Rapid TGF beta 1 effects on actin cytoskeleton of astrocytes: comparison with other factors and implications for cell motility.

We have previously shown that long-term treatment of primary cultured astrocytes with TGF beta 1 induces morphological changes accompanied by increases in actin and GFAP synthesis, and a profound rearrangement of the cytoskeleton. The present report describes the short-term reorganization of actin filaments induced by TGF beta 1 in rat cerebellum cultured astrocytes and in an astrocytic cell line. TGF beta 1 caused the appearance of new actin and vinculin organizations, without protein synthesis. This cytoskeletal rearrangement was followed by altered cell-cell interactions. All these changes induced by TGF beta 1 were different and slower than those induced by serum, PDGF, and endothelin. TGF beta 1 induced the appearance of lamellipodia, organelles found at the cell front of motile cells in low-density cultures of immortalized astrocytes. These results indicate that the changes in the astrocyte cytoskeleton induced by TGF beta 1 are probably associated with cell movement. The events promoted by TGF beta 1 might help to clarify its action in the brain during embryogenesis and in tissue repair.