title: Differential regulation of cardiac glucose and fatty acid uptake by endosomal pH and actin filaments.
abstract: Insulin and contraction stimulate both cardiac glucose and long-chain fatty acid (LCFA) uptake via translocation of the substrate transporters GLUT4 and CD36, respectively, from intracellular compartments to the sarcolemma. Little is known about the role of vesicular trafficking elements in insulin- and contraction-stimulated glucose and LCFA uptake in the heart, especially whether certain trafficking elements are specifically involved in GLUT4 versus CD36 translocation. Therefore, we studied the role of coat proteins, actin- and microtubule-filaments and endosomal pH on glucose and LCFA uptake into primary cardiomyocytes under basal conditions and during stimulation with insulin or oligomycin (contraction-like AMP-activated protein kinase activator). Inhibition of coat protein targeting to Golgi/endosomes decreased insulin/oligomycin-stimulated glucose (-42%/-51%) and LCFA (-39%/-68%) uptake. Actin disruption decreased insulin/oligomycin-stimulated glucose uptake (-41%/-75%), while not affecting LCFA uptake. Microtubule disruption did not affect substrate uptake under any condition. Endosomal alkalinization increased basal sarcolemmal CD36 (2-fold), but not GLUT4, content, and concomitantly decreased basal intracellular membrane GLUT4 and CD36 content (-60% and -62%, respectively), indicating successful CD36 translocation and incomplete GLUT4 translocation. Additionally, endosomal alkalinization elevated basal LCFA uptake (1.4-fold) in a nonadditive manner to insulin/oligomycin, and decreased insulin/oligomycin-stimulated glucose uptake (-32%/-68%). In conclusion, 1) CD36 translocation, just like GLUT4 translocation, is a vesicle-mediated process depending on coat proteins, and 2) GLUT4 and CD36 trafficking are differentially dependent on endosomal pH and actin filaments. The latter conclusion suggests novel strategies to alter cardiac substrate preference as part of metabolic modulation therapy.
authors.affiliation: Department of Molecular Genetics, Maastricht University, Maastricht, Netherlands. laura.steinbusch@gen.unimaas.nl
authors.forename: Laura K M
authors.initials: LK
authors.lastname: Steinbusch
authors.forename: Wino
authors.initials: W
authors.lastname: Wijnen
authors.forename: Robert W
authors.initials: RW
authors.lastname: Schwenk
authors.forename: Will A
authors.initials: WA
authors.lastname: Coumans
authors.forename: Nicole T H
authors.initials: NT
authors.lastname: Hoebers
authors.forename: D Margriet
authors.initials: DM
authors.lastname: Ouwens
authors.forename: Will A
authors.initials: WA
authors.lastname: Coumans
authors.forename: Nicole T H
authors.initials: NT
authors.lastname: Hoebers
authors.forename: Michaela
authors.initials: M
authors.lastname: Diamant
authors.forename: Arend
authors.initials: A
authors.lastname: Bonen
authors.forename: Jan F C
authors.initials: JF
authors.lastname: Glatz
authors.forename: Joost J F P
authors.initials: JJ
authors.lastname: Luiken
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D001692:Biological Transport; D020126:Brefeldin A / Q000494:pharmacology; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D018955:CD36 Antigens / Q000378:metabolism*; D020756:Coatomer Protein / Q000378:metabolism; D003078:Colchicine / Q000494:pharmacology; D003847:Deoxyglucose / Q000378:metabolism*; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D004789:Enzyme Activation; D020536:Enzyme Activators / Q000494:pharmacology; D051275:Glucose Transporter Type 4 / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000378:metabolism; D008297:Male; D009200:Myocardial Contraction; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D009840:Oligomycins / Q000494:pharmacology; D019308:Palmitic Acid / Q000378:metabolism*; D021381:Protein Transport; D051381:Rats; D011917:Rats, Inbred Lew; D053778:Thiazolidines / Q000494:pharmacology; D050257:Tubulin Modulators / Q000494:pharmacology
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D018955:CD36 Antigens; C008132:Cd36 protein, rat; D020756:Coatomer Protein; D020536:Enzyme Activators; D051275:Glucose Transporter Type 4; D007328:Insulin; D009840:Oligomycins; C495694:Slc2a4 protein, rat; D053778:Thiazolidines; D050257:Tubulin Modulators; D020126:Brefeldin A; D019308:Palmitic Acid; D003847:Deoxyglucose; D055372:AMP-Activated Protein Kinases; C037068:latrunculin B; D003078:Colchicine