MYPT1 O-GlcNAc modification controls the sensitivity of fibroblasts to sphingosine-1-phosphate mediated cellular contraction

Abstract

Many intracellular proteins can be modified by N-acetylglucosamine, a posttranslational modification known as O-GlcNAc.Because this modification is found on serine and threonine side-chains, O-GlcNAc has the potential to dynamically regulate cellular signaling pathways through interplay with phosphorylation. Here, we discover and characterize one such pathway.First, we find that O-GlcNAcylation levels control the sensitivity of fibroblasts to actin contraction induced by the signaling lipid sphingosine-1-phosphate (S1P). In subsequent mechanistic investigations, we find that S1P agonizes the S1PR2 receptor, resulting in activation of the Rho/Rho kinase signaling pathway. This pathway typically culminates in the phosphorylation of myosin light chain (MLC), resulting in myosin activation and cellular contraction. We find that O-GlcNAcylation of the phosphatase subunit MYPT1 inhibits this pathway by blocking MYPT1 phosphorylation, maintaining its activity and causing the dephosphorylation of MLC. Therefore, MYTP1 O-GlcNAcylation levels function as a rheostat to regulate the sensitivity of cells to S1P-mediated cellular contraction. Our findings have important implications for the role of in fibroblast motility and differentiation, as well as several other signaling pathways that use MLC/MYTP1 to control actin contraction in various tissues.