Ligand independent signaling by VDR in Keratinocytes

角质形成细胞中 VDR 的配体独立信号传导

• 批准号: 7739864
• 负责人: PAUL N MACDONALD
• 金额: $ 17.66万
• 依托单位: CASE WESTERN RESERVE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2011-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7739864
• 关键词: Ablation; Alopecia; Binding; Biological Models; Biology; CYP27B1 gene; Calcitriol; Calcium; Cell Proliferation; Cell model; Cells; Cyst; DNA Damage; Data; Dermal; Dietary Calcium; EGF gene; Endocrine system; Endocrinology; Ensure; Environmental Carcinogens; Enzymes; Fibroblasts; Gene Expression; Gene Expression Profile; Gene Targeting; Genes; Genetic; Genetic Models; Goals; Growth; Hair follicle structure; Heterodimerization; Homeostasis; Hormonal; Human; In Vitro; Intestinal Absorption; Kidney; Knock-out; Knockout Mice; Laboratories; Ligands; Malignant Neoplasms; Mediating; Mixed Function Oxygenases; Modeling; Molecular; Molecular Profiling; Mus; Nuclear Receptors; Organ; Osteoblasts; Osteoclasts; Pathology; Pathway interactions; Pharmacologic Substance; Phenotype; Physiological; Process; Property; Proteins; Psoriasis; Publishing; RXR; Regulation; Research; Research Proposals; Resistance; Role; Signal Transduction; Skin; Skin Neoplasms; Skin Tissue; Source; Stem cells; System; Transactivation; Tumor Suppressor Proteins; UV induced; Vitamin D; Vitamin D3 Receptor; Work; analog; base; cell type; clinically relevant; cohort; in vivo; keratinocyte; keratinocyte differentiation; knowledge base; monocyte; mouse model; mutant; novel; public health relevance; receptor; skin disorder; tool; tumorigenesis

DESCRIPTION (provided by applicant): The classic physiological role for 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) is to maintain appropriate calcium homeostasis by ensuring adequate intestinal absorption of dietary calcium. However, 1,25(OH)2D3 and its cognate receptor, the vitamin D receptor (VDR), also have critical roles in the skin and in keratinocyte biology. In fact, VDR is a clinically relevant target for the use of 1,25(OH)2D3 analogs in the treatment of psoriasis, a hyperproliferative disorder of the skin. The focus of this research proposal is on the vitamin D endocrine system in epidermal keratinocytes and, specifically, on the use of murine models of the vitamin D endocrine system as tools to explore the in vivo role and identify potential mechanisms of vitamin D action in the skin. In particular, the VDR knockout mouse (VDRKO) is highly susceptible to chemically-induced skin tumorigenesis. In contrast, our preliminary data show that genetic ablation of CYP27B1, the gene encoding the renal 1alpha- hydroxylase (1aOHase), the enzyme that generates the bioactive 1,25(OH)2D3 hormonal ligand, is completely resistant to chemically-induced skin tumorigenesis. These data as well as published data on hair follicle cycling in these mouse models and in humans, point to a novel ligand-independent role for VDR in keratinocytes. The molecular details involved in the tumor suppressor role for unliganded VDR in the skin are completely unknown. Our preliminary in vivo and in vitro data support a model in which the VDR-RXR heterodimer is activated by EGF in the absence of its 1,25(OH)2D3 ligand selectively in keratinocytes. EGF treatment drives heterodimerization of VDR and RXR in the absence of the 1,25(OH)2D3 ligand and this in turn promotes heterodimer binding to select keratinocyte genes involved in diverse processes such as hair follicle cycling and in protecting skin tissue from tumorigenesis initiated by DNA-damaging agents. Importantly, this mechanism exists for select target genes, i.e., not all established VDR target genes are regulated by unliganded VDR. It is this class of undefined genes whose expression is controlled by unliganded VDR-RXR that need to be defined in order to understand the in vivo biologies of the VDRKO and 11OHaseKO mice. In order to define the genes that are direct targets for unliganded VDR-RXR in keratinocytes, we will use gene expression array analysis of mouse keratinocytes and purified bulge stem cells from WT, VDRKO, and 1aOHaseKO mice. PUBLIC HEALTH RELEVANCE: The molecular details involved in the tumor suppressor role for unliganded VDR in the skin are completely unknown. Our working hypothesis states that EGF signaling in keratinocytes impinges on VDR to promote VDR-RXR heterodimerization and transactivation of select target genes in the absence of the 1,25(OH)2D3 ligand. The main goal of this proposal is to define target genes for unliganded VDR-RXR heterodimers in keratinocytes.

描述（由申请人提供）：1，25-二羟基维生素D3（1，25（OH）2D 3）的经典生理作用是通过确保膳食钙的充分肠道吸收来维持适当的钙稳态。然而，1，25（OH）2D 3及其同源受体维生素D受体（VDR）在皮肤和角质形成细胞生物学中也具有关键作用。事实上，VDR是使用1，25（OH）2D 3类似物治疗银屑病（一种皮肤过度增殖性疾病）的临床相关靶标。这项研究计划的重点是表皮角质形成细胞中的维生素D内分泌系统，特别是使用维生素D内分泌系统的小鼠模型作为工具来探索体内作用并确定维生素D在皮肤中作用的潜在机制。特别是，VDR敲除小鼠（VDRKO）对化学诱导的皮肤肿瘤发生高度敏感。相比之下，我们的初步数据显示，CYP 27 B1（编码肾1 α-羟化酶（1aOHase）的基因，产生生物活性1，25（OH）2D 3激素配体的酶）的基因消融对化学诱导的皮肤肿瘤发生具有完全抗性。这些数据以及已发表的关于这些小鼠模型和人类毛囊周期的数据，指出了VDR在角质形成细胞中的新的配体非依赖性作用。在皮肤中未配体的VDR的肿瘤抑制作用所涉及的分子细节是完全未知的。我们的初步体内和体外数据支持一种模型，其中VDR-RXR异源二聚体在角质形成细胞中选择性地在不存在其1，25（OH）2D 3配体的情况下被EGF激活。EGF治疗驱动VDR和RXR的异源二聚化，在缺乏1，25（OH）2D 3配体的情况下，这反过来促进异源二聚体结合到选择的角质形成细胞基因，所述角质形成细胞基因参与不同的过程，例如毛囊循环和保护皮肤组织免受DNA损伤剂引发的肿瘤发生。重要的是，这种机制存在于选择的靶基因中，即，并非所有已建立的VDR靶基因都受未配体的VDR调节。这类未定义的基因的表达由未配体的VDR-RXR控制，需要对其进行定义，以了解VDRKO和11 OHaseKO小鼠的体内生物学。为了确定角质形成细胞中未配体VDR-RXR的直接靶基因，我们将使用小鼠角质形成细胞和来自WT、VDRKO和1aOHaseKO小鼠的纯化隆突干细胞的基因表达阵列分析。公共卫生相关性：与皮肤中未配体VDR的肿瘤抑制作用有关的分子细节完全未知。我们的工作假设表明，在角质形成细胞中的EGF信号传导影响VDR，以促进VDR-RXR异源二聚化和在不存在1，25（OH）2D 3配体的情况下选择靶基因的反式激活。该提议的主要目标是确定角质形成细胞中未配体的VDR-RXR异源二聚体的靶基因。