Dataset Information

OGT Regulates Mitochondrial Biogenesis and Function via Diabetes Susceptibility Gene Pdx1.

ABSTRACT: O-GlcNAc transferase (OGT), a nutrient sensor sensitive to glucose flux, is highly expressed in the pancreas. However, the role of OGT in the mitochondria of β-cells is unexplored. In this study, we identified the role of OGT in mitochondrial function in β-cells. Constitutive deletion of OGT (βOGTKO) or inducible ablation in mature β-cells (iβOGTKO) causes distinct effects on mitochondrial morphology and function. Islets from βOGTKO, but not iβOGTKO, mice display swollen mitochondria, reduced glucose-stimulated oxygen consumption rate, ATP production, and glycolysis. Alleviating endoplasmic reticulum stress by genetic deletion of Chop did not rescue the mitochondrial dysfunction in βOGTKO mice. We identified altered islet proteome between βOGTKO and iβOGTKO mice. Pancreatic and duodenal homeobox 1 (Pdx1) was reduced in in βOGTKO islets. Pdx1 overexpression increased insulin content and improved mitochondrial morphology and function in βOGTKO islets. These data underscore the essential role of OGT in regulating β-cell mitochondrial morphology and bioenergetics. In conclusion, OGT couples nutrient signal and mitochondrial function to promote normal β-cell physiology.

SUBMITTER: Mohan R

PROVIDER: S-EPMC8564412 | biostudies-literature | 2021 Nov

REPOSITORIES: biostudies-literature

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OGT Regulates Mitochondrial Biogenesis and Function via Diabetes Susceptibility Gene Pdx1.

Mohan Ramkumar R Jo Seokwon S Lockridge Amber A Ferrington Deborah A DA Murray Kevin K Eschenlauer Arthur A Bernal-Mizrachi Ernesto E Fujitani Yoshio Y Alejandro Emilyn U EU

Diabetes 20210830 11

<i>O</i>-GlcNAc transferase (OGT), a nutrient sensor sensitive to glucose flux, is highly expressed in the pancreas. However, the role of OGT in the mitochondria of β-cells is unexplored. In this study, we identified the role of OGT in mitochondrial function in β-cells. Constitutive deletion of OGT (βOGTKO) or inducible ablation in mature β-cells (iβOGTKO) causes distinct effects on mitochondrial morphology and function. Islets from βOGTKO, but not iβOGTKO, mice display swollen mitochondria, red ...[more]

PMID: 34462257

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Project description:ObjectivesUnderstanding how loci identified by genome wide association studies (GWAS) contribute to pathogenesis requires new mechanistic insights. Variants within CDKAL1 are strongly linked to an increased risk of developing type 2 diabetes and obesity. Investigations in mouse models have focused on the function of Cdkal1 as a tRNALys modifier and downstream effects of Cdkal1 loss on pro-insulin translational fidelity in pancreatic β-cells. However, Cdkal1 is broadly expressed in other metabolically relevant tissues, including adipose tissue. In addition, the Cdkal1 homolog Cdk5rap1 regulates mitochondrial protein translation and mitochondrial function in skeletal muscle. We tested whether adipocyte-specific Cdkal1 deletion alters systemic glucose homeostasis or adipose mitochondrial function independently of its effects on pro-insulin translation and insulin secretion.MethodsWe measured mRNA levels of type 2 diabetes GWAS genes, including Cdkal1, in adipose tissue from lean and obese mice. We then established a mouse model with adipocyte-specific Cdkal1 deletion. We examined the effects of adipose Cdkal1 deletion using indirect calorimetry on mice during a cold temperature challenge, as well as by measuring cellular and mitochondrial respiration in vitro. We also examined brown adipose tissue (BAT) mitochondrial morphology by electron microscopy. Utilizing co-immunoprecipitation followed by mass spectrometry, we performed interaction mapping to identify new CDKAL1 binding partners. Furthermore, we tested whether Cdkal1 loss in adipose tissue affects total protein levels or accurate Lys incorporation by tRNALys using quantitative mass spectrometry.ResultsWe found that Cdkal1 mRNA levels are reduced in adipose tissue of obese mice. Using adipose-specific Cdkal1 KO mice (A-KO), we demonstrated that mitochondrial function is impaired in primary differentiated brown adipocytes and in isolated mitochondria from A-KO brown adipose tissue. A-KO mice displayed decreased energy expenditure during 4 °C cold challenge. Furthermore, mitochondrial morphology was highly abnormal in A-KO BAT. Surprisingly, we found that lysine codon representation was unchanged in Cdkal1 A-KO adipose tissue. We identified novel protein interactors of CDKAL1, including SLC25A4/ANT1, an inner mitochondrial membrane ADP/ATP translocator. ANT proteins can account for the UCP1-independent basal proton leak in BAT mitochondria. Cdkal1 A-KO mice had increased ANT1 protein levels in their white adipose tissue.ConclusionsCdkal1 is necessary for normal mitochondrial morphology and function in adipose tissue. These results suggest that the type 2 diabetes susceptibility gene CDKAL1 has novel functions in regulating mitochondrial activity.

Project description:Mitochondrial biogenesis, the generation of new mitochondrial DNA and proteins, has been linked to osteoclast (OC) differentiation and function. In this study we used mice with mutations in key alternative NF-?B pathway proteins, RelB and NF-?B-inducing kinase (NIK), to dissect the complex relationship between mitochondrial biogenesis and osteoclastogenesis. In OC precursors lacking either NIK or RelB, receptor activator of NF-?B ligand (RANKL) was unable to increase mitochondrial DNA or oxidative phosphorylation (OxPhos) protein expression, which was associated with lower oxygen consumption rates. Transgenic OC precursors expressing constitutively active NIK showed normal RANKL-induced mitochondrial biogenesis (OxPhos expression and mitochondria copy number) compared to controls, but larger mitochondrial dimensions and increased oxygen consumption rates, suggesting increased mitochondrial function. To deduce the mechanism for mitochondrial biogenesis defects in NIK-deficient and RelB-deficient precursors, we examined expression of genes known to control this process. PGC-1? (Ppargc1b) expression, but not PGC-1?, PPRC1, or ERR?, was significantly reduced in RelB(-/-) and NIK(-/-) OCs. Because PGC-1? has been reported to positively regulate both mitochondrial biogenesis and differentiation in OCs, we retrovirally overexpressed PGC-1? in RelB(-/-) cells, but surprisingly found that it did not affect differentiation, nor did it restore RANKL-induced mitochondrial biogenesis. To determine whether the blockade in osteoclastogenesis in RelB-deficient cells precludes mitochondrial biogenesis, we rescued RelB(-/-) differentiation via overexpression of NFATc1. Mitochondrial parameters in neither WT nor RelB-deficient cultures were affected by NFATc1 overexpression, and bone resorption in RelB(-/-) was not restored. Furthermore, NFATc1 co-overexpression with PGC-1?, although allowing OC differentiation, did not rescue mitochondrial biogenesis or bone resorption in RelB(-/-) OCs, by CTX-I levels. Thus, our results indicate that the alternative NF-?B pathway plays dual, but distinct, roles in controlling the independent processes of OC differentiation and OC mitochondrial biogenesis. Furthermore, the inability of PGC-1? to drive mitochondrial biogenesis in OCs without RelB indicates a cell-type specificity in mitochondria regulation.

Dataset Information

OGT Regulates Mitochondrial Biogenesis and Function via Diabetes Susceptibility Gene Pdx1.

Publications

OGT Regulates Mitochondrial Biogenesis and Function via Diabetes Susceptibility Gene Pdx1.

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