Promotion of microfilament polymerization by depolymerized glia filament preparation through interaction of vimentin with actin.

We investigated the in vitro interaction between microfilaments and glia filaments in the presence of alpha-sialosylcholesterol (SC). The depolymerized glia filament preparation (GF) that had been extracted from a crude cytoskeletal fraction of cultured rat astrocytes promoted markedly the polymerization of the depolymerized microfilament preparation (MF) in the presence of SC. The ability of GF to promote the MF polymerization was highest in the concentration range 7.5-15 microM SC. The polymerization of MF at the concentration of 10 micrograms protein/200 microliters was enhanced to the highest level by 4 micrograms protein/200 microliters of GF in the presence of 15 microM SC. The MF polymerization was promoted more efficiently by GF than by MF: for example, the polymerization of actin in MF (7.5 micrograms/200 microliters) was enhanced by the addition of 5 micrograms GF protein/200 microliters to a twice greater extent than by the addition of 5 micrograms MF protein/200 microliters in the presence of 15 microM SC. GF enhanced the MF polymerization by over three-fold at 4-37 degrees C, and the GF activity became greater with an increase in incubation temperature. Vimentin promoted the G-actin polymerization in the presence of 11.3 microM alpha-SC. The finding suggested that the interaction between vimentin and actin was one of the factors to cause GF to promote the MF polymerization.