Synaptic disruption and CREB‐regulated transcription are restored by K ⁺ channel blockers in ALS

Abstract

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease, which is still missing effective therapeutic strategies. Although manipulation of neuronal excitability has been tested in murine and human ALS models, it is still under debate whether neuronal activity might represent a valid target for efficient therapies. In this study, we exploited a combination of transcriptomics, proteomics, optogenetics and pharmacological approaches to investigate the activity-related pathological features of iPSC-derived C9orf72-mutant motoneurons (MN). We found that human ALS C9orf72 MN are characterized by accumulation of aberrant aggresomes, reduced expression of synaptic genes, loss of synaptic contacts and a dynamic "malactivation" of the transcription factor CREB. A similar phenotype was also found in TBK1-mutant MN and upon overexpression of poly(GA) aggregates in primary neurons, indicating a strong convergence of pathological phenotypes on synaptic dysregulation. Notably, these alterations, along with neuronal survival, could be rescued by treating ALS-related neurons with the K + channel blockers Apamin and XE991, which, respectively, target the SK and the Kv7 channels. Thus, our study shows that restoring the activitydependent transcriptional programme and synaptic composition exerts a neuroprotective effect on ALS disease progression.

Aging-Dependent Altered Transcriptional Programs Underlie Activity Impairments in Human C9orf72-Mutant Motor Neurons

“…In contrast, reduced neuronal activity has been observed in ALS-related human MN by various other groups: Naujock and colleagues reported less spontaneous firing and synaptic inputs in human MN with FUS and SOD1 mutations than in cultures from healthy controls ( Naujock et al, 2016 ). In addition, another study linked reduced excitability in C9orf72-mutant MN to increased expression of K + channels ( Sareen et al, 2013 ) and, more recently, the K + channel blocker Apamin proved neuroprotective in human C9orf72-mutant MN (and Drosophila) by two independent research teams ( Castelli et al, 2021 ; Catanese et al, 2021 ).…”

P53 Protein Modulates Muscle Metabolism and Generates a Non-Genetic Risk Environment that Contributes to Triggering Amyotrophic Lateral Sclerosis

“…Further study of these ion channels to discern when and why cortical and peripheral hyperexcitability begins is crucial. Its modulators could correct muscle fiber stiffness in ALS and stabilize motoneuronal action potentials [123,124,125,126]. 7.9.…”

Emerging Mechanisms Underpinning Neurophysiological Impairments in C9ORF72 Repeat Expansion-Mediated Amyotrophic Lateral Sclerosis/Frontotemporal Dementia

“…Commensurate with cortical disease progression, synaptic loss in lower motor neurons is an established observation in the latter stages of ALS and is expected to be a major physiological determinant preventing lower motor neuron function in the later stages of disease ( Sasaki and Maruyama, 1994 ). Synaptic loss accompanied by CREB-dependent transcriptomic and proteomic changes is observed in C9ORF72 RE iPSC-derived motor neurons maintained for extended culture time ( Catanese et al, 2021 ). A number of hypotheses center upon disturbances in glutamate-mediated signaling and altered excitability being major contributors to synaptic loss and other sites of lower motor neuron injury.…”

“…The rescue of both hypoexcitability and hyperexcitability in motor neurons has been a pharmacological target in recent years. The promotion of increased excitability via pharmacological inhibition of small conductance calcium-activated potassium (SK) channels promotes survival and restores the activity-dependent transcriptional profiles and synaptic composition in C9ORF72 RE iPSC-derived motor neurons, and furthermore, promotes locomotor function in a Drosophila model containing 36 hexanucleotide repeats ( Castelli et al, 2021 ; Catanese et al, 2021 ). C9ORF72 RE motor neurons also demonstrated an increase in the expression of SK channel subunits, which could be corrected using specific inhibition of the SRSF1-dependent nuclear export of pathological C9ORF72 RE transcripts ( Castelli et al, 2021 ).…”

“…Increased excitability via pharmacological inhibition of small conductance calcium-activated potassium (SK) channels promotes survival and restores the activity-dependent transcriptional profiles and synaptic composition in iPSC-derived C9ORF72 RE motor neurons, and furthermore, promotes locomotor function in a Drosophila model containing 36 hexanucleotide repeats (Castelli et al, 2021;Catanese et al, 2021).…”