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XB-ART-4106
J Membr Biol 2003 Nov 01;1961:71-81. doi: 10.1007/s00232-003-0626-y.
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Downregulation of the Na(+)- D-glucose cotransporter SGLT1 by protein RS1 (RSC1A1) is dependent on dynamin and protein kinase C.

Veyhl M, Wagner CA, Gorboulev V, Schmitt BM, Lang F, Koepsell H.


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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.

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Species referenced: Xenopus laevis
Genes referenced: amelx rs1 rsc1a1 slc15a1 slc2a1 slc5a1 slc5a1.2

References [+] :
Arndt, Interaction of cations, anions, and weak base quinine with rat renal cation transporter rOCT2 compared with rOCT1. 2001, Pubmed, Xenbase