RESUMEN
We developed a panel of non-obese diabetic (NOD) mice deficient in major lysosomal cysteine proteases (cathepsins S, L and B) to identify protease enzymes essential for autoimmune diabetes. Null alleles for cathepsins (Cts) S, L or B were introgressed onto the NOD genetic background with 19 Idd markers at homozygosity. Diabetes onset was determined among females aged up to 6 months. We evaluated insulitis and sialadenitis in tissues using histology and computer assisted morphology. NOD mice deficient in Ctss or Ctsb were partially protected from diabetes with incidence at 33% and 28%, respectively, versus wild-type NOD (69%; p < 0.00001). NODs lacking cathepsin L (Ctsl-/-) are completely protected from IDDM, as originally shown by others. Ctsl, Ctss, or Ctsb heterozygous mice were able to develop IDDM, although incidence levels were significantly lower for Ctsb+/- (50%) and Ctsl+/- (55%) as compared to NODs (69%; p < 0.03). Ctsl-/- mice contain functional, diabetogenic T cells and an enriched Foxp3+ regulatory T cell population, and diabetes resistance was due to the presence of an expanded population of regulatory T cells. These data provide additional information about the potency of the diabetogenic T cell population in Ctsl-/- mice which were comparable in potency to wild-type NOD mice. These data illustrate the critical contribution of each of these proteases in determining IDDM in the NOD mouse and provide a useful set of models for further studies.
Asunto(s)
Catepsina B/metabolismo , Catepsina L/metabolismo , Catepsinas/metabolismo , Diabetes Mellitus Tipo 1/metabolismo , Edad de Inicio , Animales , Antígenos CD4/biosíntesis , Catepsina B/genética , Catepsina B/inmunología , Catepsina L/genética , Catepsina L/inmunología , Catepsinas/genética , Catepsinas/inmunología , Movimiento Celular/genética , Diabetes Mellitus Tipo 1/genética , Diabetes Mellitus Tipo 1/patología , Diabetes Mellitus Tipo 1/fisiopatología , Femenino , Factores de Transcripción Forkhead/biosíntesis , Linfopenia , Ratones , Ratones Congénicos , Ratones Endogámicos C57BL , Ratones Endogámicos NOD , Ratones Noqueados , Pancreatitis , Sialadenitis , Subgrupos de Linfocitos T/patología , Linfocitos T Reguladores/patologíaRESUMEN
Posttranslational histone modifications and histone variants form a unique epigenetic landscape on mammalian chromosomes where the principal epigenetic heterochromatin markers, trimethylated histone H3(K9) and the histone H2A.Z, are inversely localized in relation to each other. Trimethylated H3(K9) marks pericentromeric constitutive heterochromatin and the male Y chromosome, while H2A.Z is dramatically reduced at these chromosomal locations. Inactivation of a lysosomal and nuclear protease, cathepsin L, causes a global redistribution of epigenetic markers. In cathepsin L knockout cells, the levels of trimethylated H3(K9) decrease dramatically, concomitant with its relocation away from heterochromatin, and H2A.Z becomes enriched at pericentromeric heterochromatin and the Y chromosome. This change is also associated with global relocation of heterochromatin protein HP1 and histone H3 methyltransferase Suv39h1 away from constitutive heterochromatin; however, it does not affect DNA methylation or chromosome segregation, phenotypes commonly associated with impaired histone H3(K9) methylation. Therefore, the key constitutive heterochromatin determinants can dynamically redistribute depending on physiological context but still maintain the essential function(s) of chromosomes. Thus, our data show that cathepsin L stabilizes epigenetic heterochromatin markers on pericentromeric heterochromatin and the Y chromosome through a novel mechanism that does not involve DNA methylation or affect heterochromatin structure and operates on both somatic and sex chromosomes.
Asunto(s)
Catepsinas/metabolismo , Centrómero/genética , Cisteína Endopeptidasas/metabolismo , Heterocromatina/metabolismo , Histonas/metabolismo , Termodinámica , Cromosoma Y/metabolismo , Animales , Catepsina L , Catepsinas/antagonistas & inhibidores , Catepsinas/deficiencia , Núcleo Celular/metabolismo , Cromatina/genética , Segregación Cromosómica/genética , Cromosomas de los Mamíferos/genética , Cisteína Endopeptidasas/deficiencia , Metilación de ADN , Epigénesis Genética , Fibroblastos/citología , Expresión Génica , Marcadores Genéticos , Heterocromatina/genética , Humanos , Lisina/metabolismo , Masculino , Metiltransferasas/genética , Metiltransferasas/metabolismo , Ratones , Ratones Noqueados , Células 3T3 NIH , Proteínas Represoras/genética , Proteínas Represoras/metabolismo , Cromosoma Y/genéticaRESUMEN
The endosomal pathway of antigen presentation leads to the display of peptides on major histocompatibility complex (MHC) class II molecules at the cell surface of antigen-presenting cells (APCs). The pathway involves two major steps, invariant chain degradation and antigen processing, which take place in the late endosomes/lysosomes. So far, of the known lysosomal proteases, only cathepsin L and cathepsin S have been shown to have a non-redundant role in endosomal presentation in vivo. Besides being engaged in the degradation of invariant chain, these enzymes also mediate the processing of antigens in distinct cell types. Surprisingly, these enzymes are active in different types of APCs, and this defined expression pattern seems to be enforced by regulatory mechanisms acting on multiple levels.