Edmondson S R, Werther G A, Wraight C J
Center for Hormone Research, Murdoch Childrens Research Institute, Parkville, Victoria, Australia.
J Invest Dermatol. 2001 Apr;116(4):491-7. doi: 10.1046/j.0022-202x.2001.temp.doc.x.
The insulin-like growth factor (IGF) system is essential for epidermal homeostasis. Insulin-like growth factor binding protein 3 (IGFBP-3), a modulator of IGF action that also exhibits IGF-independent activity, is localized to selected keratinocytes in the basal epidermal layer and may thus contribute to keratinocyte differentiation. We have utilized the human keratinocyte cell line, HaCaT, to examine the effect of calcium on the regulation of components of the IGF system. Western ligand and northern blot analyses revealed secreted IGFBP-3 and IGFBP-3 mRNA were reduced by an elevation in calcium levels in the culture medium. At 1.0 and 1.2 mM CaCl2 culture conditions IGFBP-3 abundance was reduced to 36% +/- 1.6% and 26% +/- 7.1%, respectively, of that from cells grown at 0.03 mM CaCl2. IGFBP-3 mRNA levels in 0.7 mM and 1.2 mM CaCl2 were reduced to 46% +/- 17.4% and 24% +/- 4.6%, respectively, compared with IGFBP-3 mRNA levels at 0.03 mM CaCl2. The observed reduction of IGFBP-3 was not associated with IGFBP-3 proteolysis. In contrast IGF-I receptor protein and mRNA levels remained unchanged. The IGF-I stimulated proliferative response of HaCaT keratinocytes showed that under low (0.03 mM) and high (1.2 mM) CaCl2 conditions IGF-I at 100 and 1000 ng per ml similarly increased cell number 2.4- and 2.7-fold, respectively, with similar dose-response curves. HaCaT keratinocytes grown under medium (0.7 mM) and high (1.2 mM), but not low (0.03 mM), CaCl2 conditions for 21 d revealed an induction of profilaggrin mRNA, a marker of keratinocyte differentiation. These studies indicate that the exposure of HaCaT keratinocytes to elevated calcium levels is associated with a decline in IGFBP-3 but not IGF-I receptor levels. These findings suggest a potential mechanism for the distribution of IGFBP-3 in the epidermis, which may be involved in the process of keratinocyte differentiation.
胰岛素样生长因子（IGF）系统对表皮稳态至关重要。胰岛素样生长因子结合蛋白3（IGFBP - 3）是IGF作用的调节剂，也具有不依赖IGF的活性，定位于基底表皮层的特定角质形成细胞，因此可能有助于角质形成细胞的分化。我们利用人角质形成细胞系HaCaT来研究钙对IGF系统各组分调节的影响。Western配体分析和Northern印迹分析显示，培养基中钙水平升高会使分泌的IGFBP - 3和IGFBP - 3 mRNA减少。在1.0 mM和1.2 mM CaCl2培养条件下，IGFBP - 3丰度分别降至在0.03 mM CaCl2条件下生长的细胞的36%±1.6%和26%±7.1%。与0.03 mM CaCl2时的IGFBP - 3 mRNA水平相比，0.7 mM和1.2 mM CaCl2时的IGFBP - 3 mRNA水平分别降至46%±17.4%和24%±4.6%。观察到的IGFBP - 3减少与IGFBP - 3蛋白水解无关。相反，IGF - I受体蛋白和mRNA水平保持不变。IGF - I刺激的HaCaT角质形成细胞增殖反应表明，在低（0.03 mM）和高（1.2 mM）CaCl2条件下，每毫升100和1000 ng的IGF - I同样分别使细胞数量增加2.4倍和2.7倍，剂量反应曲线相似。在中等（0.7 mM）和高（1.2 mM）但非低（0.03 mM）CaCl2条件下培养21天的HaCaT角质形成细胞显示出丝聚蛋白原mRNA的诱导，这是角质形成细胞分化的标志物。这些研究表明，HaCaT角质形成细胞暴露于升高的钙水平与IGFBP - 3水平下降但IGF - I受体水平不变有关。这些发现提示了IGFBP - 3在表皮中分布的潜在机制，这可能参与角质形成细胞的分化过程。
