Cellular localization of MAGI-1 caspase cleavage products and their role in apoptosis.

MAGI-1 is a membrane-associated guanylate kinase (MAGUK) protein present at adherent and tight junctions, where it acts as a structural and signaling scaffold. During apoptosis, MAGI-1 is cleaved by caspases at Asp761 into N- and C-terminal cleavage products, allowing further dismantling of the cell junctions, one of the key features of apoptosis. Here, we investigated the cellular distribution and possible proapototic role of MAGI-1 caspase cleavage products. Full-length MAGI-1 exhibited submembrane localization, while the N-terminal caspase cleavage product of MAGI-1 is translocated to the cytosol and the C-terminal caspase cleavage product accumulates in the nucleus. When overexpressed in MDCK cells, both N- and C-terminal MAGI-1 caspase cleavage products exhibited minor proapoptotic activity, although their role in apoptosis is probably more passive.