Glucocorticoid receptor phosphorylation in v-mos-transformed cells.
Nucleocytoplasmic shuttling of glucocorticoid receptors (GRs) is disrupted in v-mos-transformed cells leading to the redistribution of hormone-bound receptors from the nuclear to cytoplasmic compartments. We show here that GRs from v-mos-transformed cells are hyperphosphorylated on a specific peptide and maintain hormone-induced phosphorylations upon a prolonged hormone treatment that is associated with disruptions in its nucleocytoplasmic shuttling. Since similar effects on GR nucleocytoplasmic shuttling and phosphorylation were exerted upon treatment of nontransformed cells with the protein phosphatase inhibitor okadaic acid, we examined whether hyperphosphorylation of GRs in v-mos-transformed cells resulted from inhibition of receptor dephosphorylation. Protein phosphatase activity, measured using various substrates in vitro, was identical in cell-free extracts prepared from v-mos-transformed and nontransformed cells. Analysis of phosphate turnover in vivo from either the sum of all GR phosphorylation sites or from individual sites using pulse-chase analysis, did not reveal any significant difference between v-mos-transformed cells versus nontransformed cells. Thus, hyperphosphorylation of GR in v-mos-transformed cells does not appear to result from inhibition of GR dephosphorylation, but rather from stimulation of GR phosphorylation.
Borror
K C
KC
Department of Biological Sciences, University of Pittsburgh, Pennsylvania 15260, USA.
Garabedian
M J
MJ
DeFranco
D B
DB
D000818:Animals; D002461:Cell Line, Transformed; D002472:Cell Transformation, Viral; D002855:Chromatography, Thin Layer; D006657:Histones / Q000302:isolation & purification / Q000378:metabolism; D008980:Moloney murine sarcoma virus / Q000235:genetics; D017232:Oncogene Proteins v-mos / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry; D010710:Phosphates / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010762:Phosphorylase a / Q000378:metabolism; D010766:Phosphorylation; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000737:chemistry / Q000378:metabolism*; D015398:Signal Transduction; D013696:Temperature; D013997:Time Factors
D006657:Histones; D017232:Oncogene Proteins v-mos; D010446:Peptide Fragments; D010710:Phosphates; D011965:Receptors, Glucocorticoid; D010762:Phosphorylase a; D010749:Phosphoprotein Phosphatases