Lipids regulate P2X7-receptor-dependent actin assembly by phagosomes via ADP translocation and ATP synthesis in the phagosome lumen.
Latex bead phagosomes isolated from J774 macrophages polymerize actin. We show here that five lipids--phosphatidylinositol-4-phosphate, phosphatidylinositol-(4,5)-bisphosphate, sphingosine-1-phosphate (S1P), ceramide-1-phosphate and phosphatidic acid--stimulate both actin assembly and transport of ADP across the phagosomal membrane into the lumen. Once there, this ADP is converted to ATP by adenylate kinase activity. High luminal ATP concentrations correlated well with phagosome actin assembly under different conditions. The ATP-binding P2X7 receptor (P2X7R) was detected in phagosomes. Although S1P stimulated actin assembly by phagosomes from P2X7R-containing bone marrow macrophages, S1P-stimulated actin assembly was inhibited in phagosomes from cells lacking P2X7R. We propose that luminal ATP accumulates in response to selected lipids and activates the P2X7R that signals across the phagosomal membrane to trigger actin assembly on the cytoplasmic membrane surface. In the accompanying paper by Kuehnel et al. (doi:10.1242/jcs.034207), more evidence is provided in support of this model from the analysis of actin assembly at the plasma membrane of intact macrophages.
Kuehnel
Mark P
MP
EMBL, Meyerhofstr. 1, 69117 Heidelberg, Germany.
Rybin
Vladimir
V
Anand
Paras K
PK
Anes
Elsa
E
Griffiths
Gareth
G
D000199:Actins / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000263:Adenylate Kinase / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D018929:Cell Culture Techniques; D002462:Cell Membrane / Q000378:metabolism; D002518:Ceramides / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D008246:Lysophospholipids / Q000378:metabolism; D008563:Membrane Lipids / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008863:Microspheres; D010588:Phagosomes / Q000378:metabolism*; D010712:Phosphatidic Acids / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058486:Receptors, Purinergic P2X7; D013110:Sphingosine / Q000031:analogs & derivatives / Q000378:metabolism
D000199:Actins; D002518:Ceramides; D008246:Lysophospholipids; D008563:Membrane Lipids; C546469:P2rx7 protein, mouse; D010712:Phosphatidic Acids; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; C065576:ceramide 1-phosphate; C037178:phosphatidylinositol 4-phosphate; C060506:sphingosine 1-phosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D000263:Adenylate Kinase; D013110:Sphingosine