Program in Molecular Medicine
*Adaptor Proteins, Signal Transducing; Amino Acid Sequence; Animals; Base Sequence; Binding Sites; Caenorhabditis elegans; DNA Primers; DNA, Complementary; Drosophila melanogaster; GRB2 Adaptor Protein; Humans; Molecular Sequence Data; Photoreceptors, Invertebrate; Protein Binding; Proteins; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-cbl; Proto-Oncogenes; Receptor, Epidermal Growth Factor; Sequence Homology, Amino Acid; *Ubiquitin-Protein Ligases; src Homology Domains
Life Sciences | Medicine and Health Sciences
The human proto-oncogene product c-Cbl and a similar protein in Caenorhabditis elegans (Sli-1) contain a proline-rich COOH-terminal region that binds Src homology 3 (SH3) domains of proteins such as the adapter Grb2. Cb1-Grb2 complexes can be recruited to tyrosine-phosphorylated epidermal growth factor (EGF) receptors through the SH2 domain of Grb2. Here we identify by molecular cloning a Drosophila cDNA encoding a protein (Drosophila Cbl [D-Cbl]) that shows high sequence similarity to the N-terminal region of human c-Cbl but lacks proline-rich sequences and fails to bind Grb2. Nonetheless, in COS-1 cells, expression of hemagglutinin epitope-tagged D-Cbl results in its coimmunoprecipitation with EGF receptors in response to EGF. EGF also caused tyrosine phosphorylation of D-Cbl in such cells, but no association of phosphatidylinositol 3-kinase was detected in assays using anti-p85 antibody. A point mutation in D-Cbl (G305E) that suppresses the negative regulation of LET-23 by the Cbl homolog Sli-1 in C. elegans prevented tyrosine phosphorylation of D-Cbl as well as binding to the liganded EGF receptor in COS-1 cells. Colocalization of EGF receptors with both endogenous c-Cbl or expressed D-Cbl in endosomes of EGF-treated COS-1 cells is also demonstrated by immunofluorescence microscopy. In lysates of adult transgenic Drosophila melanogaster, GST-DCbl binds to the tyrosine-phosphorylated 150-kDa torso-DER chimeric receptor. Expression of D-Cbl directed by the sevenless enhancer in intact Drosophila compromises severely the development of the R7 photoreceptor neuron. These data suggest that despite the lack of Grb2 binding sites, D-Cbl functions as a negative regulator of receptor tyrosine kinase signaling in the Drosophila eye by a mechanism that involves its association with EGF receptors or other tyrosine kinases.
Mol Cell Biol. 1997 Apr;17(4):2217-25.
Molecular and cellular biology
Meisner H, Daga A, Buxton JM, Fernandez B, Chawla A, Banerjee U, Czech MP. (1997). Interactions of Drosophila Cbl with epidermal growth factor receptors and role of Cbl in R7 photoreceptor cell development. Open Access Articles. Retrieved from https://escholarship.umassmed.edu/oapubs/1452