| dc.description.abstract | Microtubules and actin filaments coordinate to remodel the cytoskeleton to facilitate proper cell migration. The coordination between microtubules and actin filaments are regulated by 1) chemical signals and 2) physical crosslinking by associated proteins. In recent years, an extensive collection of proteins that physically couple both microtubules and actin filaments have been identified and need further investigation into the molecular mechanisms underlying their function. Cytoplasmic linker associated proteins (CLASPs) are a family of microtubule-associated proteins that have been implicated in the microtubule and actin crosstalk in cells. Specifically, CLASPs are implicated to interact with actin, however it remains unknown if CLASPs can simultaneously bind to microtubules and actin filaments. This thesis investigates the roles of CLASPs in microtubule-actin interactions, where it was established that CLASP2 can weakly interact with actin filaments and robustly crosslink actin filaments to the microtubule lattice. Interestingly, the TOG2 domain and serine-arginine rich region of CLASP2 is sufficient for weak actin filament binding and coalignment interactions with microtubules. CLASP2 localized along the microtubule facilitates accumulation of multiple actin filaments, suggesting a particular organization around the microtubule. Consistent with CLASPs’ weak affinity for actin filaments, CLASP2 can mediate actin filament elongation along microtubule templates and form bridges between microtubules. Intriguingly, ventral actin stress fibers in rat vascular smooth muscle cells are severely disrupted when CLASPs are depleted by siRNA. Furthermore, there are fewer instances of microtubule and actin coalignment in CLASP-depleted cells. Together, these results demonstrate that CLASP2 can served as a microtubule-actin crosslinker and suggests an important role between microtubules, CLASPs, and the formation of higher-order actin structures in cells. | |
