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

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-3β is responsible for this asymmetric distribution of CLASPs. However, it is not known how GSK-3β 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-3β 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-3β 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-3β appears to control the regional linkage of microtubules to actin filaments through IQGAP1 for cell migration.

Signaling Scaffold Protein IQGAP1 Interacts with Microtubule Plus-end Tracking Protein SKAP and Links Dynamic Microtubule Plus-end to Steer Cell Migration

“…Importantly, endogenous SKAP accumulates at the cell leading edge in MDA-MB-231 cells, suggesting that SKAP interacts with proteins distributed at the cell cortex. Many ϩTIPs are involved in cell migration by interaction with the cortical cytoskeleton protein, IQGAP1 (7,11,37). Our results also reveal that SKAP binds to IQGAP1 and serves as a linkage between MT plus-ends and the cell cortex.…”

“…Because the selective stabilization of MTs is essential for cell migration (3), ϩTIPs modulating MT plasticity and dynamics in cells are pro-posed to be regulatory factors involved in cell migration. In recent years, many ϩTIPs have been identified as IQGAP1-interacting proteins (7,11). Despite decades of research, the mechanism remains partially elusive.…”

Plus-end tracking proteins, CLASPs, and a viral Akt mimic regulate herpesvirus-induced stable microtubule formation and virus spread

“…Similar to HSV-1-infected cells, depletion of CLASPs results in MT looping (43) and reduced levels of Ac-MTs (29,41,43,44). CLASPs link MTs to the cell cortex to control polarized trafficking, as well as persistent cell motility and migration (41,(44)(45)(46)(47)(48)(49). Additional, more specialized properties of CLASPs may explain their specific importance to HSV-1.…”

Parallel Genetic and Proteomic Screens Identify Msps as a CLASP–Abl Pathway Interactor in Drosophila

“…CLASPs possess actin-binding activity (Tsvetkov et al 2007), and CLASP-decorated MT tips track along actin filament bundles in the growth cone peripheral domain (Lee et al 2004). Moreover, CLASP was recently shown to bind to the actin-binding protein, IQGAP1, and phosphorylation of CLASP controls linkage of MTs to actin through IQGAP1 for cell migration (Watanabe et al 2009). From our work, it appears that CLASP may have numerous other effector proteins that can modulate its interaction with the actin network.…”