RESUMEN
gamma-Secretase inhibitors have been shown to reduce the production of beta-amyloid, a component of the plaques that are found in brains of patients with Alzheimer's disease. A novel series of heterocyclic sulfonamide gamma-secretase inhibitors that reduce beta-amyloid levels in cells is reported. Several examples of compounds within this series demonstrate a higher propensity to inhibit the processing of amyloid precursor protein compared to Notch, an alternative gamma-secretase substrate.
Asunto(s)
Enfermedad de Alzheimer/tratamiento farmacológico , Secretasas de la Proteína Precursora del Amiloide/antagonistas & inhibidores , Secretasas de la Proteína Precursora del Amiloide/metabolismo , Compuestos Heterocíclicos/química , Compuestos Heterocíclicos/farmacología , Sulfonamidas/química , Sulfonamidas/farmacología , Péptidos beta-Amiloides/antagonistas & inhibidores , Péptidos beta-Amiloides/metabolismo , Animales , Células CHO , Cricetinae , Cricetulus , Compuestos Heterocíclicos/síntesis química , Humanos , Estructura Molecular , Unión Proteica , Receptores Notch/metabolismo , Relación Estructura-Actividad , Sulfonamidas/síntesis químicaRESUMEN
Using a cell-based assay, we have identified a new series of Notch-sparing gamma-secretase inhibitors from HTS screening leads 2a and 2e. Lead optimization studies led to the discovery of analog 8e with improved gamma-secretase inhibitory potency and Notch-sparing selectivity.
Asunto(s)
Secretasas de la Proteína Precursora del Amiloide/antagonistas & inhibidores , Química Farmacéutica/métodos , Inhibidores Enzimáticos/síntesis química , Inhibidores Enzimáticos/farmacología , Receptores Notch/metabolismo , Enfermedad de Alzheimer/tratamiento farmacológico , Amiloide/química , Secretasas de la Proteína Precursora del Amiloide/química , Carbono/química , Diseño de Fármacos , Evaluación Preclínica de Medicamentos , Humanos , Modelos Químicos , Receptores Notch/antagonistas & inhibidores , Relación Estructura-ActividadRESUMEN
Although studies in recombinant cells indicate that scavenger receptor class B, type I (SR-BI) can promote cholesterol efflux, investigations in transgenic mice overexpressing or deficient in SR-BI endorse its physiological function as selectively sequestering cholesteryl esters from high-density lipoproteins (HDLs). Less clear is the role of SR-BII, a splice variant of the SR-B gene that differs only in the C-terminal cytoplasmic domain. Here, we identify several putative signalling motifs in the C-terminus of human SR-BII, which are absent from SR-BI, and hypothesize that these motifs interact with signalling molecules to mobilize stored cholesteryl esters and/or promote the efflux of intracellular free cholesterol. 'Pull-down' assays using a panel of tagged SH3 (Src homology 3) domains showed that cytoplasmic SR-BII, but not cytoplasmic SR-BI, bound the SH3 domain of phospholipase C-gamma1; this interaction was not, however, detected under more physiological conditions. Specific anti-peptide antisera identified SR-BII in human monocyte/macrophage THP-1 cells and, in recombinant cells, revealed receptor localization to caveolae, a plasma membrane microdomain that concentrates signal-transducer molecules and acts as a conduit for cholesterol flux between cells and lipoproteins. Consistent with its caveolar localization, expression of human SR-BII in recombinant Chinese hamster ovary cells (CHO-SR-BII) was associated with increased HDL-mediated cholesterol efflux. Nevertheless, when CHO-SR-BII cells were pre-loaded with cholesteryl [(3)H]oleate and incubated with HDL, cholesteryl ester stores were not reduced compared with control cells. We conclude that although human SR-BII is expressed by macrophages, contains cytoplasmic signalling motifs and localizes to caveolae, its ability to stimulate cholesterol efflux does not reflect enhanced hydrolysis of stored cholesteryl esters.
