title: Protein kinase C controls vesicular transport and secretion of apolipoprotein E from primary human macrophages.
abstract: Macrophage-specific apolipoprotein E (apoE) secretion plays an important protective role in atherosclerosis. However, the precise signaling mechanisms regulating apoE secretion from primary human monocyte-derived macrophages (HMDMs) remain unclear. Here we investigate the role of protein kinase C (PKC) in regulating basal and stimulated apoE secretion from HMDMs. Treatment of HMDMs with structurally distinct pan-PKC inhibitors (calphostin C, Ro-31-8220, Go6976) and a PKC inhibitory peptide all significantly decreased apoE secretion without significantly affecting apoE mRNA or apoE protein levels. The PKC activator phorbol 12-myristate 13-acetate (PMA) stimulated apoE secretion, and both PMA-induced and apoAI-induced apoE secretion were inhibited by PKC inhibitors. PKC regulation of apoE secretion was found to be independent of the ATP binding cassette transporter ABCA1. Live cell imaging demonstrated that PKC inhibitors inhibited vesicular transport of apoE to the plasma membrane. Pharmacological or peptide inhibitor and knockdown studies indicate that classical isoforms PKCα/β and not PKCδ, -ε, -θ, or -ι/ζ isoforms regulate apoE secretion from HMDMs. The activity of myristoylated alanine-rich protein kinase C substrate (MARCKS) correlated with modulation of PKC activity in these cells, and direct peptide inhibition of MARCKS inhibited apoE secretion, implicating MARCKS as a downstream effector of PKC in apoE secretion. Comparison with other secreted proteins indicated that PKC similarly regulated secretion of matrix metalloproteinase 9 and chitinase-3-like-1 protein but differentially affected the secretion of other proteins. In conclusion, PKC regulates the secretion of apoE from primary human macrophages.
authors.affiliation: Centre for Vascular Research, School of Medical Sciences, University of New South Wales, Sydney, Australia.
authors.forename: Denuja
authors.initials: D
authors.lastname: Karunakaran
authors.forename: Maaike
authors.initials: M
authors.lastname: Kockx
authors.forename: Dylan M
authors.initials: DM
authors.lastname: Owen
authors.forename: John R
authors.initials: JR
authors.lastname: Burnett
authors.forename: Wendy
authors.initials: W
authors.lastname: Jessup
authors.forename: Leonard
authors.initials: L
authors.lastname: Kritharides
mesh_terms: D001057:Apolipoproteins E / Q000378:metabolism*; D050197:Atherosclerosis / Q000378:metabolism; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D002470:Cell Survival; D002478:Cells, Cultured / Q000166:cytology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D008264:Macrophages / Q000166:cytology* / Q000378:metabolism; D008954:Models, Biological; D009000:Monocytes / Q000166:cytology; D020033:Protein Isoforms; D011493:Protein Kinase C / Q000378:metabolism / Q000502:physiology*; D034741:RNA, Small Interfering / Q000378:metabolism; D013997:Time Factors
chemical_list: D001057:Apolipoproteins E; D004791:Enzyme Inhibitors; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D011493:Protein Kinase C