title: Regulation of platelet-activating factor receptor and PAF receptor-mediated arachidonic acid release by protein kinase C activation in rat Kupffer cells.
abstract: Phorbol 12-myristate 13-acetate (PMA), a potent protein kinase C activator, caused down-regulation of receptors for platelet-activating factor (AGEPC) on the plasma membrane of rat Kupffer cells (40-50% reduction) but had a relatively minor effect on the binding affinity of the receptors for AGEPC (Kd = 0.30 nM vs 0.56 nM) when incubated with the cells for a short period of time (30-60 min). As a consequence, the AGEPC receptor-mediated arachidonic acid release was attenuated. The PMA-induced down-regulation of AGEPC receptors was concentration-dependent, specific, and transient (the maximal effect was observed at about 1 h and the level of specific [3H]AGEPC binding gradually returned to the control level within 8.5 h and even higher than the control level at 24 h after addition of PMA). Upon removing PMA from the culture medium, more than half of the lost receptors were replaced within 1 h at 37 degrees C and the recovery process appeared to be independent of protein synthesis. The ability of PMA to down-regulate the AGEPC receptors was lost in cells "down-regulated" for protein kinase C, suggesting that the receptor-regulatory effect of PMA is protein kinase C-dependent. Protein kinase C appeared to be involved in the AGEPC-induced arachidonic acid release since 1-(5-isoquinolinesulfonyl)-2-methyl-piperazine dihydrochloride, a protein kinase C inhibitor, attenuated the stimulatory effect of AGEPC in this system. In addition, AGEPC-induced [3H]arachidonic acid release was inhibited significantly in cells down-regulated for protein kinase C. The present study thus demonstrates that protein kinase C has dual actions in the regulation of AGEPC-mediated events, i.e., a positive forward action, regulating AGEPC-stimulated arachidonic acid release, and a negative action, which inactivates or down-regulates AGEPC receptors.
authors.affiliation: Department of Biochemistry, University of Texas Health Science Center, San Antonio 78284-7760.
authors.forename: W
authors.initials: W
authors.lastname: Chao
authors.forename: H
authors.initials: H
authors.lastname: Liu
authors.forename: D J
authors.initials: DJ
authors.lastname: Hanahan
authors.forename: M S
authors.initials: MS
authors.lastname: Olson
mesh_terms: D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism*; D000001:Calcimycin / Q000494:pharmacology; D002478:Cells, Cultured; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects; D004789:Enzyme Activation; D007700:Kinetics; D007728:Kupffer Cells / Q000187:drug effects / Q000378:metabolism*; D015240:Phorbol 12,13-Dibutyrate / Q000378:metabolism; D010972:Platelet Activating Factor / Q000378:metabolism* / Q000494:pharmacology; D010980:Platelet Membrane Glycoproteins; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000502:physiology*; D043562:Receptors, G-Protein-Coupled; D013755:Tetradecanoylphorbol Acetate / Q000378:metabolism
chemical_list: D001095:Arachidonic Acids; D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; C039351:platelet activating factor receptor; D016718:Arachidonic Acid; D015240:Phorbol 12,13-Dibutyrate; D000001:Calcimycin; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D004121:Dimethyl Sulfoxide