Cell migration is an essential characteristic of cells in numerous fundamental biological processes, such as embryogenesis, tissue development, wound healing, and migration of lymphocytes in the immune response system. The molecular mechanism that governs this important cellular process is extensively studied. However, despite intensive characterizations, several important knowledge gaps remain, especially regarding the functional role of the key player, Ca-calmodulin (CaM), in the cell migration process. We have observed that the p68-CaM interaction is necessary for epithelial cell migration. Upon cell migration stimulation, the p68-CaM interaction was substantially enhanced. Binding to CaM caused localization of p68 from the cell nucleus to the cytoplasm. In the migrating cells, p68 and CaM co-localized to the migration leading edges (lamellipodia or fillopodia). Mutations that abolished p68 ATPase activity blocked the localization of CaM to the leading edge of migrating cells. Expression of a p68-calmodulin fusion protein led to the formation of lamellipodium and cell morphological changes and dramatically increased cell motility. The immunopurified p68-CaM fusion protein interacted with the cytoskeleton microtubule in vitro. In addition, a peptide derived from p68 IQ motifs strongly inhibited cell migration. As a consequence, treatment of tumor bearing mouse with the IQ peptide almost completely abolished cancer metastasis. Our observations suggest that the p68-CaM interaction is a new player in regulating the cell migration. The goal of this proposed research project is to understand the role of the p68-CaM interaction in cell migration process. We propose three specific aims to investigate the functional significance of p68-CaM interaction in cell migration.
In specific aim 1, we will elucidate the mechanism that regulates the p68-CaM interaction. We will test our hypothesis that cell migration signals trigger phosphorylation of p68, which subsequently lead to the p68-CaM interaction.
In specific aim 2, we will unravel the function of p68 at migration leading edge.
In specific aim 3, we plan to focus on addressing the molecular mechanism that governors the substrate selection of p68 in different cellular processes. We believe that our results will ultimately be applied to develop new strategies for diseases diagnosis/prognosis and treatments.
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