Involvement of activator protein 1 complexes in the epithelium-specific activation of the laminin γ2-chain gene promoter by hepatocyte growth factor (scatter factor)

Abstract

Laminin-5 is a trimer of laminin α3, β3 and γ2 chains that is found in the intestinal basement membrane. Deposition of the laminin γ2 chain at the basement membrane is of great interest because it undergoes a developmental shift in its cellular expression. Here we study the regulatory elements that control basal and cytokine-activated transcriptional expression of the LAMC2 gene, which encodes the laminin γ2 chain. By using transient transfection experiments we demonstrated the presence of constitutive and cytokine-responsive cis-elements. Comparison of the transcriptional activity of the LAMC2 promoter in the epithelial HT29mtx cells with that in small-intestinal fibroblastic cells (C20 cells) led us to conclude that two regions with constitutive epithelium-specific activity are present between positions -1.2 and -0.12 kb. This was further validated by transfections of primary foetal intestinal endoderm and mesenchyme. A 2.5 kb portion of the LAMC2 5ʹ flanking region was equally responsive to PMA and hepatocyte growth factor (HGF), whereas it was less responsive to transforming growth factor β1. A minimal promoter limited to the initial 120 bp upstream of the transcriptional start site maintained inducibility by PMA and HGF. This short promoter fragment contains two activator protein 1 (AP-1) elements and the 5ʹ-most of these is a composite AP-1/Sp1 element. The 5ʹAP-1 element is crucial to the HGF-mediated activity of the promoter; analysis of interacting nuclear proteins demonstrated that AP-1 proteins containing JunD mediate the response to HGF.

Hepatocyte growth factor inhibits the formation of the basement membrane of alveolar epithelial cells in vitro

“…Once the basement membrane architecture had been assembled, however, HGF-associated degradation was slight. Although HGF stimulates expression of the laminin ␥ 2 -chain gene in human intestinal epithelial cells (22), HGF failed to enhance the secretion of laminin-1 or the ␣ 2 -chain of type IV collagen in rat alveolar epithelial cells. Moreover, HGF induced both the proteolytic activities and protein levels of MMP-9 and uPA but not the production of TIMP-1, TIMP-2, or PAI-1.…”

Alterations of Collagen XVII Expression During Transformation of Oral Epithelium to Dysplasia and Carcinoma

“…PMA is a potent tumor promoter capable of inducing several genes that have a role in carcinogenesis and tumor invasion (Blumberg 1981). The laminin-5 ␥2 chain gene promoter is one of the targets for PMA activation, occurring via inter- action with the activator protein 1 complexes (Olsen et al 2000). It is known that the biological effect of phorbol esters is mediated by activation of protein kinase C, resulting in various changes in transcription patterns.…”

Function and regulation of AP-1 subunits in skin physiology and pathology

“…AP-1-regulated genes may also a ect this type of regulatory mechanism. AP-1 binding sites have been identi®ed in the promoter regions of avian beta-3 integrin (Cao et al, 1993), alpha2 (Zutter et al, 1994), alpha5 (Corbi et al, 2000) alpha6 (Nishida et al, 1997) and alpha7 integrins (Ziober and Kramer, 1996), laminin B1 (Matsui, 1996), laminin gamma2-chain (Olsen et al, 2000), decorin and tenascin-C (Mettouchi et al, 1997). Only in some cases, speci®c AP-1 subunit compositions have been described, which may be responsible for regulation of these genes, such as JunD regulating expression of laminin gamma2 by HGF (Olsen et al, 2000), and JunD/Fra-2 modulating basal and TGF-b-dependent laminin alpha 3A transcription (Virolle et al, 1998).…”