Crkl is complexed with tyrosine-phosphorylated Cbl in Ph-positive leukemia.
The deregulated tyrosine kinase activity of the Bcr/Abl protein has been causally linked to the development of Philadelphia (Ph) chromosome-positive leukemia in mice and man. Abnormally tyrosine-phosphorylated substrates of the Bcr/Abl kinase in Ph-positive cells are likely to contribute to leukemogenesis by interfering with normal signal transduction pathways. We have previously shown that the adaptor molecule Crkl is a major in vivo substrate for the Bcr/Abl tyrosine kinase, and it is thought to connect Bcr/Abl with downstream effectors. In the current study, a tyrosine-phosphorylated protein with a molecular mass of approximately 120 kDa was identified which binds only to the Crkl Src homology 2 (SH2) domain in cells, including Ph-positive patient material, containing an active Bcr/Abl protein. We demonstrate here that this protein is Cbl, originally discovered as an oncogene which induces B-cell and myeloid leukemias in mice. The Crkl SH2 domain binds specifically to Cbl. The Src homology 3 (SH3) domains of Crkl do not bind to Cbl, but do bind Bcr/Abl. These findings suggest the existence of a trimolecular complex involving Bcr/Abl, Crkl, and Cbl and are consistent with a model in which Crkl mediates the oncogenic signal of Bcr/Abl to Cbl.
de Jong
R
R
Department of Pathology, Childrens Hospital of Los Angeles, California 90027, USA.
ten Hoeve
J
J
Heisterkamp
N
N
Groffen
J
J
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D016044:Fusion Proteins, bcr-abl / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D004915:Leukemia, Erythroblastic, Acute; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000097:blood / Q000378:metabolism*; D051379:Mice; D008970:Molecular Weight; D009687:Nuclear Proteins / Q000302:isolation & purification / Q000378:metabolism*; D050722:Oncogene Protein v-cbl; D010766:Phosphorylation; D019000:Phosphotyrosine; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015682:Retroviridae Proteins, Oncogenic / Q000302:isolation & purification / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis
D048868:Adaptor Proteins, Signal Transducing; C082869:CRKL protein; D009687:Nuclear Proteins; D050722:Oncogene Protein v-cbl; D011993:Recombinant Fusion Proteins; D015682:Retroviridae Proteins, Oncogenic; D019000:Phosphotyrosine; D014443:Tyrosine; D005982:Glutathione Transferase; D016044:Fusion Proteins, bcr-abl