Bellei Barbara, Flori Enrica, Izzo Enzo, Maresca Vittoria, Picardo Mauro
Laboratory of Cutaneous Physiopatology, San Gallicano Dermatological Institute, Rome, Italy.
Cell Signal. 2008 Oct;20(10):1750-61. doi: 10.1016/j.cellsig.2008.06.001. Epub 2008 Jun 12.
Glycogen synthase kinase 3beta (GSK3beta) is implicated in many biological events, including embryonic development, cell differentiation, apoptosis, and the insulin response. GSK3beta also plays a key role in the Wnt/beta-catenin pathway. The master regulator of the pigmentation microphthalmia-associated transcription factor (MITF) is a target for the Wnt pathway, however, to date, the regulatory role of GSK3beta in the control of melanogenesis has not been elucidated. In this study, we evaluated the effect of inhibiting GSK3beta activity on the regulation of melanocyte differentiation. Exposure of the murine melanoma cell line B16 and normal human melanocytes to GSK3beta specific inhibitors (SB216763, SB415286, BIO, and LiCl) resulted in a dose-dependent accumulation of beta-catenin. This is associated with the induction of melanocyte differentiation-associated markers such as melanin synthesis, tyrosinase activity, and expression of tyrosinase and the microphthalmia-associated transcription factor. Attenuation of GSK3beta activity has an inhibitory effect on cell growth, and this was accompanied by morphological changes. Moreover, treatment of B16 cells with a siRNA targeted against beta-catenin completely abolished the promelanogenic effect of GSK3beta inhibition, however, the overexpression of a constitutively active mutant form of beta-catenin (pCS2beta-cat-mut) only slightly increased the degree of pigmentation. These results demonstrated that GSK3beta is implicated in the regulation of melanogenesis and that pharmacological inhibition of its activity could increase melanin synthesis through mechanisms probably not restricted to Wnt/beta-catenin pathway activation.
糖原合酶激酶3β（GSK3β）参与许多生物学事件，包括胚胎发育、细胞分化、细胞凋亡和胰岛素反应。GSK3β在Wnt/β-连环蛋白信号通路中也起着关键作用。小眼畸形相关转录因子（MITF）作为色素沉着的主要调节因子，是Wnt信号通路的一个靶点，然而，迄今为止，GSK3β在黑素生成调控中的作用尚未阐明。在本研究中，我们评估了抑制GSK3β活性对黑素细胞分化调控的影响。将小鼠黑色素瘤细胞系B16和正常人黑素细胞暴露于GSK3β特异性抑制剂（SB216763、SB415286、BIO和LiCl）后，β-连环蛋白呈剂量依赖性积累。这与黑素细胞分化相关标志物的诱导有关，如黑色素合成、酪氨酸酶活性以及酪氨酸酶和小眼畸形相关转录因子的表达。GSK3β活性的减弱对细胞生长有抑制作用，并伴有形态学变化。此外，用针对β-连环蛋白的小干扰RNA（siRNA）处理B16细胞完全消除了GSK3β抑制的促黑素生成作用，然而，组成型活性突变形式的β-连环蛋白（pCS2β-cat-mut）的过表达仅略微增加了色素沉着程度。这些结果表明，GSK3β参与黑素生成的调控，其活性的药理抑制可能通过不限于Wnt/β-连环蛋白信号通路激活的机制增加黑色素合成。
