Structure of the DOCK2\u2212ELMO1 complex provides insights into regulation of the auto-inhibited state

Leifu Chang,Leifu Chang,Jean-Francois Côté,Afnan Abu-Thuraia,Ryan C Killoran,Andreas Boland,Andreas Boland,Jing Yang,Matthew J Smith,Matthew J Smith,David Barford,Chang Hwa Jo,Chang Hwa Jo,Ryan C Killoran,Ziguo Zhang,Stephen H Mclaughlin

doi:10.1038/s41467-020-17271-9

Abstract

DOCK (dedicator of cytokinesis) proteins are multidomain guanine nucleotide exchange factors (GEFs) for RHO GTPases that regulate intracellular actin dynamics. DOCK proteins share catalytic (DOCKDHR2) and membrane-associated (DOCKDHR1) domains. The structurally-related DOCK1 and DOCK2 GEFs are specific for RAC, and require ELMO (engulfment and cell motility) proteins for function. The N-terminal RAS-binding domain (RBD) of ELMO (ELMORBD) interacts with RHOG to modulate DOCK1/2 activity. Here, we determine the cryo-EM structures of DOCK2−ELMO1 alone, and as a ternary complex with RAC1, together with the crystal structure of a RHOG−ELMO2RBD complex. The binary DOCK2−ELMO1 complex adopts a closed, auto-inhibited conformation. Relief of auto-inhibition to an active, open state, due to a conformational change of the ELMO1 subunit, exposes binding sites for RAC1 on DOCK2DHR2, and RHOG and BAI GPCRs on ELMO1. Our structure explains how up-stream effectors, including DOCK2 and ELMO1 phosphorylation, destabilise the auto-inhibited state to promote an active GEF.

Highlights

DOCK proteins are multidomain guanine nucleotide exchange factors (GEFs) for RHO GTPases that regulate intracellular actin dynamics
The molecular weight of the complex of ~600 kDa estimated by size exclusion chromatography (Supplementary Fig. 1b) indicated the formation of a tetramer formed of two DOCK2−ELMO1 protomers
This is consistent with the observation that DOCK2 homo-dimerization is required for DOCK2-mediated RAC activation in vivo and for lymphocyte migration[34], and with previous DHR2 domain crystal structures[31,43,44]

Summary

Introduction

DOCK (dedicator of cytokinesis) proteins are multidomain guanine nucleotide exchange factors (GEFs) for RHO GTPases that regulate intracellular actin dynamics. RHO family small GTPases are critical regulators of cell motility, polarity, adhesion, cytoskeletal organization, proliferation, gene expression and apoptosis These diverse functions are stimulated by the active GTP-bound state of RHO proteins that engage a diverse array of effector proteins, thereby triggering down-stream signal transduction pathways[1,2]. Conversion of these biomolecular switches to the GTP-bound state is controlled by two families of guanine nucleotide exchange factors (GEFs); the Dbl family and the DOCK family[3,4,5,6]. All DOCK proteins contain a catalytic DHR2 domain of ~450 residues situated within their C-terminal region (DOCKDHR2)[13,15]

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