Concanavalin A and mistletoe lectin I differentially activate cation entry and exocytosis in human neutrophils: lectins may activate multiple subtypes of cation channels.

Journal/Book: J-Leukoc-Biol 60 (3), 345-355. 1996;

Abstract: The mannose-specific lectin, concanavalin A (ConA), activates Ca2+ entryin human neutrophils by an as yet poorly defined mechanism. The questionof whether the sugar specificity of lectins influences signaltransduction is unresolved too. Therefore, we studied the effects ofConA in comparison to those of the beta-galactoside-specific lectin,mistletoe lectin I (MLI), on cation entry and exocytosis in humanneutrophils. ConA- and MLI-activated influx of Ca2+, Mn2+, Ba2+, Sr2+,and Na+. Lectin-induced cation influxes were inhibited by1-(beta-(3-(4-methoxyphenyl)propoxy)-4-methoxy-phenethyl) -1H-imidazolehydrochloride (SK&F 96365) and Gd3+. There were differences in theeffectiveness of lectins to activate cation entry and of SK&F 96365,Gd3+, and modulators of protein phosphorylation to block entry. MLI butnot ConA inhibited thapsigargin-induced Ca2+ entry. Under whole-cellvoltage-clamp conditions, MLI activated an inward current that wassubstantially reduced by removal of extracellular Na+. ConA and MLIsynergistically activated Ca2+ entry and lysozyme release. SK&F 96365and removal of extracellular Ca2+ and Na+ partially inhibitedexocytosis. Our data show the following: (1) ConA and MLI activatemonovalent and divalent cation entry in human neutrophils by a SK&F96365- and Gd3+-sensitive pathway, presumably nonselective cationchannels. (2) Ca2+ and Na+ entry are involved in the activation ofexocytosis by lectins. (3) The differential and/or synergistic effectsof ConA and MLI on cation entry and exocytosis may be attributable tomannose- and beta-galactoside-specific activation of signal transductionpathways, i.e., activation of multiple and differentially regulatedsubtypes of nonselective cation channels. Author.

Keyword(s): BARIUM/BL (blood)

Zurück | Weiter