Periodontal disease is a widespread, chronic condition at afflicts a large portion o the adult U.S. population. A loss of tooth attachment and resorption of alveolar bone characterize this disease process. Osteoclasts mediate the resorption process. How these cells are recruited to the resorption site is poorly understood. One mechanism may be through the local release of chemoattractants. Colony stimulating factor-1 (CSF-1), is an important chemoattractant for osteoclasts. CSF-1 is released by osteoblasts and stromal cells in response to LPS, TNF-alpha and a wide variety of other hormones and cyokines. Cytokinesis, the process of cell movement, involves prominent cytoskeletal changes and we have found that CSF-1 induces rapid cytoplasmic spreading and actin reorganization in osteoclasts. We have also found that PI 3-kianse (PI 3-K) is required for CSF-1's effects on osteoclasts. CSF-1 activates PI 3-K in osteoclasts and a direct molecular interaction between the SH3 domain of c-src and proline rich sequences in PI 3-K is necessary for full activation of PI 3-K. We have identified the guanine nucleotide exchange factor, Vav and the small GTPase Rac-1, as down-stream effector molecules in the signaling cascade from activated PI-3 K. We hypothesize that Vav and Rac-1 are both required for CSF-1-induced actin remodeling and that down-stream from Rac-1 are molecules that complete the signaling cascade from cfms to actin. We further hypothesize that this signaling cascade will also be critical for CSF-1-induced osteoclast motility. To explore these hypotheses we will determine if osteoclasts isolated from Vav -/- animals have an altered response to CSF-1 and use dominant negative constructs and microinjection techniques to determine if the serine kinase, LIMK-1 is one of the final links between c-fms and the actin cytoskeleton. We will employ a yeast two-hybrid screen to isolate novel Rac-1 interacting proteins in ositoclasts. Finally we will evaluate the role of these molecules in mediating CSF-1 chemotaxsis in mature rat osteoclasts. These studies should better define the mechanisms by which CSF-1 influences the motility of mature osteoclasts and lead to more effective strategies for improving dental health.
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