Ureter obstruction is a highly prevalent event during embryonic development and is a major cause of pediatric kidney disease. We have reported that ureteric bud-specific ablation of the exocyst Exoc5 subunit in late-murine gestation results in failure of urothelial stratification, cell death, and complete ureter obstruction. However, the mechanistic connection between disrupted exocyst activity, urothelial cell death, and subsequent ureter obstruction was unclear. Here, we report that inhibited urothelial stratification does not drive cell death during ureter development. Instead, we demonstrate that the exocyst plays a critical role in autophagy in urothelial cells, and that disruption of autophagy activates a urothelial NF-κB stress response. Impaired autophagy first provokes canonical NF-κB activity which is progressively followed by increasing non-canonical NF-κB activity and cell death if the stress remains unresolved. Furthermore, we demonstrate that ureter obstructions can be completely rescued in Exoc5 conditional knockout mice by administering a single dose of pan-caspase inhibitor z-VAD-FMK at E16.5 prior to urothelial cell death. Taken together, ablation of Exoc5 disrupts autophagic stress response and activates progressive NF-κB signaling which promotes obstructive uropathy.
Ureter obstruction is a highly prevalent event during embryonic development and is a major cause of pediatric kidney disease. We have reported that ureteric bud specific ablation of the exocyst Exoc5 subunit in late murine gestation results in failure of urothelial stratification, cell death, and complete ureter obstruction. However, the mechanistic connection between disrupted exocyst activity, urothelial cell death, and subsequent ureter obstruction was unclear. Here, we report that inhibited urothelial stratification does not drive cell death during ureter development. Instead, we demonstrate that the exocyst plays a critical role in autophagy in urothelial cells, and that disruption of autophagy activates a urothelial NF-κB stress response. Impaired autophagy first provokes canonical NF κB activity which is progressively followed by increasing non-canonical NF-κB activity and cell death if the stress remains unresolved. Furthermore, we demonstrate that ureter obstructions can be completely rescued in Exoc5 conditional knockout mice by administering a single dose of pan-caspase inhibitor z VAD-FMK at E16.5 prior to urothelial cell death. Taken together, ablation of Exoc5 disrupts autophagic stress response and activates progressive NF-κB signaling which promotes obstructive uropathy.
Objectives: Skeletal muscle cells are responsible for 80-90% of the insulin-induced glucose uptake in the body. Insulin signaling in skeletal muscle results in the targeted trafficking of glucose transporter type 4 (GLUT4) onto the cell membrane, enabling glucose uptake. Insulin resistant cells show defects in insulin-induced GLUT4 exocytosis. The eight-protein exocyst complex has an essential role in the insulin-induced exocytosis of GLUT4 vesicles in cultured adipocytes but it is not known if the exocyst-mediated molecular mechanism is conserved in other, insulin-responsive tissues, such as the skeletal muscle. We hypothesized that the exocyst complex is essential for the insulin-induced exocytosis of GLUT4-containing vesicles in skeletal muscle as well and that the exocyst is a master regulator of glucose homeostasis in insulin-responsive tissues. Methods/Results: We have generated a tamoxifen-inducible skeletal muscle-specific knockout mouse strain of exocyst central subunit Exoc5 (Exoc5-SMKO) to assess the exocyst’s role in glucose homeostasis in vivo. Exoc5 knockout does not affect grip strength, motor coordination or locomotor activity levels in these animals. Both male and female Exoc5-SMKO mice present with elevated fasting glucose levels, as compared to control littermates. Glucose tolerance testing revealed an impaired glucose clearance in Exoc5-SMKO mice, while insulin tolerance, fasting insulin levels, and A1C levels were similar between knockouts and controls. Conclusion: Our findings suggest that Exoc5 and the exocyst are necessary for insulin-stimulated glucose uptake in skeletal muscle. Ongoing work will further investigate the molecular mechanism of exocyst-mediated GLUT4 trafficking in skeletal muscle. Disclosure B. Fujimoto: None. L.T. Carter: None. A.M. Wong: None. M.W. Pitts: None. R.K. Villiger: None. M. Young: None. B. Fogelgren: None. N. Polgar: None. Funding National Institute of General Medical Sciences (5P20GM113134)
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.