MARK3-mediated phosphorylation of ARHGEF2 couples microtubules to the actin cytoskeleton to establish cell polarity

Sci Signal. 2017 Oct 31;10(503):eaan3286. doi: 10.1126/scisignal.aan3286.


The PAR-1-MARK pathway controls cell polarity through the phosphorylation of microtubule-associated proteins. Rho-Rac guanine nucleotide exchange factor 2 (ARHGEF2), which activates Ras homolog family member A (RHOA), is anchored to the microtubule network and sequestered in an inhibited state through binding to dynein light chain Tctex-1 type 1 (DYNLT1). We showed in mammalian cells that liver kinase B1 (LKB1) activated the microtubule affinity-regulating kinase 3 (MARK3), which in turn phosphorylated ARHGEF2 at Ser151 This modification disrupted the interaction between ARHGEF2 and DYNLT1 by generating a 14-3-3 binding site in ARHGEF2, thus causing ARHGEF2 to dissociate from microtubules. Phosphorylation of ARHGEF2 by MARK3 stimulated RHOA activation and the formation of stress fibers and focal adhesions, and was required for organized cellular architecture in three-dimensional culture. Protein phosphatase 2A (PP2A) dephosphorylated Ser151 in ARHGEF2 to restore the inhibited state. Thus, we have identified a regulatory switch controlled by MARK3 that couples microtubules to the actin cytoskeleton to establish epithelial cell polarity through ARHGEF2.

MeSH terms

  • AMP-Activated Protein Kinase Kinases
  • Actin Cytoskeleton / metabolism*
  • Animals
  • COS Cells
  • Cell Polarity / physiology*
  • Chlorocebus aethiops
  • Dyneins / genetics
  • Dyneins / metabolism
  • Focal Adhesions / metabolism
  • HEK293 Cells
  • Humans
  • Microtubules / metabolism*
  • Phosphorylation
  • Protein Phosphatase 2 / genetics
  • Protein Phosphatase 2 / metabolism
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism*
  • Rho Guanine Nucleotide Exchange Factors / genetics
  • Rho Guanine Nucleotide Exchange Factors / metabolism*
  • Serine / metabolism
  • Stress Fibers / metabolism
  • rhoA GTP-Binding Protein / genetics
  • rhoA GTP-Binding Protein / metabolism


  • ARHGEF2 protein, human
  • DYNLT1 protein, human
  • Rho Guanine Nucleotide Exchange Factors
  • RHOA protein, human
  • Serine
  • MARK3 protein, human
  • Protein Serine-Threonine Kinases
  • STK11 protein, human
  • AMP-Activated Protein Kinase Kinases
  • Protein Phosphatase 2
  • Dyneins
  • rhoA GTP-Binding Protein