Edmondson S R, Murashita M M, Russo V C, Wraight C J, Werther G A
Centre for Hormone Research, Royal Children's Hospital, Parkville, Victoria, Australia.
J Cell Physiol. 1999 May;179(2):201-7. doi: 10.1002/(SICI)1097-4652(199905)179:2<201::AID-JCP10>3.0.CO;2-9.
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 (TGFbeta1), 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 TGFbeta1 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 TGFbeta1 (50 ng/ml) reduced IGFBP-3 abundance to 15+/-6% and 22+/-9%, respectively. Using Northern blot analysis, we found EGF and TGFbeta1 (50 ng/ml) to reduce IGFBP-3 mRNA levels in keratinocytes to 51+/-12% and 50+/-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 TGFbeta1 and possibly other local growth factors specifically regulate the availability of IGF-I to its keratinocyte receptors.
胰岛素样生长因子-I（IGF-I）对正常表皮稳态至关重要；然而，IGF结合蛋白（IGFBPs）作为IGF作用的调节因子，其作用仍不清楚。在此，我们研究了表皮生长因子（EGF）、转化生长因子β1（TGFβ1）和IGF-I对人角质形成细胞产生的IGFBPs的调节作用，这些生长因子在皮肤中具有活性。在未添加生长因子的情况下，IGFBP-3是原代角质形成细胞分泌到培养基中的主要结合蛋白。与未处理的对照细胞相比，向角质形成细胞培养物中添加EGF或TGFβ1会导致条件培养基中IGFBP-3丰度显著降低。具体而言，EGF（50 ng/ml）和TGFβ1（50 ng/ml）分别将IGFBP-3丰度降低至15±6%和22±9%。通过Northern印迹分析，我们发现与未处理的对照细胞相比，EGF和TGFβ1（50 ng/ml）分别将角质形成细胞中IGFBP-3 mRNA水平降低至51±12%和50±38%。用IGF-I或其类似物des(1-3)IGF-I处理未导致IGFBP-3丰度出现任何一致变化。然而，100 ng/ml的IGF-I和des(1-3)IGF-I均导致角质形成细胞中IGFBP-3 mRNA水平适度增加，提示IGFBP-3丰度存在转录后调节。我们提出，IGFBP-3丰度的局部调节可能代表表皮中生长因子作用调节的另一个层面，其中EGF和TGFβ1以及可能的其他局部生长因子特异性调节IGF-I对其角质形成细胞受体的可及性。
