Biology subjects

Krout, M.

Publications and source records attributed to Krout, M..

4 recordsLinked to original sources

bioRxiv2024

Small molecule modulator of neuronal lysosome positioning and function resolves Alzheimers Disease-linked pathologies in cultured human neurons

Abnormal increase in axonal lysosome abundance is associated with multiple neurodegenerative diseases including Alzheimers disease. However, the underlying mechanisms and disease relevance are not fully understood. We have recently identified RH1115 as a small molecule modulator of the autophagy-lysosomal pathway that regulates lysosome positioning in neurons. This allowed us to manipulate neuronal lysosome distribution including in axons and interrogate its contribution to both optimal neuronal functioning and to disease pathology. We demonstrate that the small molecule not only rescues aberrant buildup of both axonal autophagic and lysosomal intermediates but also reduces secreted A{beta}42 levels in human iPSC-derived neurons lacking the lysosomal adaptor, JIP3. We thus demonstrate that restoring efficient axonal lysosome transport has an anti-amyloidogenic effect in human neurons and is a promising therapeutic strategy for Alzheimers disease. Furthermore, we show that the small molecule enhances neuronal lysosome degradation, requires the lysosomal adaptor JIP4 to rescue the axonal lysosome pathology in the JIP3 KO neurons and increases levels of the JIP4-interacting lysosomal membrane protein, TMEM55B. Lastly, treatment with the small molecule led to a striking rescue of locomotor defects in JIP3 KO zebrafish larvae. Thus, we have identified a small molecule which can be impactful in neurodegenerative diseases that have a lysosomal pathology and have determined its molecular targets in modulating axonal lysosome abundance.

cell biology↗

bioRxiv2023

Neuroendocrine control of synaptic transmission by PHAC-1 in C. elegans.

A dynamic interplay between synaptic and neuromodulatory signalling guarantees flexible but robust neuronal circuits. Presynaptic modulation plays a crucial role in controlling the excitatory-inhibitory balance within networks. Here, we designed a genetic screen to identify genes involved in the neuromodulation of the C. elegans neuromuscular junctions (NMJ) and identified the orthologs of the Protein Phosphatase 1 regulatory subunit PHACTR1 (phac-1) and the presynaptic phosphoproteins Synapsin (snn-1). Five de novo variants of human PHACTR1 are associated with severe early-onset epilepsies (DEE70). To understand the impact of these variants, we introduced the DEE70 mutations into phac-1. These mutations resulted in the formation of a constitutively active PP1-PHAC-1 holoenzyme that disrupts cholinergic signalling at the NMJ. By using quantitative fluorescence imaging, electron microscopy and electrophysiology, we found that the constitutive holoenzyme alters the synaptic vesicle cycle, reduces the synaptic vesicle reserve pool, and increases neuropeptide release by dense-core vesicles. Notably, while SNN-1 phosphoregulation contributes to NMJ signalling, genetic interactions suggest that SNN-1 is not the main effector of PP1-PHAC-1 holoenzyme signalling. Collectively, our results confirm the pathogenicity of DEE70 variants, clarify their dominant-positive effects, and provide evidence of a presynaptic mode of action for DEE70.

neuroscience↗

bioRxiv2022

The Epithelial Na+ Channel UNC-8 promotes an endocytic mechanism that recycles presynaptic components from old to new boutons in remodeling neurons

SummaryPresynaptic terminals are actively relocated during development to refine circuit function, but the underlying cell biological mechanisms are largely unknown. In C. elegans, the presynaptic boutons of GABAergic DD neurons are moved to new locations during early larval development. We show that developmentally regulated expression of a presynaptic Epithelial Na+ Channel (ENaC), UNC-8, promotes a Ca2+-dependent mechanism, resembling Activity-Dependent Bulk Endocytosis (ADBE), that dismantles presynaptic material for reassembly at nascent DD synapses. ADBE normally functions in highly active neurons to accelerate local recycling of synaptic vesicles. We show that DD presynaptic remodeling depends on canonical features of ADBE including elevated intracellular Ca2+, the phosphatase Calcineurin and its targets, dynamin and the F-BAR protein syndapin, and Arp2/3-driven actin polymerization. Thus, our findings suggest that a native mechanism (ADBE) for maintaining neurotransmitter release at local synapses has been repurposed, in this case, to dismantle presynaptic terminals for reassembly at new locations. HighlightsO_LIDeveloping GABAergic neurons dismantle presynaptic terminals for reassembly at new locations. C_LIO_LIThe DEG/ENaC protein, UNC-8, promotes presynaptic disassembly and recycling C_LIO_LICa2+-dependent endocytosis drives presynaptic disassembly and recycling to new boutons C_LI

neuroscience↗

bioRxiv2018

Bile acid metabolites control Th17 and Treg cell differentiation

Bile acids are abundantly present in the mammalian gut, where they undergo bacteria-mediated transformation, generating a large pool of bioactive molecules. While they have been shown to affect host metabolism, cancer progression and innate immunity, it is unknown whether bile acids affect the function of adaptive immune cells such as T cells expressing IL-17a (Th17 cells) and regulatory T cells (Tregs) that mediate inflammatory and anti-inflammatory responses, respectively. By screening a small-molecule library primarily composed of bile acid metabolites, we identified two distinct derivatives of lithocholic acid (LCA), 3-oxoLCA and isoalloLCA, as specific regulators of Th17 and Treg cells. While 3-oxoLCA inhibited Th17 cell differentiation by directly binding to its key transcription factor ROR{gamma}t (retinoid-related orphan receptor {gamma} t), isoalloLCA enhanced differentiation of Tregs through mitochondrial-dependent metabolic changes, leading to an increased expression of Foxp3. IsoalloLCA-dependent Treg enhancement required an intronic Foxp3 enhancer, the conserved noncoding sequence 3 (CNS3), which acts as an epigenetic switch that confers a poised state to the Foxp3 promoter. Lastly, oral administration of 3-oxoLCA and isoalloLCA to mice led to reduced Th17 and increased Treg cell differentiation in the intestinal lamina propria. Altogether, our data suggest novel mechanisms by which bile acid metabolites control host immune responses by directly modulating the Th17 and Treg balance.

immunology↗