Autophagic dysfunction and gut microbiota dysbiosis cause chronic immune activation in a Drosophila model of Gaucher disease

Abstract

Mutations in the GBA1 gene cause the lysosomal storage disorder Gaucher disease (GD) and are the greatest known genetic risk factors for Parkinson’s disease (PD). Communication between the gut and brain and immune dysregulation are increasingly being implicated in neurodegenerative disorders such as PD. Here, we show that flies lacking the Gba1b gene, the main fly orthologue of GBA1, display widespread NF-kB signalling activation, including gut inflammation, and brain glial activation. We also demonstrate intestinal autophagic defects, gut dysfunction, and microbiome dysbiosis. Remarkably, modulating the microbiome of Gba1b knockout flies, by raising them under germ-free conditions, partially ameliorates lifespan, locomotor and immune phenotypes. Moreover, we show that modulation of the immune deficiency (IMD) pathway is detrimental to the survival of Gba1 deficient flies. We also reveal that direct stimulation of autophagy by rapamycin treatment achieves similar benefits to germ-free conditions independent of gut bacterial load. Consistent with this, we show that pharmacologically blocking autophagosomal-lysosomal fusion, mimicking the autophagy defects of Gba1 depleted cells, is sufficient to stimulate intestinal immune activation. Overall, our data elucidate a mechanism whereby an altered microbiome, coupled with defects in autophagy, drive chronic activation of NF-kB signaling in a Gba1 loss-of-function model. It also highlights that elimination of the microbiota or stimulation of autophagy to remove immune mediators, rather than prolonged immunosuppression, may represent effective therapeutic avenues for GBA1-associated disorders.

Lysosomal storage, impaired autophagy and innate immunity in Gaucher and Parkinson's diseases: insights for drug discovery

“…In keeping with the autophagy impairments in GD, increased LC3-II/LC3-I ratios and p62 accumulation, both consistent with a defect in autophagosome-lysosome fusion, have been observed in mouse [52], patient iPSCderived neuronal models [50] and fly models of nGD [48,49]. Moreover, studies in iPSC-derived midbrain dopaminergic neurons from patients with GBA1 mutations demonstrated an increase in both LC3 and LAMP1, with a low co-localization index, suggesting a block specifically at the fusion stage of autophagy [53].…”

“…Given the role of the lysosome in several intracellular degradative processes, including the various forms of autophagy, defects in such pathways are increasingly being linked to GD [46][47][48]. Lysosomal-autophagic dysfunction has been well described in GD and PD linked to GBA1 mutations (GBA-PD) [46][47][48][49]. Studies in post-mortem GBA-PD brains demonstrated that mutant forms of GCase at the lysosomal surface impair CMA degradation of αSyn [37].…”

“…Lysosomal-autophagic dysfunction has been well described in GD and PD linked to GBA1 mutations (GBA-PD) [ 46 – 49 ]. Studies in post-mortem GBA-PD brains demonstrated that mutant forms of GCase at the lysosomal surface impair CMA degradation of αSyn [ 37 ].…”

“…Further upstream, mTOR phosphorylates the CLEAR (Coordinated Lysosomal Expression and Regulation) network activator TFEB to prevent its nuclear export, thus repressing transcription of autophagic–lysosomal genes. Accordingly, in a fly model of nGD, mTOR activity was dysregulated and MITF / TFEB was upregulated, in response to a block in lysosomal–autophagic function [ 48 , 49 ]. GD induced pluripotent stem cell (iPSC)-derived neuronal progenitors and differentiated neurons also displayed evidence of mTORC1 hyperactivation and increased TFEB phosphorylation.…”

Smpd1regulates chitin-clearance for tracheal gas-filling in theDrosophilaembryo in a ceramide-specific manner

“…Thus, Smpd1 displays a secreted rather than a lysosomal role in Drosophila embryos. Evidence of an increase in autophagosomes is in keeping with other Drosophila lysosomal storage disorder (LSD) models, underscoring common mechanisms between diverse LSDs (Atilano et al, 2023, Hull et al, 2024). Furthermore, Smpd1 is abundantly expressed in adulthood in the glia and fat body, suggesting important roles in adulthood, and adult-specific knockout of Smpd1 may produce more canonical LSD phenotypes.…”