RESUMO
The gamma-secretase complex plays a role in Alzheimer's disease and cancer progression. The development of clinically useful inhibitors, however, is complicated by the role of the gamma-secretase complex in regulated intramembrane proteolysis of Notch and other essential proteins. Different gamma-secretase complexes containing different Presenilin or Aph1 protein subunits are present in various tissues. Here we show that these complexes have heterogeneous biochemical and physiological properties. Specific inactivation of the Aph1B gamma-secretase in a mouse Alzheimer's disease model led to improvements of Alzheimer's disease-relevant phenotypic features without any Notch-related side effects. The Aph1B complex contributes to total gamma-secretase activity in the human brain, and thus specific targeting of Aph1B-containing gamma-secretase complexes may help generate less toxic therapies for Alzheimer's disease.
Assuntos
Doença de Alzheimer/metabolismo , Secretases da Proteína Precursora do Amiloide/química , Secretases da Proteína Precursora do Amiloide/metabolismo , Peptídeos beta-Amiloides/metabolismo , Encéfalo/metabolismo , Endopeptidases/metabolismo , Doença de Alzheimer/tratamento farmacológico , Secretases da Proteína Precursora do Amiloide/antagonistas & inibidores , Secretases da Proteína Precursora do Amiloide/genética , Peptídeos beta-Amiloides/análise , Peptídeos beta-Amiloides/química , Precursor de Proteína beta-Amiloide/metabolismo , Animais , Modelos Animais de Doenças , Endopeptidases/química , Endopeptidases/genética , Feminino , Humanos , Aprendizagem em Labirinto , Proteínas de Membrana/metabolismo , Memória , Camundongos , Neurônios/metabolismo , Fragmentos de Peptídeos/análise , Fragmentos de Peptídeos/metabolismo , Peptídeo Hidrolases/metabolismo , Presenilina-1/química , Presenilina-1/genética , Presenilina-1/metabolismo , Subunidades Proteicas/química , Subunidades Proteicas/metabolismo , Receptor Notch1/metabolismo , Transdução de SinaisRESUMO
BACKGROUND: Atherosclerosis is a common multifactorial disease resulting from an interaction between susceptibility genes and environmental factors. The causative genes that contribute to atherosclerosis are elusive. Based on recent findings with a Wistar rat model, we speculated that the gamma-secretase pathway may be associated with atherosclerosis. METHODOLOGY/PRINCIPAL FINDINGS: We have tested for association of premature coronary atherosclerosis with a non-synonymous single-nucleotide polymorphism (SNP) in the gamma-secretase component APH1B (Phe217Leu; rs1047552), a SNP previously linked to Alzheimer's disease. Analysis of a Dutch Caucasian cohort (780 cases; 1414 controls) showed a higher prevalence of the risk allele in the patients (odds ratio (OR) = 1.35), albeit not statistically different from the control population. Intriguingly, after gender stratification, the difference was significant in males (OR = 1.63; p = 0.033), but not in females (OR = 0.50; p = 0.20). Since Phe217Leu-mutated APH1B showed reduced gamma-secretase activity in mouse embryonic fibroblasts, the genetic variation is likely functional. CONCLUSION/SIGNIFICANCE: We conclude that, in a male-specific manner, disturbed gamma-secretase signalling may play a role in the susceptibility for premature coronary atherosclerosis.
Assuntos
Doença da Artéria Coronariana/genética , Proteínas de Membrana/genética , Polimorfismo de Nucleotídeo Único , Adulto , Idade de Início , Substituição de Aminoácidos , Animais , Linhagem Celular , Estudos de Coortes , Doença da Artéria Coronariana/epidemiologia , Endopeptidases , Feminino , Fibrinogênio/análise , Fibroblastos/metabolismo , Humanos , Masculino , Proteínas de Membrana/metabolismo , Camundongos , Pessoa de Meia-Idade , Países Baixos/epidemiologia , Peptídeo Hidrolases , Prevalência , Proteínas Recombinantes de Fusão/metabolismo , Fatores de Risco , Distribuição por Sexo , Fatores Sexuais , Especificidade por Substrato , População Branca/genéticaRESUMO
Rhomboids, evolutionarily conserved integral membrane proteases, participate in crucial signaling pathways. Presenilin-associated rhomboid-like (PARL) is an inner mitochondrial membrane rhomboid of unknown function, whose yeast ortholog is involved in mitochondrial fusion. Parl-/- mice display normal intrauterine development but from the fourth postnatal week undergo progressive multisystemic atrophy leading to cachectic death. Atrophy is sustained by increased apoptosis, both in and ex vivo. Parl-/- cells display normal mitochondrial morphology and function but are no longer protected against intrinsic apoptotic death stimuli by the dynamin-related mitochondrial protein OPA1. Parl-/- mitochondria display reduced levels of a soluble, intermembrane space (IMS) form of OPA1, and OPA1 specifically targeted to IMS complements Parl-/- cells, substantiating the importance of PARL in OPA1 processing. Parl-/- mitochondria undergo faster apoptotic cristae remodeling and cytochrome c release. These findings implicate regulated intramembrane proteolysis in controlling apoptosis.
Assuntos
Apoptose/fisiologia , Citocromos c/metabolismo , GTP Fosfo-Hidrolases/metabolismo , Metaloproteases/metabolismo , Mitocôndrias/metabolismo , Membranas Mitocondriais/metabolismo , Proteínas Mitocondriais/genética , Animais , Caquexia/genética , Linhagem Celular , Células Cultivadas , Regulação para Baixo/genética , Feminino , GTP Fosfo-Hidrolases/genética , Genes Letais , Linfócitos/metabolismo , Linfócitos/patologia , Metaloproteases/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mitocôndrias/genética , Mitocôndrias/ultraestrutura , Membranas Mitocondriais/ultraestrutura , Proteínas Mitocondriais/metabolismoRESUMO
Gamma-secretase is the protease responsible for amyloid beta peptide release and is needed for Notch, N-Cadherin, and possibly other signaling pathways. The protease complex consists of at least four subunits, i.e., Presenilin, Aph1, Pen2, and Nicastrin. Two different genes encode Aph1A and Aph1B in man. A duplication of Aph1B in rodents has given rise to a third gene, Aph1C. Different mixes of gamma-secretase subunits assemble in at least four human and six rodent complexes but it is not known whether they have different activities in vivo. We report here the inactivation of the three Aph1 genes in mice. Aph1A-/- embryos show a lethal phenotype characterized by angiogenesis defects in the yolk sac, neuronal tube malformations, and mild somitogenesis defects. Aph1B-/- or C-/- or the combined Aph1BC-/- mice (which can be considered as a model for total Aph1B loss in human) survive into adulthood. However, Aph1BC-/- deficiency causes a mild but significant reduction in amyloid beta percursor protein processing in selective regions of the adult brain. We conclude that the biochemical and physiological repercussions of genetically reducing gamma-secretase activity via the different Aph1 components are quite divergent and tissue specific. Our work provides in vivo evidence for the concept that different gamma-secretase complexes may exert different biological functions. In the context of Alzheimer's disease therapy, this implies the theoretical possibility that targeting specific gamma-secretase subunit combinations could yield less toxic drugs than the currently available general inhibitors of gamma-secretase activity.
Assuntos
Endopeptidases/genética , Endopeptidases/metabolismo , Subunidades Proteicas/genética , Secretases da Proteína Precursora do Amiloide , Animais , Ácido Aspártico Endopeptidases , Vasos Sanguíneos/embriologia , Vasos Sanguíneos/crescimento & desenvolvimento , Endopeptidases/deficiência , Deleção de Genes , Triagem de Portadores Genéticos , Proteínas de Membrana , Camundongos , Camundongos Knockout , Isoformas de Proteínas/genética , Subunidades Proteicas/deficiênciaRESUMO
Gamma-secretase is a high molecular weight protein complex composed of four subunits, namely, presenilin (PS; 1 or 2), nicastrin, anterior pharynx defective-1 (Aph-1; A or B), and presenilin enhancer-2 (Pen-2), and is responsible for the cleavage of a number of type-1 transmembrane proteins. A fundamental question is whether different gamma-secretase complexes exist in vivo. We demonstrate here by in situ hybridization and by Northern and Western blotting that the gamma-secretase components are widely distributed in all tissues investigated. The expression of the different subunits seems tightly coregulated. However, some variation in the expression of the Aph-1 proteins is observed, Aph-1A being more general and abundantly distributed than Aph-1B. The previously uncharacterized rodent-specific Aph-1C mRNA is highly expressed in the kidney and testis but not in brain or other tissues, indicating some tissue specificity for the Aph-1 component of the gamma-secretase complex. Blue-native electrophoresis revealed size heterogeneity of the mature gamma-secretase complex in various tissues. Using co-immunoprecipitations and blue-native electrophoresis at endogenous protein levels, we find evidence that several independent gamma-secretase complexes can coexist in the same cell type. In conclusion, our results suggest that gamma-secretase is a heterogeneous family of protein complexes widely expressed in the adult organism.