Pak1 regulates multiple c-Kit mediated Ras-MAPK gain-in-function phenotypes in Nf1+/- mast cells

Blood. 2008 Dec 1;112(12):4646-54. doi: 10.1182/blood-2008-04-155085. Epub 2008 Sep 2.

Abstract

Neurofibromatosis type 1 (NF1) is a common genetic disorder caused by mutations in the NF1 locus, which encodes neurofibromin, a negative regulator of Ras. Patients with NF1 develop numerous neurofibromas, which contain many inflammatory mast cells that contribute to tumor formation. Subsequent to c-Kit stimulation, signaling from Ras to Rac1/2 to the MAPK pathway appears to be responsible for multiple hyperactive mast cell phenotypes; however, the specific effectors that mediate these functions remain uncertain. p21-activated kinase 1 (Pak1) is a downstream mediator of Rac1/2 that has been implicated as a positive regulator of MAPK pathway members and is a modulator of cell growth and cytoskeletal dynamics. Using an intercross of Pak 1(-/-) mice with Nf1(+/-) mice, we determined that Pak1 regulates hyperactive Ras-dependent proliferation via a Pak1/Erk pathway, whereas a Pak1/p38 pathway is required for the increased migration in Nf1(+/-) mast cells. Furthermore, we confirmed that loss of Pak1 corrects the dermal accumulation of Nf1(+/-) mast cells in vivo to levels found in wild-type mice. Thus, Pak1 is a novel mast cell mediator that functions as a key node in the MAPK signaling network and potential therapeutic target in NF1 patients.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Biomarkers / metabolism
  • Cell Differentiation / genetics
  • Cell Proliferation
  • Cells, Cultured
  • Genes, Neurofibromatosis 1* / physiology
  • Heterozygote
  • Mast Cells / metabolism*
  • Mast Cells / pathology
  • Mast Cells / physiology
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Mitogen-Activated Protein Kinases / metabolism
  • Mitogen-Activated Protein Kinases / physiology*
  • Neurofibromatosis 1 / genetics
  • Neurofibromatosis 1 / metabolism
  • Neurofibromatosis 1 / pathology
  • Neurofibromin 1 / metabolism
  • Phenotype
  • Proto-Oncogene Proteins c-kit / genetics
  • Proto-Oncogene Proteins c-kit / metabolism
  • Proto-Oncogene Proteins c-kit / physiology*
  • Proto-Oncogene Proteins p21(ras) / genetics
  • Proto-Oncogene Proteins p21(ras) / metabolism
  • Proto-Oncogene Proteins p21(ras) / physiology*
  • Signal Transduction / genetics
  • Signal Transduction / physiology
  • p21-Activated Kinases / genetics
  • p21-Activated Kinases / metabolism
  • p21-Activated Kinases / physiology*

Substances

  • Biomarkers
  • Neurofibromin 1
  • Proto-Oncogene Proteins c-kit
  • Pak1 protein, mouse
  • p21-Activated Kinases
  • Mitogen-Activated Protein Kinases
  • Proto-Oncogene Proteins p21(ras)