GM1 enhances the association of neuron-specific MAP2 with actin in MAP2-transfected 3T3 cells

The ganglioside GM1 is a glycosphingolipid which enhances process formation of several neuronal lines and potentiates some growth factor-mediated resp onses. Previously we have shown that 24 h exposure of Neuro 2a cells to GM1 mobilized the neuron-specific microtubule-associated protein, MAP2, away f rom microtubule-rich areas to areas of neurite sprouting where MAP2 was mor e closely associated with the subcortical actin network. To examine the rol e of GM1 in fostering the shift of the association of MAP2 from tubulin to actin, NIH 3T3 cells were co-transfected with pHook-1(TM), which expresses a surface antigen, and a construct expressing MAP2. Transfected cells were selected with magnetic beads coated with a hapten that binds to the express ed surface antigen and treated with 150 mu g/ml GM1 for 18-24 h. Actin and MAP2 or tubulin and MAP2 were immunolocalized and examined with confocal mi croscopy. MAP2 was found throughout the cytoplasm as well as associated wit h actin filaments. As observed previously with Neuro 2a, GM1 treatment of t ransfected fibroblasts redistributed the MAP2 away from direct association with microtubules to peripheral areas where the association of MAP2 with ac tin was enhanced. GM1 did not induce neurite-like processes in MAP2-transfe cted cells. Treatment with cytochalasin B, which is reported to result in p rocess' formation, also did not induce neurite-like processes. These studie s suggest that GM1's ability to mobilize MAP2 and promote its association w ith actin is not restricted to neurons. (C) 2000 Elsevier Science B.V. All rights reserved.