Exocytosis of CTLA-4 is dependent on phospholipase D and ADP ribosylation factor-1 and stimulated during activation of regulatory T cells.
CTLA-4 is an essential protein in the regulation of T cell responses that interacts with two ligands found on the surface of APCs (CD80 and CD86). CTLA-4 is itself poorly expressed on the T cell surface and is predominantly localized to intracellular compartments. We have studied the mechanisms involved in the delivery of CTLA-4 to the cell surface using a model Chinese hamster ovary cell system and compared this with activated and regulatory human T cells. We have shown that expression of CTLA-4 at the plasma membrane (PM) is controlled by exocytosis of CTLA-4-containing vesicles and followed by rapid endocytosis. Using selective inhibitors and dominant negative mutants, we have shown that exocytosis of CTLA-4 is dependent on the activity of the GTPase ADP ribosylation factor-1 and on phospholipase D activity. CTLA-4 was identified in a perinuclear compartment overlapping with the cis-Golgi marker GM-130 but did not colocalize strongly with lysosomal markers such as CD63 and lysosome-associated membrane protein. In regulatory T cells, activation of phospholipase D was sufficient to trigger release of CTLA-4 to the PM but did not inhibit endocytosis. Taken together, these data suggest that CTLA-4 may be stored in a specialized compartment in regulatory T cells that can be triggered rapidly for deployment to the PM in a phospholipase D- and ADP ribosylation factor-1-dependent manner.
Mead
Karen I
KI
Medical Research Council Centre for Immune Regulation, University of Birmingham Medical School, Birmingham, United Kingdom.
Zheng
Yong
Y
Manzotti
Claire N
CN
Perry
Laura C A
LC
Liu
Michael K P
MK
Burke
Fiona
F
Powner
Dale J
DJ
Wakelam
Michael J O
MJ
Sansom
David M
DM
D020823:ADP-Ribosylation Factor 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016466:CHO Cells; D060908:CTLA-4 Antigen; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D006224:Cricetinae; D004705:Endocytosis; D004789:Enzyme Activation; D005089:Exocytosis; D006801:Humans; D066298:In Vitro Techniques; D008213:Lymphocyte Activation; D016297:Mutagenesis, Site-Directed; D010739:Phospholipase D / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism*; D014162:Transfection; D014443:Tyrosine / Q000737:chemistry
D015703:Antigens, CD; D000943:Antigens, Differentiation; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; D011994:Recombinant Proteins; D014443:Tyrosine; D010739:Phospholipase D; D020823:ADP-Ribosylation Factor 1