Role of L-3 phosphoserine phosphatase in epidermal apoptosis and carcinogenesis

说明(申请人提供)：L-3-磷酸丝氨酸磷酸酶(L3PSP)是卤酸脱卤酶(HAD)超家族中广泛表达的成员，其活性是L-丝氨酸生物合成过程中不可逆的限速步骤。L-丝氨酸生物合成失调表现为神经系统疾病、威廉姆斯-博伦综合征、皮肤鱼鳞病和多种上皮性肿瘤。然而，L3PSP活性改变在这些疾病的发病和病程中的意义仍不清楚。我们最近通过基因芯片分析发现，L3PSP在一个整合素转基因小鼠模型中发生了改变，该模型易于发生表皮增生和皮肤炎症，表明L3PSP可能是表皮动态平衡的关键调节因子。该提案的目的是确定L3PSP在皮肤发育和表皮疾病中的作用。我们的初步结果表明，L3PSP在表皮增殖层的异位表达导致毛囊形态发生缺陷、毛囊数量减少和毛囊周期紊乱。我们还发现了新的L3PSP相互作用候选蛋白，它们在苏莫化途径中发挥作用，以及介导Fas配体凋亡的蛋白。我们将确定L3PSP表达在毛囊生长和周期中断中的作用是否依赖于其磷酸酶活性，以及L3PSP表达是否刺激表皮角质形成细胞经历凋亡。为了证明L3PSP在L丝氨酸生物合成之外的新作用(S)，我们将进行生化研究，以验证L3PSP与酵母双杂交分析确定的候选蛋白之间的假定相互作用。最后，为了确定在表皮动态平衡中对L3PSP的需求，我们将产生L3PSP表达缺失的小鼠和人皮肤，并测量其对表皮增殖、细胞凋亡和毛囊形态发生的影响。总结：总体而言，我们计划确定一种通常被认为在基本细胞氨基酸代谢中起作用的蛋白质是否也可以通过刺激皮肤细胞中的程序性细胞死亡途径来调节毛囊的生长和维持。在这样做的时候，这项提案中概述的研究将对毛囊生物学和总体上皮细胞的生存产生重要的影响。

DESCRIPTION (provided by applicant): L-3-phosphoserine phosphatase (L3PSP) is a widely expressed member of the haloacid dehalogenase (HAD) superfamily and its enzyme activity is the irreversible and rate limiting step in L-serine biosynthesis. Dysregulation of L-serine biosynthesis is featured in neurological disorders, Williams-Beuren syndrome, skin ichthyosis and a variety of epithelial neoplasms. However, the significance of altered L3PSP activity on the initiation and course of these diseases is still not clear. We recently identified L3PSP by microarray analysis to be altered in an integrin transgenic mouse model that is predisposed to epidermal hyperplasia and skin inflammation indicating that L3PSP may be a critical regulator of epidermal homeostasis. The goal of this proposal is to define the role for L3PSP in skin development and epidermal disease. Our preliminary results show that ectopic expression of L3PSP in the proliferative layer of the epidermis leads to defects in hair follicle morphogenesis, decreased hair follicle number and dysregulated hair follicle cycling. We have also uncovered novel L3PSP interaction candidate proteins that function in sumoylation pathways and proteins that mediate Fas ligand apoptosis. We will determine if the effects of L3PSP expression in disrupted hair follicle growth and cycling are dependent on its phosphatase activity and if L3PSP expression stimulates epidermal keratinocytes to undergo apoptosis. To demonstrate a new role(s) for L3PSP outside of L-serine biosynthesis we will conduct biochemical studies to validate putative interactions between L3PSP and candidate proteins identified by yeast two-hybrid analysis. Finally, to determine the requirement for L3PSP in epidermal homeostasis we will generate murine and human skin that is deficient in L3PSP expression and measure the effect on epidermal proliferation, apoptosis and hair follicle morphogenesis. Lay summary: Overall we plan to ascertain whether a protein normally thought to function in basic cellular amino acid metabolism may also regulate the growth and maintenance of hair follicles by stimulating programmed cell death pathways in skin cells. In doing so, the studies outlined in this proposal will have important implications for hair follicle biology and epithelial cell survival in general.