Lipoxin A4 redistributes myosin IIA and Cdc42 in macrophages: implications for phagocytosis of apoptotic leukocytes.
Lipoxins (LXs) are endogenously produced anti-inflammatory agents that modulate leukocyte trafficking and stimulate nonphlogistic macrophage phagocytosis of apoptotic neutrophils, thereby promoting the resolution of inflammation. Previous data suggest a role for altered protein phosphorylation and cytoskeletal rearrangement in LX-stimulated phagocytosis but the exact mechanisms remain unclear. In this study we examine the effects of LXA4 on the protein phosphorylation pattern of THP-1 cells differentiated into a macrophage-like phenotype. THP-1 cells stimulated with LXA4 (1 nM) exhibit dephosphorylation of a 220-kDa protein. Using mass spectrometry, this protein was identified as MYH9, a nonmuscle myosin H chain II isoform A, which is involved in cytoskeleton rearrangement. THP-1 cells treated with LXA4 adopt a polarized morphology with activated Cdc42 localized toward the leading edge and MYH9 localized at the cell posterior. Polarized distribution of Cdc42 is associated with Akt/PKB-mediated Cdc42 activation. Interestingly, the annexin-derived peptide Ac2-26, a recently described agonist for the LXA4 receptor, also stimulates macrophage phagocytosis, MYH9 dephosphorylation, and MYH9 redistribution. In addition, we demonstrate that LXA4 stimulates the phosphorylation of key polarity organization molecules: Akt, protein kinase Czeta, and glycogen synthase kinase-3beta. Inhibition of LXA4-induced Akt and protein kinase Czeta activity with specific inhibitors prevented LXA4-stimulated phagocytosis of both apoptotic polymorphonuclear neutrophils and lymphocytes, highlighting a potential use for LXA4 in the treatment of autoimmune diseases. Furthermore, phosphorylation and subsequent inactivation of glycogen synthase kinase-3beta resulted in an increase in phagocytosis similar to that of LXA4. These data highlight an integrated mechanism whereby LXA4 regulates phagocytosis through facilitative actin cytoskeleton rearrangement and cell polarization.
Reville
Keira
K
School of Medicine and Medical Sciences, Conway Institute, University College Dublin, Belfield, Ireland.
Crean
John K
JK
Vivers
Sharon
S
Dransfield
Ian
I
Godson
Catherine
C
D000595:Amino Acid Sequence; D017209:Apoptosis / Q000276:immunology*; D002478:Cells, Cultured; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D007962:Leukocytes / Q000166:cytology* / Q000276:immunology*; D044045:Lipoxins / Q000502:physiology*; D008264:Macrophages / Q000378:metabolism*; D008969:Molecular Sequence Data; D024507:Nonmuscle Myosin Type IIA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010587:Phagocytosis / Q000276:immunology*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*; D000099221:Protein Kinase C zeta
D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D044045:Lipoxins; D024507:Nonmuscle Myosin Type IIA; D011493:Protein Kinase C; D051057:Proto-Oncogene Proteins c-akt; D020764:cdc42 GTP-Binding Protein; D000099221:Protein Kinase C zeta; C040527:lipoxin A4; C000605506:GSK3B protein, human