Loss of Nix in Pdx1-deficient mice prevents apoptotic and necrotic β cell death and diabetes.
Mutations in pancreatic duodenal homeobox (PDX1) are linked to human type 2 diabetes and maturity-onset diabetes of the young type 4. Consistent with this, Pdx1-haploinsufficient mice develop diabetes. Both apoptosis and necrosis of β cells are mechanistically implicated in diabetes in these mice, but a molecular link between Pdx1 and these 2 forms of cell death has not been defined. In this study, we introduced an shRNA into mouse insulinoma MIN6 cells to deplete Pdx1 and found that expression of proapoptotic genes, including NIP3-like protein X (Nix), was increased. Forced Nix expression in MIN6 and pancreatic islet β cells induced programmed cell death by simultaneously activating apoptotic and mitochondrial permeability transition-dependent necrotic pathways. Preventing Nix upregulation during Pdx1 suppression abrogated apoptotic and necrotic β cell death in vitro. In Pdx1-haploinsufficient mice, Nix ablation normalized pancreatic islet architecture, β cell mass, and insulin secretion and eliminated reactive hyperglycemia after glucose challenge. These results establish Nix as a critical mediator of β cell apoptosis and programmed necrosis in Pdx1-deficient diabetes.
Division of Endocrinology, Metabolism and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Kei
K
Fujimoto
Eric L
EL
Ford
Hung
H
Tran
Burton M
BM
Wice
Seth D
SD
Crosby
Gerald W
GW
Dorn
Kenneth S
KS
Polonsky
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D045744:Cell Line, Tumor; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D020869:Gene Expression Profiling; D005947:Glucose / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000378:metabolism* / Q000473:pathology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D046228:Microarray Analysis; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D009336:Necrosis; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*
D018398:Homeodomain Proteins; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; C501741:Nix protein, mouse; D015534:Trans-Activators; C084010:pancreatic and duodenal homeobox 1 protein; D005947:Glucose