Putative adapter protein involved in asymmetrical cell division and cell polarization processes. May play a role in the formation of epithelial tight junctions. Interacts with PARD6B. Interacts with INSC/inscuteable. Partially localized along the cell-cell contact region. Colocalizes with TJP1 to epithelial tight junctions. Highly expressed in kidney, lung and skeletal muscle. Expressed at intermediate levels in brain, heart, placenta, liver and pancreas. Isoform 1 is predominant, while isoform 2 and isoform 3 are expressed at lower levels. The N-terminal part (1-351) part blocks the association of the tight junction marker TJP1 with the cell-cell boundary when it is overexpressed. Belongs to the PAR3 family.