Mechanistic insight into GPCR-mediated activation of the microtubule-associated RhoA exchange factor GEF-H1

Nat Commun. 2014 Sep 11;5:4857. doi: 10.1038/ncomms5857.

Abstract

The RhoGEF GEF-H1 can be sequestered in an inactive state on polymerized microtubules by the dynein motor light-chain Tctex-1. Phosphorylation of GEF-H1 Ser885 by PKA or PAK kinases creates an inhibitory 14-3-3-binding site. Here we show a new mode of GEF-H1 activation in response to the G-protein-coupled receptor (GPCR) ligands lysophosphatidic acid (LPA) or thrombin that is independent of microtubule depolymerization. LPA/thrombin stimulates disassembly of the GEF-H1:dynein multi-protein complex through the concerted action of Gα and Gβγ. Gα binds directly to GEF-H1 and displaces it from Tctex-1, while Gβγ binds to Tctex-1 and disrupts its interaction with the dynein intermediate chain, resulting in the release of GEF-H1. Full activation of GEF-H1 requires dephosphorylation of Ser885 by PP2A, which is induced by thrombin. The coordinated displacement of GEF-H1 from microtubules by G-proteins and its dephosphorylation by PP2A demonstrate a multistep GEF-H1 activation and present a unique mechanism coupling GPCR signalling to Rho activation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 14-3-3 Proteins / metabolism
  • Animals
  • Dyneins / metabolism*
  • GTP-Binding Protein alpha Subunits, G12-G13 / drug effects
  • GTP-Binding Protein alpha Subunits, G12-G13 / metabolism
  • GTP-Binding Protein beta Subunits / drug effects
  • GTP-Binding Protein beta Subunits / metabolism
  • GTP-Binding Protein gamma Subunits / drug effects
  • GTP-Binding Protein gamma Subunits / metabolism
  • Lysophospholipids / pharmacology
  • Mice
  • Mice, Knockout
  • Microtubules / metabolism*
  • Phosphorylation
  • Receptors, G-Protein-Coupled / drug effects
  • Receptors, G-Protein-Coupled / metabolism*
  • Rho Guanine Nucleotide Exchange Factors / drug effects
  • Rho Guanine Nucleotide Exchange Factors / metabolism*
  • Thrombin / pharmacology
  • p21-Activated Kinases / metabolism

Substances

  • 14-3-3 Proteins
  • Arhgef2 protein, mouse
  • Dynlt1b protein, mouse
  • GTP-Binding Protein beta Subunits
  • GTP-Binding Protein gamma Subunits
  • Lysophospholipids
  • Receptors, G-Protein-Coupled
  • Rho Guanine Nucleotide Exchange Factors
  • p21-Activated Kinases
  • Thrombin
  • Dyneins
  • GTP-Binding Protein alpha Subunits, G12-G13
  • lysophosphatidic acid