PubMed: 29121589

Title
Pharmacological targeting of GSK-3 and NRF2 provides neuroprotection in a preclinical model of tauopathy.
Journal
Redox biology
Volume
14
Issue
None
Pages
522-534
Date
2018-04-01
Authors
Cuadrado A | Kügler S | Lastres-Becker I

Evidence 840593c52a

Wild-type MEFs treated with DMF (20 μM) showed a time-dependent response effect activating phosphorylation of ERK (Fig. 2A, B) and p38 (Fig. 2A, C), that was maximal within 5 min. The Ser/Thr protein kinase AKT, an upstream regulator of GSK-3β, was also activated after 5 min as determined by increased phosphorylation of S473 (Fig. 2A, D)

Evidence 654e89c26d

DMF increased the phosphorylation levels of GSK-3βSer9 in both genotypes, indicating that this effect is upstream of NRF2 as shown in Fig. 3A.

Evidence d11b4017bd

Taken together, our results show that DMF reduces GSK-3 activity in vivo as determined by a significant and subtle reduction in the phosphorylation levels of its two substrates TAU and CRMP2 respectively.

Evidence 11be4dff2a

Astrocytes displayed enlarged bodies and ramifications (Type B morphology), consistent with a reactive state after TAUP301L expression in Nrf2+/+ and Nrf2−/− mice (Fig. 6A left panels). However, only astrocytes from Nrf2+/+ mice treated with DMF were maintained in a resting morphology (Type A) (Fig. 6A right panels). Concerning microglia, TAUP301L expression induced a very significant increase in IBA1+ microglia at the ipsilateral hippocampal side of Nrf2+/+ and Nrf2−/− mice (Fig. 7A), which was confirmed by stereological quantification (Fig. 7B). DMF treatment reduced significantly this microgliosis in Nrf2+/+ but not in Nrf2−/− mice, reinforcing the idea of NRF2-dependent anti-inflammatory effect

Evidence eb6772c96e

Messenger RNA analysis of two pro-inflammatory markers such as IL-1β and inducible nitric oxide synthase (iNOS) indicate that TAUP301L expression induce Il-1β (Fig. 6D) and iNOS (Fig. 7D) mRNA expression in both genotypes and DMF treatment decreased this expression only in Nrf2+/+ mice.

Evidence 1d1b0d3cc5

The second mechanism is related to GSK-3, which phosphorylates NRF2 creating a recognition site for β-Transducin Repeat Containing E3 Ubiquitin Protein Ligase (β-TrCP). β-TrCP leads to Cullin-1/Rbx1-mediated NRF2 ubiquitination and its subsequent degradation [8]. Since GSK-3β is inhibited by phosphorylation at Ser9 by Ser/Thr protein kinases such as AKT, it has been suggested that NRF2 might be up-regulated through activation of AKT and permanent inactivation of GSK-3 [9], [10].

Evidence a5ed14a8a5

NRF2 is regulated principally by two different mechanisms. The best established mechanism is the control of protein stability by Kelch-like ECH-associated protein 1 (KEAP1). KEAP1 is an ubiquitin E3 ligase substrate adapter for a Cullin3/Rbx1-dependent E3 ubiquitin ligase complex; henceforth binding of KEAP1 to NRF2 mediates ubiquitination and subsequent proteasomal degradation of NRF2 [7].

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