Vascular O-GlcNAcylation augments reactivity to constrictor stimuli by prolonging phosphorylated levels of the myosin light chain

• Published in: Brazilian journal of medical and biological research Vol. 47; no. 10; pp. 826 - 833
• Main Authors: Lima, V V, Lobato, N S, Filgueira, F P, Webb, R C, Tostes, R C, Giachini, F R
• Format: Journal Article
• Language: English; Portuguese
• Published: Brazil Associacao Brasileira de Divulgacao Cientifica (ABDC) 01.10.2014; Associação Brasileira de Divulgação Científica
• Subjects: Acetylglucosamine - analogs & derivatives; Acetylglucosamine - pharmacology; Acylation - drug effects; Acylation - physiology; Aminoimidazole Carboxamide - analogs & derivatives; Aminoimidazole Carboxamide - pharmacology; Analysis; Animals; Aorta, Thoracic; Azepines - pharmacology; beta-N-Acetylhexosaminidases - antagonists & inhibitors; BIOLOGY; Biomedical Sciences; Blotting, Western; Calcium-binding proteins; Enzyme Inhibitors - pharmacology; Health aspects; Hypoglycemic Agents - pharmacology; Male; MEDICINE, RESEARCH & EXPERIMENTAL; Muscle proteins; Muscle, Smooth, Vascular - drug effects; Muscle, Smooth, Vascular - metabolism; Muscle, Smooth, Vascular - physiology; Myosin; Myosin light chain; Myosin Light Chains - metabolism; Myosin-Light-Chain Kinase - metabolism; Myosin-Light-Chain Phosphatase - metabolism; O-GlcNAcylation; Oxazoles - pharmacology; Oximes - pharmacology; Phenylcarbamates - pharmacology; Phenylephrine - agonists; Phosphatases; Phosphorylation - drug effects; Phosphorylation - physiology; Protein kinases; Protein Processing, Post-Translational - physiology; Rats, Wistar; Ribonucleotides - pharmacology; Vascular reactivity; Vasoconstriction - drug effects; Vasoconstriction - physiology; Vasoconstrictor Agents - pharmacology; Vascular reactivity; O-GlcNAcylation; Myosin light chain
• ISSN: 0100-879X; 1414-431X; 1414-431X
• DOI: 10.1590/1414-431X20144001

O-GlcNAcylation is a modification that alters the function of numerous proteins. We hypothesized that augmented O-GlcNAcylation levels enhance myosin light chain kinase (MLCK) and reduce myosin light chain phosphatase (MLCP) activity, leading to increased vascular contractile responsiveness. The vascular responses were measured by isometric force displacement. Thoracic aorta and vascular smooth muscle cells (VSMCs) from rats were incubated with vehicle or with PugNAc, which increases O-GlcNAcylation. In addition, we determined whether proteins that play an important role in the regulation of MLCK and MLCP activity are directly affected by O-GlcNAcylation. PugNAc enhanced phenylephrine (PE) responses in rat aortas (maximal effect, 14.2 ± 2 vs 7.9 ± 1 mN for vehicle, n=7). Treatment with an MLCP inhibitor (calyculin A) augmented vascular responses to PE (13.4 ± 2 mN) and abolished the differences in PE-response between the groups. The effect of PugNAc was not observed when vessels were preincubated with ML-9, an MLCK inhibitor (7.3 ± 2 vs 7.5 ± 2 mN for vehicle, n=5). Furthermore, our data showed that differences in the PE-induced contractile response between the groups were abolished by the activator of AMP-activated protein kinase (AICAR; 6.1 ± 2 vs 7.4 ± 2 mN for vehicle, n=5). PugNAc increased phosphorylation of myosin phosphatase target subunit 1 (MYPT-1) and protein kinase C-potentiated inhibitor protein of 17 kDa (CPI-17), which are involved in RhoA/Rho-kinase-mediated inhibition of myosin phosphatase activity. PugNAc incubation produced a time-dependent increase in vascular phosphorylation of myosin light chain and decreased phosphorylation levels of AMP-activated protein kinase, which decreased the affinity of MLCK for Ca(2+)/calmodulin. Our data suggest that proteins that play an important role in the regulation of MLCK and MLCP activity are directly affected by O-GlcNAcylation, favoring vascular contraction.