GLUCOCORTICOID RECEPTOR INHIBITS MICROTUBULE ASSEMBLY IN-VITRO

The effect of glucocorticoid hormones, purified glucocorticoid recepto r (GR) and purified heat shock protein M(r) 90 000 (hsp90) on microtub ule (MT) assembly in vitro was tested by a spectrophotometric MT assem bly assay and electron microscopy. GR significantly prolonged the nucl eation phase, slowed down the assembly rate and reduced the maximal am plitude of MT assembly compared with control. The effects were partial ly reversed by the addition of glucocorticoid hormone. GR associated w ith MTs. These results indicate that GR affects MT assembly in vitro, which may be a functional correlate to the structural association of G R with MTs. This implies that factors affecting GR may affect MT assem bly in vivo.