Mechanisms of microtubule diassembly in vivo: studies in normal and chronic granulomatous disease leucocytes

Abstract

Microtubule assembly in human polmorphonuclear leucocytes is a dynamic process that can be initiated by binding of the plant lectin Concanavalin A to surface receptors. Colchicine inhibits lectin-induced microtubule assembly and promotes the movement of Concanavalin A into surface caps. Inhibition of microtubule assembly and enhanced Concanavalin A cap formation also follow treatment of normal leucocytes with two specific glutathione-oxidizing agents, 'diamide' and tertiary butylhydroperoxide. Our objective here was to determine if microtubule inhibition is mediated via glutathione disulphide or via hydrogen peroxide that is generated in Concanavalin A-treated leucocytes and may accumulate when cells are depleted of reduced glutathione. We show that exogenous hydrogen peroxide induces Concanavalin A capping on normal polymorphonuclear leucocytes but only at concentrations that simultaneously oxidize glutathione. We also show that 'diamide' and tertiary butylhydroperoxide cause Concanavalin A cap formation in leucocytes from patients with chronic granulomatous disease. These cells cannot generate significant amounts of superoxide or hydrogen peroxide. Thus, it seems likely that the reversible inhibition of microtubule assembly and function caused by glutathione oxidants requires only increased glutathione disulphide and is not dependent on subsequent accumulation of other metabolites.