MYPT1 O-GlcNAc modification regulates sphingosine-1-phosphate mediated contraction

Abstract

Many intracellular proteins are modified by N-acetylglucosamine, a posttranslational modification termed O-GlcNAc. This modification is found on serine and threonine side-chains and has the potential to regulate signaling pathways through interplay with phosphorylation. Here, we discover and characterize one such example. We find that O-GlcNAc levels control the sensitivity of fibroblasts to actin contraction induced by the signaling lipid sphingosine-1-phosphate (S1P), culminating in the phosphorylation of myosin light chain (MLC) and cellular contraction. Specifically, O-GlcNAc modification of the phosphatase subunit MYPT1 inhibits this pathway by blocking MYPT1 phosphorylation, maintaining its activity and causing the dephosphorylation of MLC. Finally, we demonstrate that O-GlcNAc levels alter the sensitivity of primary human dermal fibroblasts in a collagen-matrix model of wound healing. Our findings have important implications for the role of O-GlcNAc in fibroblast motility and differentiation, particularly in diabetic wound healing.

O-GlcNAc modification of MYPT1 modulates lysophosphatidic acid–induced cell contraction in fibroblasts

“…These results are highly consistent with the timing of cellular contraction and the fact that the NIH3T3 cells will eventually return to a relaxed state. Again, this supports the model built upon our published S1P data ( 26 ) where non- O -GlcNAc-modified MYPT1 can be phosphorylated and deactivated by ROCK ( Fig. 3 ).…”

“…In our previous publication ( 26 ), we showed that MYPT1 is heavily O -GlcNAc modified at multiple sites in a serine/threonine-rich region located between residues 550 and 600. We also found that deletion of this entire region, yielding a protein we term MYPT1Δ, was required to notably reduce the overall O -GlcNAc levels but did not adversely affect MYPT1 phosphatase activity against MLC.…”

“…Recently, we discovered one such signaling pathway initiated by the lipid sphingosine-1-phosphate (S1P) ( 26 ). S1P is an agonist of a family of G-protein-coupled receptors, the S1P receptors ( 27 , 28 , 29 , 30 , 31 , 32 ), resulting in the potential activation of a variety of downstream signaling pathways that regulate inflammation, cell motility, differentiation, etc.…”

Hypoxic acclimation improves cardiac redox homeostasis and protects heart against ischemia-reperfusion injury through upregulation of O-GlcNAcylation

“…O-GlcNAc modifications are catalyzed by OGT and removed by OGA, which utilizes UDP-GlcNAc, the final product of the HBP pathway as its substrate. Recent studies suggested that O-GlcNAcylation modulates the function of numerous proteins under both physiological and pathological conditions, emerging as a key mediator of many cardiovascular pathophysiological processes [ [30] , [31] , [32] , [33] , [34] , [35] , [36] ]. Upregulation of HBP and increased O-GlcNAc modification have been shown to be protective against acute I/R injury in previous studies by ourselves and others [ 26 , 37 , 38 ].…”

Centrosomes: Til O-GlcNAc Do Us Apart

“…Almost concomitantly, Pedowitz et al ( 21 ) also studied MYPT1 O-GlcNAcylation. They unraveled that under basal conditions it antagonizes pT696, which is an inhibitory phosphorylation for the myosin phosphatase, and controls actin contraction.…”