Rapid Apoptosis Induction by IGFBP-3 Involves an Insulin-like Growth Factor-independent Nucleomitochondrial Translocation of RXRα/Nur77

Abstract

Insulin-like growth factor-binding protein-3 (IGFBP-3) induces apoptosis by its ability to bind insulin-like growth factors (IGFs) as well as its IGF-independent effects involving binding to other molecules including the retinoid X receptor-␣ (RXR␣).Here we describe that in response to IGFBP-3, the RXR␣ binding partner nuclear receptor Nur77 rapidly undergoes translocation from the nucleus to the mitochondria, initiating an apoptotic cascade resulting in caspase activation within 6 h. This translocation is a type 1 IGF receptor-signaling independent event as IGFBP-3 induces Nur77 translocation in R-cells. IGFBP-3 and Nur77 are additive in inducing apoptosis. GFP-Nur77 transfection into RXR␣ wildtype and knock-out mouse embryonic fibroblasts and subsequent treatment with IGFBP-3 show that RXR␣ is required for IGFBP-3-induced Nur77 translocation and apoptosis. Addition of IGFBP-3 to 22RV1 cell lysates enhanced the ability of GST-RXR␣ to "pull down" Nur77, and overexpression of IGFBP-3 enhanced the accumulation of mitochondrial RXR␣. This unique nongenotropic nuclear pathway supports an emerging role for IGFBP-3 as a novel, multicompartmental signaling molecule involved in induction of apoptosis in malignant cells.Over the past decade, multiple lines of investigation have validated insulin-like growth factor-binding protein-3 (IGFBP-3)1 as an inducer of cellular apoptosis, effects that can be unrelated to its IGF binding (1). Most importantly, several groups have now reported successful in vivo treatment of cancer models with IGFBP-3, either as a single agent or in combination with chemotherapeutic agents (2-4). However, the molecular mechanisms by which IGFBP-3 induces apoptosis remain largely unknown at present.Several novel IGFBP-3 binding partners have been recently identified that may participate in its IGF-independent proapoptotic effects (1). We and others demonstrated that retinoid X receptor-␣ (RXR␣) is a binding partner for IGFBP-3 (5, 6) and that RXR␣ is required for IGFBP-3 apoptotic effects (5). Indeed, IGFBP-3 potentiates RXRE-mediated signaling while inhibiting signaling via other RXR␣ heterodimeric partners (5-7). Our discovery of IGFBP-3 binding to RXR␣ suggested that its apoptotic effects might involve an RXR␣-dependent transcriptional mechanism. Most published reports have evaluated IGFBP-3-induced apoptosis at 24 -72 h (8 -11), consistent with a transcriptional mechanism. However, we have recently described apoptosis activation by IGFBP-3 (as evidenced by caspase activation and histone associated DNA fragmentation ELISA) as early as 1-6 h after IGFBP-3 exposure, suggesting a mechanism that does not require de novo gene transcription (12, 13). The orphan nuclear receptor Nur77 (also known as NGFI-B (14) and TR3 (15)) is a nuclear receptor transcription factor and is an important regulator of apoptosis in different cells (16). It is a member of the orphan steroid receptor family, which also includes Nor1 and Nurr1. This family is essential for apoptosis of self-reactive immature thymocytes followi...

Molecular Portrait of Metastasis-Competent Circulating Tumor Cells in Colon Cancer Reveals the Crucial Role of Genes Regulating Energy Metabolism and DNA Repair

“…3A). The "colon CTC signature" included the defensin ␣ genes [defensin alpha 5 (DEFA5) and defensin alpha 6 (DEFA6)], 10 and chemokines [C-X-C motif chemokine ligand 2 (CXCL2), C-X-C motif chemokine ligand 6 (CXCL6), C-X-C motif chemokine ligand 10 (CXCL10), C-X-C motif chemokine ligand 11 (CXCL11), C-C motif chemokine ligand 5 (CCL5), and C-C motif chemokine ligand 28 (CCL28)] also were overexpressed in HT-29 cells. Finally, the Gene Set Enrichment Analysis showed that several tumorigenesis-related genes were enriched in the "colon CTC signature," such as carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5) and carcinoembry- IL15, interleukin 15; IL1R1, interleukin 1 receptor type 1; CXCL2, C-X-C motif chemokine ligand 2; CXCL6, C-X-C motif chemokine ligand 6; CXCL10, C-X-C motif chemokine ligand 10; CXCL11, C-X-C motif chemokine ligand 11; CCL5, C-C motif chemokine ligand 5; CCL28, C-C motif chemokine ligand 28 onic antigen-related cell adhesion molecule 6 (CEACAM6), phospholipase A2 group 2A (PLA2G2A), and aldehyde dehydrogenase 3 family member A1 (ALDH3A1).…”

IGF binding protein-3 regulates hematopoietic stem cell and endothelial precursor cell function during vascular development

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Regulation of Nur77 nuclear export by c-Jun N-terminal kinase and Akt

“…We have previously demonstrated a new paradigm in cancer cell apoptosis, in which Nur77 is induced, then translocates from the nucleus to the mitochondria, leading to release of cytochrome c from the mitochondria (Li et al, 2000). The apoptosis-associated nuclear egress of Nur77 has been observed in cancer cells from the lung, ovary, colon, stomach and breast (Dawson et al, 2001;Holmes et al, 2002Holmes et al, , 2003Liu et al, 2002;Wu et al, 2002;Jeong et al, 2003;Kolluri et al, 2003;Wilson et al, 2003;Cao et al, 2004;Jacobs et al, 2004;Lin et al, 2004;Lee et al, 2005). Nur77 mitochondrial localization is also involved in Sindbis virus-induced apoptosis (Lee et al, 2002).…”

“…The Nur77-dependent apoptotic process is triggered by a number of apoptosis inducers, including retinoidrelated molecule 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalenecar-boxylic acid (AHPN) (also called CD437) (Li et al, 2000) and its analogs (Li et al, 2000;Dawson et al, 2001;Holmes et al, 2002Holmes et al, , 2003Kolluri et al, 2003;Cao et al, 2004;Lin et al, 2004), etoposide (Li et al, 2000;Liu et al, 2002;Wilson et al, 2003), and insulin-like growth factor binding protein-3 (Lee et al, 2005). The importance of Nur77-dependent apoptotic pathway in mediating the anticancer activity of chemotherapeutic agents is supported by the positive correlation between Nur77 family member Nor-1 expression and survival in diffuse large B-cell lymphoma patients treated with therapeutic drugs (Shipp et al, 2002).…”