[Cite as http://purl.org/au-research/grants/nhmrc/303208]
Dr Christine Thien
Prof Wallace Langdon
Brief description c-Cbl is a member of a multi-adaptor protein family that can interact with many signalling proteins via its different domains. Cbl proteins have been implicated as negative regulators of signalling pathways involving protein tyrosine kinases (PTKs). PTKs are enzymes which add phosphate groups to tyrosine residues on other protein substrates, and the process of tyrosine phosphorylation acts as a potent biochemical switch to turn signalling cascades on and off. Studies of Cbl-deficient (knockout) mice show that Cbl proteins are important in regulating the development of, and signalling by, cells of the immune system called T cells. c-Cbl knockout mice show greatly enhanced PTK-signalling responses and deregulated activity of a PTK called ZAP-70. The mechanism of this is not known, but analysis of a c-Cbl mutant mouse shows that this is not dependent on the tyrosine kinase binding (TKB) domain of c-Cbl. Therefore other functional domains of Cbl must be responsible for the increased signalling response in the c-Cbl knockout mouse. One candidate is the highly conserved RING finger domain which can modify Cbl-associated PTKs by addition of ubiquitin molecules. Ubiquitination of a protein often, but not always, leads to its degradation, and this could be how Cbl controls the strength and duration of signalling in T cells. However there may be other functions of the conserved RING finger yet to be identified. c-Cbl itself is prominently and very rapidly modified by tyrosine phosphorylation on tyrosine 737 by the Fyn PTK following T cell activation, but the role of this modification is not known and could also be essential for c-Cbl s function in T cells. We plan to investigate the roles of the RING finger domain and Fyn-mediated tyrosine phosphorylation in c-Cbl regulation of T cell signalling by analyzing knock-in mice that carry specific mutations disrupting the RING finger or tyrosine 737 in the c-Cbl gene.
Funding Amount $AUD 527,250.00
Funding Scheme NHMRC Project Grants
Standard Project Grant