap1 has been implicated in regulation of cell adhesion, cell polarity, and organization of the cytoskeleton. Like other members of the family, the protein encoded by this gene contains RapGAP and PDZ domains. In addition, this protein contains a C-terminal leucine zipper domain. This gene is proposed to function in epithelial cell morphogenesis and establishment or maintenance of polarity. Consistently, expression of the protein in cell culture showed localization to cell-cell borders in apical regions, and downregulation of the gene in 3D Caco2 cell culture resulted in abnormal cell polarity and morphogenesis. Allelic variants of this gene have been associated with congenital cataracts in humans. [provided by RefSeq, Feb 2016].