Hyaluronan synthesis is controlled through protein O‐GlcNAcylation in vascular smooth muscle cells

The accumulation of hyaluronan (HA) into vessel wall supports neointima formation and cardiovascular disease progression, here we reported the intracellular regulation of HA synthesis throughout O‐GlcNacylation. The excess of glucose could enter in the hexosamine biosynthetic pathway (HBP) that increases the concentration of the HA precursor UDP‐N‐acetylglucosamine (UDP‐GlcNac) leading to an increase of HA synthesis. In this study, we tested the role the HBP in the regulation of HA biosynthesis in human primary aortic smooth muscle cells. UDP‐GlcNAc can be the donor of GlcNAc for O‐GlcNacylation, a type of cytoplasmic protein O‐glycosylation to ser/thr residues. We found that the inhibition of O‐GlcNacylation strongly reduced HA production whereas treatments that induced protein O‐GlcNacylation increased HA secretion. Gene expression studies revealed that HAS2 mRNA (i.e., the main HA synthesizing enzyme located in the plasma membrane) was the most sensible to O‐GlcNacylation and accumulated after its induction. We found evidences that the transcription regulator YY1 activates HAS2 expression after O‐GlcNacylation. At protein level, experiments with wheat germ agglutinin and recombinant 6myc‐HAS2 revealed that this enzyme was actually O‐GlcNacylated. Further, HAS2 O‐GlcNacylation increased HAS activity in purified microsomes leading to HA accumulation. This work was supported by FAR and Onlus Varesotto‐ITALY.