Summary: Sporadic Parkinson’s disease appears to be caused by a blockage in the pathway that helps regulate mitochondria.
Source: University of Copenhagen
12,000 people in Denmark and 7 to 10 million people worldwide suffer from Parkinson’s Disease (PD). It is the second most common neurogenerative disorder of aging and the most common movement disorder, but the cause of the disease is largely unknown.
In a new study, researchers from the University of Copenhagen show that the most common form of the disease, encompassing 90 to 95 percent of all Parkinson’s Disease cases known as sporadic PD, is caused by a blockage of a pathway that regulates the nerve cell’s powerhouse, the mitochondria.
‘Just like when people eat, cells take what they need and get rid of the rest waste products. But if our brain cells have this specific kind of signaling blockage, it means that the powerhouse of the cell – mitochondria – cannot get cleaned up after being damaged’, explains corresponding author and group leader Professor Shohreh Issazadeh-Navikas at the Biotech Research & Innovation Centre.
The blockage leads to an accumulation of high amounts of damaged mitochondria, while not being able to produce enough energy for the cells. It causes neurons to gradually die, which is the reason for the development of Parkinson’s Disease symptoms, and why it leads to dementia.
The blockage is caused by a dysregulation of the immune genes, more specifically a pathway called type 1 interferon, which is normally important for fight against viruses, but now we show that it is also responsible for regulating the energy supply of the nerve cells.
‘Every part of our body needs to be regulated. We get a signal to stop eating, when we are full, and the same thing happens everywhere else in our body. If we get an infection, parts of our body need to fight it and stop it from replicating. But when the infection is cleaned up, the signal should subside. This is the job of a protein called PIAS2. That causes the blockage of the type 1 interferon-pathway, and when the infection is over, the blockage should stop and go back to normal. But that does not seem to be the case in patients with Parkinson’s Disease. We further demonstrate that this dysregulation leads to a defect in the mitochondrial energy supply, as mentioned before’, says Shohreh Issazadeh-Navikas.
These pathways are very important for brain functions, but they are also associated with microbial and virus recognition. For example, they are very important for fighting COVID-19, and a mutation in the related gene has been shown to be linked to a deadly outcome after contracting COVID-19.
The researchers combined and analyzed four data sets, which studied neurons from brains with Parkinson’s Disease and looked at what type of genes they express.
They then looked at which gene patterns were disturbed in patients with Parkinson’s Disease and especially those who had also developed PD with dementia.
In order to test the results, the major findings of the combined data was tried in three different mouse models using a negative regulator of the type I interferon pathway, PIAS2, which had been identified from the patients study as one of the key proteins linked to the progression of Parkinson’s Disease and dementia.
‘We show that a high accumulation of the PIAS2-protein is what is causing the blockage in the pathway, which should have activated the processes responsible for removing damaged protein and mitochondrial garbage’, says Shohreh Issazadeh-Navikas.
‘The accumulation of damaged mitochondrial mass further leads to increase of other toxic proteins. So when we compare patients to same-aged healthy patients without Parkinson’s Disease, we see that this PIAS2-protein is highly expressed in the neurons, which is why this pathway should be evaluated for potential roles in the other forms of familial Parkinson’s Disease that we have not studied here.’
The researchers hope the study will encourage research to counteract the pathway blockage, which could have a beneficial impact on the disease and towards preventing dementia.
In the next stages, the Shohreh Group will study how the pathway contributes to neuronal homeostasis and survival, as well as how its dysregulation causes neuronal cell death.
About this Parkinson’s disease research news
Source: University of Copenhagen Contact: Shohreh Issazadeh-Navikas – University of Copenhagen Image: The image is in the public domain
Original Research: Open access. “PIAS2-mediated blockade of IFN-β signaling: a basis for sporadic Parkinson disease dementia” by Joana Magalhaes, Emilie Tresse, Patrick Ejlerskov, Erling Hu, Yawei Liu, Andrea Marin, Alexia Montalant, Letizia Satriano, Carsten Friis Rundsten, Eva Maria Meier Carlsen, Rasmus Rydbirk, Ali Sharifi-Zarchi, Jesper Bøje Andersen, Susana Aznar, Tomasz Brudek, Konstantin Khodosevich, Marco Prinz, Jean-François Marie Perrier, Manu Sharma, Thomas Gasser & Shohreh Issazadeh-Navikas. Molecular Psychiatry
PIAS2-mediated blockade of IFN-β signaling: a basis for sporadic Parkinson disease dementia
Familial Parkinson disease (PD) is associated with rare genetic mutations, but the etiology in most patients with sporadic (s)PD is largely unknown, and the basis for its progression to dementia (sPDD) is poorly characterized. We have identified that loss of IFNβ or IFNAR1, the receptor for IFNα/β, causes pathological and behavioral changes resembling PDD, prompting us to hypothesize that dysregulated genes in IFNβ-IFNAR signaling pathway predispose one to sPD.
By transcriptomic analysis, we found defective neuronal IFNβ-IFNAR signaling, including particularly elevated PIAS2 associated with sPDD. With meta-analysis of GWASs, we identified sequence variants in IFNβ-IFNAR-related genes in sPD patients. Furthermore, sPDD patients expressed higher levels of PIAS2 mRNA and protein in neurons.
To determine its function in brain, we overexpressed PIAS2 under a neuronal promoter, alone or with human α-synuclein, in the brains of mice, which caused motor and cognitive impairments and correlated with intraneuronal phosphorylated (p)α-synuclein accumulation and dopaminergic neuron loss.
Ectopic expression of neuronal PIAS2 blocked mitophagy, increased the accumulation of senescent mitochondrial and oxidative stress, as evidenced by excessive oxDJ1 and 8OHdG, by inactivating ERK1/2-P53 signaling. Conversely, PIAS2 knockdown rescued the clinicopathological manifestations of PDD in Ifnb–/– mice on restoring mitochondrial homeostasis, oxidative stress, and pERK1/2-pP53 signaling. The regulation of JAK-STAT2-PIAS2 signaling was crucial for neurite outgrowth and neuronal survival and excitability and thus might prevent cognitive impairments.
Our findings provide insights into the progression of sPD and dementia and have implications for new therapeutic approaches.