title: Protein kinase C beta and delta isoenzymes mediate cholesterol accumulation in PMA-activated macrophages.
abstract: Previously, we showed that PMA activation of human monocyte-derived macrophages stimulates macropinocytosis (i.e., fluid-phase endocytosis) of LDL and transforms these macrophages into foam cells. The current study aimed to learn which PKC isoenzymes mediate cholesterol accumulation in PMA-activated human macrophages incubated with LDL. Cholesterol accumulation by PMA-activated macrophages incubated with LDL was nearly completely inhibited (>85%) by the pan PKC inhibitors Go6850, Go6983, and RO 32-0432, but only was inhibited about 50% by the classical group PKC inhibitor, Go6976. This indicated that cholesterol accumulation was mediated by both a classical group and some other PKC isoenzyme. PKC beta was determined to be the classical group isoenzyme that mediated PMA-stimulated cholesterol accumulation. A pseudosubstrate myristoylated peptide inhibitor of PKC alpha and beta showed partial inhibition (congruent with 50%) of cholesterol accumulation. However, a small molecule inhibitor of PKC alpha, HBDDE, show minimal inhibition of cholesterol accumulation while a small molecule inhibitor of PKC beta, LY333513, could completely account for the inhibition of cholesterol accumulation by the classical group PKC isoenzyme. Thus, our findings show that beta and some other PKC isoenzyme, most likely delta, mediate cholesterol accumulation when macropinocytosis of LDL is stimulated in PMA-activated human monocyte-derived macrophages.
authors.affiliation: Section of Experimental Atherosclerosis, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892-1422, USA.
authors.forename: Hong-Tao
authors.initials: HT
authors.lastname: Ma
authors.forename: Wan-Wan
authors.initials: WW
authors.lastname: Lin
authors.forename: Bin
authors.initials: B
authors.lastname: Zhao
authors.forename: Wen-Tung
authors.initials: WT
authors.lastname: Wu
authors.forename: Wei
authors.initials: W
authors.lastname: Huang
authors.forename: Yifu
authors.initials: Y
authors.lastname: Li
authors.forename: Nancy L
authors.initials: NL
authors.lastname: Jones
authors.forename: Howard S
authors.initials: HS
authors.lastname: Kruth
mesh_terms: D050197:Atherosclerosis / Q000378:metabolism / Q000473:pathology; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005487:Foam Cells / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes; D008264:Macrophages / Q000378:metabolism*; D008954:Models, Biological; D009000:Monocytes / Q000378:metabolism; D011493:Protein Kinase C / Q000737:chemistry* / Q000502:physiology*; D064546:Protein Kinase C beta; D051745:Protein Kinase C-delta / Q000737:chemistry* / Q000502:physiology*; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D007527:Isoenzymes; D002784:Cholesterol; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D051745:Protein Kinase C-delta; D013755:Tetradecanoylphorbol Acetate