RabGEF1 regulates stem cell factor/c-Kit-mediated signaling events and biological responses in mast cells.
We recently reported that RabGEF1 is a negative regulator of high-affinity Fc receptor for IgE (Fc epsilonRI)-dependent mast cell activation and that mice lacking RabGEF1 develop severe skin inflammation and increased numbers of dermal mast cells. To better understand how RabGEF1 can regulate signaling events and biological responses in mast cells, we examined the responses of bone marrow-derived cultured mast cells (BMCMCs) from wild-type (+/+) and Rabgef1 knockout (-/-) mice after stimulation with the c-Kit ligand, stem cell factor (SCF), an important regulator of mast cell development, survival, proliferation, and activation. We found that RabGEF1-deficient mast cells exhibited enhanced and prolonged activation of Ras and extracellular regulated kinase, and significantly elevated IL-6 secretion, after stimulation with SCF. SCF-induced activation of c-Jun N-terminal kinase was increased in Rabgef1-/- BMCMCs, but without corresponding significant increases in SCF-induced migration or adhesion. SCF-mediated activation of the survival-enhancing kinase, Akt, also was increased in Rabgef1-/- BMCMCs, and these cells had a survival advantage over their +/+ counterparts in vitro. Despite enhanced Ras activation in the absence of RabGEF1, SCF-induced proliferation was lower in Rabgef1-/- BMCMCs compared with their +/+ counterparts. Finally, we found that c-Kit internalization was delayed in the absence of RabGEF1, probably reflecting a positive role for RabGEF1 in the regulation of endocytic events, and that infection of Rabgef1-/- BMCMCs with a wild-type RabGEF1 lentiviral construct normalized c-Kit internalization to the levels seen in +/+ BMCMCs. Thus, RabGEF1 plays a critical role in the regulation of SCF/c-Kit-mediated signaling events and biological responses in mast cells.
Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5324, USA.
Janet
J
Kalesnikoff
Eon J
EJ
Rios
Ching-Cheng
CC
Chen
Susumu
S
Nakae
Brian A
BA
Zabel
Eugene C
EC
Butcher
Mindy
M
Tsai
See-Ying
SY
Tam
Stephen J
SJ
Galli
D000818:Animals; D001854:Bone Marrow Cells / Q000187:drug effects / Q000378:metabolism; D002448:Cell Adhesion / Q000235:genetics; D002465:Cell Movement / Q000235:genetics; D049109:Cell Proliferation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005822:Genetic Vectors; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000502:physiology*; D015850:Interleukin-6 / Q000378:metabolism; D016086:Lentivirus / Q000235:genetics; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D008407:Mast Cells / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism*; D015398:Signal Transduction; D019089:Stem Cell Factor / Q000378:metabolism* / Q000494:pharmacology; D014162:Transfection; D018631:ras Proteins / Q000378:metabolism
D020662:Guanine Nucleotide Exchange Factors; D015850:Interleukin-6; C510870:RabGEF1 protein, mouse; D019089:Stem Cell Factor; D019009:Proto-Oncogene Proteins c-kit; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D048670:MAP Kinase Kinase 4; D018631:ras Proteins