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

Jiajia Zhou,Xuebiao Yao,Wenwen Wang,Xia Ding,Huihui Wu,Dongmei Wang,Saima Akram,Bo Qin,Zeqi Su,Dan Cao,Xiwei Wang,Donald L Hill,Changjiang Jin,Xing Liu,Gregory Adams,Xiaoxuan Zhuang,Lifang Liu

doi:10.1074/jbc.m115.673517

Abstract

Cell migration is orchestrated by dynamic interaction of microtubules with the plasma membrane cortex. However, the regulatory mechanisms underlying the cortical actin cytoskeleton and microtubule dynamics are less characterized. Our earlier study showed that small GTPase-activating proteins, IQGAPs, regulate polarized secretion in epithelial cells (1). Here, we show that IQGAP1 links dynamic microtubules to steer cell migration via interacting with the plus-end tracking protein, SKAP. Biochemical characterizations revealed that IQGAP1 and SKAP form a cognate complex and that their binding interfaces map to the WWIQ motif and the C-terminal of SKAP, respectively. The WWIQ peptide disrupts the biochemical interaction between IQGAP1 and SKAP in vitro, and perturbation of the IQGAP1-SKAP interaction in vivo using a membrane-permeable TAT-WWIQ peptide results in inhibition of directional cell migration elicited by EGF. Mechanistically, the N-terminal of SKAP binds to EB1, and its C terminus binds to IQGAP1 in migrating cells. Thus, we reason that a novel IQGAP1 complex orchestrates directional cell migration via coupling dynamic microtubule plus-ends to the cell cortex.

Highlights

IQGAP1 is a scaffold protein essential for cellular signaling in response to external cues
Identification of a Novel SKAP-IQGAP1 Complex in Interphase Cells—Our previous studies revealed the functional importance of SKAP in kinetochore and microtubule plus-end dynamics during mitosis [19, 21]
To study the molecular association of SKAP with other microtubule end-binding proteins, we carried out an affinity isolation of a SKAP-containing protein complex followed by mass spectrometric identification of tryptic peptides derived from the complex as described previously [19, 24]

Summary

Introduction

IQGAP1 is a scaffold protein essential for cellular signaling in response to external cues. Results: Perturbation of the IQGAP1-SKAP interaction results in inhibition of directional cell migration. Conclusion: The IQGAP1-SKAP interaction links to dynamic microtubules at the leading edge to steer cell migration. Significance: IQGAP1 serves as a signaling hub for dynamic interaction between microtubule plus-ends and the cell cortex. We show that IQGAP1 links dynamic microtubules to steer cell migration via interacting with the plus-end tracking protein, SKAP. The WWIQ peptide disrupts the biochemical interaction between IQGAP1 and SKAP in vitro, and perturbation of the IQGAP1-SKAP interaction in vivo using a membrane-permeable TAT-WWIQ peptide results in inhibition of directional cell migration elicited by EGF. The N-terminal of SKAP binds to EB1, and its C terminus binds to IQGAP1 in migrating cells. We reason that a novel IQGAP1 complex orchestrates directional cell migration via coupling dynamic microtubule plus-ends to the cell cortex

Methods

Results

Conclusion