Uptake of LPS/E. coli/latex beads via distinct signalling pathways in medfly hemocytes: the role of MAP kinases activation and protein secretion.
In response to LPS/E. coli treatment, extracellular signal-regulated kinase (ERK) is activated in medfly hemocytes. To explore the molecular mechanisms underlying LPS/E. coli/latex beads endo- and phagocytosis, we studied the signalling pathways leading to p38 and c-jun N-terminal kinase (JNK) activation. JNK and p38-like proteins were initially identified within medfly hemocytes. Flow cytometry analysis revealed that mitogen-activated protein kinases (MAPK) are required for phagocytosis. Inhibition of specific MAPK signalling pathways, with manumycin A, toxin A, cytochalasin D and latrunculin A, revealed activation of p38 via Ras/Rho/actin remodelling pathway and activation of JNK that was independent of actin cytoskeleton reorganization. ERK and p38 pathways, but not JNK, appeared to be involved in LPS-dependent hemocyte secretion, whereas all MAPK subfamilies seemed to participate in E. coli-dependent secretion. In addition, flow cytometry experiments in hemocytes showed that the LPS/E. coli-induced release was a prerequisite for LPS/E. coli uptake, whereas latex bead phagocytosis did not depend on hemocyte secretion. This is a novel aspect, as in mammalian monocytes/macrophages LPS/E. coli-triggered release has not been yet correlated with phagocytosis. It is of interest that these data suggest distinct mechanisms for the phagocytosis of E. coli and latex beads in medfly hemocytes.
Lamprou
Irene
I
Laboratory of Biology, Department of Biology, University of Patras, 26500 Patras, Greece.
Tsakas
Sotiris
S
Theodorou
Georgios L
GL
Karakantza
Marina
M
Lampropoulou
Maria
M
Marmaras
Vassilis J
VJ
D008841:Actin Cytoskeleton / Q000378:metabolism; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D033622:Ceratitis capitata / Q000378:metabolism; D015638:Cytochalasin D / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004926:Escherichia coli / Q000378:metabolism; D006434:Hemocytes / Q000187:drug effects / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008863:Microspheres; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D010587:Phagocytosis; D010766:Phosphorylation; D011090:Polyenes / Q000494:pharmacology; D053284:Polyunsaturated Alkamides; D021381:Protein Transport; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D019086:Bridged Bicyclo Compounds, Heterocyclic; D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; D019384:Nucleic Acid Synthesis Inhibitors; D011090:Polyenes; D053284:Polyunsaturated Alkamides; D013844:Thiazoles; D053778:Thiazolidines; D015638:Cytochalasin D; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C054474:manumycin; C037067:latrunculin A