Uncommon Endocytic and Trafficking Pathway of the Natural Killer Cell CD94/NKG2A Inhibitory Receptor

Abstract

The CD94/NKG2A inhibitory receptor, expressed by natural killer and T cells, is constantly exposed to its HLA-E ligand expressed by surrounding cells. Ligand exposure often induces receptor downregulation. For CD94/NKG2A, this could potentiate activation receptor(s) induced responses to normal bystander cells. We investigated CD94/NKG2A endocytosis and found that it occurs by an amiloride-sensitive, Rac1-dependent macropinocytic-like process; however, it does not require clathrin, dynamin, ADP ribosylation factor-6, phosphoinositide-3 kinase or the actin cytoskeleton. Once endocytosed, CD94/NKG2A traffics to early endosomal antigen 1 + , Rab5+ early endosomes. It does appear in Rab4 + early/sorting endosome, but, in the time period examined, fails to reach Rab11 + recycling or Rab7 + late endosomes or lysosome-associated membrane protein-1 + lysosomes. These results indicate that CD94/NKG2A utilizes a previously undescribed endocytic mechanism coupled with an abbreviated trafficking pattern, perhaps to insure surface expression.

Granzyme B is recovered by natural killer cells via clathrin-dependent endocytosis

“…Soluble HLA-G, which is the ligand of KIR2DL4, is also known to be re-cycled by endocytosis into the KIR2DL4-containing compartments, facilitating the re-engagement of KIR2DL4 to induce a unique package of cytokine/chemokine secretions [31]. Furthermore, one of the inhibitory receptors of NK cells, known as CD94/NKG2A utilizes an uncommon means of endocytosis that is associated with rapid recycling into the cell surface [27]. Endocytosis of both KIR2DL4 and CD94/ NKG2A receptors are triggered by soluble ligands or antibodies.…”

“…CTL or NK cells that have secretory lysosomes package both lysosomal and secretory proteins in one compartment [2]. Secretory lysosomes have no specific markers but share similar surface markers with conventional lysosome, such as lysosome-associated membrane protein-1 (LAMP-1) and CD63, so also called LAMP-1-positive lysosome [2,27]. In this experiment, predominant incidences of overlapping of granzyme B and LAMP-1 in NK cells were observed post-PEC stimulation for 60 min.…”

p85α recruitment by the CD300f phosphatidylserine receptor mediates apoptotic cell clearance required for autoimmunity suppression

“…The LAIR-1-EGFP plasmid and EGFP-tagged dominant-negative form of Rac1(T17N) were described previously 59,60 . The dominant-negative form of Cdc42 (T17N) was generated using QuickChange Site-directed Mutagenesis Kit (Stratagene) with the Cdc42 plasmid as the template kindly supplied by Dr Debbie C. Thurmond (Indiana University School of Medicine, Indianapolis, IN, USA) and sub-cloned into pEGFP-N1 plasmid (Clontech).…”

The effect of mifepristone on the peripheral blood natural killer cell's cytotoxicity and expression of CD94/NKG2A and NKG2D during the implantation phase

“…They suggest that CD94/NKG2A-mediated inhibition of T cells may be limited to particular circumstances. Also, some researchers considered that CD94/NKG2A is a potential activating receptor(s) and could induce responses to normal bystander cells (37). We presume that CD94/NKG2A may exert an action of activating receptors induced by mifepristone.…”