Endogenous IGFBP-3 Mediates Intrinsic Apoptosis Through Modulation of Nur77 Phosphorylation and Nuclear Export
Endogenous IGFBP-3 Mediates Intrinsic Apoptosis Through Modulation of Nur77 Phosphorylation and Nuclear Export
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DOI：
10.1210/en.2015-1215
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发表时间：
2015-11-01
期刊：
影响因子：
4.8
通讯作者：
Cohick, Wendie S.
中科院分区：
文献类型：
--
作者：
Agostini-Dreyer, Allyson;Jetzt, Amanda E.;Cohick, Wendie S.
在未转化的牛乳腺上皮细胞中，内源性凋亡诱导剂anisomycin （ANS）诱导IGFBP-3的表达和核定位，而IGFBP-3的敲低可减弱ANS诱导的细胞凋亡。其他研究表明，在前列腺癌细胞中，外源性IGFBP-3通过促进孤儿核受体Nur77及其结合伙伴视黄酮X受体α (RXR α)的核输出诱导细胞凋亡。本研究的目的是确定内源性IGFBP-3是否通过促进非转化细胞中Nur77和/或RXR α的核转运而在ans诱导的细胞凋亡中发挥作用。用siRNA敲低Nur77可减少ans诱导的caspase-3和-7及其下游靶标PARP的裂解，表明Nur77在ans诱导的细胞凋亡中起作用。在转染了IGFBP-3的细胞中，在基础条件下，IGFBP-3与RXR α相关，而与Nur77无关。然而，在ans处理的细胞中，IGFBP-3与这两种蛋白的磷酸化形式共沉淀。间接免疫荧光和细胞分离技术表明，ANS诱导了Nur77的磷酸化和从细胞核到细胞质的转运，这些作用通过敲除IGFBP-3而减弱。这些数据表明，内源性IGFBP-3通过促进Nur77的磷酸化和核输出到细胞质中发挥其凋亡作用，从而在细胞内凋亡中发挥作用。该机制是否涉及内源性IGFBP-3与Nur77或RXR α之间的物理关联仍有待确定。
In nontransformed bovine mammary epithelial cells, the intrinsic apoptosis inducer anisomycin (ANS) induces IGFBP-3 expression and nuclear localization and knockdown of IGFBP-3 attenuates ANS-induced apoptosis. Others haveshownin prostate cancer cells that exogenous IGFBP-3 induces apoptosis by facilitating nuclear export of the orphan nuclear receptor Nur77 and its binding partner, retinoid X receptor-alpha (RXR alpha). The goal of the present work was to determine whether endogenous IGFBP-3 plays a role in ANS-induced apoptosis by facilitating nuclear transport of Nur77 and/ or RXR alpha in nontransformed cells. Knockdown of Nur77 with siRNA decreased ANS-induced cleavage of caspase-3 and -7 and their downstream target, PARP, indicating a role for Nur77 in ANS-induced apoptosis. In cells transfected with IGFBP-3, IGFBP-3 associated with RXR alpha but not Nur77 under basal conditions, however, IGFBP-3 co-precipitated with phosphorylated forms of both proteins in ANS-treated cells. Indirect immunofluorescence and cell fractionation techniques showed that ANS induced phosphorylation and transport of Nur77 from the nucleus to the cytoplasm and these effects were attenuated by knockdown of IGFBP-3. These data suggest that endogenous IGFBP-3 plays a role in intrinsic apoptosis by facilitating phosphorylation and nuclear export of Nur77 to the cytoplasm where it exerts its apoptotic effect. Whether this mechanism involves a physical association between endogenous IGFBP-3 and Nur77 or RXR alpha remains to be determined.