Expression of insulin-like growth factor binding protein-3 (IGFBP-3) in human keratinocytes is regulated by EGF and TGFβ1

✍ Scribed by Stephanie R. Edmondson; Mari M. Murashita; Vincenzo C. Russo; Christopher J. Wraight; George A. Werther

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 195 KB
• Volume: 179
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/(sici)1097-4652(199905)179:2<201::aid-jcp10>3.0.co;2-9

✦ Synopsis

Insulin-like growth factor-I (IGF-I) is essential for normal epidermal homeostasis; however, the role of IGF binding proteins (IGFBPs), regulators of IGF action, remains unclear. Here we examine the regulation of human keratinocyte-produced IGFBPs by epidermal growth factor (EGF), transforming growth factor beta 1 (TGF␤1), and IGF-I, growth factors known to be active in skin. In the absence of added growth factors, IGFBP-3 was the major binding protein secreted into the medium by primary keratinocytes. Addition of EGF or TGF␤1 to keratinocyte cultures resulted in a significant decrease in IGFBP-3 abundance in conditioned medium when compared with control, untreated cells. Specifically, EGF (50 ng/ml) and TGF␤1 (50 ng/ml) reduced IGFBP-3 abundance to 15 Ϯ 6% and 22 Ϯ 9%, respectively. Using Northern blot analysis, we found EGF and TGF␤1 (50 ng/ml) to reduce IGFBP-3 mRNA levels in keratinocytes to 51 Ϯ 12% and 50 Ϯ 38%, respectively, when compared with control, untreated cells. Treatment with IGF-I or its analogue des(1-3)IGF-I did not lead to any consistent change in IGFBP-3 abundance. However, both IGF-I and des(1-3)IGF-I at 100 ng/ml led to a modest increase in IGFBP-3 mRNA levels in keratinocytes, suggesting posttranscriptional regulation of IGFBP-3 abundance. We propose that local modulation of IGFBP-3 abundance may represent another level of regulation of growth factor action in the epidermis, where EGF and TGF␤1 and possibly other local growth factors specifically regulate the availability of IGF-I to its keratinocyte receptors.