Correlation between chemotactic peptide-induced changes in chlorotetracycline fluorescence and F-actin content in human neutrophils: a role for membrane-associated calcium in the regulation of actin polymerization?
Several observations indicate that the triggering event for receptor-mediated actin polymerization takes place in or close to the plasma membrane. Stimulation of human neutrophils with the chemotactic peptide formylmethionyl-leucyl-phenylalanine (fMet-Leu-Phe) causes rapid and transient changes in both chlorotetracycline (CTC) fluorescence and the cellular content of filamentous actin (F-actin), thus suggesting a regulatory role for membrane-bound calcium in actin polymerization. In the present study, tetracaine, a proposed antagonist to membrane-bound calcium, totally inhibited the rebinding of the membrane calcium released by fMet-Leu-Phe. This was accompanied by a magnified and sustained increase in the cellular content of F-actin. In agreement, N-ethylmaleimide, an inhibitor of motile functions, completely abolished the fMet-Leu-Phe-triggered changes in both CTC fluorescence and F-actin content and rapidly reversed the responses when added after the peptide. The tumor promoter phorbol-12-myristate-13-acetate, caused only small changes in CTC fluorescence and F-actin content, and reduced a subsequent fMet-Leu-Phe-induced CTC response and actin polymerization. Inhibition of the breakdown of phosphatidylinositol 4,5-bisphosphate, by calcium depletion, had no significant effects on the fMet-Leu-Phe-induced CTC response and alterations in F-actin content, whereas pretreatment with pertussis toxin totally inhibited both these responses. Consequently, the strong correlation between changes in CTC fluorescence and F-actin content, found in this study, suggests a triggering or modulating role of membrane-associated calcium on actin polymerization in human neutrophils.
Bengtsson
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Department of Medical Microbiology, University of Linköping, Sweden.
D000199:Actins / Q000378:metabolism*; D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002465:Cell Movement / Q000187:drug effects; D002751:Chlortetracycline / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology; D005453:Fluorescence; D006801:Humans; D066298:In Vitro Techniques; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology*; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D011108:Polymers; D011493:Protein Kinase C / Q000378:metabolism; D013748:Tetracaine / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism
D000199:Actins; D011108:Polymers; D013748:Tetracaine; D009240:N-Formylmethionine Leucyl-Phenylalanine; D011493:Protein Kinase C; D010738:Type C Phospholipases; D013755:Tetradecanoylphorbol Acetate; D005033:Ethylmaleimide; D002118:Calcium; D002751:Chlortetracycline