RESUMEN
KDEL receptors are responsible for retrotransporting endoplasmic reticulum (ER) chaperones from the Golgi complex to the ER. Here we describe a role for KDEL receptor 1 (KDELR1) that involves the regulation of integrated stress responses (ISR) in T cells. Designing and using an N-ethyl-N-nitrosourea (ENU)-mutant mouse line, T-Red (naïve T-cell reduced), we show that a point mutation in KDELR1 is responsible for the reduction in the number of naïve T cells in this model owing to an increase in ISR. Mechanistic analysis shows that KDELR1 directly regulates protein phosphatase 1 (PP1), a key phosphatase for ISR in naïve T cells. T-Red KDELR1 does not associate with PP1, resulting in reduced phosphatase activity against eIF2α and subsequent expression of stress responsive genes including the proapoptotic factor Bim. These results demonstrate that KDELR1 regulates naïve T-cell homeostasis by controlling ISR.
Asunto(s)
Proteína Fosfatasa 1/metabolismo , Receptores de Péptidos/metabolismo , Linfocitos T/fisiología , Secuencia de Aminoácidos , Animales , Proteínas Reguladoras de la Apoptosis/metabolismo , Proteína 11 Similar a Bcl2 , Factor 2 Eucariótico de Iniciación/metabolismo , Femenino , Homeostasis , Memoria Inmunológica , Proteínas de la Membrana/metabolismo , Ratones Endogámicos C3H , Ratones Endogámicos C57BL , Ratones Noqueados , Datos de Secuencia Molecular , Fenotipo , Mutación Puntual , Proteínas Proto-Oncogénicas/metabolismo , Receptores de Péptidos/genética , Estrés FisiológicoRESUMEN
The tissue inhibitor of the metalloproteinase-3 (TIMP-3) gene was isolated as a gene involved in the process of ascorbate-induced differentiation of mouse MC3T3-E1 cells by the differential display method. The functional roles of TIMP-3 were characterized by establishing stable cell lines, which constitutively expressed the TIMP-3 gene. The TIMP-3 transfectants produced type I collagen at the same level as that of normal cells in response to ascorbic acid 2-phosphate (AscP). However, the expression of the other osteoblastic marker proteins such as alkaline phosphatase (ALPase), osteopontin (OP), osteocalcin (OC), osteonectin (ON) and matrix metalloproteinases (MMPs) remained at a low level even in the presence of AscP. Furthermore, no mineralization of the extracellular matrix (ECM) occurred with the transfectants. Remodeling ECM through TIMPs and MMPs is concluded to be required for osteoblastic differentiation.