Proprotein convertase subtilisin kexin type 9 (PCSK9) lowers the abundance of surface low-density lipoprotein (LDL) receptor through an undefined mechanism. The structure of human PCSK9 shows the subtilisin-like catalytic site blocked by the prodomain in a noncovalent complex and inaccessible to exogenous ligands, and that the C-terminal domain has a novel fold. Biosensor studies show that PCSK9 binds the extracellular domain of LDL receptor with K(d) = 170 nM at the neutral pH of plasma, but with a K(d) as low as 1 nM at the acidic pH of endosomes. The D374Y gain-of-function mutant, associated with hypercholesterolemia and early-onset cardiovascular disease, binds the receptor 25 times more tightly than wild-type PCSK9 at neutral pH and remains exclusively in a high-affinity complex at the acidic pH. PCSK9 may diminish LDL receptors by a mechanism that requires direct binding but not necessarily receptor proteolysis.

Chronic kidney disease (CKD), a condition when the kidneys are unable to clear waste products, affects 700 million people globally. Genome-wide association (GWA) studies identified sequence variants for CKD; however, the biological basis of GWAS remains poorly understood. To address this issue, we created an expression quantitative trait loci (eQTL) atlas for the glomerular and tubular compartments of the human kidney. Integrating the CKD GWAS with eQTL, single-cell RNA sequencing and regulatory region maps, we identified novel genes for CKD. Putative causal genes were enriched for proximal tubule expression and endo-lysosomal function, where DAB2, an adaptor protein in the TGFβ pathway, formed a central node. Functional experiments confirmed that reducing Dab2 expression in renal tubules protected mice from CKD. In conclusion, compartment-specific eQTL analysis is an important avenue for the identification of novel genes and cellular pathways involved in CKD development and thus potential new opportunities for its treatment.

Generation and deposition of the amyloid b (Ab) peptide following proteolytic processing of the amyloid precursor protein (APP) by BACE-1 and c-secretase is central to the aetiology of Alzheimer's disease. Consequently, inhibition of BACE-1, a rate-limiting enzyme in the production of Ab, is an attractive therapeutic approach for the treatment of Alzheimer's disease. We have designed a selective non-peptidic BACE-1 inhibitor, GSK188909, that potently inhibits b-cleavage of APP and reduces levels of secreted and intracellular Ab in SHSY5Y cells expressing APP. In addition, we demonstrate that this compound can effectively lower brain Ab in vivo. In APP transgenic mice, acute oral administration of GSK188909 in the presence of a p-glycoprotein inhibitor to markedly enhance the exposure of GSK188909 in the brain decreases b-cleavage of APP and results in a significant reduction in the level of Ab40 and Ab42 in the brain. Encouragingly, subchronic dosing of GSK188909 in the absence of a p-glycoprotein inhibitor also lowers brain Ab. This pivotal first report of central Ab lowering, following oral administration of a BACE-1 inhibitor, supports the development of BACE-1 inhibitors for the treatment of Alzheimer's disease.

Sterol regulatory element-binding proteins (SREBPs) are major transcriptional regulators of cholesterol, fatty acid, and glucose metabolism. Genetic disruption of SREBP activity reduces plasma and liver levels of cholesterol and triglycerides and insulin-stimulated lipogenesis, suggesting that SREBP is a viable target for pharmacological intervention. The proprotein convertase SREBP site 1 protease (S1P) is an important posttranscriptional regulator of SREBP activation. This report demonstrates that 10 M PF-429242 (Bioorg Med Chem Lett 17:4411-4414, 2007), a recently described reversible, competitive aminopyrrolidineamide inhibitor of S1P, inhibits endogenous SREBP processing in Chinese hamster ovary cells. The same compound also down-regulates the signal from an SREluciferase reporter gene in human embryonic kidney 293 cells and the expression of endogenous SREBP target genes in cultured HepG2 cells. In HepG2 cells, PF-429242 inhibited cholesterol synthesis, with an IC 50 of 0.5 M. In mice treated with PF-429242 for 24 h, the expression of hepatic SREBP target genes was suppressed, and the hepatic rates of cholesterol and fatty acid synthesis were reduced. Taken together, these data establish that small-molecule S1P inhibitors are capable of reducing cholesterol and fatty acid synthesis in vivo and, therefore, represent a potential new class of therapeutic agents for dyslipidemia and for a variety of cardiometabolic risk factors associated with diabetes, obesity, and the metabolic syndrome.

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