Growth factors change nuclear distribution of estrogen receptor-alpha via mitogen-activated protein kinase or phosphatidylinositol 3-kinase cascade in a human breast cancer cell line.
In the present study, to examine the dynamic changes in the localization of nuclear estrogen receptor (ER)alpha induced by growth factors, we used time-lapse confocal microscopy to directly visualized ERalpha fused with green fluorescent protein (GFP-ERalpha) in single living cells treated with epidermal growth factor (EGF) or IGF-I. We observed that 17beta-estradiol (E2) changed the normally diffuse distribution of GFP-ERalpha throughout the nucleoplasm to a hyperspeckled distribution within 10 min. Both EGF and IGF-I also changed the nuclear distribution of GFP-ERalpha, similarly to E2 treatment. However, the time courses of the nuclear redistribution of GFP-ERalpha induced by EGF or IGF-I were different from that induced by E2 treatment. In the EGF-treated cells, the GFP-ERalpha nuclear redistribution was observed at 30 min and reached a maximum at 60 min, whereas in the IGF-I-treated cells, the GFP-ERalpha nuclear redistribution was observed at 60 min and reached a maximum at 90 min. The EGF-induced redistribution of GFP-ERalpha was blocked by pretreatment with a MAPK cascade inhibitor, PD98059, whereas the IGF-I-induced redistribution of GFP-ERalpha was blocked by pretreatment with a phosphatidylinositol 3-kinase inhibitor, LY294002. Analysis using an activation function-2 domain deletion mutant of GFP-ERalpha showed that the change in the distribution of GFP-ERalpha was not induced by E2, EGF, or IGF-I treatment. These data suggest that MAPK and phosphatidylinositol 3-kinase cascades are involved in the nuclear redistribution of ERalpha by EGF and IGF-I, respectively, and that the activation function-2 domain of ERalpha may be needed for the nuclear redistribution of ERalpha.
Takahashi
Toshifumi
T
Department of Obstetrics and Gynecology, Yamagata University, School of Medicine, 2-2-2 Iidanishi, Yamagata 990-9585, Japan.
Ohmichi
Masahide
M
Kawagoe
Jun
J
Ohshima
Chika
C
Doshida
Masakazu
M
Ohta
Tsuyoshi
T
Saitoh
Maki
M
Mori-Abe
Akiko
A
Du
Botao
B
Igarashi
Hideki
H
Takahashi
Kazuhiro
K
Kurachi
Hirohisa
H
D000818:Animals; D001943:Breast Neoplasms; D019556:COS Cells; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D004958:Estradiol / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000502:physiology; D016296:Mutagenesis; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D015533:Transcriptional Activation / Q000187:drug effects / Q000502:physiology
D004815:Epidermal Growth Factor; D004958:Estradiol; D047628:Estrogen Receptor alpha; D049452:Green Fluorescent Proteins; D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases