MAP4K4 Is a Threonine Kinase That Phosphorylates FARP1

ACS Chem Biol. 2015 Dec 18;10(12):2667-71. doi: 10.1021/acschembio.5b00679. Epub 2015 Sep 30.

Abstract

Mitogen-activated protein kinase 4 (MAP4K4) regulates the MEK kinase cascade and is implicated in cytoskeletal rearrangement and migration; however, identifying MAP4K4 substrates has remained a challenge. To ascertain MAP4K4-dependent phosphorylation events, we combined phosphoproteomic studies of MAP4K4 inhibition with in vitro assessment of its kinase specificity. We identified 235 phosphosites affected by MAP4K4 inhibition in cells and found that pTP and pSP motifs were predominant among them. In contrast, in vitro assessment of kinase specificity showed that MAP4K4 favors a pTL motif. We showed that MAP4K4 directly phosphorylates and coimmunoprecipitates with FERM, RhoGEF, and pleckstrin domain-containing protein 1 (FARP1). MAP4K4 inhibition in SH-SY5Y cells increases neurite outgrowth, a process known to involve FARP1. As FARP1 and MAP4K4 both contribute to cytoskeletal rearrangement, the results suggest that MAP4K4 exerts some of its effects on the cytoskeleton via phosphorylation of FARP1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biological Assay
  • Hep G2 Cells
  • Humans
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Molecular Structure
  • Phosphorylation
  • Protein Serine-Threonine Kinases / metabolism*
  • Proteomics
  • Rho Guanine Nucleotide Exchange Factors / metabolism*

Substances

  • FARP1 protein, human
  • Intracellular Signaling Peptides and Proteins
  • Rho Guanine Nucleotide Exchange Factors
  • MAP4K4 protein, human
  • Protein Serine-Threonine Kinases