The Ser82 RAGE Variant Affects Lung Function and Serum RAGE in Smokers and sRAGE Production In Vitro

Abstract

IntroductionGenome-Wide Association Studies have identified associations between lung function measures and Chronic Obstructive Pulmonary Disease (COPD) and chromosome region 6p21 containing the gene for the Advanced Glycation End Product Receptor (AGER, encoding RAGE). We aimed to (i) characterise RAGE expression in the lung, (ii) identify AGER transcripts, (iii) ascertain if SNP rs2070600 (Gly82Ser C/T) is associated with lung function and serum sRAGE levels and (iv) identify whether the Gly82Ser variant is functionally important in altering sRAGE levels in an airway epithelial cell model.MethodsImmunohistochemistry was used to identify RAGE protein expression in 26 human tissues and qPCR was used to quantify AGER mRNA in lung cells. Gene expression array data was used to identify AGER expression during lung development in 38 fetal lung samples. RNA-Seq was used to identify AGER transcripts in lung cells. sRAGE levels were assessed in cells and patient serum by ELISA. BEAS2B-R1 cells were transfected to overexpress RAGE protein with either the Gly82 or Ser82 variant and sRAGE levels identified.ResultsImmunohistochemical assessment of 6 adult lung samples identified high RAGE expression in the alveoli of healthy adults and individuals with COPD. AGER/RAGE expression increased across developmental stages in human fetal lung at both the mRNA (38 samples) and protein levels (20 samples). Extensive AGER splicing was identified. The rs2070600T (Ser82) allele is associated with higher FEV1, FEV1/FVC and lower serum sRAGE levels in UK smokers. Using an airway epithelium model overexpressing the Gly82 or Ser82 variants we found that HMGB1 activation of the RAGE-Ser82 receptor results in lower sRAGE production.ConclusionsThis study provides new information regarding the expression profile and potential role of RAGE in the human lung and shows a functional role of the Gly82Ser variant. These findings advance our understanding of the potential mechanisms underlying COPD particularly for carriers of this AGER polymorphism.

Genetic risk factors for the development of pulmonary disease identified by genome‐wide association

“…A reductionist RAGE recombinant cell model was used to study the function effects of the different alleles on the same genetic background and it was shown that the Ser82 variant of the receptor resulted in lower levels of secretion of soluble RAGE, demonstrating that the specific variant has functional consequences . Rather counterintuitively, serum or plasma levels of sRAGE in COPD patients are lower compared to controls.…”

“…AGER mRNA is also expressed in the foetal lung, with increasing levels across the pseudoglandular and canalicular stages of human lung development. This finding correlated with protein expression during lung development . The study also showed that there was an association between rs2070600T and higher FEV 1 and FEV 1 /FVC as well as providing evidence that individuals with the Ser82 variant had significantly lower levels of serum sRAGE compared to Gly82 genotype individuals …”

“…49,50,74,75 Miller et al conducted a study showing that the Ser82 variant had effects on lung function as well as acting as an eQTL for soluble RAGE in both the serum of UK smokers and RAGE production in a recombinant cell system. 76 RAGE is a member of the Ig superfamily which when activated, by a diverse range of ligands, has many downstream effects including inflammatory regulation and cell migration, proliferation and adhesion. RAGE expression was identified by immunohistochemistry in the alveoli and bronchi of control and COPD lungs.…”

The Receptor for Advanced Glycation Endproducts (RAGE) and Mediation of Inflammatory Neurodegeneration

“…sRAGE is a short, soluble isoform of RAGE, and putative "decoy" receptor. Because it lacks the intracellular and cytoplasmic domains required for signaling, sRAGE is predicted to protect against inflammation and RAGE-dependent cellular stress by sequestering RAGE ligands and preventing their engagement of the full-length, transmembrane RAGE [72,73]. Thus, in humans bearing this SNP, lower sRAGE concentrations may directly amplify ligand burden and availability for signal transduction through full-length RAGE.…”

Progress in disease progression genetics: dissecting the genetic origins of lung function decline in COPD

“…Additional work is required to link these loci to pathophysiology. Functional studies on GWAS loci involving HHIP ,12 13 FAM13A ,14 HTR4 ,15 AGER 16 and IREB2 17 have already provided important insights into the biological mechanisms for genetic determinants of COPD and/or lung function.…”