Identification of a cytoplasmic region of CD20 required for its redistribution to a detergent-insoluble membrane compartment.
CD20 is a B lymphocyte integral membrane protein with signal-transducing properties. Abs directed toward extracellular CD20 epitopes activate nonreceptor tyrosine kinases and modulate cell cycle progression of B lymphocytes. Recently, we demonstrated that binding of CD20 Abs to B cells induces the rapid redistribution of up to 95% of CD20 molecules to low density, detergent-insoluble membrane microdomains and induces the appearance of an approximately 50-kDa tyrosine-phosphorylated protein in the same compartment. Active relocalization of CD20 may thus be critical to the initiation of signaling events by CD20. The CD20 cDNA sequence predicts a nonglycosylated protein with four transmembrane-spanning regions and intracellular amino and carboxyl termini. Here we provide verification of the location of both the intracellular and extracellular regions of the CD20 molecule and identify a membrane-proximal sequence in the cytoplasmic carboxyl tail that is required for CD20 to redistribute to detergent-insoluble membrane microdomains.
Department of Biochemistry and Molecular Biology, University of Calgary, Alberta, Canada.
M J
MJ
Polyak
S H
SH
Tailor
J P
JP
Deans
D000918:Antibody Specificity; D018951:Antigens, CD20 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D002451:Cell Compartmentation / Q000276:immunology*; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D003545:Cysteine / Q000378:metabolism; D003593:Cytoplasm / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007106:Immune Sera / Q000737:chemistry; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D017830:Octoxynol; D019308:Palmitic Acid / Q000378:metabolism; D010446:Peptide Fragments / Q000276:immunology / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion / Q000276:immunology; D012995:Solubility
D018951:Antigens, CD20; D007106:Immune Sera; D008565:Membrane Proteins; D010446:Peptide Fragments; D019308:Palmitic Acid; D017830:Octoxynol; D003545:Cysteine