Exclusion of lipid rafts and decreased mobility of CD94/NKG2A receptors at the inhibitory NK cell synapse.
CD94/NKG2A is an inhibitory receptor expressed by most human natural killer (NK) cells and a subset of T cells that recognizes human leukocyte antigen E (HLA-E) on potential target cells. To elucidate the cell surface dynamics of CD94/NKG2A receptors, we have expressed CD94/NKG2A-EGFP receptors in the rat basophilic leukemia (RBL) cell line. Photobleaching experiments revealed that CD94/NKG2A-EGFP receptors move freely within the plasma membrane and accumulate at the site of contact with ligand. The enriched CD94/NKG2A-EGFP is markedly less mobile than the nonligated receptor. We observed that not only are lipid rafts not required for receptor polarization, they are excluded from the site of receptor contact with the ligand. Furthermore, the lipid raft patches normally observed at the sites where FcepsilonR1 activation receptors are cross-linked were not observed when CD94/NKG2A was coengaged along with the activation receptor. These results suggest that immobilization of the CD94/NKG2A receptors at ligation sites not only promote sustenance of the inhibitory signal, but by lipid rafts exclusion prevent formation of activation signaling complexes.
Sanni
Tolib B
TB
Receptor Cell Biology Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland 20852, USA.
Masilamani
Madhan
M
Kabat
Juraj
J
Coligan
John E
JE
Borrego
Francisco
F
D000818:Animals; D015703:Antigens, CD / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D015870:Gene Expression; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000235:genetics; D006801:Humans; D007694:Killer Cells, Natural / Q000502:physiology; D037181:Lectins, C-Type / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D021962:Membrane Microdomains / Q000276:immunology / Q000502:physiology*; D055654:NK Cell Lectin-Like Receptor Subfamily C; D051920:NK Cell Lectin-Like Receptor Subfamily D; D038761:Photobleaching; D051381:Rats; D011971:Receptors, Immunologic / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D055607:Receptors, Natural Killer Cell; D015398:Signal Transduction / Q000502:physiology
D015703:Antigens, CD; C527054:KLRC1 protein, human; C497869:KLRD1 protein, human; C497871:Klrd1 protein, rat; D037181:Lectins, C-Type; D055654:NK Cell Lectin-Like Receptor Subfamily C; D051920:NK Cell Lectin-Like Receptor Subfamily D; D011971:Receptors, Immunologic; D055607:Receptors, Natural Killer Cell; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins