TY - JOUR
T1 - Non-PKC DAG/phorbol-ester receptor(s) inhibit complement receptor-3 and nPKC inhibit scavenger receptor-AI/II-mediated myelin phagocytosis but cPKC, PI3K, and PLCγ activate myelin phagocytosis by both
AU - Cohen, Goni
AU - Makranz, Chen
AU - Spira, Maya
AU - Kodama, Tatsuhiko
AU - Reichert, Fanny
AU - Rotshenker, Shlomo
PY - 2006/4/1
Y1 - 2006/4/1
N2 - Complement-receptor-3 (CR3/MAC-1), scavenger-receptor-AI/ II (SRAI/II), and Fcγ-receptor (FcγR) can mediate myelin phagocytosis in macrophages and microglia. Paradoxically, after injury to CNS axons these receptors are expressed but myelin is not phagocytosed, suggesting that phagocytosis is subject to regulation between efficient and inefficient states. In the present work, we focus on CR3/MAC-1 and SRAI/II-mediated myelin phagocytosis. Phagocytosis by CR3/MAC-1 and SRAI/II was inhibited by cPKC inhibitor Go-6976, general-PKC inhibitors Ro-318220 and calphostin-C, and BAPTA/AM, which chelates intracellular Ca2+ required for cPKC activation. Signaling/activation by cPKC are thus suggested. PMA, which mimics diacylglycerol (DAG) as an activator of cPKC, novel-PKC (nPKC), and non-PKC DAG-driven molecule(s), produced a dose-dependent dual effect on phagocytosis by CR3/MAC-1 and SRAI/II, i.e., augmentation at low concentrations and inhibition at high concentrations. Inhibition of phagocytosis by CR3/MAC-1 was enhanced by combining inhibiting concentrations of PMA with PKC inhibitors Go-6976 or Ro-318220, suggesting inhibition by PMA/ DAG-driven non-PKC molecule(s). In contrast, inhibition of phagocytosis by SRAI/II was enhanced by combining inhibiting concentrations of PMA with cPKC inhibitor Go-6976 but not with general-PKC inhibitor Ro-318220, suggesting inhibition by nPKC. Phagocytosis by CR3/MAC-1 and SRAI/II was further inhibited by PI3K inhibitors wortmannin and LY-294002 and PLCγ inhibitor U-73122. Altogether, our observations suggest that CR3/MAC-1 and SRAI/II-mediated myelin phagocytosis share activation by PI3K, PLCγ and cPKC. The two differ, however, in that non-PKC DAG-driven molecule(s) inhibit CR3/MAC-1-mediated phagocytosis, whereas nPKC inhibit SRAI/II-mediated phagocytosis. Each of these signaling steps may be targeted for regulating CR3/ MAC-1 and/or SRAI/II-mediated phagocytosis between efficient and inefficient states.
AB - Complement-receptor-3 (CR3/MAC-1), scavenger-receptor-AI/ II (SRAI/II), and Fcγ-receptor (FcγR) can mediate myelin phagocytosis in macrophages and microglia. Paradoxically, after injury to CNS axons these receptors are expressed but myelin is not phagocytosed, suggesting that phagocytosis is subject to regulation between efficient and inefficient states. In the present work, we focus on CR3/MAC-1 and SRAI/II-mediated myelin phagocytosis. Phagocytosis by CR3/MAC-1 and SRAI/II was inhibited by cPKC inhibitor Go-6976, general-PKC inhibitors Ro-318220 and calphostin-C, and BAPTA/AM, which chelates intracellular Ca2+ required for cPKC activation. Signaling/activation by cPKC are thus suggested. PMA, which mimics diacylglycerol (DAG) as an activator of cPKC, novel-PKC (nPKC), and non-PKC DAG-driven molecule(s), produced a dose-dependent dual effect on phagocytosis by CR3/MAC-1 and SRAI/II, i.e., augmentation at low concentrations and inhibition at high concentrations. Inhibition of phagocytosis by CR3/MAC-1 was enhanced by combining inhibiting concentrations of PMA with PKC inhibitors Go-6976 or Ro-318220, suggesting inhibition by PMA/ DAG-driven non-PKC molecule(s). In contrast, inhibition of phagocytosis by SRAI/II was enhanced by combining inhibiting concentrations of PMA with cPKC inhibitor Go-6976 but not with general-PKC inhibitor Ro-318220, suggesting inhibition by nPKC. Phagocytosis by CR3/MAC-1 and SRAI/II was further inhibited by PI3K inhibitors wortmannin and LY-294002 and PLCγ inhibitor U-73122. Altogether, our observations suggest that CR3/MAC-1 and SRAI/II-mediated myelin phagocytosis share activation by PI3K, PLCγ and cPKC. The two differ, however, in that non-PKC DAG-driven molecule(s) inhibit CR3/MAC-1-mediated phagocytosis, whereas nPKC inhibit SRAI/II-mediated phagocytosis. Each of these signaling steps may be targeted for regulating CR3/ MAC-1 and/or SRAI/II-mediated phagocytosis between efficient and inefficient states.
KW - Axonal injury
KW - Macrophage
KW - Microglia
KW - Myelin degeneration
KW - Wallerian degeneration
UR - http://www.scopus.com/inward/record.url?scp=33645387750&partnerID=8YFLogxK
U2 - 10.1002/glia.20304
DO - 10.1002/glia.20304
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C2 - 16374778
AN - SCOPUS:33645387750
SN - 0894-1491
VL - 53
SP - 538
EP - 550
JO - GLIA
JF - GLIA
IS - 5
ER -