Protein kinase C beta2-dependent phosphorylation of core 2 GlcNAc-T promotes leukocyte-endothelial cell adhesion: a mechanism underlying capillary occlusion in diabetic retinopathy.
Increased leukocyte-endothelial cell adhesion is a key early event in the development of retinopathy and atherogenesis in diabetic patients. We recently reported that raised activity of glycosylating enzyme [beta]1,6 acetylglucosaminyltransferase (core 2 GlcNAc-T) is responsible for increased leukocyte-endothelial cell adhesion and capillary occlusion in retinopathy. Here, we demonstrate that elevated glucose increases the activity of core 2 GlcNAc-T and adhesion of human leukocytes to retinal capillary endothelial cells, in a dose-dependent manner, through diabetes-activated serine/threonine protein kinase C beta2 (PKCbeta2)-dependent phosphorylation. This regulatory mechanism, involving phosphorylation of core 2 GlcNAc-T, is also present in polymorphonuclear leukocytes isolated from type 1 and type 2 diabetic patients. Inhibition of PKCbeta2 activation with the specific inhibitor, LY379196, attenuated serine phosphorylation of core 2 GlcNAc-T and prevented increased leukocyte-endothelial cell adhesion. Raised activity of core 2 GlcNAc-T was associated with a threefold increase in O-linked glycosylation of P-selectin glycoprotein ligand-1 on the surface of leukocytes of diabetic patients compared with age-matched control subjects. PKCbeta2-dependent phosphorylation of core 2 GlcNAc-T may thus represent a novel regulatory mechanism for activation of this key enzyme in mediating increased leukocyte-endothelial cell adhesion and capillary occlusion in diabetic retinopathy.
Chibber
Rakesh
R
Centre for Cardiovascular Biology & Medicine, Guy's, King's and St. Thomas' School of Biomedical Sciences, King's College London, 2nd Floor New Hunt's House, London SE1 1UL, U.K. rakesh.chibber@kcl.ac.uk
Ben-Mahmud
Bahaedin M
BM
Mann
Giovanni E
GE
Zhang
Jin J
JJ
Kohner
Eva M
EM
D000818:Animals; D002196:Capillaries / Q000201:enzymology / Q000502:physiology / Q000503:physiopathology*; D002417:Cattle; D002448:Cell Adhesion / Q000502:physiology*; D003922:Diabetes Mellitus, Type 1 / Q000201:enzymology / Q000503:physiopathology*; D003924:Diabetes Mellitus, Type 2 / Q000201:enzymology / Q000503:physiopathology*; D003930:Diabetic Retinopathy / Q000201:enzymology / Q000503:physiopathology*; D004730:Endothelium, Vascular / Q000502:physiology*; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D007962:Leukocytes / Q000502:physiology*; D017351:N-Acetylglucosaminyltransferases / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D064546:Protein Kinase C beta; D012016:Reference Values; D012171:Retinal Vessels / Q000201:enzymology / Q000503:physiopathology; D020298:U937 Cells
D006442:Glycated Hemoglobin; D017351:N-Acetylglucosaminyltransferases; D011493:Protein Kinase C; D064546:Protein Kinase C beta; C063313:alpha-1,6-mannosyl-glycoprotein beta-1,2-N-acetylglucosaminyltransferase; C579054:PRKCB protein, human