Physical and Functional Interaction of Fyn Tyrosine Kinase With a Brain-Enriched Rho GTPase-activating Protein TCGAP

J Biol Chem. 2006 Aug 18;281(33):23611-9. doi: 10.1074/jbc.M511205200. Epub 2006 Jun 15.


Fyn, a member of the Src family of tyrosine kinases, is implicated in both brain development and adult brain function. In the present study, we identified a Rho GTPase-activating protein (GAP), TCGAP (Tc10/Cdc42 GTPase-activating protein), as a novel Fyn substrate. TCGAP interacted with Fyn and was phosphorylated by Fyn, with Tyr-406 in the GAP domain as a major Fyn-mediated phosphorylation site. Fyn suppressed the GAP activity of wild-type TCGAP but not the Y406F mutant of TCGAP in a phosphorylation-dependent manner, suggesting that Fyn-mediated Tyr-406 phosphorylation negatively regulated the TCGAP activity. In situ hybridization analyses showed that TCGAP mRNA was expressed prominently in both immature and adult mouse brain, with high levels in cortex, corpus striatum, hippocampus, and olfactory bulb. Overexpression of wild-type TCGAP in PC12 cells suppressed nerve growth factor-induced neurite outgrowth, whereas a GAP-defective mutant of TCGAP enhanced the neurite outgrowth. Nerve growth factor enhanced tyrosine phosphorylation of TCGAP through activation of Src family kinases. These results suggest that TCGAP is involved in Fyn-mediated regulation of axon and dendrite outgrowth.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Substitution / genetics
  • Animals
  • Brain / embryology
  • Brain / enzymology*
  • Brain / metabolism
  • Cell Line
  • Enzyme Activation / physiology
  • GTPase-Activating Proteins / biosynthesis
  • GTPase-Activating Proteins / genetics
  • GTPase-Activating Proteins / metabolism*
  • GTPase-Activating Proteins / physiology
  • Gene Expression Regulation, Developmental
  • Growth Inhibitors / physiology
  • Humans
  • Nerve Growth Factor / antagonists & inhibitors
  • Nerve Growth Factor / physiology
  • Neurites / physiology
  • PC12 Cells
  • Phenylalanine / genetics
  • Phosphorylation
  • Proto-Oncogene Proteins c-fyn / chemistry*
  • Proto-Oncogene Proteins c-fyn / metabolism
  • Proto-Oncogene Proteins c-fyn / physiology*
  • Rats
  • Sorting Nexins
  • Subcellular Fractions / metabolism
  • Tyrosine / genetics
  • rho GTP-Binding Proteins / metabolism*


  • ARHGAP33 protein, human
  • GTPase-Activating Proteins
  • Growth Inhibitors
  • Sorting Nexins
  • Tyrosine
  • Phenylalanine
  • Nerve Growth Factor
  • FYN protein, human
  • Proto-Oncogene Proteins c-fyn
  • rho GTP-Binding Proteins