Enhanced phosphatidylinositol 3-kinase activity and high phosphorylation state of its downstream signalling molecules mediated by ret with the MEN 2B mutation.
We compared the intracellular signalling pathways through Ret tyrosine kinase activated by glial cell line-derived neurotrophic factor (GDNF), multiple endocrine neoplasia (MEN) 2A, or MEN 2B mutation. Tyrosine phosphorylation of Grb2-associated binder-1 (Gab1) and activation of phosphatidylinositol 3-kinase (PI 3-kinase) were induced at higher levels by GDNF stimulation or the MEN 2B mutation than by the MEN 2A mutation. Tyrosine-phosphorylated Gab1 was a major component that interacted with the active PI 3-kinase in vivo. In addition, we found that p62Dok and PKB/Akt were phosphorylated in a PI 3-kinase-dependent manner and the levels of their phosphorylation were significantly higher in the MEN 2B transfectant than in the MEN 2A transfectant. Tyrosine phosphorylation of p62Dok resulted in its complex formation with the Ras GTPase-activating protein (RasGAP) and the Nck adaptor protein. These findings thus suggested that high levels of activation of PI 3-kinase and of phosphorylation of its downstream signalling molecules may be associated with the clinical phenotype of MEN 2B.
Murakami
H
H
Department of Pathology, Nagoya University School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, 466-8550, Japan.
Iwashita
T
T
Asai
N
N
Shimono
Y
Y
Iwata
Y
Y
Kawai
K
K
Takahashi
M
M
D048868:Adaptor Proteins, Signal Transducing; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D004789:Enzyme Activation / Q000187:drug effects; D020690:GTPase-Activating Proteins; D051100:Glial Cell Line-Derived Neurotrophic Factor; D051097:Glial Cell Line-Derived Neurotrophic Factor Receptors; D006801:Humans; D018813:Multiple Endocrine Neoplasia Type 2a / Q000235:genetics; D018814:Multiple Endocrine Neoplasia Type 2b / Q000235:genetics*; D009154:Mutation; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins / Q000494:pharmacology; D009447:Neuroblastoma; D015513:Oncogene Proteins / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt; D051096:Proto-Oncogene Proteins c-ret; D016601:RNA-Binding Proteins; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection; D014407:Tumor Cells, Cultured; D020703:ras GTPase-Activating Proteins
D048868:Adaptor Proteins, Signal Transducing; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D020690:GTPase-Activating Proteins; D051100:Glial Cell Line-Derived Neurotrophic Factor; D051097:Glial Cell Line-Derived Neurotrophic Factor Receptors; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; D015513:Oncogene Proteins; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D019000:Phosphotyrosine; D017346:Protein Serine-Threonine Kinases; D011506:Proteins; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D051096:Proto-Oncogene Proteins c-ret; D016601:RNA-Binding Proteins; D020794:Receptor Protein-Tyrosine Kinases; D020703:ras GTPase-Activating Proteins; C489560:DOK1 protein, human; C098587:GAB1 protein, human; C074561:GAP-associated protein p62; C495039:GDNF protein, human; C078332:Nck protein; C416649:Ret protein, Drosophila; C494918:AKT1 protein, human