Novel splice variants of the receptor for advanced glycation end-products expressed in human vascular endothelial cells and pericytes, and their putative roles in diabetes-induced vascular injury

Abstract

The binding of advanced glycation end-products (AGE) to the receptor for AGE (RAGE) is known to deteriorate various cell functions and is implicated in the pathogenesis of diabetic vascular complications. In the present study, we show that the cellular constituents of small vessels, endothelial cells (EC) and pericytes express novel splice variants of RAGE mRNA coding for the isoforms that lack the N-terminal V-type immunoglobulin-like domain (N-truncated) or the C-terminal transmembrane domain (C-truncated), as well as the known full-length mRNA. The ratio of the expression of the three variants was different between EC and pericytes; the content of the C-truncated form was highest in EC, whereas the full-length form was the most abundant in pericytes. Transfection experiments with COS-7 cells demonstrated that those variant mRNAs were translated into proteins as deduced; C-truncated RAGE was efficiently secreted into the culture media, and N-truncated RAGE was located mainly on the plasma membrane. The three isoforms were also detected in primary cultured human EC and pericytes. Further, full-length and C-truncated forms of RAGE bound to an AGE-conjugated column, whereas N-truncated RAGE did not. The AGE induction of extracellular-signal-related kinase phosphorylation and vascular endothelial growth factor in EC and of the growth and cord-like structure formation of EC was abolished completely by C-truncated RAGE, indicating that this endogenous secretory receptor (endogenous secretory RAGE) is cytoprotective against AGE. The results may contribute to our understanding of the molecular basis for the diversity of cellular responses to AGE and for individual variations in the susceptibility to diabetic vascular complications.

Levels of soluble receptor for AGE are cross-sectionally associated with cardiovascular disease in type 1 diabetes, and this association is partially mediated by endothelial and renal dysfunction and by low-grade inflammation: the EURODIAB Prospective Complications Study

“…This is the first study that has investigated the associations between sRAGE and macro-and microvascular complications in a large sample of individuals with type 1 diabetes, and has also addressed potential mechanisms that could explain the observed associations. Human endothelial cells express at least three RAGE variants [4]. The first one is the full-length RAGE, the second, the N-terminally truncated variant with a still unknown function, and the third, the C-terminally truncated soluble form.…”

“…The first one is the full-length RAGE, the second, the N-terminally truncated variant with a still unknown function, and the third, the C-terminally truncated soluble form. This naturally occurring form of sRAGE, as well as artificially produced sRAGE, can potentially bind to an AGE ligand thereby acting as a decoy, preventing AGE-RAGE interaction and activation [4]. This could thus explain any inverse association observed between sRAGE and vascular complications.…”

“…Different cell types including human endothelial cells express RAGE [4]. In addition to cell-bound RAGE, soluble forms of RAGE appear in the plasma [4,5], as different splice variants of RAGE (e.g.…”

“…Different cell types including human endothelial cells express RAGE [4]. In addition to cell-bound RAGE, soluble forms of RAGE appear in the plasma [4,5], as different splice variants of RAGE (e.g. endogenous secretory receptor for AGE [esRAGE]) leaking through the transmembrane and cytosolic domain [4,6], and as a proteolytically cleaved form of RAGE (sRAGE), which is most probably shed into the circulation by the sheddase, known as a disintegrin and metalloprotease 10 (ADAM 10) [7].…”

Receptor for advanced glycation end-products-mediated inflammation and diabetic vascular complications

“…In the strict sense of the word, sRAGE is a heterogeneous population of total sRAGE proteins, including soluble splice variants of RAGE and the proteinase‐cleaved forms of membrane‐bound RAGE and of the soluble variants. Endogenous secretory RAGE (esRAGE) 5 is one of the major splice variants of RAGE existing in the circulation and also being widely distributed to the cell surface and cytoplasm of neurons, EC, pneumocytes, mesothelium, pancreatic β‐cells, monocytes, macrophages, salivary glands, digestive tracts, renal tubules, prostate, skin, thyroid and bronchioles. The sRAGE is thought to act locally and systemically as a decoy receptor.…”