MECHANISMS OF POLARIZED SECRETION BY BONE CELLS

骨细胞偏振分泌的机制

• 批准号: 7858352
• 负责人: Steven L Teitelbaum
• 金额: $ 33.86万
• 依托单位: WASHINGTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-06-01 至 2014-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7858352
• 关键词: Affinity; Albers-Schonberg disease; Binding; Bone Resorption; Bone Surface; Cell Polarity; Cell membrane; Cell physiology; Cells; Collagen Type I; Cytoskeleton; Data; Disease; Enzymes; Exocytosis; Family; Homeostasis; Link; Maintenance; Mediating; Modeling; Monomeric GTP-Binding Proteins; Mus; Osteoblasts; Osteoclasts; Osteoporosis; Pathway interactions; Pharmaceutical Preparations; Posture; Proteins; Protons; Recruitment Activity; Signal Pathway; Signal Transduction; Site; Vesicle; atypical protein kinase C; bone; bone cell; bone mass; bone turnover; cathepsin K; extracellular; novel; public health relevance; skeletal; synaptotagmin; synaptotagmin VII; vacuolar H+-ATPase

DESCRIPTION (provided by applicant): Maintenance of bone mass requires the integrated activity of osteoclasts (OCs) and osteoblasts (OBs). While they are functionally distinct, both are polarized and execute their activities by regulated secretion of bone-degrading and -synthesizing molecules, respectively. Bone resorption necessitates extracellular proton transport as a result of insertion of the vacuolar H+ATPase into the bone-apposed OC plasma membrane and targeted secretion of the collagenolytic enzyme cathepsin K. Similarly, skeletal synthesis involves secretion of specific matrix proteins such as type 1 collagen onto existing bone surfaces. Thus, the exocytic capacity of bone cells is fundamental to skeletal homeostasis. Regulated secretion, also called exocytosis, requires cell polarity in which intracellular, cargo-containing vesicles are delivered, by organization of the cytoskeleton, to an exocytic plasma membrane domain, which in OCs and OBs is that apposed to bone. Upon arrival at the site of exocytosis, the cargo-containing vesicles fuse with the plasma membrane via a number of linked steps, including high affinity binding of a synaptotagmin, a family of vesicle-associated adaptors, with several plasma membrane-residing proteins. We show data that synaptotagmin VII regulates exocytosis by OCs and OBs in a cell-autonomous manner. In consequence, mice lacking synaptotagmin VII have decreased remodeling and are a model for type II or low turnover osteoporosis. Cell polarity, a pre-requisite for exocytosis, is regulated by a conserved signaling pathway wherein activated cdc42 recruits an atypical protein kinase C, which phosphorylates essential downstream targets, including atypical PKCs such as PKC;. We find that RANKL-mediated organization of the OC cytoskeleton, and the cell's capacity to resorb bone, involve activation of the cdc42/PKC; pathway. Providing additional support for this posture, mice whose OCs express increased levels of active cdc42 are osteoporotic and those lacking the small GTPase have osteopetrosis. Similarly, cell-specific deletion of PKC; generates OCs that fail to polarize or resorb bone. These observations suggest a model in which 1) PKC;, activated by cdc42, promotes OC polarization and 2) following polarization, synaptotagmin VII controls exocytosis of bone- regulating molecules by OCs. Additionally Syt VII regulates OB exocytosis. Hence, our specific aims are to determine the mechanisms by which 1) PKC; signaling promotes OC polarization and 2) synaptotagmin VII controls exocytosis by OCs and OBs. PUBLIC HEALTH RELEVANCE: Maintenance of bone mass requires optimal and coordinated function of the cells regulating this parameter. We have identified novel proteins that individually control bone turnover. We propose to identify the mechanisms by which these two proteins control bone mass, with the view of generating novel drugs to treat diseases such as osteoporosis.

描述（由申请人提供）：骨骼质量的维持需要破骨细胞（OCS）和成骨细胞的综合活性（obs）。尽管它们在功能上是不同的，但都通过调节骨降解和 - 融合分子的分泌来执行其活性。由于将液泡H+ATPase插入骨粘附的OC质膜中，骨吸收需要细胞外质子的转运，并针对分泌胶原式酶的酶组织蛋白酶K。同样，骨骼合成涉及特定的Matrix蛋白的分泌，例如现有的1型胶质骨骼，涉及特定的Matrix蛋白的分泌。因此，骨细胞的胞外能力是骨骼稳态的基础。受调节的分泌，也称为胞吞作用，需要细胞极性，其中细胞内的，含货物的囊泡通过组织的细胞骨架将其传递到胞外质膜结构域，在OCS和OBS中，该结构域与骨骼相处。到达胞吞作用部位后，含货物的囊泡与质膜融合，通过多个链接的步骤融合，包括突触的高亲和力结合，这是一个囊泡相关的衔接子，与几种质子膜膜膜的蛋白质。我们显示的数据表明，Synaptotagmin VII通过OCS和OBS以细胞自主方式调节胞吐作用。因此，缺乏突触毒素VII的小鼠的重塑降低，是II型或低周转骨质疏松症的模型。细胞极性是胞吞作用的先决条件，受保守信号通路的调节，其中激活的Cdc42募集了非典型蛋白激酶C，该蛋白激酶C磷酸化，该蛋白质激活了基本的下游靶标，包括诸如PKC等非典型PKC；我们发现RANKL介导的OC细胞骨架的组织以及细胞的吸收骨骼能力涉及CDC42/PKC的激活；路径。为这种姿势提供额外的支撑，OCS表达活性Cdc42水平的小鼠是骨质疏松症，而缺乏小GTPase的小鼠患有骨质骨质肌。同样，PKC的细胞特异性缺失；产生无法偏振或吸收骨骼的OC。这些观察结果表明了一个模型，其中1）PKC;，被Cdc42激活，促进OC极化，2）在极化后，突触神经素VII控制OCS对骨调节分子的胞吐作用。另外，SYT VII调节OB胞吐作用。因此，我们的具体目的是确定1）PKC的机制；信号传导促进OC极化，2）OCS和OBS的突触神经素VII控制胞吐作用。公共卫生相关性：骨骼质量的维持需要调节该参数的细胞的最佳和协调功能。我们已经确定了单独控制骨转换的新型蛋白质。我们建议确定这两种蛋白质控制骨骼量的机制，以产生新的药物来治疗诸如骨质疏松症之类的疾病。