Phosphorylation of RhoB by CK1 impedes actin stress fiber organization and epidermal growth factor receptor stabilization

Exp Cell Res. 2008 Sep 10;314(15):2811-21. doi: 10.1016/j.yexcr.2008.06.011. Epub 2008 Jun 18.

Abstract

RhoB is a small GTPase implicated in cytoskeletal organization, EGF receptor trafficking and cell transformation. It is an immediate-early gene, regulated at many levels of its biosynthetic pathway. Herein we show that the serine/threonine protein kinase CK1 phosphorylates RhoB in vitro but not RhoA or RhoC. With the use of specific CK1 inhibitors, IC261 and D4476, we show that the kinase phosphorylates also RhoB in HeLa cells. Mass spectrometry analysis demonstrates that RhoB is monophosphorylated by CK1, in its C-terminal end, on serine 185. The substitution of Ser185 by Ala dramatically inhibited the phosphorylation of RhoB in cultured cells. Lastly we show that the inhibition of CK1 activates RhoB and promotes RhoB dependent actin fiber formation and EGF-R level. Our data provide the first demonstration of RhoB phosphorylation and indicate that this post-translational maturation would be a novel critical mechanism to control the RhoB functions.

MeSH terms

  • Actin Cytoskeleton / metabolism
  • Actin Cytoskeleton / ultrastructure
  • Actins / metabolism*
  • Amino Acid Sequence / physiology
  • Amino Acid Substitution / physiology
  • Casein Kinase Ialpha / antagonists & inhibitors
  • Casein Kinase Ialpha / metabolism*
  • Enzyme Activation / drug effects
  • Enzyme Activation / physiology
  • Enzyme Inhibitors / pharmacology
  • ErbB Receptors / metabolism*
  • HeLa Cells
  • Humans
  • Molecular Sequence Data
  • Phosphorylation
  • Protein Processing, Post-Translational / physiology
  • Protein-Serine-Threonine Kinases / antagonists & inhibitors
  • Protein-Serine-Threonine Kinases / metabolism*
  • Sequence Homology, Amino Acid
  • Serine / metabolism
  • Stress Fibers / metabolism*
  • Stress Fibers / ultrastructure
  • rhoB GTP-Binding Protein / chemistry
  • rhoB GTP-Binding Protein / metabolism*

Substances

  • Actins
  • Enzyme Inhibitors
  • Serine
  • ErbB Receptors
  • Casein Kinase Ialpha
  • Protein-Serine-Threonine Kinases
  • rhoB GTP-Binding Protein