Cytolytic T lymphocyte-associated antigen-4 and the TCR zeta/CD3 complex, but not CD28, interact with clathrin adaptor complexes AP-1 and AP-2.
The negative signaling receptor cytolytic T lymphocyte-associated Ag-4 (CTLA-4) resides primarily in intracellular compartments such as the Golgi apparatus of T cells. However, little is known regarding the molecular mechanisms that influence this accumulation. In this study, we demonstrate binding of the clathrin adaptor complex AP-1 with the GVYVKM motif of the cytoplasmic domain of CTLA-4. Binding occurred primarily in the Golgi compartment of T cells, unlike with AP-2 binding that occurs mostly with cell surface CTLA-4. Although evidence was not found to implicate AP-1 binding in the retention of CTLA-4 in the Golgi, AP-1 appears to play a role in shuttling of excess receptor from the Golgi to the lysosomal compartments for degradation. In support of this, increased CTLA-4 synthesis resulted in an increase in CTLA-4/AP-1 binding and a concomitant increase in the appearance of CTLA-4 in the lysosomal compartment. At the same time, the level of intracellular receptor was maintained at a constant level, suggesting that CTLA-4/AP-1 binding represents one mechanism to ensure steady state levels of intracellular CTLA-4 in T cells. Finally, we demonstrate that the TCR zeta/CD3 complex (but not CD28) also binds to AP-1 and AP-2 complexes, thus providing a possible link between these two receptors in the regulation of T cell function.
Schneider
H
H
Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Boston, MA 02115, USA.
Martin
M
M
Agarraberes
F A
FA
Yin
L
L
Rapoport
I
I
Kirchhausen
T
T
Rudd
C E
CE
D000069594:Abatacept; D033965:Adaptor Protein Complex alpha Subunits; D033942:Adaptor Proteins, Vesicular Transport; D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites / Q000235:genetics / Q000276:immunology; D018106:CD28 Antigens / Q000378:metabolism*; D060908:CTLA-4 Antigen; D002118:Calcium / Q000378:metabolism / Q000502:physiology; D002966:Clathrin / Q000378:metabolism*; D006801:Humans; D006825:Hybridomas; D018796:Immunoconjugates; D007424:Intracellular Fluid / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000378:metabolism; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology / Q000378:metabolism*
D033965:Adaptor Protein Complex alpha Subunits; D033942:Adaptor Proteins, Vesicular Transport; D015703:Antigens, CD; D000943:Antigens, Differentiation; D018106:CD28 Antigens; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; D002966:Clathrin; C556707:Ctla4 protein, mouse; D018796:Immunoconjugates; D008565:Membrane Proteins; D010446:Peptide Fragments; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D011948:Receptors, Antigen, T-Cell; C054979:antigen T cell receptor, zeta chain; D000069594:Abatacept; D002118:Calcium