INVESTIGADORES
GALIGNIANA Mario Daniel
artículos
Título:
Inhibition of glucocorticoid receptor nucleocytoplasmic shuttling by okadaic acid requires intact cytoskeleton
Autor/es:
GALIGNIANA MD, HOUSLEY PR, DEFRANCO DB, PRATT WB
Revista:
JOURNAL OF BIOLOGICAL CHEMISTRY
Editorial:
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
Referencias:
Año: 1999 vol. 274 p. 16222 - 16227
ISSN:
0021-9258
Resumen:
It has been shown previously that glucocorticoid receptors (GRs) that
have undergone hormone-dependent translocation to the nucleus and have
subsequently exited the nucleus upon hormone withdrawal are unable to
recycle into the nucleus if cells are treated during hormone withdrawal
with okadaic acid, a cell-permeable inhibitor of certain
serine/threonine protein phosphatases. Using a green fluorescent protein
(GFP) GR chimera (GFP-GR), we report here that okadaic acid inhibition
of steroid-dependent receptor recycling to the nucleus is abrogated in
cells treated for 1 h with colcemid to eliminate microtubule networks
prior to steroid addition. After withdrawal of colcemid, normal
cytoskeletal architecture is restored and okadaic acid inhibition of
steroid-dependent GFP-GR nuclear recycling is restored. When okadaic
acid is present during hormone withdrawal, GR that is recycled to the
cytoplasm becomes complexed with hsp90 and binds steroid, but it does
not undergo the normal agonist-dependent dissociation from hsp90 upon
retreatment with steroid. However, when the cytoskeleton is disrupted by
colcemid, the GR in okadaic acid-treated cells recycles from the
cytoplasm to the nucleus in an agonist-dependent manner without
dissociating from hsp90. This suggests that under physiological
conditions where the cytoskeleton is intact, a dephosphorylation event
is required for loss of high affinity binding to hsp90 that is required
for receptor translocation through the cytoplasm to the nucleus along
cytoskeletal tracts.