Transient elevations in Ca2+ have previously been shown to promote focal adhesion disassembly and cell motility. Yet the targets of these Ca2+ transients have not been fully examined. In this study, we demonstrate that CaMK-II, a Ca2+/calmodulin dependent protein kinase, is activated in response to β1 integrin engagement with fibronectin to influence fibroblast adhesion and motility. We also show that CaMK-II is dynamically localized to the cell surface using Total Internal Reflection Fluorescence microscopy (TIRFm) and that inhibition of CaMK-II with two mechanistically distinct, membrane permeant inhibitors accelerates spreading on fibronectin, enlarges paxillin-containing focal adhesions and blocks cell motility. On the other hand, expression of constitutively active CaMK-II reduces cell attachment, eliminates paxillin from focal adhesions and decreases the phospho-tyrosine levels of both FAK and paxillin. Cell spreading, paxillin incorporation into focal adhesions and phospho-tyrosine levels of FAK and paxillin are restored when cells expressing constitutively active CaMK-II are subsequently treated with myr-AIP, a specific CaMK-II catalytic inhibitor. Like CaMK-II inhibition, constitutively active CaMK-II blocks cell motility. Thus, both CaMK-II inhibition and constitutive activation block cell motility through over-stabilization or destabilization of focal adhesions, respectively. These findings provide the first direct evidence that CaMK-II promotes focal adhesion turnover and thus enables cell motility by stimulating tyrosine dephosphorylation of focal adhesion proteins.
| Identifer | oai:union.ndltd.org:vcu.edu/oai:scholarscompass.vcu.edu:etd-2584 |
| Date | 01 January 2008 |
| Creators | Easley, Charles, IV |
| Publisher | VCU Scholars Compass |
| Source Sets | Virginia Commonwealth University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | © The Author |
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