Protein kinase C impairs the coupling of the GTP-binding protein to LTB4 receptor in neutrophil.
In the present study, the mechanism of LTB4 receptor down regulation by protein kinase C (PKC) has been investigated using porcine neutrophil membranes. Pretreatment of intact porcine neutrophils with 12-O-tetradecanoylphorbol-13-acetate (TPA) for 2 min prior to the preparation of plasma membrane, demonstrated a reduced binding sites (Bmax) for LTB4 without altering the receptor affinity (Kd). This effect of TPA on LTB4 receptor binding was found to be due to the activation of PKC as membrane treated with purified PKC (type III) produced the same effect. When membranes from neutrophils pretreated with TPA were exposed to non-hydrolyzable GTP analog, GTP-gamma S, or GMP-PNP, no further decrease in receptor Kd was observed, while the Bmax was reduced to the level observed in TPA treated samples. Treatment of isolated neutrophil membranes with purified PKC reduced the Bmax and blocked the effect of GTP analogs on the receptor affinity. These results suggest that, PKC interrupts the receptor binding to G-protein.
Dryden
P
P
Department of Medicine, University of British Columbia, Jack Bell Research Centre, Vancouver, Canada.
Allen
B
B
Wong
S
S
Reaney
A
A
Merali
T
T
Salari
H
H
D000818:Animals; D001667:Binding, Competitive; D004789:Enzyme Activation / Q000187:drug effects; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006150:Guanine Nucleotides / Q000494:pharmacology; D007975:Leukotriene B4 / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism*; D011493:Protein Kinase C / Q000097:blood*; D011971:Receptors, Immunologic / Q000378:metabolism*; D018102:Receptors, Leukotriene B4; D013552:Swine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D006150:Guanine Nucleotides; D011971:Receptors, Immunologic; D018102:Receptors, Leukotriene B4; D007975:Leukotriene B4; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D013755:Tetradecanoylphorbol Acetate