Regulation of osteoclast biology by anion exchanger SLC4A2 in mouse and human sys

描述（由申请人提供）：骨是一种动态组织，可重塑以生长、适应应力并保持完整性。两种细胞类型控制这一过程，成骨细胞（OB）和破骨细胞（OC），分别合成和降解骨。骨重建的病理不平等有利于吸收而不是形成，导致骨质疏松症、类风湿性关节炎和转移性骨癌等疾病。目前，超过3000万美国人骨质疏松，近1%的人口患有类风湿性关节炎。这些疾病每年的医疗费用负担是巨大的。目前批准的靶向OC的治疗剂是不够的，需要发现新的靶标。为了吸收骨，破骨细胞分泌盐酸。为了防止细胞质碱基的相互积累，通过阴离子交换剂发生碳酸氢盐与氯离子的电中性交换。这种交换剂的身份一直无法确定，直到我们最近的报告显示溶质载体家族4，阴离子交换剂，成员2（Slc 4a 2，Ae 2）是破骨细胞在发育过程中活性所必需的。在缺乏它的情况下，小鼠发展为严重的骨硬化症。最近的出版物已经在缺乏SLC 4A 2的牛中鉴定出几乎相同的表型。迄今为止，只有少数突变已被确定，如此显着地削减破骨细胞的能力，再吸收钙化组织。我们的初步数据表明，SCL 4A 2在OC生理学中起着意想不到的复杂作用。我们已经发现，SLC 4A 2缺陷不仅阻止OC正常分泌酸和进行阴离子交换，而且深刻地影响其细胞骨架的组织。关于OC中SLC 4A 2的生物学仍然存在许多重要问题。我们不知道SLC 4A 2是否在发育期后的骨重建或炎症性骨骼疾病的发病机制中起重要作用。SLC 4A 2的胞质和跨膜结构域对破骨细胞生物学调节的相对贡献尚不清楚。此外，人类破骨细胞是否利用SLC 4A 2是不确定的。提出了四个具体的目标来回答这些问题：1）建立SLC 4A 2的OC-内在作用并解决骨石化症对Slc 4a 2-/-小鼠的致死表型的贡献; 2）在炎性关节炎的小鼠模型中建立SLC 4A 2的需求; 3）在OC中进行SLC 4A 2的结构-功能分析和4）确认SLC 4A 2在人OC中的作用。我将利用波士顿独特的环境来促进这些研究。与阴离子交换生理学、OC细胞生物学、RA小鼠模型和RNA干扰方面的当地专家建立了合作关系。通过分析一个基因的功能，如此深刻地影响OC生物学，这笔赠款将推进骨骼重塑的基本理解，作出重要贡献，一般细胞生物学和信号转导，最重要的是，定义一个新的目标，以抑制病理性骨丢失。

DESCRIPTION (provided by applicant): Bone is a dynamic tissue that remodels to grow, adapt to stress and maintain integrity. Two cell types control this process, the osteoblast (OB) and the osteoclast (OC), which synthesize and degrade bone, respectively. Pathologic inequality in bone remodeling favoring resorption over formation leads to diseases such as osteoporosis, rheumatoid arthritis and metastatic bone cancer. Currently, over 30 million Americans have low bone mass and nearly 1% of our population suffers from rheumatoid arthritis. The yearly health care cost burden of these diseases is immense. Currently approved therapeutics targeting OCs are inadequate, necessitating the discovery of new targets. To resorb bone, osteoclasts secrete hydrochloric acid. To prevent a reciprocal build up of cytoplasmic base, electroneutral exchange of bicarbonate for chloride occurs through an anion exchanger. The identity of this exchanger eluded identification until our recent report showing Solute carrier family 4, anion exchanger, member 2 (Slc4a2, Ae2) is absolutely required for osteoclast activity during development. In its absence, mice develop profound osteopetrosis. A recent publication has identified a nearly identical phenotype in cattle that lack SLC4A2. To date, only a handful of mutations have been identified that so dramatically curtail the ability of osteoclasts to resorb calcified tissue. Our preliminary data suggest that SCL4A2 plays an unexpected complex role in OC physiology. We have found that SLC4A2 deficiency not only prevents OCs from properly secreting acid and performing anion exchange, but also profoundly affects the organization of their cytoskeleton. Many important questions remain regarding the biology of SLC4A2 in the OC. We do not know whether SLC4A2 is important in bone remodeling beyond the developmental period or in the pathogenesis of inflammatory skeletal disease. The relative contribution of the cytoplasmic and transmembrane domains of SLC4A2 to the regulation of osteoclast biology is unknown. Moreover, whether human osteoclasts utilize SLC4A2 is undefined. Four specific aims are proposed to answer these questions: 1) Establish the OC-intrinsic role of SLC4A2 and resolve the contribution of osteopetrosis to the lethal phenotype of Slc4a2-/- mice; 2) Establish the requirement of SLC4A2 in a mouse model of inflammatory arthritis; 3) Perform a structure-function analysis of SLC4A2 in OCs and 4) Confirm a role for SLC4A2 in human OCs. I will take advantage of the unique environment in Boston to facilitate these studies. Collaborations have been established with local experts in anion exchange physiology, OC cell biology, mouse models of RA and RNA interference. By analyzing the function of a gene that so profoundly affects OC biology, this grant will advance basic understanding of skeletal remodeling, make important contributions to general cell biology and signal transduction and, most importantly, define a new target to suppress pathologic bone loss.