Alternative splicing of the murine receptor for advanced glycation end‐products (RAGE) gene

Abstract

The alternative splicing of pre-mRNAs is a critical mechanism in genomic complexity, disease, and development. Studies of the receptor for advanced glycation end-products (RAGE) indicate that this gene undergoes a variety of splice events in humans. However, no studies have extensively analyzed the tissue distribution in other species or compared evolutionary differences of RAGE isoforms. Because the majority of studies probing RAGE function have been performed in murine models, we therefore performed studies to identify and characterize the splice variants of the murine RAGE gene, and we compared these to human isoforms. Here, using mouse tissues, we identified numerous splice variants including changes in the extracellular domain or the removal of the transmembrane and cytoplasmic domains, which produce soluble splice isoforms. Comparison of splice variants between humans and mice revealed homologous regions in the RAGE gene that undergo splicing as well as key species-specific mechanisms of splicing. Further analysis of tissue splice variant distribution in mice revealed major differences between lung, kidney, heart, and brain. To probe the potential impact of disease-like pathological states, we studied diabetic mice and report that RAGE splice variation changed dramatically, resulting in an increase in production of soluble RAGE (sRAGE) splice variants, which were not associated with detectable levels of sRAGE in murine plasma. In conclusion, we have determined that the murine RAGE gene undergoes extensive splicing with distinct splice isoforms being uniquely distributed in different tissues. These differences in RAGE splicing in both physiological and pathogenic states further expand our understanding of the biological repertoire of this receptor in health and disease.

Multiple levels of regulation determine the role of the receptor for AGE (RAGE) as common soil in inflammation, immune responses and diabetes mellitus and its complications

“…While diabetic mice demonstrated a significant increase in RAGE splice variants, the latter was not associated with any detectable level of sRAGE protein in murine plasma [23]. Since sRAGE can be readily detected in human plasma, this observation not only indicates important differences between human and murine RAGE [23], but further implies that sRAGE observed in humans is, in the main, produced by shedding mechanisms [49]. Since in vitro and experimental animal models have demonstrated that exogenous sRAGE functions as a decoy by preventing ligands from interacting with cellular RAGE, it was supposed that sRAGE might counteract RAGE-mediated cell activation [53].…”

“…The quaternary structure of the RAGE extracellular domain, but also post-translational modifications of its primary structure, might account for the diversity of ligand recognition. It remains unknown whether differences in splice variants between humans and mice [23] might also influence ligand specificity in different diseases. Thus, the postulated promiscuity of RAGE, which would make it potentially able to bind almost damage-associated molecular patterns [24], does not in fact exist, since post-translational modifications affect the relative specificity of a given ligand in a given situation of cellular activation.…”

“…Circulating sRAGE is either produced by receptor ectodomain shedding [49,50] or represents splice variants of RAGE such as endogenous secreted RAGE (esRAGE) [51]. Comparison of splice variants between humans and mice revealed homologous and species-specific mechanisms for splicing of the RAGE gene, but also tissuespecific splice variant distribution and the absence of plasma sRAGE in mice [23,52]. While diabetic mice demonstrated a significant increase in RAGE splice variants, the latter was not associated with any detectable level of sRAGE protein in murine plasma [23].…”

“…Comparison of splice variants between humans and mice revealed homologous and species-specific mechanisms for splicing of the RAGE gene, but also tissuespecific splice variant distribution and the absence of plasma sRAGE in mice [23,52]. While diabetic mice demonstrated a significant increase in RAGE splice variants, the latter was not associated with any detectable level of sRAGE protein in murine plasma [23]. Since sRAGE can be readily detected in human plasma, this observation not only indicates important differences between human and murine RAGE [23], but further implies that sRAGE observed in humans is, in the main, produced by shedding mechanisms [49].…”

RAGE Does Not Contribute to Renal Injury and Damage upon Ischemia/Reperfusion-Induced Injury

“…The receptor for advanced glycation end products (RAGE) is a multiligand PRR that is expressed in all tissues and on a wide range of cell types, including renal mesangial cells, (proximal) tubuli, podocytes and Bowman's capsule [2][3][4][5][6] and mediates a variety of inflammatory responses in renal diseases [7] . RAGE blockade or deficiency has been shown to suppress hepatic, cardiac, lung and brain I/R-induced injury [8][9][10][11][12] ; however, the contribution of RAGE in renal I/R-induced injury is unknown [13] .…”