Analysing the cell biology of SNX10 in endosomal sorting and signaling: implications for osteoclast function in osteopetrosis

所有人类细胞都由一个外部边界组成，该边界由称为质膜的蛋白质和脂质的复杂混合物定义。这包围了一个充满液体的三维空间，称为胞质溶胶，其中含有额外的膜富集区室，每个区室由蛋白质和脂质的独特组合组成。为了使细胞正常发挥功能，蛋白质和脂质必须有效地转运到这个迷宫般的膜内正确的膜富集区室。毫不奇怪，如果这种转运受到干扰，使得错误的蛋白质和脂质被递送到不正确的膜富集区室，细胞功能可能受到不利影响，这反过来又导致各种疾病的发展。因此，建立细胞实现调节蛋白质和脂质转运的机制是细胞生物学中的一个重大挑战，直接影响我们对人类疾病的理解。10多年来，我们的实验室一直致力于描述细胞膜迷宫（称为内吞网络）中控制蛋白质和脂质转运的机制细节。特别是，我们研究了一个古老的，进化保守的蛋白质家族，分类连接蛋白。在这个家族中，我们已经广泛分析了retromer复合物的功能，这对各种病原体感染细胞期间内体网络的扰动功能产生了新的见解，以及包括阿尔茨海默病和帕金森病在内的多种疾病。在当前的提议中，我们试图利用我们在研究分选连接蛋白方面的丰富经验来定义分选连接蛋白10（SNX10）的功能。在调节骨骼重塑中的作用。这源于研究表明SNX10的突变与常染色体隐性骨硬化症有关，这是一种遗传异质性疾病，由称为破骨细胞的特定类型的细胞减少骨吸收引起。然而，目前我们还不了解SNX10的基本功能，因此对为什么它的突变会导致这种使人衰弱的疾病的理解非常有限。我们拟议的研究将解决以下问题：1）. SNX10是RANK和下游RANKL信号传导的内体分选所必需的吗？2）。其他受体的细胞表面表达是否也受SNX10调节？3）。SNX10介导的内体分选的分子细节是什么？4）。SNX10介导的内体分选的分子细节是否能进一步了解骨稳态疾病？总体而言，来自拟议研究的数据将通过同行评审出版物和国际会议上的口头报告传播，将定义SNX10在破骨细胞功能中的作用，这些知识将更好地了解导致骨硬化症和其他相关骨骼疾病的细胞缺陷。从长远来看，这项研究可能为携带SNX10突变和其他骨硬化相关突变的患者提供治疗干预的依据。

All human cells are composed of an outer boundary that is defined by a complex mixture of protein and lipids called the plasma membrane. This encircles a fluid filled 3-dimensional space, termed the cytosol, which contains additional membrane-enriched compartments each composed of a unique combination of proteins and lipids. For cells to functional normally, proteins and lipids must be efficiently transported to the correct membrane-enriched compartment within this maze of membranes. Not surprisingly, if such transport is perturbed, so that the wrong proteins and lipids are delivered to the incorrect membrane-enriched compartment, cell function can be adversely affected which in turn leads to the development of various diseases. Establishing the mechanisms through which cells achieve regulated protein and lipid transport is therefore a major challenge in cell biology with direct implication for our understanding of human disease.For over 10 years our laboratory has focused on describing the mechanistic details that control regulated transport of proteins and lipids within a specific aspect of the cell's membranous maze termed the endocytic network. In particular, we have studied a family of ancient, evolutionary conserved proteins, the sorting nexins. Within this family we have extensively analysed the function of retromer complexes, and this is generating new insight into the perturbed function of the endosomal network during cell infection by various pathogens, as well as a variety of diseases including Alzheimer's disease and Parkinson's disease.In the current proposal we seek to utilize our extensive experience of studying sorting nexins to define the function of sorting nexin-10 (SNX10) in the regulation of bone re-modeling. This stems from research showing that mutations in SNX10 are linked with autosomal recessive osteopetrosis, a genetically heterogenous disorder caused by reduced bone resorption by a specific class of cells termed osteoclasts. However, at present we do not understand the basic function of SNX10, and hence have a very limited appreciation of why its mutation leads to this debilitating disease.Our proposed research will address the following questions:1). Is SNX10 required for endosomal sorting of RANK and downstream RANKL signaling?2). Is the cell surface expression of other receptors also regulated by SNX10?3). What are the molecular details of SNX10-mediated endosomal sorting?4). Do the molecular details of SNX10-mediated endosomal sorting generate further insight into diseases of bone homeostasis?Overall, data derived from the proposed research, which will be disseminated through peer-review publications and oral presentation at international meetings, will define the role of SNX10 in osteoclast function, knowledge that will achieve a greater appreciation of the cellular defects that lead to osteopetrosis and possibly other related bone diseases. Longer term, the research may provide a rationale for therapeutic intervention in patients carrying the SNX10 mutations and other osteopetrosis-linked mutations.