Regulation of melanogenesis via FBXO11-mediated tyrosinase degradation

说明(申请人提供)：酪氨酸酶催化黑色素合成过程中的第一个限速反应，黑色素是一种保护皮肤免受紫外线辐射损伤的色素，从而降低患皮肤癌的风险。酪氨酸酶折叠和转运的中断会导致几种形式的眼皮肤白化。此外，酪氨酸酶基因多态性与患白癜风和黑色素瘤的风险增加有关，该蛋白也可能在帕金森氏病、黄斑变性和先天性青光眼中发挥作用。酪氨酸酶也是皮肤色素沉着的决定因素。浅色皮肤和深色皮肤的酶活性相差十倍之多；然而，mRNA的表达水平却非常相似。因此，酪氨酸酶的调节是翻译后的。我们的目标是阐明调节黑色素合成的机制，并描述酪氨酸酶相关疾病的发病机制。在这项研究中，我们旨在确定含有Skp，cullin，F-box(SCF)的复合体，特别是FBXO11组分，在酪氨酸酶调节中的作用。SCF是一种多蛋白E3泛素连接酶复合体，是泛素蛋白酶体系统(UPS)的重要组成部分。SCF复合体催化蛋白质的泛素化，从而靶向蛋白酶体的降解。FBox家族蛋白FBXO11最近被认为与酪氨酸酶的降解有关，而FBXO11的下调与白癜风的脱色障碍有关。以前的研究和我们自己的研究都表明，FBXO11表达降低的黑素细胞显示出更高的酪氨酸酶水平。相反，过度表达FBXO11的黑素细胞显示酪氨酸酶水平降低。在特定的目标1中，我们将研究FBXO11介导的酪氨酸酶靶向的机制。一些外部刺激，如暴露在白癜风诱发的酚或脂肪酸中，会促进酪氨酸酶水平的降低。在特定的目标2.1中，我们将探索这些刺激是否促进FBXO11介导的酪氨酸酶的降解。此外，在紫外线照射下促进酪氨酸酶表达的P53本身也是FBXO11的靶标。在具体目标2.2中，我们将确定 在黑素细胞中，P53是否也是FBXO11的靶标，以及降解是否影响酪氨酸酶水平。鉴于P53在细胞周期调节和细胞存活中的关键作用，FBXO1也可能在决定黑素细胞活性方面发挥作用。因此，我们还将探讨FXBO11的表达对黑素细胞活力的影响，在特定目的2.3中，暴露于紫外线诱导的应激或白癜风诱导的酚。因此，FBXO11可能在正常色素沉着的调节和白癜风等色素沉着障碍的发病机制中发挥关键作用。了解这种蛋白在黑素细胞中的作用对于阐明色素沉着障碍的病因和开发有效的治疗方法至关重要。

DESCRIPTION (provided by applicant): Tyrosinase catalyzes the first and rate-limiting reaction during the synthesis of melanin, the pigment that protects skin against ultraviolet radiation-induced damage, thus reducing the risk of developing cutaneous cancers. Disruption of tyrosinase folding and trafficking results in several forms of oculocutaneous albinism. In addition, tyrosinase polymorphisms are associated with increased risk of developing vitiligo and melanoma, and the protein may also play a role in Parkinson's disease, macular degeneration, and congenital glaucoma. Tyrosinase is also a determinant of skin pigmentation. Enzyme activity varies as much as ten-fold in lightly versus darkly pigmented skin; however, mRNA expression levels are remarkably similar. Tyrosinase regulation is therefore post-translational. Our objective is to elucidate the mechanisms that regulate melanin synthesis and characterize the pathogenesis of tyrosinase-related disorders. In this study, we aim to define the role of the Skp, Cullin, F-box (SCF) containing complexes, particularly the FBXO11 component, in tyrosinase regulation. SCF is a multi-protein E3 ubiquitin ligase complex that is a crucial component of the ubiquitin proteasome system (UPS). SCF complexes catalyze the ubiquitylation of proteins, thereby targeting them for proteasomal degradation. The F Box family protein FBXO11 has recently been implicated in the degradation of tyrosinase, while downregulation of FBXO11 is associated with the depigmentation disorder vitiligo. Previous studies as well as our own have demonstrated that melanocytes with reduced FBXO11 expression display increased levels of tyrosinase. Conversely, melanocytes overexpressing FBXO11 exhibit decreased levels of tyrosinase. In Specific Aim 1, we will investigate the mechanisms involved in FBXO11-mediated tyrosinase targeting. A number of external stimuli, such as exposure to vitiligo-inducing phenols or fatty acids, promote a reduction in tyrosinase levels. In Specific Aim 2.1, we will explore whether these stimuli promote FBXO11-mediated degradation of tyrosinase. In addition, p53, which promotes tyrosinase expression in response to ultraviolet light exposure, is itself a target of FBXO11. In Specific Aim 2.2, we will determine whether p53 is also targeted by FBXO11 in the melanocyte and whether degradation impacts tyrosinase levels. Given the critical role of p53 in cell cycle regulation and cell survival, FBXO1 may also play a role in determining melanocyte viability. We will thus also explore the effects of FXBO11 expression on melanocyte viability following exposure to stress induced by ultraviolet light or vitiligo-inducing phenols in Specific Aim 2.3. FBXO11 may thus play a key role in the regulation of normal pigmentation and in the pathogenesis of pigmentation disorders such as vitiligo. Understanding the role of this protein in the melanocyte will be crucial for delineating he etiology of pigmentation disorders and developing effective therapies.