MOLECULAR MECHANISMS OF OSTEOCLASTIC BONE RESORPTION

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DESCRIPTION (Adapted from the investigator's Abstract): The overall goal of the proposed studies is to determine the role of OC-116 kDa, a newly-described molecule, in osteoclast function and to apply this knowledge to the control of osteolytic diseases. The proposed studies involve an in-depth analysis of the expression, regulation, and function of OC-116 kDa in osteoclastic bone resorption. The hypothesis of the proposed studies is that OC-116 kDa is expressed selectively in osteoclasts; that it constitutes an integral part of the osteoclast proton pump; and that it plays a key functional role in the acidification of the subosteoclastic lacuna. In Aim 1, the expression of OC-116 kDa will be determined in vivo, using RT-PCR, RNase protection, in situ hybridization and immunochemistry, at the cellular and ultrastructural levels. In Aim 2, the association of OC-116 kDa as part of the osteoclast proton pump will be determined by coprecipitation of OC-116 kDa with known subunits of the pump, and functionally by antisense inhibition in vitro. In Aim 3, the function of OC-116 kDa will be established using targeted disruption of the endogenous gene. The effect of the null mutation on phenotype and osteoclast function in embryonic, neonatal and adult mice will be determined. In Aim 4, the regulation of OC-116 kDa in osteoclasts by stimulators and inhibitors of bone resorption will be assessed. In addition, studies of the mechanisms of cell-specific regulation of OC-116 kDa will be initiated using promoter-reporter transgenic animals. In Aim 5, specific inhibitors of OC-116 kDa will be sought and their effect on bone resorption determined. By virtue of its selective expression, OC-116 kDa may be useful as a target of specific therapeutic inhibitors of resorption.