Advanced glycation end products suppress neuropilin-1 expression in podocytes by a reduction in Sp1-dependent transcriptional activity.
BACKGROUND
Neuropilin-1 (NRP1) is a transmembrane glycoprotein, initially defined as a receptor for members of the semaphorin family. We observed that NRP1 expression was downregulated by the addition of advanced glycation end products-modified bovine serum albumin (AGE-BSA). The present study was undertaken to unravel the molecular mechanisms underlying AGE-BSA-mediated NRP1 suppression.


METHODS
Expression of NRP1 was analyzed in podocytes. The transcriptional activity of the NRP1 promoter was investigated using wild-type and mutant NRP1 promoter reporter constructs. Electrophoretic mobility assays were performed.


RESULTS
NRP1 expression was downregulated in podocytes by the addition of AGE-BSA. In contrast, phorbolester induced NRP1 mRNA and protein expression. The wild-type promoter transcriptional activity was significantly reduced when podocytes were treated with AGE-BSA compared with control, unmodified BSA. Point mutations of proximal and distal Sp1-like sites inhibited basal NRP1 promoter activity. AGE-BSA failed to further suppress transcriptional activity of these constructs. Double mutation of the Sp1A and Sp1B binding sites completely abolished NRP1 transcriptional activity. Gel shift analysis showed a specific binding of the Sp1 transcription factor. Treatment of podocytes with AGE-BSA revealed a decrease in Sp1 binding to consensus sequences, but no effect on AP1 binding.


CONCLUSIONS
AGE-BSA inhibits NRP1 promoter transcriptional activity in podocytes by reducing the binding ability of the Sp1 transcription factor to attach to the NRP1 promoter.
Bondeva
Tzvetanka
T
Department of Internal Medicine III, Friedrich Schiller University, Jena, Germany.
Wolf
Gunter
G
D000818:Animals; D002461:Cell Line, Transformed; D003928:Diabetic Nephropathies / Q000378:metabolism / Q000503:physiopathology*; D024202:Electrophoretic Mobility Shift Assay; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D017127:Glycation End Products, Advanced / Q000378:metabolism / Q000494:pharmacology*; D051379:Mice; D039942:Neuropilin-1 / Q000235:genetics* / Q000378:metabolism; D050199:Podocytes / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D017354:Point Mutation; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000494:pharmacology; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology; D014162:Transfection
D017127:Glycation End Products, Advanced; D012333:RNA, Messenger; D016329:Sp1 Transcription Factor; D039942:Neuropilin-1; D012710:Serum Albumin, Bovine