Phosphotyrosine binding domain-dependent upregulation of the platelet- derived growth factor receptor α signaling cascade by transforming mutants of Cbl: Implications for Cbl's function and oncogenicity

David P. Bonita, Sachiko Miyake, Mark L. Lupher, Wallace Y. Langdon, Hamid Band

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Abstract

Recent studies have demonstrated that Cbl, the 120-kDa protein product of the c-cbl proto-oncogene, serves as a substrate of a number of receptor- coupled tyrosine kinases and forms complexes with SH3 and SH2 domain- containing proteins, pointing to its role in signal transduction. Based on genetic evidence that the Caenorhabditis elegans Cbl homolog, SLI-1, functions as a negative regulator of the LET-23 receptor tyrosine kinase and our demonstration that Cbl's evolutionarily conserved N-terminal transforming region (Cbl-N; residues 1 to 357) harbors a phosphotyrosine binding (PTB) domain that binds to activated ZAP-70 tyrosine kinase, we examined the possibility that oncogenie Cbl mutants may activate mitogenic signaling by deregulating cellular tyrosine kinase machinery. Here, we show that expression of Cbl-N and two other transforming Cbl mutants (CblY368Δ and Cbl366-382Δ or Cbl70Z), but not wild-type Cbl, in NIH 3T3 fibroblasts leads to enhancement of endogenous tyrosine kinase signaling. We identified platelet-derived growth factor receptor a (PDGFRα) as one target of mutant Cbl-induced deregulation. In mutant Cbl transfectants, PDGFRα was hyperphosphorylated and constitutively complexed with a number of SH2 domain- containing proteins. PDGFRα hyperphosphorylation and enhanced proliferation of mutant Cbl-transfected NIH 3T3 cells were drastically reduced upon serum starvation, and PDGF-AA substituted for the maintenance of these traits. PDGF-AA stimulation of serum-starved Cbl transfectants induced the in vivo association of transfected Cbl proteins with PDGFRα. In vitro, Cbl-N directly bound to PDGFRα derived from PDGF-AA-stimulated cells but not to that from unstimulated cells, and this binding was abrogated by a point mutation (G306E) corresponding to a loss-of-function mutation in SLI-1. The Cbl-N/G306E mutant protein, which failed to induce enhanced growth and transformation of NIH 3T3 cells; also failed to induce hyperphosphorylation of PDGFRα. Altogether, these findings identify a novel mechanism of Cbl's physiological function and oncogenesis, involving its PTB domain-dependent direct interaction with cellular tyrosine kinases.

Original languageEnglish (US)
Pages (from-to)4597-4610
Number of pages14
JournalMolecular and cellular biology
Volume17
Issue number8
StatePublished - Aug 1 1997

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Platelet-Derived Growth Factor Receptors
Phosphotyrosine
Up-Regulation
Protein-Tyrosine Kinases
src Homology Domains
NIH 3T3 Cells
Receptor Protein-Tyrosine Kinases
Proto-Oncogene Proteins c-cbl
ZAP-70 Protein-Tyrosine Kinase
Linear Energy Transfer
Proteins
Caenorhabditis elegans
Mutant Proteins
Starvation
Serum
Point Mutation
Signal Transduction
Carcinogenesis
Fibroblasts
Maintenance

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

Cite this

Phosphotyrosine binding domain-dependent upregulation of the platelet- derived growth factor receptor α signaling cascade by transforming mutants of Cbl : Implications for Cbl's function and oncogenicity. / Bonita, David P.; Miyake, Sachiko; Lupher, Mark L.; Langdon, Wallace Y.; Band, Hamid.

In: Molecular and cellular biology, Vol. 17, No. 8, 01.08.1997, p. 4597-4610.

Research output: Contribution to journalArticle

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