title: Pak1 regulates multiple c-Kit mediated Ras-MAPK gain-in-function phenotypes in Nf1+/- mast cells.
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.
authors.affiliation: Department of Microbiology and Immunology, Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis 46202, USA.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: McDaniel
authors.forename: Jayme D
authors.initials: JD
authors.lastname: Allen
authors.forename: Su-Jung
authors.initials: SJ
authors.lastname: Park
authors.forename: Zahara M
authors.initials: ZM
authors.lastname: Jaffer
authors.forename: Elizabeth G
authors.initials: EG
authors.lastname: Michels
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Burgin
authors.forename: Shi
authors.initials: S
authors.lastname: Chen
authors.forename: Waylan K
authors.initials: WK
authors.lastname: Bessler
authors.forename: Clemens
authors.initials: C
authors.lastname: Hofmann
authors.forename: David A
authors.initials: DA
authors.lastname: Ingram
authors.forename: Jonathan
authors.initials: J
authors.lastname: Chernoff
authors.forename: D Wade
authors.initials: DW
authors.lastname: Clapp