ATP2A2-Regulated Keratinocyte Ca2+ Signaling Mechanisms

描述(由申请人提供)：理论基础：细胞内钙储存在钙诱导的角质形成细胞分化信号中起着关键作用。角质形成细胞内质网(ER)的钙储存库由钙离子ATPase ATP2A2维持，而与之密切相关的一种钙ATPase ATP2C1定位于高尔基体并维持该细胞器的钙储存库。ATP2A2的突变是人类皮肤疾病达里尔病(DD)的基础，其特征是角质形成细胞分化不完全。我们和其他实验室的工作表明，ATP2A2和ATP2C1共同作用于细胞外钙升高刺激的钙信号，使角质形成细胞成为已知的第一个同时受到内质网和高尔基体钙库双重控制的哺乳动物细胞。我们的初步研究表明，DD角质形成细胞中的ATP2A2功能障碍可以部分通过ATP2C1上调而得到补偿。这些代偿性变化使DD角质形成细胞保持存活，因为在DD角质形成细胞中ATP2C1完全失活会导致细胞死亡。然而，ATP2C1代偿性上调也导致胞浆钙浓度异常低，这可能是DD角质形成细胞异常分化的独特模式的基础。在这项提案中，我们计划重点研究ATP2A2功能障碍和ATP2C1上调导致钙离子诱导的DD角质形成细胞异常分化的分子机制。假设：DD的角质形成细胞分化特征受损，既是由于突变的ATP2A2控制的钙信号通路下游的异常，也是由于其他钙信号蛋白的代偿性变化，特别是ATP2C1和质膜离子通道。这种异常分化可以通过纠正钙稳态的缺陷，应用其他前分化药物绕过参与总蛋白合成的钙反应途径，或这些策略的组合来正常化。具体目的：目的#1：研究DD角质形成细胞中的钙信号缺陷和适应性反应。目的#2：探讨细胞内钙离子浓度的异常降低、细胞器钙稳态异常引起的病理性ERK信号转导、抑或SERCA2依赖的核钙信号转导功能受损是导致钙诱导分化障碍的原因。目的#3：通过改善钙稳态、增强Involucrin启动子的激活，或两者兼而有之，使细胞分化正常化。这个项目的目标是确定导致Darier病异常分化的致病信号通路，从而改善患有这种疾病的患者的皮肤病理。

DESCRIPTION (provided by applicant): RATIONALE: Intracellular Ca stores play a critical role in signaling Ca2+ -induced keratinocyte differentia- tion. Keratinocyte endoplasmic reticulum (ER) Ca2+ stores are maintained by the Ca2+ ATPase ATP2A2, while a closely related Ca2+ATPase, ATP2C1, localizes to the Golgi and maintains the Ca2+ store in this organelle. Mutations in the ATP2A2 underlie the human skin condition Darier's disease (DD), characterized by incomplete keratinocyte differentiation. Work from ours and other laboratories demonstrates that the ATP2A2 and ATP2C1 act jointly to shape Ca2+ signaling stimulated by raised extracellular Ca2+, making keratinocytes the first mammalian cells known to be under dual control of both ER and Golgi Ca2+ stores. Our preliminary studies reveal that ATP2A2 dysfunction in DD keratinocytes is compensated, in part, by ATP2C1 upregulation. These compensatory changes allow DD keratinocytes to remain viable, since completely inactivating ATP2C1 in DD keratinocytes leads to cell death. However, compensatory ATP2C1 upregulation also leads to abnormally low cytosolic Ca2+ concentrations, and may underlie the unique pattern of abnormal differentiation seen in DD keratinocytes. In this proposal, we plan to focus on the molecular mechanisms by which ATP2A2 dysfunction and ATP2C1 upregulation lead to abnormal Ca2+-induced differentiation in DD keratinocytes. HYPOTHESIS: The impaired keratinocyte differentiation characteristic of DD results both from downstream abnormalities in Ca2+ signaling pathways controlled by the mutated ATP2A2 and by the compensatory changes in other Ca2+ signaling proteins, especially the ATP2C1 and plasma membrane ion channels. This abnormal differentiation can be normalized by correcting defects in Ca2+ homeostasis, applying other prodifferentiative agents that bypass the Ca2+-responsive pathways involved in involucrin synthesis, or a combination of these strategies. SPECIFIC AIMS: Aim#1: To Characterize the Ca2+ Signaling Defects and Adaptive Responses in DD Keratinocytes. Aim #2: To Determine Whether Impaired Ca2+ -induced Differentiation in DD is Caused by Abnormally Decreased Cytosolic Ca2+, Pathologic ERK Signaling Due to Abnormal Organelle Ca2+ Homeostasis, or Impaired SERCA2-dependent Nuclear Ca2+ Signaling Aim #3: To Normalize Differentiation in DD by Improving Ca2+ Homeostasis, Enhancing Involucrin Promoter Activation, or Both. The goal of this project is to define the pathogenic signaling pathways that lead to abnormal differentiation in Darier's disease, thus ameliorating the skin pathology of patients suffering from this condition.