Mitochondrial localization of the OAS1 p46 isoform associated with a common single nucleotide polymorphism

Abstract

BackgroundThe expression of 2′-5′-Oligoadenylate synthetases (OASs) is induced by type 1 Interferons (IFNs) in response to viral infection. The OAS proteins have a unique ability to produce 2′-5′ Oligoadenylates, which bind and activate the ribonuclease RNase L. The RNase L degrades cellular RNAs which in turn inhibits protein translation and induces apoptosis. Several single nucleotide polymorphisms (SNPs) in the OAS1 gene have been associated with disease. We have investigated the functional effect of two common SNPs in the OAS1 gene. The SNP rs10774671 affects splicing to one of the exons in the OAS1 gene giving rise to differential expression of the OAS1 isoforms, and the SNP rs1131454 (former rs3741981) resides in exon 3 giving rise to OAS1 isoforms with either a Glycine or a Serine at position 162 in the core OAS unit.ResultsWe have used three human cell lines with different genotypes in the OAS1 SNP rs10774671, HeLa cells with the AA genotype, HT1080 cells with AG, and Daudi cells with GG. The main OAS1 isoform expressed in Daudi and HT1080 cells was p46, and the main OAS1 isoform expressed in HeLa cells was p42. In addition, low levels of the OAS1 p52 mRNA was detected in HeLa cells and p48 mRNA in Daudi cells, and trace amounts of p44a mRNA were detected in the three cell lines treated with type 1 interferon. We show that the OAS1 p46 isoform was localized in the mitochondria in Daudi cells, whereas the OAS1 isoforms in HeLa cells were primarily localized in cytoplasmic vacuoles/lysosomes. By using recombinantly expressed OAS1 mutant proteins, we found that the OAS1 SNP rs1131454 (former rs3741981) did not affect the enzymatic OAS1 activity.ConclusionsThe SNP rs10774671 determines differential expression of the OAS1 isoforms. In Daudi and HT1080 cells the p46 isoform is the most abundantly expressed isoform associated with the G allele, whereas in HeLa cells the most abundantly expressed isoform is p42 associated with the A allele. The SNP rs1131454 (former rs3741981) does not interfere with OAS1 enzyme activity. The OAS1 p46 isoform localizes to the mitochondria, therefore a full 2-5A system can now be found in the mitochondria.

The Cellular Localization of the p42 and p46 Oligoadenylate Synthetase 1 Isoforms and Their Impact on Mitochondrial Respiration

“…HeLa (ATTC: CCL-2) and HT1080 (ATCC: CCL-121) cells were cultured as adherent cells at 37 • C with 5% CO 2 in Dulbecco's modified Eagle's medium with high glucose and with sodium pyruvate (Life Technologies Europe BV, Naerum, Denmark) with added 10% sterile-filtered fetal bovine serum (FBS) (Sigma-Aldrich, Søborg, Denmark ) and 1% Penicillin-Streptomycin (Pen-Strep) solution (Sigma-Aldrich) at 37 • C and 5% CO2. The human HT1080 and HeLa cell lines used have the AG genotype and the AA genotype, respectively, regarding the SNP rs10774671 [9]. For interferon treatments, both HeLa and HT1080 cells were grown to~80% confluence and were treated with 1000 U/mL IFN-β or left untreated for 24-48 h before analysis.…”

“…The subcellular localization of the two OAS1 isoforms also seems to be different. We have previously observed that the OAS1 p46 isoform is localized in the mitochondria, whereas the p42 is more evenly distributed in the cytosol [9]. We have hypothesized that this difference could be due to the presence of a CaaX motif (C = Cysteine, a = aliphatic amino acid, X = terminal amino acid) in the C-terminal of only the p46 isoform, which could be important in directing the protein to the mitochondria.…”

“…Two of these isoforms are the p42 and p46 variants which are the focus of this study. The two isoforms are so named due to their theoretical size of~42 and~46 kDa and the expression pattern between these two variants is related to one single nucleotide polymorphism (SNP), the SNP rs10774671 [8,9]. The SNP is an A/G variation located in the splice acceptor site of exon 7 which results in either the A allele expressing the p42 isoform or the G allele expressing the p46 isoform.…”

Impact of IL28B and OAS gene family polymorphisms on interferon treatment response in Caucasian children chronically infected with hepatitis B virus

“…However, the molecular basis for this association is not well understood. In several studies, it was shown that polymorphisms in the OAS genes result in variations in enzyme activity by influencing basal enzyme activity[39], gene expression[17] or cellular localization[40]. …”

Functional prediction and comparative population analysis of variants in genes for proteases and innate immunity related to SARS-CoV-2 infection

“…The comparative population analysis pointed to the 7 coding variants in PLG, TMPRSS11a, MBL2 and OAS1 with noticeable divergence in allelic frequencies between analyzed populations. [42] and multiple sclerosis [43], but a more recent study showed that this variant was found not to interfere with OAS1 enzyme activity [44].…”