The plasma membrane-associated protein RS1 decreases transcription of the transporter SGLT1 in confluent LLC-PK1 cells.
Previously we cloned RS1, a 67-kDa polypeptide that is associated with the intracellular side of the plasma membrane. Upon co-expression in Xenopus laevis oocytes, human RS1 decreased the concentration of the Na(+)-D-glucose co-transporter hSGLT1 in the plasma membrane (Valentin, M., Kühlkamp, T., Wagner, K., Krohne, G., Arndt, P., Baumgarten, K., Weber, W.-M., Segal, A., Veyhl, M., and Koepsell, H. (2000) Biochim. Biophys. Acta 1468, 367-380). Here, the porcine renal epithelial cell line LLC-PK1 was used to investigate whether porcine RS1 (pRS1) plays a role in transcriptional up-regulation of SGLT1 after confluence and in down-regulation of SGLT1 by high extracellular D-glucose concentrations. Western blots indicated a dramatic decrease of endogenous pRS1 protein at the plasma membrane after confluence but no significant effect of D-glucose. In confluent LLC-PK1 cells overexpressing pRS1, SGLT1 mRNA, protein, and methyl-alpha-D-glucopyranoside uptakes were drastically decreased; however, the reduction of methyl-alpha-D-glucopyranoside uptake after cultivation with 25 mm D-glucose remained. In confluent pRS1 antisense cells, the expression of SGLT1 mRNA and protein was strongly increased, whereas the reduction of SGLT1 expression during cultivation with high D-glucose was not influenced. Nuclear run-on assays showed that the transcription of SGLT1 was 10-fold increased in the pRS1 antisense cells. The data suggest that RS1 participates in transcriptional up-regulation of SGLT1 after confluence but not in down-regulation by D-glucose.
Korn
T
T
Institute of Anatomy of the Bayerische Julius-Maximilians-Universität, 97070 Würzburg, Germany.
Kühlkamp
T
T
Track
C
C
Schatz
I
I
Baumgarten
K
K
Gorboulev
V
V
Koepsell
H
H
D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D018398:Homeodomain Proteins / Q000378:metabolism* / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D018374:LLC-PK1 Cells; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis / Q000378:metabolism*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D009865:Oocytes / Q000378:metabolism; D010940:Plant Proteins; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism; D012964:Sodium / Q000494:pharmacology; D051269:Sodium-Glucose Transporter 1; D013552:Swine; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection; D015854:Up-Regulation; D014982:Xenopus laevis
D018398:Homeodomain Proteins; D008562:Membrane Glycoproteins; D009004:Monosaccharide Transport Proteins; D016376:Oligonucleotides, Antisense; D010940:Plant Proteins; D012333:RNA, Messenger; C095847:Rs1 protein, Zea mays; C495674:SLC5A1 protein, human; D051269:Sodium-Glucose Transporter 1; D012964:Sodium; D005947:Glucose