Project description:The genetic programs that maintain hematopoiesis during steady state in physiologic conditions are different from those activated during stress. Here we show that hematopoietic stem cells (HSCs) with deficiencies in components of the alternative NFkB pathway (the NFkB inducing kinase, NIK, and the downstream molecule NFkB2) had a defect in response to stressors such as supraphysiological doses of cytokines, chemotherapy and hematopoietic transplantation. NIK-deficient mice had peripheral blood and bone marrow leukocyte numbers within normal ranges (except for the already reported defects in B-cell maturation), however, HSCs showed significantly slower expansion capacity in in vitro cultures compared to wild type HSCs. This was due to a delayed cell cycle and increased apoptosis. In vivo experiments showed that NIK-deficient HSCs did not recover at the same pace as controls when challenged with myeloablative chemotherapy. Finally, NIK-deficient HSCs showed a significantly decreased competitive repopulation capacity in vivo. Using HSCs from mice deficient in one of two downstream targets of NIK, i.e., either NFkB2 or c-Rel, only NFkB2 deficiency recapitulated the defects detected with NIK-deficient HSCs. Our results underscore the role of NIK and the alternative NFkB pathway for the recovery of normal levels of hematopoiesis after stress.
Project description:2 This project is to identify the potential neddylation sites in human NF-kB inducing kinase (A.k.a. Map3K14). NIK-HA or NIK-HA in combination with FLAG-NEDD8 were co-expressed in HEK293T cells. NIK-HA were pulled down via denaturing immunoprecipitation protocol, subject to SDS-PAGE, in-gel trypsin digestion, and Nano LC-MS/MS Analysis. The potential peptides containing K-GG sites were identified.
Project description:The NF-κB pathway is a master regulator of inflammatory processes and is implicated in insulin resistance and pancreatic beta cell dysfunction in the metabolic syndrome. While canonical NF-κB signaling is well studied, there is little information on the divergent non-canonical NF-κB pathway in the context of pancreatic islet dysfunction in diabetes. Here, we demonstrate that pharmacological activation of the non-canonical NF-κB inducing kinase (NIK) disrupts glucose homeostasis in zebrafish in vivo. Further, we identify NIK as a critical negative regulator of beta cell function as pharmacological NIK activation results in impaired glucose-stimulated insulin secretion in mouse and human islets. NIK levels are elevated in pancreatic islets isolated from diet-induced obese (DIO) mice, which exhibit increased processing of non-canonical NF-κB components p100 to p52, and accumulation of RelB. Tumor necrosis factor α (TNFα) and receptor activator of NF-κB ligand (RANKL), two ligands associated with diabetes, induce NIK in islets. Mice with constitutive beta cell intrinsic NIK activation present impaired insulin secretion with DIO. NIK activation triggers the non-canonical NF-κB transcriptional network to induce genes identified in human type 2 diabetes genome-wide association studies linked to beta cell failure. These studies reveal that NIK contributes a central mechanism for beta cell failure in diet-induced obesity. We identify a role for Nuclear Factor inducing κB (NIK) in pancreatic beta cell failure. NIK activation disrupts glucose homeostasis in zebrafish in vivo and impairs glucose-stimulated insulin secretion in mouse and human islets in vitro. NIK activation also perturbs beta cell insulin secretion in a diet-induced obesity mouse model. These studies reveal that NIK contributes a central mechanism for beta cell failure in obesity. To uncover the role of NIK in pancreatic beta cells, we performed a gene expression microarray analysis comparing pancreatic islets with constitutive beta cell intrinsicNIK activation from the 16 week old mice (beta cell specific TRAF2 and TRAF2 knockout mice) to their controls (n=3 per group).
