Cellular localization and functional role of phosphatidylcholine-specific phospholipase C in NK cells.
Although several classes of phospholipases have been implicated in NK cell-mediated cytotoxicity, no evidence has been reported to date on involvement of phosphatidylcholine-specific phospholipase C (PC-PLC) in NK activation by lymphokines and/or in lytic granule exocytosis. This study demonstrated the expression of two PC-PLC isoforms (M(r) 40 and 66 kDa) and their IL-2-dependent distribution between cytoplasm and ectoplasmic membrane surface in human NK cells. Following cell activation by IL-2, cytoplasmic PC-PLC translocated from the microtubule-organizing center toward cell periphery, essentially by kinesin-supported transport along microtubules, while PC-PLC exposed on the outer cell surface increased 2-fold. Preincubation of NK cells with a PC-PLC inhibitor, tricyclodecan-9-yl-xanthogenate, strongly reduced NK-mediated cytotoxicity. In IL-2-activated cells, this loss of cytotoxicity was associated with a decrease of PC-PLC exposed on the cell surface, and accumulation of cytoplasmic PC-PLC in the Golgi region. Massive colocalization of PC-PLC-rich particles with perforin-containing granules was found in the cytoplasm of NK-activated (but not NK-resting) cells; both organelles clustered at the intercellular contact region of effector-target cell conjugates. These newly detected mechanisms of PC-PLC translocation and function support an essential role of this enzyme in regulated granule exocytosis and NK-mediated cytotoxicity.
Ramoni
C
C
Laboratories of. Immunology and Cell Biology, Istituto Superiore di Sanità, Rome, Italy. ramoni@iss.it
Spadaro
F
F
Menegon
M
M
Podo
F
F
D001952:Bridged-Ring Compounds / Q000494:pharmacology; D002460:Cell Line; D003594:Cytoplasmic Granules / Q000201:enzymology; D003599:Cytoskeleton / Q000201:enzymology; D003602:Cytotoxicity, Immunologic / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D007694:Killer Cells, Natural / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000378:metabolism; D020409:Molecular Motor Proteins / Q000378:metabolism; D009636:Norbornanes; D015388:Organelles / Q000201:enzymology; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D013347:Subcellular Fractions / Q000201:enzymology; D013859:Thiocarbamates; D013871:Thiones / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D001952:Bridged-Ring Compounds; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D008562:Membrane Glycoproteins; D020409:Molecular Motor Proteins; D009636:Norbornanes; D052899:Pore Forming Cytotoxic Proteins; D013859:Thiocarbamates; D013871:Thiones; D054353:Perforin; C046498:tricyclodecane-9-yl-xanthogenate; D010738:Type C Phospholipases; C105598:phosphatidylcholine-specific phospholipase C