Disruption of cellular proteostasis by H1N1 influenza A virus causes α-synuclein aggregation

Abstract

Neurodegenerative diseases feature specific misfolded or misassembled proteins associated with neurotoxicity. The precise mechanisms by which protein aggregates first arise in the majority of sporadic cases have remained unclear. Likely, a first critical mass of misfolded proteins starts a vicious cycle of a prion-like expansion. We hypothesize that viruses, having evolved to hijack the host cellular machinery for catalyzing their replication, lead to profound disturbances of cellular proteostasis, resulting in such a critical mass of protein aggregates. Here, we investigated the effect of influenza virus (H1N1) strains on proteostasis of proteins associated with neurodegenerative diseases in Lund human mesencephalic dopaminergic cells in vitro and infection ofRagknockout mice in vivo. We demonstrate that acute H1N1 infection leads to the formation of α-synuclein and Disrupted-in-Schizophrenia 1 (DISC1) aggregates, but not of tau or TDP-43 aggregates, indicating a selective effect on proteostasis. Oseltamivir phosphate, an antiinfluenza drug, prevented H1N1-induced α-synuclein aggregation. As a cell pathobiological mechanism, we identified H1N1-induced blocking of autophagosome formation and inhibition of autophagic flux. In addition, α-synuclein aggregates appeared in infected cell populations connected to the olfactory bulbs following intranasal instillation of H1N1 inRagknockout mice. We propose that H1N1 virus replication in neuronal cells can induce seeds of aggregated α-synuclein or DISC1 that may be able to initiate further detrimental downstream events and should thus be considered a risk factor in the pathogenesis of synucleinopathies or a subset of mental disorders. More generally, aberrant proteostasis induced by viruses may be an underappreciated factor in initiating protein misfolding.

SARS‐CoV‐2: At the Crossroad Between Aging and Neurodegeneration

“…The loss of ability of properly activating stress response mechanisms in the elderly can lead to severe phenotypes, including a decrease of protein solubility and accumulation of aggregates, such as those characteristic of various age‐associated neurodegenerative disorders, including PD. Indeed, infection of dopaminergic cells expressing alpha‐synuclein (aSyn), the major protein component of Lewy bodies and Lewy neurites, with the H1N1 influenza virus, resulted in the formation of aSyn aggregates, but not of tau or TDP‐43, suggesting selectivity . In this study, the molecular mechanisms pointed to H1N1‐mediated blocking of autophagic flux, which has long been associated with aSyn accumulation in models of PD.…”

“…Therefore, viruses can interfere with protein degradation pathways to maintain the correct concentration and function of viral proteins. H1N1 blocks autophagic flux at early stages and leads to a decreased number of autophagosomes, whereas at the late stages, it inhibits autophagosome fusion with lysosomes . However, for (+) strand RNA viruses, autophagosomes can facilitate assembly of replicase proteins.…”

COVID-19: dealing with a potential risk factor for chronic neurological disorders

“…The mechanisms underlying this association may imply a direct neuronal injury due to the central nervous system (CNS) invasion by viruses and subsequent loss of dopaminergic cells into the SNpc. Indeed, it has been recently demonstrated in Rag knockout mice that H1N1 Influenza-A virus infection inhibits protein degradation at autophagosome-lysosome system level and precipitates α-syn accumulation [11]. Further experimental evidence showed that Influenza-A virus disrupts mitochondrial activity and increase oxidative stress [12,13], whereas hepatitis C virus impairs dopaminergic transmission and affects the blood-brain barrier (BBB) integrity [10].…”

Amitriptyline interferes with autophagy-mediated clearance of protein aggregates via inhibiting autophagosome maturation in neuronal cells

“…To verify the effect of amitriptyline on the protein accumulation in more pathophysiologically relevant in vitro model, we examined the amitriptyline effects in differentiated Lund human mesencephalic (LUHMES) cells. LUHMES cells are human embryonic neuronal precursor cells and differentiated into human dopaminergic neurons, which characterized by increased expression of dopaminergic neuronal markers 32,33 . Because LUHMES cells express α-synuclein and the accumulation of endogenous α-synuclein aggregate is associated with PD pathology 33 , we also evaluated whether accumulation of α-synuclein was induced by amitriptyline.…”

“…LUHMES cells are human embryonic neuronal precursor cells and differentiated into human dopaminergic neurons, which characterized by increased expression of dopaminergic neuronal markers 32,33 . Because LUHMES cells express α-synuclein and the accumulation of endogenous α-synuclein aggregate is associated with PD pathology 33 , we also evaluated whether accumulation of α-synuclein was induced by amitriptyline. LUHMES cells were differentiated for 5 days and treated with amitriptyline for additional 24 h. The expression of dopaminergic neuronal marker was confirmed by immunoblotting against tyrosine hydroxylase ( Fig.…”