Phosphatidylinositol 3-kinase, phosphoinositide-specific phospholipase-Cgamma and protein kinase-C signal myelin phagocytosis mediated by complement receptor-3 alone and combined with scavenger receptor-AI/II in macrophages.
Complement-receptor-3 (CR3/MAC-1), scavenger-receptor-AI/II (SRAI/II) and Fcgamma-receptor (FcgammaR) can mediate phagocytosis of degenerated myelin in macrophages and microglia. However, CR3/MAC-1 and SRAI/II, but not FcgammaR, mediate phagocytosis after axonal injury. We tested for phosphatidylinositol 3-kinase (PI3K), phosphoinositide-specific phospholipase-Cgamma (PLCgamma) and protein kinase-C (PKC) signaling in myelin phagocytosis mediated by CR3/MAC-1 alone and by CR3/MAC-1 combined with SRAI/II. Phagocytosis was inhibited by PI3K inhibitors wortmannin and LY-294002, PLCgamma inhibitor U-73122, classical PKC (cPKC) inhibitor Go-6976, general PKC inhibitors Ro-318220 and calphostin-C, and BAPTA/AM which chelates intracellular Ca(2+) required for cPKC activation. PKC activator PMA augmented phagocytosis and further alleviated inhibitions induced by PI3K and PLCgamma inhibitors. Overall, altering PKC activity modulated phagocytosis 4- to 6-fold between inhibition and augmentation. PLCgamma activation did not require tyrosine phosphorylation. Thus, signaling of myelin phagocytosis mediated by CR3/MAC-1 alone and by CR3/MAC-1 combined with SRAI/II involves PI3K, PLCgamma and cPKC, the cascade PI3K-->PLCgamma-->cPKC, and wide-range modulation by PKC. This pathway may thus be targeted for in vivo modulation, which may explain differences in the efficiency of CR3/MAC-1-mediated myelin phagocytosis in different pathological conditions.
Department of Anatomy and Cell Biology, Hebrew University-Hadassah Medical School and the Eric Roland Center for Neurodegenerative Diseases, Jerusalem, Israel.
Chen
C
Makranz
Goni
G
Cohen
Ayellet
A
Baron
Lital
L
Levidor
Tatsuhiko
T
Kodama
Fanny
F
Reichert
Shlomo
S
Rotshenker
D000818:Animals; D001369:Axons / Q000201:enzymology / Q000276:immunology / Q000473:pathology; D018955:CD36 Antigens / Q000378:metabolism*; D045744:Cell Line, Tumor; D002614:Chelating Agents / Q000494:pharmacology; D003711:Demyelinating Diseases / Q000201:enzymology / Q000235:genetics / Q000503:physiopathology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016177:Macrophage-1 Antigen / Q000378:metabolism*; D008264:Macrophages / Q000201:enzymology* / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D009186:Myelin Sheath / Q000276:immunology / Q000378:metabolism*; D009410:Nerve Degeneration / Q000201:enzymology / Q000235:genetics / Q000503:physiopathology; D009416:Nerve Regeneration / Q000502:physiology; D010587:Phagocytosis / Q000276:immunology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051966:Phospholipase C gamma; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D021122:Protein Subunits / Q000037:antagonists & inhibitors / Q000378:metabolism; D051117:Scavenger Receptors, Class A; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D018955:CD36 Antigens; D002614:Chelating Agents; D004791:Enzyme Inhibitors; D016177:Macrophage-1 Antigen; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051966:Phospholipase C gamma; D011493:Protein Kinase C; D021122:Protein Subunits; D051117:Scavenger Receptors, Class A; D010738:Type C Phospholipases