Rare familial forms of Alzheimer's disease (AD) are thought to be caused by elevated proteolytic production of the 〈␤42 peptide from the ␤-amyloid-precursor protein (APP). Although the pathogenesis of the more common late-onset AD (LOAD) is not understood, BACE1, the protease that cleaves APP to generate the N terminus of A␤42, is more active in patients with LOAD, suggesting that increased amyloid production processing might also contribute to the sporadic disease. Using high-throughput siRNA screening technology, we assessed 15,200 genes for their role in 〈␤42 secretion and identified leucine-rich repeat transmembrane 3 (LRRTM3) as a neuronal gene that promotes APP processing by BACE1. siRNAs targeting LRRTM3 inhibit the secretion of A␤40, A␤42, and sAPP␤, the N-terminal APP fragment produced by BACE1 cleavage, from cultured cells and primary neurons by up to 60%, whereas overexpression increases A␤ secretion. LRRTM3 is expressed nearly exclusively in the nervous system, including regions affected during AD, such as the dentate gyrus. Furthermore, LRRTM3 maps to a region of chromosome 10 linked to both LOAD and elevated plasma A␤42, and is structurally similar to a family of neuronal receptors that includes the NOGO receptor, an inhibitor of neuronal regeneration and APP processing. Thus, LRRTM3 is a functional and positional candidate gene for AD, and, given its receptor-like structure and restricted expression, a potential therapeutic target.is the most common form of dementia and a debilitating neurodegenerative disease. In the majority of cases, the disease presents after age 65 because of largely unknown causes. However, in familial AD (FAD), the likely pathogenic trigger is release of amyloidogenic A␤ peptides from amyloid-precursor protein (APP), a transmembrane domain protein present in neuronal and other cells (1). A␤, the primary constituent of amyloid plaques, is generated from APP by proteolysis of the extracellular domain by BACE1 (Fig. 1A, 2), followed by intramembranous cleavage within its residual transmembrane domain by ␥-secretase [composed of presenilin-1 (PSEN1) or -2 (PSEN2) plus nicastrin (NCSTN), aph-1 (APH1), and pen-2 (PSENEN) (3)]. ␥-Secretase cleaves at multiple sites and yields mostly the 40-aa A␤40 peptide along with the more amyloidogenic 42-aa A␤42 (1). Alternatively, APP is cleaved by ␣-secretase within A␤, resulting in nonamyloidogenic metabolites. Mutations in APP or the presenilins account for most cases of FAD, and all increase A␤42 production from APP (1, 4, 5). These data are the basis of the amyloid hypothesis of AD.In late-onset (LO)AD, the etiology is not understood, but the major genetic risk factor is APOE4, which promotes A␤ deposition in the brains of mice (6), and BACE1 protein and activity are increased in LOAD (7-9). Furthermore, LOAD (10-12) and circulating A␤42 (13) levels were independently linked to chromosome 10q21-22, suggesting that genetic modifiers of LOAD risk also regulate A␤ metabolism. These data raise the possibility that genes regulating A␤ metabol...

␤-Site amyloid precursor protein (APP)-cleaving enzyme (BACE) 1 cleavage of amyloid precursor protein is an essential step in the generation of the potentially neurotoxic and amyloidogenic A␤42 peptides in Alzheimer's disease. Although previous mouse studies have shown brain A␤ lowering after BACE1 inhibition, extension of such studies to nonhuman primates or man was precluded by poor potency, brain penetration, and pharmacokinetics of available inhibitors. In this study, a novel tertiary carbinamine BACE1 inhibitor, tertiary carbinamine (TC)-1, was assessed in a unique cisterna magna ported rhesus monkey model, where the temporal dynamics of A␤ in cerebrospinal fluid (CSF) and plasma could be evaluated. TC-1, a potent inhibitor (IC 50 ϳ 0.4 nM), has excellent passive membrane permeability, low susceptibility to P-glycoprotein transport, and lowered brain A␤ levels in a mouse model. Intravenous infusion of TC-1 led to a significant but transient lowering of CSF and plasma A␤ levels in conscious rhesus monkeys because it underwent CYP3A4-mediated metabolism. Oral codosing of TC-1 with ritonavir, a potent CYP3A4 inhibitor, twice daily over 3.5 days in rhesus monkeys led to sustained plasma TC-1 exposure and a significant and sustained reduction in CSF sAPP␤, A␤40, A␤42, and plasma A␤40 levels. CSF A␤42 lowering showed an EC 50 of ϳ20 nM with respect to the CSF [TC-1] levels, demonstrating excellent concordance with its potency in a cell-based assay. These results demonstrate the first in vivo proof of concept of CSF A␤ lowering after oral administration of a BACE1 inhibitor in a nonhuman primate.

We describe the discovery and optimization of tertiary carbinamine derived inhibitors of the enzyme beta-secretase (BACE-1). These novel non-transition-state-derived ligands incorporate a single primary amine to interact with the catalytic aspartates of the target enzyme. Optimization of this series provided inhibitors with intrinsic and functional potency comparable to evolved transition state isostere derived inhibitors of BACE-1.

Over half of all antibiotics target the bacterial ribosome-Nature's complex, 2.5 MDa nanomachine responsible for decoding mRNA and synthesizing proteins. Macrolide antibiotics, exemplified by erythromycin, bind the 50S subunit with nM affinity and inhibit protein synthesis by blocking the passage of nascent oligopeptides. Solithromycin (1), a third-generation semisynthetic macrolide discovered by combinatorial copper-catalyzed click chemistry, was synthesized in situ by incubating either E. coli 70S ribosomes or 50S subunits with macrolidefunctionalized azide 2 and 3-ethynylaniline (3) precursors. The ribosome-templated in situ click method was expanded from a binary reaction (i.e., one azide and one alkyne) to a sixcomponent reaction (i.e., azide 2 and five alkynes) and ultimately to a sixteen-component reaction (i.e., azide 2 and fifteen alkynes). The extent of triazole formation correlated with ribosome affinity for the anti (1,4)-regioisomers as revealed by measured K d values. Computational analysis using the Site-Identification by Ligand Competitive Saturation (SILCS) approach indicated that the relative affinity of the ligands was associated with the alteration of macrolactone+desosamine- HHS Public Access

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