Post-transcriptional regulation of Na+/glucose cotransporter (SGTL1) gene expression in LLC-PK1 cells. Increased message stability after cyclic AMP elevation or differentiation inducer treatment.
We have further investigated the molecular basis of increased differentiation-regulated expression of SGTL1, a Na+/glucose cotransporter, in the renal epithelial cell line LLC-PK1. Treatment of confluent monolayers either with the differentiation inducer hexamethylene bisacetamide (HMBA) or with cyclic AMP-elevating agents promoted increased levels of the SGLT1 mRNA, the immunodetectable 75-kDa cotransporter subunit, and the transport activity. Two molecular species of SGLT1 mRNA (2.2 and 3.9 kilobases (kb)) are transcribed from the same gene in LLC-PK1 cells and differ only in the length of the 3'-untranslated region. The larger transcript is less stable (t1/2 = 2 h) than the smaller one (t1/2 = 10 h) in control, confluent monolayers. The 3.9-kb species was stabilized from degradation after either cyclic AMP elevation (t1/2 = 14 h) or HMBA addition (t1/2 = 8 h), with negligible effects on the stability of the 2.2-kb species (t1/2 = 11 h). Inhibition of translation by cycloheximide resulted in a 10-fold increase in the t1/2 of the 3.9-kb transcript and a 2-fold increase in that of the 2.2-kb species in control monolayers. Our results demonstrate that post-transcriptional regulation of message stability plays a major role in differentiation-dependent SGTL1 expression promoted by either HMBA or cyclic AMP.
Peng
H
H
Department of Biochemistry and Molecular Biology, University of Texas Medical School, Houston 77225, USA.
Lever
J E
JE
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology*; D000081:Acetamides / Q000494:pharmacology; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D015153:Blotting, Western; D002454:Cell Differentiation / Q000187:drug effects; D000242:Cyclic AMP / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D004848:Epithelium; D005786:Gene Expression Regulation / Q000187:drug effects; D007700:Kinetics; D018374:LLC-PK1 Cells; D008562:Membrane Glycoproteins; D008565:Membrane Proteins / Q000096:biosynthesis*; D008970:Molecular Weight; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis*; D014176:Protein Biosynthesis / Q000187:drug effects; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000378:metabolism; D051269:Sodium-Glucose Transporter 1; D013552:Swine; D014158:Transcription, Genetic
D000081:Acetamides; D000970:Antineoplastic Agents; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; D051269:Sodium-Glucose Transporter 1; D003609:Dactinomycin; D000242:Cyclic AMP; C014026:hexamethylene bisacetamide; D015056:1-Methyl-3-isobutylxanthine