Rapid morphological changes in astrocytes are accompanied by redistribution but not by quantitative changes of cytoskeletal proteins

Astrocytes have the potential to acquire very different morphologies, depen ding on their regional location in the CNS and on their functional interact ions with other cell types. Morphological changes between a flat or a fibro blast-like and a stellate or process-bearing appearance, and vice versa, ca n occur rapidly, but very little is known as to whether morphological trans formations are based on quantitative changes of cytoskeletal proteins in mi crofilaments, intermediate filaments, and/or microtubules. Using a cell cul ture of selective type 1 astrocytes, we compared the distribution and prote in amounts of a number of cytoskeletal proteins both during primary process growth induced by specific media conditions and after secondary transforma tions induced by dBcAMP. Our data presented in this report support the idea that astrocytes can undergo dramatic changes in their morphology requiring subcellular redistribution of most cytoskeletal proteins but no quantitati ve modifications of the amount of the respective proteins. After pharmacolo gical treatment with lysophosphatic acid and genistein we show that astrocy tes can acquire intermediate morphologies reminiscent of both fibroblast an d stellate-like cells. These experiments demonstrate that the recently desc ribed RhoA-mediated signaling cascade between the cell surface and cytoskel etal proteins is only one of several signaling pathways acting on the astro cytic cytoskeleton. (C) 2001 Wiley-Liss, Inc.