Interaction of the Cytoplasmic Tail of CTLA-4 (CD152) with a Clathrin-Associated Protein Is Negatively Regulated by Tyrosine Phosphorylation
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- 作者：Jeffrey D. Bradshaw ; Pin Lu ; Gina Leytze ; Julie Rodgers ; Gary L. Schieven ; Kelly L. Bennett ; Peter S. Linsley ; and Stephen E. Kurtz
- 刊名：Biochemistry
- 出版年：1997
- 出版时间：December 16, 1997
- 年：1997
- 卷：36
- 期：50
- 页码：15975 - 15982
- 全文大小：236K
- 年卷期：v.36,no.50(December 16, 1997)
- ISSN：1520-4995
文摘
CTLA-4 (CD152), high-avidity receptor for CD80 andCD86, is a powerful regulator of Tcell activation. While CTLA-4 functions at the cell surface, it isprimarily localized in intracellular vesiclesand cycles to the cell surface. The CTLA-4 cytoplasmic domaincontains sequences that direct itsintracellular localization and regulate its signaling. Here wedemonstrate that effector molecules involvedin receptor trafficking and signaling interact with distinct, butoverlapping, sequences in the CTLA-4cytoplasmic domain. Using the yeast two-hybrid method, wedemonstrate association of the 
2 subunitof AP-2, the clathrin-associated complex found in plasmamembrane-associated coated pits, with thecytoplasmic tail of CTLA-4, but not CD28. The 1 subunit ofAP-1, found in Golgi-associated coatedpits, associated with neither CTLA-4 nor CD28. Sequences requiredfor interaction of 2 and CTLA-4were localized to residues, 161TTGVY in CTLA-4; thissequence is N-terminal to, but overlaps with, apreviously identified SH2 binding motif, 165YVKM,involved in CTLA-4 signaling. 2 interactedpreferentially with CTLA-4 when residue 165Y wasnonphosphorylated, whereas a PI3 kinase SH2 domaininteracted preferentially when 165Y was phosphorylated.In co-transfection experiments, both tyrosineresidues in the cytoplasmic tail of CTLA-4 (165Y and182Y) were phosphorylated by the T lymphocyte-associated tyrosine kinase, p56lck. Thus, phosphorylation of CTLA-4residue 165Y may reciprocally regulatesignaling and trafficking of CTLA-4 by determining which effectormolecules bind to its cytoplasmictail.
2 subunitof AP-2, the clathrin-associated complex found in plasmamembrane-associated coated pits, with thecytoplasmic tail of CTLA-4, but not CD28. The 1 subunit ofAP-1, found in Golgi-associated coatedpits, associated with neither CTLA-4 nor CD28. Sequences requiredfor interaction of 2 and CTLA-4were localized to residues, 161TTGVY in CTLA-4; thissequence is N-terminal to, but overlaps with, apreviously identified SH2 binding motif, 165YVKM,involved in CTLA-4 signaling. 2 interactedpreferentially with CTLA-4 when residue 165Y wasnonphosphorylated, whereas a PI3 kinase SH2 domaininteracted preferentially when 165Y was phosphorylated.In co-transfection experiments, both tyrosineresidues in the cytoplasmic tail of CTLA-4 (165Y and182Y) were phosphorylated by the T lymphocyte-associated tyrosine kinase, p56lck. Thus, phosphorylation of CTLA-4residue 165Y may reciprocally regulatesignaling and trafficking of CTLA-4 by determining which effectormolecules bind to its cytoplasmictail.