Notch signaling suppresses glucose metabolism in mesenchymal progenitors to restrict osteoblast differentiation
Seung-Yon Lee, Fanxin Long
Seung-Yon Lee, Fanxin Long
Published December 3, 2018; First published October 4, 2018
Citation Information: J Clin Invest. 2018;128(12):5573-5586. https://doi.org/10.1172/JCI96221.
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Research Article Bone biology

Notch signaling suppresses glucose metabolism in mesenchymal progenitors to restrict osteoblast differentiation

Abstract

Notch signaling critically controls cell fate decisions in mammals, both during embryogenesis and in adults. In the skeleton, Notch suppresses osteoblast differentiation and sustains bone marrow mesenchymal progenitors during postnatal life. Stabilizing mutations of Notch2 cause Hajdu-Cheney syndrome, which is characterized by early-onset osteoporosis in humans, but the mechanism whereby Notch inhibits bone accretion is not fully understood. Here, we report that activation of Notch signaling by either Jagged1 or the Notch2 intracellular domain suppresses glucose metabolism and osteoblast differentiation in primary cultures of bone marrow mesenchymal progenitors. Importantly, deletion of Notch2 in the limb mesenchyme increases both glycolysis and bone formation in the long bones of postnatal mice, whereas pharmacological reduction of glycolysis abrogates excessive bone formation. Mechanistically, Notch reduces the expression of glycolytic and mitochondrial complex I genes, resulting in a decrease in mitochondrial respiration, superoxide production, and AMPK activity. Forced activation of AMPK restores glycolysis in the face of Notch signaling. Thus, suppression of glucose metabolism contributes to the mechanism, whereby Notch restricts osteoblastogenesis from bone marrow mesenchymal progenitors.

Authors

Seung-Yon Lee, Fanxin Long

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Figure 4

Canonical Notch signaling suppresses glycolysis.

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Canonical Notch signaling suppresses glycolysis. (A–C) Effects of retrov...
(A–C) Effects of retroviral expression of GFP or dnMaml1 on glucose consumption (A), lactate production (B) or metabolic enzymes (C) in NICD2-ST2 cells treated with vehicle or Dox for 48 hours. β-Actin was used for normalization, and quantification (mean ± SD) was determined from 3 independent samples. After normalization to β-Actin, the level in the left-most lane is designated 1, and those of the other lanes are further normalized to the left-most lane. (D) Glucose consumption and lactate production in Hey1-ST2 cells treated with vehicle or Dox for 48 hours. Western blot shows the induction of Flag-Hey1 by Dox. n = 3. (E) Relative mRNA levels of NFATc1 by RT-qPCR in Hey1-ST2 cells treated with vehicle or Dox for 48 hours. n = 3. (F) RT-qPCR analyses of Hey1 in NICD2-ST2 cells infected with lentivirus expressing 2 different Hey1 shRNAs or the control luciferase shRNA (shLuc). (G) Glucose consumption and lactate production in NICD2-ST2 cells infected with lentivirus expressing different shRNAs, with or without Dox for 48 hours. (H) Relative glucose consumption in NICD2-ST2 cells infected with lentivirus expressing different shRNAs, with or without Dox for 48 hours. Glucose consumption was normalized to the protein amount and then to the vehicle-treated group designated as 1. (I) RT-qPCR analyses of mRNA levels showing shRNA knockdown efficiency. n = 3. *P = 0.05, by 2-way ANOVA followed by Bonferroni’s post hoc test (A, B, F, and I) or 2-tailed Student’s t test (C, E, G, and H).