Gangliosides induce microfilament-dependent changes in membrane surface activity of Neuro-2a neuroblastoma cells

Abstract

Exogenous mixtures of bovine brain gangliosides (BBG) initiated a rapid series of sequential changes in surface activity in Neuro-2a neuroblastoma cells. These changes were characterized by the formation of microvilli, ridge-like projections and ruffled membranes within l min of BBG exposure. A maximum number of microvilli was reached after 10 min exposure and disappeared by 30 min. Ruffled membranes were most prominent within 5 min, but were still present after 60 min. These surface changes were accompanied by the formation of a thick subcortical meshwork of microfilaments which formed the cores of the microvilli and ruffled membranes. The simultaneous treatment of cells with BBG and an agent known to disrupt microfilaments (cytochalasin D) inhibited the formation of both microvilli and ruffles. In contrast, the simultaneous application of BBG and agents affecting microtubule polymerization (Colcemid and taxol) did not inhibit the formation of these surface structures. Treatment of Neuro-2a cells with cyclic AMP (cAMP) analogs (dibutyryl cAMP and 8-bromo cAMP) induced a similar series of surface changes which were inhibited by cytochalasin D. Furthermore, these surface changes may be specific to cAMP since neither cGMP analogs (dibutyryl cGMP and 8-bromo cGMP) nor 5′AMP induced surface changes. We propose that the initial membrane response to exogenous gangliosides is mediated by a microfilament-dependent mechanism. The basic similarities in surface responses elicited by BBG and cAMP analogs suggest that the effects of gangliosides on surface activity may be induced in part by a cAMP-dependent mechanism.