Genetic and Pharmacological Approaches to Preventing Neurodegeneration

The Insulin/Insulin-like Growth Factor 1 Signaling (IIS) pathway was first identified as a major modifier of aging in C.elegans. It has since become clear that the ability of this pathway to modify aging is phylogenetically conserved. Aging is a major risk factor for a variety of neurodegenerative diseases including the motor neuron disease, Amyotrophic Lateral Sclerosis (ALS). This raises the possibility that the IIS pathway might have therapeutic potential to modify the disease progression of ALS. In a C. elegans model of ALS we found that decreased IIS had a beneficial effect on ALS pathology in this model. This beneficial effect was dependent on activation of the transcription factor daf-16. To further validate IIS as a potential therapeutic target for treatment of ALS, manipulations of IIS in mammalian cells were investigated for neuroprotective activity. Genetic manipulations that increase the activity of the mammalian ortholog of daf-16, FOXO3, were found to be neuroprotective in a series of in vitro models of ALS toxicity. The small molecule Psammaplysene A (PA) is known to increase the nuclear abundance of FOXO3. PA was also found to be protective in mammalian in vitro models of ALS toxicity as well as a fly and worm model of neurodegeneration. Due to the wide variety of neurodegenerative diseases that share aging as a risk factor, a small molecule modifier of FOXO/daf-16 such as PA could hold great therapeutic potential. Most clinically viable drugs have certain physico-chemical properties that fall within a well-defined set of values, which unfortunately PA does not share. Due to its poor drug-likness , an investigation into the mechanism of action of PA was undertaken in order to potentially identify more drug-like compounds with similar activities. This investigation revealed the heterogeneous nuclear ribonucleoprotein K (HNRNPK) is a direct physical target of PA. PA modifies the ability of HNRNPK to stabilize rRNA but does not affect many of HNRNPK\u27s other functions. How changes in rRNA stability modify IIS or whether these changes definitively underlie PA\u27s neuroprotective mechanism remains to be determined

FOXO3a is broadly neuroprotective in vitro and in vivo against insults implicated in motor neuron diseases

Aging is a risk factor for the development of adult-onset neuro-degenerative diseases. While some of the molecular pathways regulating longevity and stress resistance in lower organisms are defined (i.e., those activating the transcriptional regulators DAF-16 and HSF-1 in C. elegans), their relevance to mammals and disease susceptibility are unknown. We studied the signaling controlled by the mammalian homolog of DAF-16, FOXO3a, in model systems of motor neuron disease. Neuron death elicited in vitro by excitotoxic insult or the expression of mutant SOD1, mutant p150(glued) or polyQ expanded androgen receptor was abrogated by expression of nuclear-targeted FOXO3a. We identify a compound (Psammaplysene A, PA) that increases nuclear localization of FOXO3a in vitro and in vivo and show that PA also protects against these insults in vitro. Administration of PA to invertebrate model systems of neurodegeneration similarly blocked neuron death in a DAF-16/FOXO3a-dependent manner. These results indicate that activation of the DAF-16/FOXO3a pathway, genetically or pharmacologically, confers protection against the known causes of motor neuron diseases

Daf-2 Signaling Modifies Mutant SOD1 Toxicity in C. elegans

The DAF-2 Insulin/IGF-1 signaling (IIS) pathway is a strong modifier of Caenorhabditis elegans longevity and healthspan. As aging is the greatest risk factor for developing neurodegenerative diseases such as Amyotrophic Lateral Sclerosis (ALS), we were interested in determining if DAF-2 signaling modifies disease pathology in mutant superoxide dismutase 1 (SOD1) expressing C. elegans. Worms with pan-neuronal G85R SOD1 expression demonstrate significantly impaired locomotion as compared to WT SOD1 expressing controls and they develop insoluble SOD1 aggregates. Reductions in DAF-2 signaling, either through a hypomorphic allele or neuronally targeted RNAi, decreases the abundance of aggregated SOD1 and results in improved locomotion in a DAF-16 dependant manner. These results suggest that manipulation of the DAF-2 Insulin/IGF-1 signaling pathway may have therapeutic potential for the treatment of ALS

Supplementary Materials for CLIP-Seq analysis enables the design of protective ribosomal RNA bait oligonucleotides against C9ORF72 ALS/FTD poly-GR pathophysiology

This PDF file includes: Figs. S1 to S10 Legends for tables S1 to S6Other Supplementary Material includes the following: Tables S1 to S6Peer reviewe

CLIP-Seq analysis enables the design of protective ribosomal RNA bait oligonucleotides against C9ORF72 ALS/FTD poly-GR pathophysiology

Amyotrophic lateral sclerosis and frontotemporal dementia patients with a hexanucleotide repeat expansion in C9ORF72 (C9-HRE) accumulate poly-GR and poly-PR aggregates. The pathogenicity of these arginine-rich dipeptide repeats (R-DPRs) is thought to be driven by their propensity to bind low-complexity domains of multivalent proteins. However, the ability of R-DPRs to bind native RNA and the significance of this interaction remain unclear. Here, we used computational and experimental approaches to characterize the physicochemical properties of R-DPRs and their interaction with RNA. We find that poly-GR predominantly binds ribosomal RNA (rRNA) in cells and exhibits an interaction that is predicted to be energetically stronger than that for associated ribosomal proteins. Critically, modified rRNA “bait” oligonucleotides restore poly-GR–associated ribosomal deficits and ameliorate poly-GR toxicity in patient neurons and Drosophila models. Our work strengthens the hypothesis that ribosomal function is impaired by R-DPRs, highlights a role for direct rRNA binding in mediating ribosomal dysfunction, and presents a strategy for protecting against C9-HRE pathophysiological mechanisms.This work was supported by the U.S. National Institutes of Health (NIH) National Institute of Neurological Disorders and Stroke (NINDS) and National Institute of Aging (NIA) grant R01NS104219 (E.K.); NIH/NINDS grant R21NS107761 (E.K.); AFM-Telethon French Muscular Dystrophy Association Trampoline Grant #23648 (J.A.O.); AFM-Telethon postdoctoral fellowship (J.A.O.); Ramon y Cajal fellowships RYC2019-026980-I (J.A.O.) and RYC2021-033294-I (I.R.S.); Gipuzkoa Foru Aldundia 2019-FELL-000017-01 (I.R.S.); Maria de Maeztu Units of Excellence CEX2021-001159-M (J.A.O.) and MDM-2017-0720 (I.R.S.); NINDS grants R01NS097850 and R01NS131409 (J.K.I.); Department of Defense grants PR211919 and W81XWH2110131 (J.K.I.); John Douglas French Alzheimer’s Foundation (J.K.I.); Center for Regenerative Nanomedicine at the Simpson Querrey Institute (S.I.S. and T.D.C.); Intramural Research Program, NIH, National Cancer Institute (NCI), Center for Cancer Research (M.B. and S.L.W.); Les Turner ALS Foundation (E.K.); and New York Stem Cell Foundation (J.K.I. and E.K.).With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2021-001159-M (J.A.O.)).Peer reviewe

Figure 2

<p>A) YFP signal was imaged in <i>G85R</i> or <i>G85R;unc119p::sid1;sid1(pk3321)</i> worms fed empty vector (EV) or G85R:YFP RNAi in order to demonstrate the efficacy of RNAi in neurons on the <i>unc119p::sid1;sid1(pk3321)</i> background B–E) Average speed normalized to size of swimming worms fed bacteria expressing the indicated RNAi.</p

Longevity analysis, percent alive per day.

<p>Longevity analysis, percent alive per day.</p

Figure 1

<p>A) Videos of worms crawling on OP50 at the indicated times were taken and used to calculate worm speed using the parallel worm tracker software. B) Average swim speed normalized to size was calculated at the indicated times using the parallel worm tracker. C) Swim speed normalized to size was calculated for <i>TDP43</i> and <i>TDP43;daf-2(e1370)</i> worms 72 hrs post egg drop.</p

The Neuroprotective Marine Compound Psammaplysene A Binds the RNA-Binding Protein HNRNPK

In previous work, we characterized the strong neuroprotective properties of the marine compound Psammaplysene A (PA) in in vitro and in vivo models of neurodegeneration. Based on its strong neuroprotective activity, the current work attempts to identify the physical target of PA to gain mechanistic insight into its molecular action. Two distinct methods, used in parallel, to purify protein-binding partners of PA led to the identification of HNRNPK as a direct target of PA. Based on surface plasmon resonance, we find that the binding of PA to HNRNPK is RNA-dependent. These findings suggest a role for HNRNPK-dependent processes in neurodegeneration/neuroprotection, and warrant further study of HNRNPK in this context