Acts as a regulator of the Hippo signaling pathway. Negatively regulates the Hippo signaling pathway by mediating the interaction of MARK3 with STK3/4, bringing them together to promote MARK3-dependent hyperphosphorylation and inactivation of STK3 kinase activity toward LATS1 (PubMed:28087714). Positively regulates the Hippo signaling by mediating the interaction of SCRIB with STK4/MST1 and LATS1 which is important for the activation of the Hippo signaling pathway. Involved in regulating cell proliferation, maintenance of epithelial polarity, epithelial-mesenchymal transition (EMT), cell migration and invasion (By similarity). Plays an important role in dendritic spine formation and synaptogenesis in cortical neurons; regulates synaptogenesis by enhancing the cell surface localization of N-cadherin (PubMed:25232112). Acts as a positive regulator of hedgehog (Hh) signaling pathway. Plays a critical role in the early point of the SMO activity cycle by interacting with SMO at the ciliary base to induce the accumulation of KIF7 and GLI2 at the ciliary tip for GLI2 activation (PubMed:25644602). Interacts with MPP1. Interacts with CTNNB1 and with the third SH3 domain of SORBS3 to form a ternary complex (By similarity). Interacts (via coiled-coil domain) with MARK3. Interacts (via PDZ domain 3) with STK3/MST2 and STK4/MST1 (PubMed:28087714). Interacts with SCRIB (By similarity). Interacts with CTNB1 (PubMed:25232112). Interacts with SMO and (via PDZ4 or guanylate kinase-like domain) with KIF7 (PubMed:25644602). Localized at sites of cell-cell contact. Brain (at protein level). The guanylate kinase-like domain interacts with the SH3 domain. Belongs to the MAGUK family.