M-RIP (myosin phosphatase Rho interacting protein), also known as MPRIP, p116Rip, RIP3 or RHOIP3, is a 1,025 amino acid cytoplasmic and cytoskeletal protein that is required for regulation of the actin cytoskeleton. M-RIP colocalizes with myosin binding subunit (MBS) to regulate the phosphorylation of myosin light chain, and colocalizes with F-actin through its N-terminus in the cytoskeleton. M-RIP also interacts with and RhoA at actin stress fibers via its adjacent coiled coil domains. M-RIP is highly expressed in ovary, with moderate levels found in brain, heart, liver, lung, skeletal muscle, testis and kidney. M-RIP depletion causes an increase of stress fibers in smooth muscle cells, whereas M-RIP over-expression causes disassembly of stress fibers in neuronal cells.