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Membrane cofactor protein (MCP; CD46): isoform-specific tyrosine phosphorylation.
G Wang1, M K Liszewski, A C Chan
1Division of Rheumatology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA.
Journal of Immunology (Baltimore, Md. : 1950)
|February 5, 2000
Summary
Membrane cofactor protein (MCP; CD46) signaling involves its CYT-2 tail, which is phosphorylated by src family kinases like Lck. This identifies a novel src-dependent pathway for MCP-mediated cellular responses.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Membrane cofactor protein (MCP; CD46) inhibits complement activation and acts as a pathogen receptor.
- MCP interactions with pathogens suggest potential signaling roles.
- MCP exists in isoforms with distinct cytoplasmic tails (CYT-1 and CYT-2).
Purpose of the Study:
- To investigate the signal transduction pathway mediated by MCP.
- To determine if MCP cytoplasmic tails are involved in signaling.
- To identify kinases responsible for MCP phosphorylation.
Main Methods:
- Analysis of MCP tail peptides.
- Antibody cross-linking experiments on human cell lines and MCP isoform transfectants.
- Western blotting and genetic/biochemical analysis to identify responsible kinases.
Main Results:
- MCP's CYT-2 tail, but not CYT-1, is phosphorylated on tyrosine.
- Src kinase systems phosphorylate MCP CYT-2 peptides.
- Src family kinases, particularly Lck, are responsible for MCP phosphorylation in cell lines.
Conclusions:
- MCP CYT-2 mediates signal transduction.
- A src family kinase-dependent pathway is involved in MCP signaling.
- Src kinases like Lck play a crucial role in MCP phosphorylation and signaling.