Article

Phosphorylation of CLASP2 by GSK-3 beta regulates its interaction with IQGAP1, EB1 and microtubules

Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, Nagoya, Aichi, Japan.
Journal of Cell Science (Impact Factor: 5.43). 09/2009; 122(Pt 16):2969-79. DOI: 10.1242/jcs.046649
Source: PubMed

ABSTRACT

Polarised cell migration is required for various cell behaviours and functions. Actin and microtubules are coupled structurally and distributed asymmetrically along the front-rear axis of migrating cells. CLIP-associating proteins (CLASPs) accumulate near the ends of microtubules at the front of migrating cells to control microtubule dynamics and cytoskeletal coupling. Regional inhibition of GSK-3beta is responsible for this asymmetric distribution of CLASPs. However, it is not known how GSK-3beta regulates the activity of CLASPs for linkage between actin and microtubules. Here we identified IQGAP1, an actin-binding protein, as a novel CLASP-binding protein. GSK-3beta directly phosphorylates CLASP2 at Ser533 and Ser537 within the region responsible for the IQGAP1 binding. Phosphorylation of CLASP2 results in the dissociation of CLASP2 from IQGAP1, EB1 and microtubules. At the leading edges of migrating fibroblasts, CLASP2 near microtubule ends partially colocalises with IQGAP1. Expression of active GSK-3beta abrogates the distribution of CLASP2 on microtubules, but not that of a nonphosphorylatable CLASP2 mutant. The phosphorylated CLASP2 does not accumulate near the ends of microtubules at the leading edges. Thus, phosphorylation of CLASP2 by GSK-3beta appears to control the regional linkage of microtubules to actin filaments through IQGAP1 for cell migration.

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Available from: Kozo Kaibuchi, Jul 08, 2015
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    • "Ch-TOG might mediate the interaction of microtubules with proteins localized at the cell cortex and thereby participates to microtubule capture and stabilization. While we cannot exclude that ch-TOG associates directly with cortical components, microtubule +end cortical interactions are more likely driven by EB1, which is known to bind SxIP motif-containing cortical proteins[18,22,303132. Reconstitution experiments strongly suggest that ch-TOG allosterically enhances the binding of EB1 to the microtubule +end[22]. "
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    • "We have also shown that the Kip2-Bim1 interaction is required for efficient localisation of Kar9 to aMT plus ends. In mammalian cells, GSK-3 phosphorylates +TIPs such as CLASP2 or APC, and weakens their interaction with MTs or other +TIPs (Rubinfeld et al., 1996; Zumbrunn et al., 2001), while local inhibition of GSK-3 stabilises microtubules and promotes their interaction with the cortical cytoskeleton during cell migration (Akhmanova et al., 2001; Etienne Manneville and Hall, 2003; Kumar et al., 2009; Watanabe et al., 2009). Regulation of Kip2 by Mck1 in budding yeast may be another example for a GSK-3-dependent mechanism utilised to couple regulation of microtubule dynamics with control of aMT-cortical interactions. "
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