A novel specific PERK activator reduces toxicity and extends survival in Huntington's disease models

Abstract

One of the pathways of the unfolded protein response, initiated by PKR-like endoplasmic reticulum kinase (PERK), is key to neuronal homeostasis in neurodegenerative diseases. PERK pathway activation is usually accomplished by inhibiting eIF2α-P dephosphorylation, after its phosphorylation by PERK. Less tried is an approach involving direct PERK activation without compromising long-term recovery of eIF2α function by dephosphorylation. Here we show major improvement in cellular (STHdh Q111/111 ) and mouse (R6/2) Huntington's disease (HD) models using a potent small molecule PERK activator that we developed, MK-28. MK-28 showed PERK selectivity in vitro on a 391-kinase panel and rescued cells (but not PERK−/− cells) from ER stress-induced apoptosis. Cells were also rescued by the commercial PERK activator CCT020312 but MK-28 was significantly more potent. Computational docking suggested MK-28 interaction with the PERK activation loop. MK-28 exhibited remarkable pharmacokinetic properties and high BBB penetration in mice. Transient subcutaneous delivery of MK-28 significantly improved motor and executive functions and delayed death onset in R6/2 mice, showing no toxicity. Therefore, PERK activation can treat a most aggressive HD model, suggesting a possible approach for HD therapy and worth exploring for other neurodegenerative disorders.HD is a neurodegenerative disease arising from an expanded CAG repeat in the exon 1 of the huntingtin gene, which translates into a polyglutamine (polyQ) tract in the huntingtin (Htt) protein 1,2 . HD is a genetic, autosomal dominant disease with late onset and progressive motor dysfunction, cognitive decline and behavioral abnormalities. In addition to these, other systemic impairments such as weight loss, muscle wasting and glucose regulation impairment were also reported 2 . The expansion of the polyQ repeats causes mutant Htt (mHtt) to aggregate in HD tissues when it includes above 35 glutamine residues, with a consequent induction of cellular stress, toxicity and cell death especially in the brain striatum and extending later to the cortex. This reflects progressively in the deterioration of the individual's biological functions 3,4 . Although several therapeutic approaches are currently being pursued, including ongoing clinical trials for lowering mHtt levels using antisense oligonucleotides (ASOs), there is currently no effective treatment for HD 5 .One of the important consequences of the gradual accumulation of misfolded mHtt is its inhibition of ER-associated degradation (ERAD), causing endoplasmic reticulum (ER) stress and induction of a conserved stress response known as the unfolded protein response (UPR) 6-12 . The function of the UPR is to either re-establish cellular homeostasis or, if this fails, to trigger cell death in order to prevent further accumulation of 1 PERK modulator, with only Tun. The graphs show the average relative apoptosis rate of at least 3 independent experiments for each compound.Cell Cycle FACS analysis. Cells were washed with PBS and fixed with ...

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“…BTdCPU and other N,N′ diaryl urea derivatives are specific HRI activators (figure, s.2), which are also con sidered as promising antitumor drugs [269]. CCT020312 and MK 28 are pharmacological activators of PERK (fig ure, s.1) and can be potentially used in the treatment of neuropathies [270,271]. Specific activators of GCN2 kinase ( figure, s.3) have not yet been sufficiently studied; however, recent screening identified two candidatessmall molecules dabrafenib and MK1775 [264].…”

Chromosome 22q11.2 deletion causes PERK-dependent vulnerability in dopaminergic neurons

“…We also evaluated the effect of another PERK activator, CCT020312,[ 36 , 37 ] on the 22DS group phenotypes. Similar to salubrinal, CCT020312 ameliorated cell vulnerability to ER stress and F-actin dynamics in the 22DS group with the upregulation of PERK activity (Supplementary Figures 11).…”

ER Stress-Sensor Proteins and ER-Mitochondrial Crosstalk—Signaling Beyond (ER) Stress Response

“…In HD condition it has been upregulated. In the follow-up study, the Lederkremer group very recently showed PERK activator MK-28 can successfully reduce toxicity and extend survival in Huntington’s disease models [ 232 ].…”