PubMed:7513045 JSONTXT

{"project":"AIMed","denotations":[{"id":"T1","span":{"begin":19,"end":22},"obj":"protein"},{"id":"T2","span":{"begin":88,"end":94},"obj":"protein"},{"id":"T3","span":{"begin":96,"end":99},"obj":"protein"},{"id":"T4","span":{"begin":163,"end":167},"obj":"protein"},{"id":"T5","span":{"begin":230,"end":233},"obj":"protein"},{"id":"T6","span":{"begin":254,"end":280},"obj":"protein"},{"id":"T7","span":{"begin":282,"end":290},"obj":"protein"},{"id":"T8","span":{"begin":292,"end":295},"obj":"protein"},{"id":"T9","span":{"begin":374,"end":382},"obj":"protein"},{"id":"T10","span":{"begin":383,"end":386},"obj":"protein"},{"id":"T11","span":{"begin":443,"end":446},"obj":"protein"},{"id":"T12","span":{"begin":526,"end":529},"obj":"protein"},{"id":"T13","span":{"begin":572,"end":578},"obj":"protein"},{"id":"T14","span":{"begin":610,"end":616},"obj":"protein"},{"id":"T15","span":{"begin":634,"end":637},"obj":"protein"},{"id":"T16","span":{"begin":643,"end":649},"obj":"protein"},{"id":"T17","span":{"begin":722,"end":725},"obj":"protein"},{"id":"T18","span":{"begin":762,"end":765},"obj":"protein"},{"id":"T19","span":{"begin":775,"end":781},"obj":"protein"},{"id":"T20","span":{"begin":882,"end":885},"obj":"protein"},{"id":"T21","span":{"begin":970,"end":978},"obj":"protein"},{"id":"T22","span":{"begin":979,"end":982},"obj":"protein"},{"id":"T23","span":{"begin":986,"end":989},"obj":"protein"},{"id":"T24","span":{"begin":1010,"end":1016},"obj":"protein"},{"id":"T25","span":{"begin":1024,"end":1027},"obj":"protein"},{"id":"T26","span":{"begin":1068,"end":1074},"obj":"protein"},{"id":"T27","span":{"begin":1078,"end":1081},"obj":"protein"},{"id":"T28","span":{"begin":1119,"end":1125},"obj":"protein"},{"id":"T29","span":{"begin":1280,"end":1286},"obj":"protein"},{"id":"T30","span":{"begin":1308,"end":1311},"obj":"protein"},{"id":"T31","span":{"begin":1426,"end":1432},"obj":"protein"},{"id":"T32","span":{"begin":1449,"end":1452},"obj":"protein"},{"id":"T33","span":{"begin":1521,"end":1524},"obj":"protein"},{"id":"T34","span":{"begin":1578,"end":1585},"obj":"protein"}],"text":"The T-cell antigen CD5 acts as a receptor and substrate for the protein-tyrosine kinase p56lck.\nCD5 is a T-cell-specific antigen which binds to the B-cell antigen CD72 and acts as a coreceptor in the stimulation of T-cell growth. CD5 associates with the T-cell receptor zeta chain (TcR zeta)/CD3 complex and is rapidly phosphosphorylated on tyrosine residues as a result of TcR zeta/CD3 ligation. However, despite this, the mechanism by which CD5 generates intracellular signals is unclear. In this study, we demonstrate that CD5 is coupled to the protein-tyrosine kinase p56lck and can act as a substrate for p56lck. Coexpression of CD5 with p56lck in the baculovirus expression system resulted in the phosphorylation of CD5 on tyrosine residues. Further, anti-CD5 and anti-p56lck coprecipitated each other in a variety of detergents, including Nonidet P-40 and Triton X-100. Anti-CD5 also precipitated the kinase from various T cells irrespective of the expression of TcR zeta/CD3 or CD4. No binding between p59fyn(T) and CD5 was detected in T cells. The binding of p56lck to CD5 induced a 10- to 15-fold increase in p56lck catalytic activity, as measured by in vitro kinase analysis. In vivo labelling with 32P(i) also showed a four- to fivefold increase in Y-394 occupancy in p56lck when associated with CD5. The use of glutathione S-transferase-Lck fusion proteins in precipitation analysis showed that the SH2 domain of p56lck could recognize CD5 as expressed in the baculovirus expression system. CD5 interaction with p56lck represents a novel variant of a receptor-kinase complex in which receptor can also serve as substrate. The CD5-p56lck interaction is likely to play roles in T-cell signalling and T-B collaboration."}