title: Downregulation of the Na(+)- D-glucose cotransporter SGLT1 by protein RS1 (RSC1A1) is dependent on dynamin and protein kinase C.
abstract: We have previously shown that the regulatory protein RS1, cloned from pig, rabbit and human (RSC1A1), is localized intracellularly and inhibits the transcription of the Na(+)- D-glucose cotransporter SGLT1 in LLC-PK(1) cells. We also reported that transport activities of human SGLT1 (hSGLT1) and human organic cation transporter hOCT2 expressed in Xenopus oocytes were decreased upon co-expression of human RS1 (hRS1). The present paper indicates that the glucose transporter GLUT1 and the peptide transporter PEPT1 are not influenced by hRS1. Voltage-clamp experiments in oocytes expressing hSGLT1 demonstrated that hRS1 reduced the maximal substrate-induced currents but did not change substrate activation, membrane potential dependence, Na(+) dependence or substrate selectivity of hSGLT1. Co-expression experiments with a dominant-negative dynamin mutant showed that the posttranslational inhibition of hSGLT1 by hRS1 was dependent on the function of dynamin. Finally, we observed that hRS1 changed the short-term effect of protein kinase C (PKC) on hSGLT1. Whereas the PKC activators phorbol-12-myristate-13-acetate (PMA) and sn-1,2-dioctanoyl glycerol (DOG) increased alpha-methyl glucose (AMG) uptake expressed by hSGLT1 alone as described earlier, PMA and DOG decreased AMG uptake mediated by hSGLT1 when hRS1 was co-expressed. Taken together, these data indicate that hRS1 modulates dynamin-dependent trafficking of intracellular vesicles containing hSGLT1 in Xenopus oocytes, and modulates PKC-dependent short-term regulation of this transporter.
authors.affiliation: Institut für Anatomie und Zellbiologie, Bayerische Julius-Maximilians Universität, Koellikerstr. 6, D-97070 Würzburg, Germany. Maike.Veyhl@mail.uni-wuerzburg.de
authors.forename: M
authors.initials: M
authors.lastname: Veyhl
authors.forename: C A
authors.initials: CA
authors.lastname: Wagner
authors.forename: V
authors.initials: V
authors.lastname: Gorboulev
authors.forename: B M
authors.initials: BM
authors.lastname: Schmitt
authors.forename: F
authors.initials: F
authors.lastname: Lang
authors.forename: H
authors.initials: H
authors.lastname: Koepsell
mesh_terms: D000818:Animals; D001693:Biological Transport, Active / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D015536:Down-Regulation / Q000502:physiology; D034281:Dynamins / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D051269:Sodium-Glucose Transporter 1; D014158:Transcription, Genetic / Q000502:physiology; D014982:Xenopus laevis
chemical_list: D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D009004:Monosaccharide Transport Proteins; C101014:RSC1A1 protein, human; D051269:Sodium-Glucose Transporter 1; D003609:Dactinomycin; D011493:Protein Kinase C; D034281:Dynamins