Induction of RAGE Shedding by Activation of G Protein-Coupled Receptors

Abstract

The multiligand Receptor for Advanced Glycation End products (RAGE) is involved in various pathophysiological processes, including diabetic inflammatory conditions and Alzheimes disease. Full-length RAGE, a cell surface-located type I membrane protein, can proteolytically be converted by metalloproteinases ADAM10 and MMP9 into a soluble RAGE form. Moreover, administration of recombinant soluble RAGE suppresses activation of cell surface-located RAGE by trapping RAGE ligands. Therefore stimulation of RAGE shedding might have a therapeutic value regarding inflammatory diseases. We aimed to investigate whether RAGE shedding is inducible via ligand-induced activation of G protein-coupled receptors (GPCRs). We chose three different GPCRs coupled to distinct signaling cascades: the V2 vasopressin receptor (V2R) activating adenylyl cyclase, the oxytocin receptor (OTR) linked to phospholipase Cβ, and the PACAP receptor (subtype PAC1) coupled to adenylyl cyclase, phospholipase Cβ, calcium signaling and MAP kinases. We generated HEK cell lines stably coexpressing an individual GPCR and full-length RAGE and then investigated GPCR ligand-induced activation of RAGE shedding. We found metalloproteinase-mediated RAGE shedding on the cell surface to be inducible via ligand-specific activation of all analyzed GPCRs. By using specific inhibitors we have identified Ca2+ signaling, PKCα/PKCβI, CaMKII, PI3 kinases and MAP kinases to be involved in PAC1 receptor-induced RAGE shedding. We detected an induction of calcium signaling in all our cell lines coexpressing RAGE and different GPCRs after agonist treatment. However, we did not disclose a contribution of adenylyl cyclase in RAGE shedding induction. Furthermore, by using a selective metalloproteinase inhibitor and siRNA-mediated knock-down approaches, we show that ADAM10 and/or MMP9 are playing important roles in constitutive and PACAP-induced RAGE shedding. We also found that treatment of mice with PACAP increases the amount of soluble RAGE in the mouse lung. Our findings suggest that pharmacological stimulation of RAGE shedding might open alternative treatment strategies for Alzheimeŕs disease and diabetes-induced inflammation.

ADAM10 modulates calcitriol‐regulated RAGE in cardiomyocytes

“…Moreover, calcitriol induced the translocation of ADAM10 to the plasma membrane and then triggered the ectodomain shedding of tumour necrosis factor receptor 1 in vascular smooth muscle cells [30]. Our findings were similar to the previous results in HeLa cells and human embryonic kidney cells, whereas control and GI254023X (1, 5 and 25 lM)-treated cells had similar RAGE protein expression [31,32]. The suppressive effect of calcitriol on RAGE was reduced by about 50% after inhibiting ADAM10, which suggested that RAGE suppression caused by calcitriol may be mediated by its effects on ADAM10 activation at least in part.…”

Effect of chronic hypoxia on RAGE and its soluble forms in lungs and plasma of mice

“…Two possible mechanisms causing shedding of membrane RAGE have been reported. One is by sheddases including MMP9 and ADAM10 [40]; the other is by G-protein coupled receptor mediated shedding [41]. In the present study mRNA expression and levels of inactive pro-ADAM10 were upregulated, whereas protein levels of the active form of the enzyme were decreased by hypoxia.…”

Downregulation of Hematopoietic MUC1 during Experimental Colitis Increases Tumor-Promoting Myeloid-Derived Suppressor Cells

“…The increase in sRAGE could be a result of cleavage of RAGE (36), given that we observed a reduction of RAGE levels in the colonic mucosa of KO→WT mice treated with AOM+DSS. RAGE activation can activate NF-κB signaling, leading to transcription of pro-inflammatory factors (37).…”