Novel role of hnRNP-A2/B1 in modulating aryl hydrocarbon receptor ligand sensitivity
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The aryl hydrocarbon receptor (AHR) is responsible for susceptibility to its ligand-dependent responses. However, the effect of non-AHR factors is less clear. To explore the non-AHR factors, we used two mouse strains with different AHR genetic variants, namely C3H/lpr and MRL/lpr strains with Ala and Val as the 375th amino acid residue, respectively. To assess the contribution of AHR alone, COS-7 cells transiently expressing AHR from each strain were treated with 6-formylindolo[3,2-b]carbazole (FICZ) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and xenobiotic-responsive element (XRE)-driven reporter gene activities were measured. FICZ-EC50 values for the C3H/lpr and MRL/lpr AHR-mediated transactivation were 0.023 and 0.046 nM, respectively, indicating a similar susceptibility in both AHR genotypes. In contrast, C3H/lpr AHR was fourfold more sensitive to TCDD than MRL/lpr AHR. By a pull-down assay using a XRE-containing PCR product as bait and the hepatic nuclear extracts of both FICZ-treated mouse strains, we identified two interacting proteins as heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP-A2) and its splicing variant (hnRNP-A2b). Immunoprecipitation assays demonstrated the AHR interaction with hnRNP-A2/B1. When hnRNP-A2 was co-expressed with the MRL/lpr or C3H/lpr AHR in COS-7, FICZ treatment decreased EC50 to about threefold in both AHR genotypes, compared with EC50 in AHR alone. Similarly, hnRNP-A2b co-expression also lowered the FICZ-EC50 values. In TCDD-treated COS-7, responses depended on the AHR genotype; while no change in TCDD-EC50 was observed for C3H/lpr AHR when hnRNP-A2 was co-expressed, the value was reduced to nearly tenfold for MRL/lpr AHR. Co-transfection with hnRNP-A2b attenuated the AHR sensitivity to TCDD. In conclusion, the hnRNP-A2/B1 interacting with AHR may be a modulator of the AHR ligand sensitivity.
KeywordsAHR Sensitivity FICZ TCDD C3H/lpr MRL/lpr hnRNP-A2/B1
This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology to E.-Y. Kim (2013R1A1A2A10010043 and 2012K2A2A4021504). This study was also supported by Grants-in-Aid for Scientific Research (S) (Nos. 21221004 and 26220103) and Challenging Exploratory Research (No. 25660228) to H.I. from Japan Society for the Promotion of Science.
- Barboro P, Borzì L, Repaci E, Ferrari N, Balbi C (2013) Androgen receptor activity is affected by both nuclear matrix localization and the phosphorylation status of the heterogeneous nuclear ribonucleoprotein K in anti-androgen-treated LNCaP cells. PLOS One 8(11). doi: 10.1371/journal.pone.0079212
- Beischlag TV, Wang S, Rose DW, Torchia J, Reisz-Porszasz S, Muhammad K, Hankinson O (2002) Recruitment of the NCoA/SRC-1/p160 family of transcriptional coactivators by the aryl hydrocarbon receptor/aryl hydrocarbon receptor nuclear translocator complex. Mol Cell Biol 22(12):4319–4333PubMedCentralCrossRefPubMedGoogle Scholar
- Clower CV, Chatterjee D, Wang Z, Cantley LC, Vander Heiden MG, Krainer AR (2010) The alternative splicing repressors hnRNP A1/A2 and PTB influence pyruvate kinase isoform expression and cell metabolism. Proc Natl Acad Sci 107(5):1894–1899Google Scholar
- Fritsche E, Schäfer C, Calles C, Bernsmann T, Bernshausen T, Wurm M, Krutmann J (2007) Lightening up the UV response by identification of the arylhydrocarbon receptor as a cytoplasmatic target for ultraviolet B radiation. Proc Natl Acad Sci USA 104(21):8851–8856PubMedCentralCrossRefPubMedGoogle Scholar
- Hestermann EV, Stegeman JJ, Hahn ME (2000) Relative contributions of affinity and intrinsic efficacy to aryl hydrocarbon receptor ligand potency. Toxicol Sci 168:160–172Google Scholar
- Kawakami T, Ishimura R, Nohara K, Takeda K, Tohyama C, Ohsako S (2006) Differential susceptibilities of Holtzman and Sprague–Dawley rats to fetal death and placental dysfunction induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) despite the identical primary structure of the aryl hydrocarbon receptor. Toxicol Appl Pharmacol 212(3):224–236CrossRefPubMedGoogle Scholar
- Matsui M, Horiguchi H, Kamma H, Fujiwara M, Ohtsubo R, Ogata T (2000) Testis-and developmental stage-specific expression of hnRNP-A2/B1 splicing isoforms, B0a/b. Biochim Biophys Acta (BBA)-Gene Struct Expr 1493(1):33–40Google Scholar
- Wu S, Sato M, Endo C, Sakurada A, Dong B, Aikawa H, Kondo T (2003) hnRNP B1 protein may be a possible prognostic factor in squamous cell carcinoma of the lung. Lung Cancer (Amsterdam, Netherlands) 41(2):179Google Scholar