Oncogene Functions of FHL2 Are Independent from NF-κBIα in Gastrointestinal Cancer
ABSTRACT Four and a half of LIM-only protein 2 (FHL2) is an adaptor protein that can interact with many transcription factors and thus
plays a variety of biological functions. Previous studies by our group have demonstrated that suppression of FHL2 was capable
of inducing tumor cell differentiation, and inhibiting the growth of experimental gastric and colon cancers. Therefore, FHL2
appears to function as an oncogene. In order to further explore the mechanisms of how FHL2 is involved in tumorigenesis, we
attempted to test whether FHL2 has any direct association with nuclear factor (NF-κB), the most important transcription factor
involved in apoptosis, inflammation, and carcinogenesis. Using an Yeast Two Hybrid (Y2H) screening system, we have shown that
FHL2 may have an interaction with NF-κBIα, the coding gene for IκBα which is the most potent endogenous inhibitor for NF-κB
activation. However, subsequent studies using co-immunoprecipitation and co-localization failed to confirm the Y2H finding.
Down-regulation of FHL2 by FHL2-siRNA down-regulated the expression of NF-κB p65. We therefore concluded that under the physiological
condition, FHL2 may activate NF-κB pathway, even though such an activation may not be mediated by a direct binding of FHL2
to NF-κB inhibitor protein IκB.
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ABSTRACT: XIAP-associated factor 1(XAF1) is a tumor suppressor with its functional mechanisms not fully understood. The zinc-finger cluster located at the N-terminus is the only domain structure. Four and a half LIM domain protein 2 (FHL2) also contains a tandem zinc finger structure, and its protein functions as an important adaptor and modifier in protein–protein interactions. Both of their structures are relatively simple, while the association between them is still unclear. In this study, we detected the interaction between XAF1 and FHL2 by using the yeast two-hybrid system. We identified FHL2 as a XAF1 binding protein. Furthermore, both XAF1 and FHL2 localized to the cytoplasm, mitochondria, and nucleus of gastric cancer cells. Over-expression of XAF1 excluded FHL2 from the nucleus and suppressed the trans-activity of FHL2 in stimulating the transcriptional activities of β-catenin and AP-1. In conclusion, our findings unraveled an antagonistic mechanism between a tumor suppressor and an oncoprotein in cancer cells. Mol. Carcinog. © 2010 Wiley-Liss, Inc.Molecular Carcinogenesis 11/2010; 50(3):199 - 207. · 4.27 Impact Factor
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ABSTRACT: The three members of the NR4A orphan nuclear receptor subfamily Nur77, Nurr1, and NOR-1, regulate a variety of biological functions including vascular disease and metabolism. In this study, we identified Four and a half LIM domains protein-2 (FHL2) as a novel interacting protein of NR4A nuclear receptors by yeast two-hybrid screen and co-immunoprecipitation studies. Each of the four LIM domains of FHL2 can bind Nur77, and both the amino-terminal domain and the DNA binding domain of Nur77 are involved in the interaction between FHL2 and Nur77. FHL2 represses Nur77 transcriptional activity in a dose-dependent manner, and short hairpin RNA-mediated knockdown of FHL2 results in increased Nur77 transcriptional activity. ChIP experiments on the enolase3 promoter revealed that FHL2 inhibits the association of Nur77 with DNA. FHL2 is highly expressed in human endothelial and smooth muscle cells, but not in monocytes or macrophages. To substantiate functional involvement of FHL2 in smooth muscle cell physiology, we demonstrated that FHL2 overexpression increases the growth of these cells, whereas FHL2 knockdown results in reduced DNA synthesis. Collectively, these studies suggest that association of FHL2 with Nur77 plays a pivotal role in vascular disease.Journal of Biological Chemistry 11/2011; 286(52):44336-43. · 4.65 Impact Factor