Prohibitin attenuates insulin-stimulated glucose and fatty acid oxidation in adipose tissue by inhibition of pyruvate carboxylase.
Prohibitin (PHB-1) is a highly conserved protein involved in mitochondrial biogenesis and function. It is secreted in lipid droplets from adipocytes and is present in the circulation. In adipose tissue it functions as a membrane receptor and can target binding partners to the mitochondria. Here we report that PHB-1 has a hitherto undescribed role as an inhibitor of pyruvate carboxylase (PC). As a consequence, it can modulate insulin-stimulated glucose and fatty acid oxidation. It had no effect on insulin-stimulated 2-deoxglucose uptake by isolated adipocytes but inhibited insulin-stimulated oxidation of [14C]glucose with a half-maximal concentration of approximately 4 nM. It also inhibited oleic acid oxidation in glucose-depleted adipocytes via depletion of oxaloacetate. In vitro experiments using broken-cell assays confirmed that PHB-1 inhibited PC. MALDI-TOF analysis of proteins identified by cross-linking of PHB-1 to adipocyte membranes indicated that PHB-1 is closely associated with PC and EH domain 2 (EHD2). On the basis of these data, we propose that PHB-1 is recycled between the extracellular space and the mitochondria by a mechanism involving lipid rafts and EHD2 and can modulate mitochondrial fuel metabolism by inhibition of PC.
Vessal
Mahmood
M
Physiology Department, University of Manitoba, Winnipeg, Canada.
Mishra
Suresh
S
Moulik
Saby
S
Murphy
Liam J
LJ
D000273:Adipose Tissue / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D005947:Glucose / Q000737:chemistry / Q000378:metabolism*; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009829:Oleic Acids / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D000091402:Prohibitins; D011766:Pyruvate Carboxylase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D019289:Pyruvic Acid / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000494:pharmacology*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods; D013329:Structure-Activity Relationship
D007328:Insulin; D009829:Oleic Acids; D000091402:Prohibitins; D012097:Repressor Proteins; D019289:Pyruvic Acid; D011766:Pyruvate Carboxylase; D005947:Glucose