Gab2 is involved in differential phosphoinositide 3-kinase signaling by two splice forms of c-Kit

J Biol Chem. 2008 Oct 10;283(41):27444-27451. doi: 10.1074/jbc.M709703200. Epub 2008 Aug 11.

Abstract

The stem cell factor receptor/c-Kit plays an important physiological role in hematopoiesis, melanogenesis, and gametogenesis. It has also been implicated in numerous human malignancies. Signal transduction pathways shown to be of importance for c-Kit-mediated transformation include the phosphoinositide 3-kinase (PI3K)/Akt pathway. We have previously shown that two alternative splice forms of c-Kit, denoted GNNK(-) and GNNK(+), mediate distinctively different signals. In this study, we found that in the hematopoietic cell line Ba/F3, GNNK(-) c-Kit mediates a substantially stronger activation of PI3K/Akt than GNNK(+) c-Kit. This difference in signaling was shown to be dependent on the association of the scaffolding protein Gab2 with c-Kit, and Src-mediated phosphorylation of Gab2 was shown to be to be independent of the direct association of PI3K with c-Kit. Furthermore, proliferation and survival of Ba/F3 cells expressing a mutant of c-Kit that fails to bind to PI3K directly were slightly decreased compared with wild-type c-Kit-expressing cells. Using small interfering RNA technology, we further verified a role of Gab2 in inducing activation of PI3K/Akt downstream of c-Kit. To summarize, we show that PI3K activation by c-Kit is both splice form-dependent and cell type-specific. Furthermore, activation of PI3K by c-Kit is dependent both on the direct PI3K-binding site in c-Kit and on the phosphorylation of Gab2. The fact that c-Kit has been found mutated in numerous human malignancies, including acute myeloid leukemia, and that Gab2 is often overexpressed in acute myeloid leukemia suggests a potential role of Gab2-mediated PI3K activation in transformation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Alternative Splicing* / genetics
  • Animals
  • Cell Transformation, Neoplastic / genetics
  • Cell Transformation, Neoplastic / metabolism*
  • Enzyme Activation / genetics
  • Gametogenesis / genetics
  • Hematopoiesis / genetics
  • Humans
  • Leukemia, Myeloid, Acute / genetics
  • Leukemia, Myeloid, Acute / metabolism*
  • Mice
  • NIH 3T3 Cells
  • Phosphatidylinositol 3-Kinases / genetics
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Phosphoproteins / genetics
  • Phosphoproteins / metabolism*
  • Phosphorylation
  • Proto-Oncogene Proteins c-akt / genetics
  • Proto-Oncogene Proteins c-akt / metabolism
  • Proto-Oncogene Proteins c-kit / genetics
  • Proto-Oncogene Proteins c-kit / metabolism*
  • RNA Splice Sites / genetics
  • Signal Transduction* / genetics
  • src-Family Kinases / genetics

Substances

  • Adaptor Proteins, Signal Transducing
  • GAB2 protein, human
  • Gab2 protein, mouse
  • Phosphoproteins
  • RNA Splice Sites
  • Phosphatidylinositol 3-Kinases
  • Proto-Oncogene Proteins c-kit
  • src-Family Kinases
  • Proto-Oncogene Proteins c-akt