Cell migration/invasion is a fundamental process necessary for embryonic development, immune function, and angiogenesis. However, deregulation of migration/invasion also contributes to unwanted migration during cancer cell metastasis. While it is believed that migratory cells must coordinately activate survival mechanisms to invade the extracellular matrix (ECM) and colonize foreign sites in the body, the signals that regulate these processes are poorly understood. Our previous work, along with novel evidence provided in this research proposal, demonstrate that motile signals that induce cell invasion of the ECM also promote cell survival by suppressing apoptosis of migratory cells. The molecular coupling of the adaptor proteins p130CAS (CAS) and c-CrkII (Crk) represents a distinct signaling pathway that induces cell invasion and protects cells from apoptosis. CAS/Crk-mediated cell invasion and survival requires activation of the small GTPase Rac, which controls the actin cytoskeleton. Interestingly, we discovered that c-Abl tyrosine kinase (Abl) coordinately regulates cell invasion and survival through its ability to phosphorylate the negative regulatory tyrosine 221 of Crk. Phosphorylation of Crk by Abl facilitates the uncoupling of Crk from CAS preventing cell migration and inducing apoptosis. Therefore, Abl kinase serves as a negative control mechanism to prevent cell migration and induce apoptosis of invasive cells. Furthermore, we discovered that Abl regulates the novel cytoskeletal-associated protein Lasp-1 (LIM and SH3 protein), which is important for cell migration and apoptosis. Thus, studies outlined in this proposal will test the hypothesis that cytoplasmic Abl tyrosine kinase is a critical negative feedback pathway that controls cell migration and apoptosis through modulation of CAS/Crk coupling and Lasp-I activation. We will utilize a molecular mutagenesis approach to directly disrupt Abl-mediated regulation of CAS/Crk and Lasp- 1 in migratory and apoptotic cells. Using green fluorescent protein (GFP) and fluorescent energy transfer technology (FRET), we will determine precisely the temporal and spatial localization and activation of the Abl/CAS/Crk/Lasp-1 signaling module in vivo. Findings from these studies are physiologically important to understanding at the molecular level how invasive cells coordinately control migration and survival during wound healing, immune responses, and cancer metastasis.
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