Nuclear insulin receptor substrate 1 interacts with estrogen receptor alpha at ERE promoters.
Insulin receptor substrate 1 (IRS-1) is a major signaling molecule activated by the insulin and insulin-like growth factor I receptors. Recent data obtained in different cell models suggested that in addition to its conventional role as a cytoplasmic signal transducer, IRS-1 has a function in the nuclear compartment. However, the role of nuclear IRS-1 in breast cancer has never been addressed. Here we report that in estrogen receptor alpha (ERalpha)-positive MCF-7 cells, (1) a fraction of IRS-1 was translocated to the nucleus upon 17-beta-estradiol (E2) treatment; (2) E2-dependent nuclear translocation of IRS-1 was blocked with the antiestrogen ICI 182,780; (3) nuclear IRS-1 colocalized and co-precipitated with ERalpha; (4) the IRS-1:ERalpha complex was recruited to the E2-sensitive pS2 gene promoter. Notably, IRS-1 interaction with the pS2 promoter did not occur in ERalpha-negative MDA-MB-231 cells, but was observed in MDA-MB-231 cells retransfected with ERalpha. Transcription reporter assays with E2-sensitive promoters suggested that the presence of IRS-1 inhibits ERalpha activity at estrogen-responsive element-containing DNA. In summary, our data suggested that nuclear IRS-1 interacts with ERalpha and that this interaction might influence ERalpha transcriptional activity.
Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA.
Catia
C
Morelli
Cecilia
C
Garofalo
Diego
D
Sisci
Sonia
S
del Rincon
Sandra
S
Cascio
Xiao
X
Tu
Andrea
A
Vecchione
Edward R
ER
Sauter
Wilson H
WH
Miller
Eva
E
Surmacz
D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D045744:Cell Line, Tumor; D017931:DNA Primers; D047628:Estrogen Receptor alpha; D006801:Humans; D055504:Insulin Receptor Substrate Proteins; D010750:Phosphoproteins / Q000378:metabolism*; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D021381:Protein Transport; D011960:Receptors, Estrogen / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic
D017931:DNA Primers; D047628:Estrogen Receptor alpha; C526292:IRS1 protein, human; D055504:Insulin Receptor Substrate Proteins; D010750:Phosphoproteins; D011960:Receptors, Estrogen