Abstract. Cholesterol-lowering drugs such as statins influence the proteolytic processing of the amyloid-β protein precursor (AβPP) and are reported to stimulate the activity of α-secretase, the major preventive secretase of Alzheimer's disease. Statins can increase the α-secretase activity by their cholesterol-lowering properties as well as by impairment of isoprenoids synthesis. In the present study, we elucidate the contribution of these pathways in α-secretase activation. We demonstrate that zaragozic acid, a potent inhibitor of squalene synthase which blocks cholesterol synthesis but allows synthesis of isoprenoids, also stimulates α-secretase activity. Treatment of human neuroblastoma cells with 50 µM zaragozic acid resulted in a ∼3 fold increase of α-secretase activity and reduced cellular cholesterol by ∼30%. These effects were comparable to results obtained from cells treated with a low lovastatin concentration (2 µM). Zaragozic acid-stimulated secretion of α-secretase cleaved soluble AβPP was dose dependent and saturable. Lovastatin-or zaragozic acid-stimulated increase of α-secretase activity was completely abolished by a selective ADAM10 inhibitor. By targeting the α-secretase ADAM10 to lipid raft domains via a glycosylphosphatidylinositol anchor, we demonstrate that ADAM10 is unable to cleave AβPP in a cholesterol-rich environment. Our results indicate that inhibition of cholesterol biosynthesis by a low lovastatin concentration is sufficient for α-secretase activation.

This article is available online at http://www.jlr.org complications, atherosclerosis, and Alzheimer's disease (AD) ( 1 ). Proteins and peptides like advanced glycation end products (AGEs), amyloid-␤ peptides (A ␤ s), S100/ calgranulin family members, and HMGB1 (amphoterin) have been identifi ed as ligands for RAGE ( 2 ). Diabetes is characterized by a high blood glucose level. This enhanced concentration of glucose is responsible for the nonenzymatic generation of AGEs. AGEs represent a heterogeneous group of proteins, lipids, and nucleic acids resulting from chemical reactions between reducing sugars and amino groups. Studies with animal models have shown that RAGE is the best known target for AGEs in the vasculature and it is well established that the AGE/RAGE interaction contributes to the progression of atherosclerotic plaques ( 3-5 ). Ligand/RAGE interaction induces activation of various pro-infl ammatory and pro-atherogenic mediators, such as the nuclear factor-B (NF-B)-dependent mediators vascular cell adhesion molecule-1, tumor necrosis factor-␣ , interleukin-6, and RAGE ( 6 ). Because RAGE itself is regulated by NF-B, this further increases its expression and promotes cellular dysfunction ( 7 ).Blockade of RAGE by using the soluble form of the receptor ameliorates the vascular complications of diabetes in animal models ( 8-10 ) and suppresses the accumulation of A ␤ s in the brain of an AD mouse model ( 11 ). These benefi cial effects of soluble RAGE are thought to be mediated by trapping ligands, thus preventing ligand binding of membrane-bound RAGE. The circulating soluble form of RAGE containing only the extracellular part of fulllength RAGE, is either produced by alternative splicing The type I transmembrane protein receptor for advanced glycation end products (RAGE), a member of the immunoglobulin superfamily, has been shown to play a crucial role in chronic infl ammatory diseases, late diabetic Press, August 21, 2013 DOI 10.1194 Statins stimulate the production of a soluble form of the receptor for advanced glycation end products Abbreviations: A ␤ , amyloid-␤ peptide; AD, Alzheimer's disease; AGE, advanced glycation end product; APP, amyloid precursor protein; esRAGE, endogenous secretory receptor for advanced glycation end products; FCS, fetal calf serum; LDS, lipid-defi cient serum; M ␤ CD, methyl-␤ -cyclodextrin; NF-B, nuclear factor-B; RAGE, receptor for advanced glycation end products; RNAi, RNA interference; siRNA, small interfering RNA; SQS, squalene synthase; sRAGE, shed receptor-the soluble form of the receptor for advanced glycation end products after proteolytic shedding of the full length receptor; ZA, zaragozic acid A . Published, JLR Papers in

The association between hypertension and an increased risk for Alzheimer's disease (AD) and dementia is well established. Many data suggest that modulation of the renin-angiotensin system may be meaningful for the prevention and therapy of neurodegenerative disorders, in particular AD. Proteolytic cleavage of the amyloid precursor protein (APP) by α-secretase precludes formation of neurotoxic Aβ peptides and is expected to counteract the development of AD. An established approach for the up-regulation of α-secretase cleavage is the activation of G protein-coupled receptors (GPCRs). Therefore, our study aimed to analyze whether stimulation of angiotensin AT or AT receptors stably expressed in HEK cells influence the nonamyloidogenic pathway of APP processing. Treatment of both receptors with angiotensin II clearly showed that only activation of the AT receptor increased several fold the α-secretase-mediated shedding of APP. This effect was completely abolished by treatment with the AT receptor-specific antagonist telmisartan. Using the BIM-46187 inhibitor, we demonstrate that the Gαq protein-mediated pathway is involved in this stimulation process. Stimulation of AT receptors with the β-arrestin-biased agonist SII was ineffective regarding α-secretase-mediated APP shedding. This result discloses that only the G protein-dependent pathway is involved in the Ang II-induced APP shedding. Blocking of Gβγ subunits by the inhibitor gallein completely prevented constitutive and Ang II-induced APP shedding. Our findings provide evidence that induction of APP shedding via Ang II/AT receptor stimulation is effected by G protein activation with Gβγ subunits playing important roles.