The scaffolding adapter Gab2, via Shp-2, regulates kit-evoked mast cell proliferation by activating the Rac/JNK pathway.
The scaffolding adapter Gab2 mediates cell signaling and responses evoked by various extracellular stimuli including several growth factors. Kit, the receptor for stem cell factor (SCF), plays a critical role in the proliferation and differentiation of a variety of cell types, including mast cells. Kit, via Tyr(567) and Tyr(719), activates Src family kinases (SFK) and PI3K respectively, which converge on the activation of a Rac/JNK pathway required for mast cell proliferation. However, how Kit Tyr(567) signals to Rac/JNK is not well understood. By analyzing Gab2(-/-) mast cells, we find that Gab2 is required for SCF-evoked proliferation, activation of Rac/JNK, and Ras. Upon Kit activation in wild-type mast cells, Gab2 becomes tyrosyl-phosphorylated and associates with Kit and Shp-2. Tyr(567), an SFK binding site in Kit, and SFK activity were required for Gab2 tyrosyl phosphorylation and association with Shp-2. By re-expressing Gab2 or a Gab2 mutant that cannot bind Shp-2 in Gab2(-/-) mast cells or acutely by deleting Shp-2 in mast cells, we found that Gab2 requires Shp-2 for SCF-evoked Rac/JNK, Ras activation, and mast cell proliferation. Lastly, by analyzing mast cells from mice with compound Gab2 and Kit Y719F mutations (i.e., Gab2(-/-): KitY719F/Y719F mice), we find that Gab2, acting in a parallel pathway to PI3K from Kit Tyr(719), regulates mast cell proliferation and development in specific tissues. Our data show that Gab2 via Shp-2 is critical for transmitting signals from Kit Tyr(567) to activate the Rac/JNK pathway controlling mast cell proliferation, which likely contributes to mast cell development in specific tissues.
Yu
Min
M
Cancer Biology Program, Division of Hematology/Oncology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA.
Luo
Jincai
J
Yang
Wentian
W
Wang
Yongping
Y
Mizuki
Masao
M
Kanakura
Yuzuru
Y
Besmer
Peter
P
Neel
Benjamin G
BG
Gu
Haihua
H
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D017209:Apoptosis; D049109:Cell Proliferation; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology*; D048670:MAP Kinase Kinase 4 / Q000378:metabolism / Q000502:physiology*; D008407:Mast Cells / Q000166:cytology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000502:physiology*; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D017027:Protein Tyrosine Phosphatases / Q000502:physiology*; D019009:Proto-Oncogene Proteins c-kit / Q000502:physiology*; D015398:Signal Transduction; D020744:rac GTP-Binding Proteins / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D047908:Intracellular Signaling Peptides and Proteins; D048670:MAP Kinase Kinase 4; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D017027:Protein Tyrosine Phosphatases; D019009:Proto-Oncogene Proteins c-kit; D020744:rac GTP-Binding Proteins; C490894:Gab2 protein, mouse; C516725:Ptpn11 protein, mouse