Thapsigargin activates univalent- and bivalent-cation entry in human neutrophils by a SK&F I3 96365- and Gd3+-sensitive pathway and is a partial secretagogue: involvement of pertussis-toxin-sensitive G-proteins and protein phosphatases 1/2A and 2B in the signal-transduction pathway.
The Ca2+-ATPase inhibitor thapsigargin (TG) activates bivalent-cation early in human neutrophils via depletion of intracellular Ca2+ stores bu little is known about the underlying mechanism and the functional role of TG-induced cation entry. We studied the effects of TG on univalent- and bivalent cation entry, lysozyme release and superoxide-anion (O2-) formation in human neutrophils. TG, like the chemotactic peptide, N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP), stimulated entry of Ca2+, Mn2+, Ba2+, Sr2+ and Na+ in a 1-{beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl}-1H-imidazole hydrochloride (SK&F 96365)- and Gd3+-sensitive manner. The inhibitors of protein phosphates 1/2A, calyculin A and okadaic acid, diminished TG-induced cation influxes, whereas the inhibitors of protein phosphatase 2B, cyclosporin A and FK-506, were potentiators. Pertussis toxin (PTX) partially inhibited the effects of TG on Ca2+ and Mn2+ entry. TG and fMLP activated inward currents with a linear current-voltage relationship and a reversal potential at about 0 mV. TG activated lysozyme release and potentiated fMLP-induced O2- formation. TG-induced lysozyme release was inhibited by SK&F 96365, PTX and the removal of extracellular Ca2+ or Na+. Our data show that TG activates a non-selective and SK&F 96365- and Gd3+-sensitive cation entry pathway and is a partial secretagogue. TG-stimulated cation entry involves PTX-sensitive G-proteins and protein phosphatases, with protein phosphatases 1/2A and 2B playing opposite roles.
Wenzel-Seifert
K
K
Institut für Pharmakologie, Universitätsklinikum Benjamin Franklin, Freie Universität Berlin, Federal Republic of Germany.
Krautwurst
D
D
Musgrave
I
I
Seifert
R
R
D002412:Cations / Q000378:metabolism; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism*; D005682:Gadolinium / Q000494:pharmacology*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D017136:Ion Transport; D008297:Male; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D037342:Pertussis Toxin; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D015398:Signal Transduction; D013729:Terpenes / Q000494:pharmacology*; D019284:Thapsigargin; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D002412:Cations; D007093:Imidazoles; D013729:Terpenes; D010566:Virulence Factors, Bordetella; D009240:N-Formylmethionine Leucyl-Phenylalanine; D019284:Thapsigargin; D005682:Gadolinium; D037342:Pertussis Toxin; D010749:Phosphoprotein Phosphatases; D019204:GTP-Binding Proteins; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole