Gastrin activates paracrine networks leading to induction of PAI-2 via MAZ and ASC-1.
The gastric hormone gastrin regulates the expression of a variety of genes involved in control of acid secretion and also in the growth and organization of the gastric mucosa. One putative target is plasminogen activator inhibitor-2 (PAI-2), which is a component of the urokinase activator system that acts extracellularly to inhibit urokinase plasminogen activator (uPA) and intracellularly to suppress apoptosis. Previous studies have demonstrated that gastrin induces PAI-2 both in gastric epithelial cells expressing the gastrin (CCK-2) receptor and, via activation of paracrine networks, in adjacent cells that do not express the receptor. We have now sought to identify the response element(s) in the PAI-2 promoter targeted by paracrine mediators initiated by gastrin. Mutational analysis identified two putative response elements in the PAI-2 promoter that were downstream of gastrin-activated paracrine signals. One was identified as a putative MAZ site, mutation of which dramatically reduced both basal and gastrin-stimulated responses of the PAI-2 promoter by a mechanism involving PGE(2) and the small GTPase RhoA. Yeast one-hybrid screening identified the other as binding the activating signal cointegrator-1 (ASC-1) complex, which was shown to be the target of IL-8 released by gastrin. RNA interference (RNAi) knockdown of two subunits of the ASC-1 complex (p50 and p65) inhibited induction of PAI-2 expression by gastrin. The data reveal previously unsuspected transcriptional mechanisms activated as a consequence of gastrin-triggered paracrine networks and emphasize the elaborate and complex cellular control mechanisms required for a key component of tissue responses to damage and infection.
Almeida-Vega
Simon
S
Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Liverpool, UK.
Catlow
Krista
K
Kenny
Susan
S
Dimaline
Rod
R
Varro
Andrea
A
D001483:Base Sequence; D001665:Binding Sites; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015232:Dinoprostone / Q000378:metabolism; D005753:Gastric Mucosa / Q000378:metabolism*; D005755:Gastrins / Q000378:metabolism*; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D019899:Paracrine Communication; D017396:Plasminogen Activator Inhibitor 2 / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D020218:Response Elements; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection; D020798:Two-Hybrid System Techniques; D015854:Up-Regulation; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
C508606:CXCL8 protein, human; D004268:DNA-Binding Proteins; D005755:Gastrins; D016209:Interleukin-8; D017396:Plasminogen Activator Inhibitor 2; D034741:RNA, Small Interfering; C459901:TRIP4 protein, human; D014157:Transcription Factors; C076035:c-MYC-associated zinc finger protein; C066737:RHOA protein, human; C013550:gastrin 17; D020742:rhoA GTP-Binding Protein; D015232:Dinoprostone