Ret oncogene signal transduction via a IRS-2/PI 3-kinase/PKB and a SHC/Grb-2 dependent pathway: possible implication for transforming activity in NIH3T3 cells

Mol Cell Endocrinol. 2000 Sep 25;167(1-2):69-76. doi: 10.1016/s0303-7207(00)00283-5.

Abstract

Multiple endocrine neoplasia 2A (MEN 2A) is an inherited disease caused by mutations of the Ret proto-oncogene. Although many different Ret mutations have been described, little is known about the signaling pathways triggered by the Ret oncogene. In this study, we have determined the signaling properties of a Ret-9bp duplication encoding amino acids 634-636, which was recently identified in a patient with all clinical features of the MEN 2A syndrome. The Ret-9bp duplication leads to constitutive activation of the Ret tyrosine kinase. Furthermore, Ret-9bp increased mitogenic and transforming activity demonstrated by thymidine incorporation as well as colony formation in soft agar. Studying intracellular signaling pathways, which may be involved in malignant transformation of Ret-9bp expressing NIH3T3 cells, we could demonstrate Ret-9bp dependent phosphorylation of insulin receptor substrate-2 (IRS-2) with consecutive activation of phosphatidylinositol 3-kinase (PI 3-kinase) and protein kinase B (PKB/AKT). Moreover, Ret-9bp induces phosphorylation of SHC resulting in growth factor receptor binding protein-2 (Grb-2) binding and activation of the mitogen activating protein (MAP) kinase pathway. In addition to these postreceptor cytoplasmic signaling events, we have studied nuclear signal by Ret-9bp and found activation of c-jun and jun-D, two members of the jun/AP-1 family of transcription factors. In summary, an oncogenic 9bp duplication of Ret causes Ret dimer formation and ligand independent activation of the tyrosine kinase. Besides the signaling steps leading to MAPK activation, we could demonstrate that Ret-9bp induced constitutive activation of a signaling pathway involving IRS-2, PI 3-kinase and PKB/AKT which could transduce the oncogenic Ret signal to increased gene transcription via activation of the jun/AP-1 transcription factor family.

MeSH terms

  • 3T3 Cells
  • Adaptor Proteins, Signal Transducing*
  • Adaptor Proteins, Vesicular Transport*
  • Amino Acid Motifs
  • Animals
  • Blotting, Western
  • Cell Transformation, Neoplastic
  • Drosophila Proteins*
  • Enzyme Induction
  • ErbB Receptors / metabolism
  • GRB2 Adaptor Protein
  • Humans
  • Insulin Receptor Substrate Proteins
  • Intracellular Signaling Peptides and Proteins
  • Mice
  • Multiple Endocrine Neoplasia Type 2a / genetics
  • Mutation
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Phosphoproteins / metabolism*
  • Phosphorylation
  • Protein-Serine-Threonine Kinases / metabolism
  • Proteins / metabolism*
  • Proto-Oncogene Proteins / biosynthesis
  • Proto-Oncogene Proteins / genetics*
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-akt
  • Proto-Oncogene Proteins c-jun / metabolism
  • Proto-Oncogene Proteins c-ret
  • Receptor Protein-Tyrosine Kinases / biosynthesis
  • Receptor Protein-Tyrosine Kinases / genetics*
  • Receptor Protein-Tyrosine Kinases / metabolism
  • Shc Signaling Adaptor Proteins
  • Signal Transduction*
  • Src Homology 2 Domain-Containing, Transforming Protein 1
  • Transfection
  • src Homology Domains

Substances

  • Adaptor Proteins, Signal Transducing
  • Adaptor Proteins, Vesicular Transport
  • Drosophila Proteins
  • GRB2 Adaptor Protein
  • GRB2 protein, human
  • Grb2 protein, mouse
  • IRS2 protein, human
  • Insulin Receptor Substrate Proteins
  • Intracellular Signaling Peptides and Proteins
  • Irs2 protein, mouse
  • Phosphoproteins
  • Proteins
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-jun
  • SHC1 protein, human
  • Shc Signaling Adaptor Proteins
  • Shc1 protein, mouse
  • Src Homology 2 Domain-Containing, Transforming Protein 1
  • Phosphatidylinositol 3-Kinases
  • ErbB Receptors
  • Proto-Oncogene Proteins c-ret
  • Receptor Protein-Tyrosine Kinases
  • Ret protein, Drosophila
  • Ret protein, mouse
  • AKT1 protein, human
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt