Beta 1 integrin cross-linking inhibits CD16-induced phospholipase D and secretory phospholipase A2 activity and granule exocytosis in human NK cells: role of phospholipase D in CD16-triggered degranulation.
Recent data indicate that integrin-generated signals can modulate different receptor-stimulated cell functions in both a positive (costimulation) and a negative (inhibition) fashion. Here we investigated the ability of beta 1 integrins, namely alpha 4 beta 1 and alpha 5 beta 1 fibronectin receptors, to modulate CD16-triggered phospholipase activation in human NK cells. beta 1 integrin simultaneous cross-linking selectively inhibited CD16-induced phospholipase D (PLD) activation, without affecting either phosphatidylinositol-phospholipase C or cytosolic phospholipase A2 (PLA2) enzymatic activity. CD16-induced secretory PLA2 (sPLA2) protein release as well as its enzymatic activity in both cell-associated and soluble forms were also found to be inhibited upon beta 1 integrin coengagement. The similar effects exerted by specific PLD pharmacological inhibitors (2,3-diphosphoglycerate, ethanol) suggest that in our experimental system, sPLA2 secretion and activation are under the control of a PLD-dependent pathway. By using pharmacological inhibitors (2,3-diphosphoglycerate, wortmannin, ethanol) we also demonstrated that PLD activation is an important step in the CD16-triggered signaling cascade that leads to NK cytotoxic granule exocytosis. Consistent with these findings, fibronectin receptor engagement, by either mAbs or natural ligands, resulted in a selective inhibition of CD16-triggered, but not of PMA/ionomycin-induced, degranulation that was reversed by the exogenous addition of purified PLD from Streptomyces chromofuscus.
Milella
M
M
Department of Experimental Medicine and Pathology, Istituto Pasteur-Fondazione Cenci Bolognetti, University of Rome La Sapienza, Italy.
Gismondi
A
A
Roncaioli
P
P
Palmieri
G
G
Morrone
S
S
Piccoli
M
M
Frati
L
L
Cifone
M G
MG
Santoni
A
A
D015550:Cell Degranulation / Q000187:drug effects / Q000276:immunology*; D002478:Cells, Cultured; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology; D004790:Enzyme Induction / Q000276:immunology; D005089:Exocytosis / Q000187:drug effects / Q000276:immunology*; D053804:Granzymes; D054501:Group II Phospholipases A2; D006801:Humans; D019012:Integrin beta1 / Q000276:immunology / Q000378:metabolism*; D015759:Ionomycin / Q000494:pharmacology; D007694:Killer Cells, Natural / Q000201:enzymology* / Q000276:immunology / Q000502:physiology; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010739:Phospholipase D / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology; D010741:Phospholipases A / Q000037:antagonists & inhibitors* / Q000378:metabolism; D054467:Phospholipases A2; D017452:Receptors, IgG / Q000037:antagonists & inhibitors / Q000502:physiology*; D012697:Serine Endopeptidases / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism