Role of NHA-oc/NHA2 in Osteoclast Differentiation and Function

描述(由申请人提供)：破骨细胞的骨吸收对于正常的骨发育是必不可少的。破骨细胞缺乏会导致骨化症，其特征是骨量增加，可能会导致骨骼变形，严重时会导致死亡。另一方面，破骨细胞数量和活性的增加会导致骨吸收增加，并可能导致骨质疏松和其他溶骨性疾病。更好地了解破骨细胞形成、活性和存活的分子调控将为控制这些疾病的治疗干预提供新的靶点。我们最近鉴定并克隆了一个编码新的Na+/H+逆向转运蛋白的基因NHAoc/NHA2，这是迄今为止第一个表征线粒体NHA的基因。NHAoc/NHA2在破骨细胞中高度和选择性地表达，并显示出真正的NHA所预期的离子转运活性。我们已经证明该基因(S)在体外正常破骨细胞分化、凋亡和骨吸收功能中发挥作用。对细菌同源物NhaA的广泛突变分析揭示了其活性所必需的一些氨基酸残基。其中一些残基在进化上是保守的，已被证明不仅对细菌中的NhaA活性是必不可少的，而且对真核生物中的NHAoc活性也是必不可少的。我们推测，进化上保守的氨基酸对NhaA逆向转运蛋白活性、pH调节和二聚化是必不可少的，这些氨基酸残基的突变将在体外和体内影响NHAoc的活性，从而影响破骨细胞的功能。 公共卫生相关性：破骨细胞是在正常的骨骼发育和维护过程中负责骨移除(‘吸收’)的细胞。另一方面，破骨细胞数量和/或活性异常会导致从骨化症到骨质疏松症的一系列疾病。这个项目试图确定我们在破骨细胞中发现的一种新基因在调节骨量中的作用，该基因被称为NHA-oc/NHA2。这项工作将帮助我们设计基于干扰NHA-oc/NHA2活性的药物的适当的新疗法，以防止病理性骨丢失。

DESCRIPTION (provided by applicant): Bone resorption by osteoclasts is essential for normal bone development. Osteoclast deficiency leads to osteopetrosis, which is characterized by increased bone mass and may lead to bone deformities or in severe cases, to death. Increased numbers and activity of osteoclasts, on the other hand, cause increased bone resorption, and may lead to osteoporosis and other osteolytic diseases. A better understanding of the molecular regulation of osteoclast formation, activity, and survival will provide novel targets for therapeutic intervention in the control of these diseases. We recently identified and cloned a gene, NHAoc/NHA2, that encodes a novel Na+/H+ antiporter that is the first mitochondrial NHA characterized to date. NHAoc/NHA2 is highly and selectively expressed in osteoclasts and displays the expected ion transport activities of a bona fide NHA. We have demonstrated that this gene plays a role(s) in normal osteoclast differentiation, apoptosis and bone resorptive function in vitro. Extensive mutational analysis of a bacterial homologue, NhaA, has revealed a number of amino acid residues essential for its activity. Some of these residues are evolutionarily conserved and have been shown to be essential not only for activity of NhaA in bacteria, but also of NHAoc in eukaryotes. We hypothesize that evolutionarily conserved amino acids that are essential for NhaA antiporter activity, pH regulation and dimerization will have a similar role in NHAoc/NHA2 and that mutations in those amino acid residues will impact NHAoc activity and therefore osteoclast function in vitro and in vivo. PUBLIC HEALTH RELEVANCE: Osteoclasts are cells that are responsible for bone removal ('resorption') during normal bone development and maintenance. Abnormal osteoclast numbers and/or activity, on the other hand, can cause a spectrum of diseases ranging from osteopetrosis to osteoporosis. This project seeks to determine the role of a novel gene that we have discovered in osteoclasts, termed 'NHA-oc/NHA2', in regulating bone mass. This work will aid us in the design of appropriate new therapies based on drugs that interfere with NHA-oc/NHA2 activity for the prevention of pathological bone loss.