title: Hexose transporters GLUT1 and GLUT3 are colocalized with hexokinase I in caveolae microdomains of rat spermatogenic cells.
abstract: Postmeiotic spermatogenic cells, but not meiotic spermatogenic cells respond differentially with glucose-induced changes in [Ca2+]i indicating a differential transport of glucose via facilitative hexose transporters (GLUTs) specifically distributed in the plasma membrane. Several studies have indicated that plasma membrane in mammalian cells is not homogeneously organized, but contains specific microdomains known as detergent-resistant membrane domains (DRMDs), lipid rafts or caveolae. The association of these domains and GLUTs isoforms has not been characterized in spermatogenic cells. We analyzed the expression and function of GLUT1 and GLUT3 in isolated spermatocytes and spermatids. The results showed that spermatogenic cells express both glucose transporters, with spermatids exhibiting a higher affinity glucose transport system. In addition, spermatogenic cells express caveolin-1, and glucose transporters colocalize with caveolin-1 in caveolin-enriched membrane fractions. Experiments in which the integrity of caveolae was disrupted by pretreatment with methyl-beta-cyclodextrin, indicated that the involvement of cholesterol-enriched plasma membrane microdomains were involved in the localization of GLUTs and uptake of 2-deoxyglucose. We also observed cofractionation of GLUT3 and caveolin-1 in low-buoyant density membranes together with their shift to higher densities after methyl-beta-cyclodextrin treatment. GLUT1 was found in all fractions isolated. Immunofluorescent studies indicated that caveolin-1, GLUT1, and hexokinase I colocalize in spermatocytes while caveolin-1, GLUT3, and hexokinase I colocalize in spermatids. These findings suggest the presence of hexose transporters in DRMDs, and further support a role for intact caveolae or cholesterol-enriched membrane microdomains in relation to glucose uptake and glucose phosphorylation. The results would also explain the different glucose-induced changes in [Ca2+]i in both cells.
authors.affiliation: Instituto de Bioquímica, Universidad Austral de Chile, Chile.
authors.forename: María Cecilia
authors.initials: MC
authors.lastname: Rauch
authors.forename: María Eliana
authors.initials: ME
authors.lastname: Ocampo
authors.forename: Joanna
authors.initials: J
authors.lastname: Bohle
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Amthauer
authors.forename: Alejandro J
authors.initials: AJ
authors.lastname: Yáñez
authors.forename: Joan E
authors.initials: JE
authors.lastname: Rodríguez-Gil
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Slebe
authors.forename: Juan G
authors.initials: JG
authors.lastname: Reyes
authors.forename: Ilona I
authors.initials: II
authors.lastname: Concha
mesh_terms: D019325:3-O-Methylglucose / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D021941:Caveolae / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D051242:Caveolin 1 / Q000032:analysis / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D003847:Deoxyglucose / Q000378:metabolism; D051272:Glucose Transporter Type 1 / Q000032:analysis / Q000378:metabolism*; D051274:Glucose Transporter Type 3 / Q000032:analysis / Q000378:metabolism*; D006593:Hexokinase / Q000032:analysis / Q000378:metabolism*; D007150:Immunohistochemistry; D007700:Kinetics; D008297:Male; D008856:Microscopy, Fluorescence; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D013087:Spermatids / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D013090:Spermatocytes / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D047392:beta-Cyclodextrins / Q000494:pharmacology
chemical_list: D051242:Caveolin 1; D051272:Glucose Transporter Type 1; D051274:Glucose Transporter Type 3; C495679:Slc2a1 protein, rat; C495690:Slc2a3 protein, rat; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; D019325:3-O-Methylglucose; D003847:Deoxyglucose; D006593:Hexokinase