p120cbl is a major substrate of tyrosine phosphorylation upon B cell antigen receptor stimulation and interacts in vivo with Fyn and Syk tyrosine kinases, Grb2 and Shc adaptors, and the p85 subunit of phosphatidylinositol 3-kinase.
We and others have demonstrated that the c-cbl proto-oncogene product is one of the earliest targets of tyrosine phosphorylation upon T cell receptor stimulation. Given the similarities in the B and T lymphocyte antigen receptors, and the induction of pre-B leukemias in mice by the v-cbl oncogene, we examined the potential involvement of Cbl in B cell receptor signaling. We demonstrate prominent and early tyrosine phosphorylation of Cbl upon stimulation of human B cell lines through surface IgM. Cbl was associated in vivo with Fyn and, to a lesser extent, other Src family kinases. B cell activation also induced a prominent association of Cbl with Syk tyrosine kinase. A substantial fraction of Cbl was constitutively associated with Grb2 and this interaction was mediated by Grb2 SH3 domains. Tyrosine-phosphorylated Shc, which prominently associated with Grb2, was detected in association with Cbl in activated B cells. Thus, Grb2 and Shc adaptors, which associate with immunoreceptor tyrosine based activation motifs, may link Cbl to the B cell receptor. B cell activation also induced a prominent association between Cbl and the p85 subunit of phosphatidylinositol (PI) 3-kinase resulting in the association of a substantial fraction of PI 3-kinase activity with Cbl. Thus, Cbl is likely to play an important role to couple the B cell receptor to the PI 3-kinase pathway. Our results strongly suggest a role for p120cbl in signaling downstream of the B cell receptor and support the idea that Cbl participates in a general signal transduction function downstream of the immune cell surface receptors.
Panchamoorthy
G
G
Lymphocyte Biology Section, Division of Rheumatology and Immunology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
Fukazawa
T
T
Miyake
S
S
Soltoff
S
S
Reedquist
K
K
Druker
B
B
Shoelson
S
S
Cantley
L
L
Band
H
H
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000502:physiology*; D002460:Cell Line; D004792:Enzyme Precursors / Q000378:metabolism; D051380:GRB2 Adaptor Protein; D005982:Glutathione Transferase; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D015448:Leukemia, B-Cell / Q000235:genetics; D046911:Macromolecular Substances; D051379:Mice; D050722:Oncogene Protein v-cbl; D009857:Oncogenes; D019869:Phosphatidylinositol 3-Kinases; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051076:Proto-Oncogene Proteins c-fyn; D011947:Receptors, Antigen, B-Cell / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015682:Retroviridae Proteins, Oncogenic / Q000378:metabolism*; D000072377:Syk Kinase; D018909:src Homology Domains
D048868:Adaptor Proteins, Signal Transducing; D004792:Enzyme Precursors; D051380:GRB2 Adaptor Protein; D005982:Glutathione Transferase; D047908:Intracellular Signaling Peptides and Proteins; D046911:Macromolecular Substances; D050722:Oncogene Protein v-cbl; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D011505:Protein-Tyrosine Kinases; D011506:Proteins; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D051076:Proto-Oncogene Proteins c-fyn; D011947:Receptors, Antigen, B-Cell; D011993:Recombinant Fusion Proteins; D015682:Retroviridae Proteins, Oncogenic; D000072377:Syk Kinase; C495948:GRB2 protein, human; C495949:Grb2 protein, mouse; C000715470:MAS1 protein, human; C494957:FYN protein, human; C494960:Fyn protein, mouse; C000606896:SYK protein, human; C000606897:Syk protein, mouse