title: Regulation of the proteasome by AMPK in endothelial cells: the role of O-GlcNAc transferase (OGT).
abstract: 26S proteasome is a macromolecular multi-subunit complex responsible for recognizing, unfolding, and ultimately destroying proteins. It remains poorly understood how 26S proteasome activity is regulated. The present study was to investigate if AMP-activated protein kinase (AMPK) functions as a physiological suppressor of the 26S proteasome in endothelial cells. 26S proteasome assembly, activity, and O-GlcNAcylation of P700 were assayed in cultured human umbilical vein endothelial cells (HUVEC) and mouse aortas isolated from C57BL6 wild type and AMPKα2 knockout mice with or without being exposed to selective AMPK activators or inhibitors. Pharmacological and genetic activation of AMPK effectively suppresses 26S proteasomes in endothelial cells. Conversely, inactivation of AMPK either pharmacologically or genetically increases 26S proteasome activity; furthermore, the inactivation decreases the O-GlcNAcylation of PA700/S10B (the regulatory complex in 26S proteasomes) and increases the assembly of 26S proteasomes. In contrast, AMPK activation increases levels of O-GlcNAcylated PA700/S10B, likely through enhanced association of PA700 with O-GlcNAc transferase (OGT), the enzyme that catalyzes protein O-GlcNAcylation. Finally, aortas from AMPK-KO vs wild type mice exhibit elevated 26S proteasome activity in parallel with decreased PA700/S10B O-GlcNAcylation and PA700/S10B-OGT association. Taken together, we conclude that AMPK functions as a physiological suppressor of 26S proteasomes.
authors.affiliation: Division of Endocrinology, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America.
authors.forename: Jian
authors.initials: J
authors.lastname: Xu
authors.forename: Shuangxi
authors.initials: S
authors.lastname: Wang
authors.forename: Benoit
authors.initials: B
authors.lastname: Viollet
authors.forename: Ming-Hui
authors.initials: MH
authors.lastname: Zou
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001011:Aorta / Q000201:enzymology / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D055785:Gene Knockdown Techniques; D055786:Gene Knockout Techniques; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D017351:N-Acetylglucosaminyltransferases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics
chemical_list: C085834:PA700 proteasome activator; D047428:Protein Kinase Inhibitors; D034741:RNA, Small Interfering; D017351:N-Acetylglucosaminyltransferases; C449880:O-GlcNAc transferase; D055372:AMP-Activated Protein Kinases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease