INVESTIGADORES
GALIGNIANA Mario Daniel
artículos
Título:
Heat shock protein 90-dependent (geldanamycin-inhibited) movement of the glucocorticoid receptor through the cytoplasm to the nucleus requires intact cytoskeleton
Autor/es:
GALIGNIANA MD, SCRUGGS JL, HERRINGTON J, WELSH MJ, CARTER-SU C, HOUSLEY PR, PRATT WB
Revista:
MOLECULAR ENDOCRINOLOGY
Editorial:
ENDOCRINE SOC
Referencias:
Año: 1998 vol. 12 p. 1903 - 1913
ISSN:
0888-8809
Resumen:
We use here a chimera of the green fluorescent protein (GFP) and the
glucocorticoid receptor (GR) to test the notion that the protein
chaperone heat shock protein-90 (hsp90) is required for
steroid-dependent translocation of the receptor through the cytoplasm
along cytoskeletal tracks. The GFP-GR fusion protein undergoes
steroid-mediated translocation from the cytoplasm to the nucleus, where
it is transcriptionally active. Treatment of 3T3 cells containing
steroid-bound GFP-GR with geldanamycin, a benzoquinone ansamycin that
binds to hsp90 and disrupts its function, inhibits
dexamethasone-dependent translocation from the cytoplasm to the nucleus.
The t1/2 for translocation in the absence of geldanamycin is
approximately 5 min, and the t1/2 in the presence of geldanamycin is
approximately 45 min. In cells treated for 1 h with the cytoskeletal
disrupting agents colcemid, cytochalasin D, and
beta,beta'-iminodipropionitrile to completely disrupt the microtubule,
microfilament, and intermediate filament networks, respectively, the
GFP-GR still translocates rapidly to the nucleus in a strictly
dexamethasone-dependent manner but translocation is no longer affected
by geldanamycin. After withdrawal of the cytoskeletal disrupting agents
for 3 h, normal cytoskeletal architecture is restored, and geldanamycin
inhibition of dexamethasone-dependent GFP-GR translocation is restored.
We suggest that in cells without an intact cytoskeletal system, the
GFP-GR moves through the cytoplasm by diffusion. However, under
physiological conditions in which the cytoskeleton is intact, diffusion
is limited, and the GFP-GR utilizes a movement machinery that is
dependent upon hsp90 chaperone activity. In contrast to the GR,
GFP-STAT5B, a signaling protein that is not complexed with hsp90,
undergoes GH-dependent translocation to the nucleus in a manner that is
not dependent upon hsp90 chaperone activity.