RESUMO
Reticulon 3 (RTN3) is an endoplasmic reticulum protein that has previously been shown to play roles in neurodegenerative diseases, but little is known about its function in the kidneys. The aim of the present study was to clarify the roles of RTN3 in chronic kidney disease (CKD) and kidney fibrosis. In this study, RTN3 levels were measured in kidney tissues from healthy controls and CKD or kidney fibrosis patients. An RTN3-null mouse model was generated to explore the pathophysiological roles of RTN3 in the kidneys. The underlying mechanisms were studied in primary proximal tubular epithelial cells and HEK293 cells in vitro. The results showed that (1) a reduction in RTN3 in mice induces CKD and kidney fibrosis; (2) decreased RTN3 expression is found in patients with CKD; (3) RTN3 plays critical roles in regulating collagen biosynthesis and mitochondrial function; and (4) mechanistically, RTN3 regulates these phenotypes by interacting with GC-Rich Promoter Binding Protein 1 (GPBP1), which activates the IGF2-JAK2-STAT3 pathway. Our study indicates that RTN3 might play crucial roles in CKD and kidney fibrosis and that a reduction in RTN3 in the kidneys might be a risk factor for CKD and kidney fibrosis.
Assuntos
Proteínas de Membrana , Proteínas do Tecido Nervoso , Insuficiência Renal Crônica , Animais , Proteínas Sanguíneas/genética , Proteínas Sanguíneas/metabolismo , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Proteínas de Ligação a DNA , Células Epiteliais/metabolismo , Fibrose , Células HEK293 , Humanos , Fator de Crescimento Insulin-Like II/genética , Fator de Crescimento Insulin-Like II/metabolismo , Janus Quinase 2/genética , Janus Quinase 2/metabolismo , Rim/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Camundongos , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Fenótipo , Insuficiência Renal Crônica/genéticaRESUMO
Previous studies have demonstrated that ischemic stroke increases beta-amyloid (Abeta) production by increasing beta-secretase (BACE1) through activation of caspase-3, and stimulates generation of mutant ubiquitin (UBB(+1)) in rat brains. In this study, we examined whether caspase-3 activation participates in the regulation of UBB(+1) generation and UBB(+1)-mediated BACE1 stability in ischemic injured brains. The results showed that UBB(+1) and activated caspase-3-immunopositive-stained cells were time dependently increased in the ipsilateral striatum of rat brains after middle cerebral artery occlusion. UBB(+1)-immunopositive cells could be co-stained with caspase-3, Abeta (UBB(+1)-Abeta), and BACE1 (UBB(+1)-BACE1). BACE1 protein could also be pulled down by immunoprecipitation with UBB(+1) antibody. Z-DEVD-FMK (DEVD), a caspase-3 inhibitor, significantly decreased the level of UBB(+1) protein and the number of UBB(+1)-Abeta and UBB(+1)-BACE1 double-stained cells in the ischemic striatum, as well as the level of UBB(+1)/BACE1 protein complex. We conclude that activation of caspase-3 might be upstream of UBB(+1) formation and that excessive UBB(+1) could bind to BACE1 and increase the stability of BACE1, thereby increasing Abeta in ischemic injured brains. These results suggest new biological and pathological effects of caspases and regulation of the ubiquitin-proteasome system in the brain. Our results provide new therapeutic targets to prevent further neurodegeneration in patients after stroke.
