The SARS-CoV-2 spike glycoprotein interacts with MAO-B and impairs mitochondrial energetics, 2023, Pileggi et al.

[SNT Gatchaman]

The SARS-CoV-2 spike glycoprotein interacts with MAO-B and impairs mitochondrial energetics
Pileggi; Parmar; Elkhatib; Stewart; Alecu; Côté; Bennett; Sandhu; Cuperlovic-Culf; Harper

SARS-CoV-2 infection is associated with both acute and post-acute neurological symptoms. Emerging evidence suggests that SARS-CoV-2 can alter mitochondrial metabolism, suggesting that changes in brain metabolism may contribute to the development of acute and post-acute neurological complications.

Monoamine oxidase B (MAOB) is a flavoenzyme located on the outer mitochondrial membrane that catalyzes the oxidative deamination of monoamine neurotransmitters. Computational analyses have revealed high similarity between the SARS-CoV-2 spike glycoprotein receptor binding domain on the ACE2 receptor and MAO-B, leading to the hypothesis that SARS-CoV-2 spike glycoprotein may alter neurotransmitter metabolism by interacting with MAO-B.

Our results empirically establish that the SARS-CoV-2 spike glycoprotein interacts with MAO-B, leading to increased MAO-B activity in SH-SY5Y neuron-like cells. Common to neurodegenerative disease pathophysiological mechanisms, we also demonstrate that the spike glycoprotein impairs mitochondrial bioenergetics, induces oxidative stress, and perturbs the degradation of depolarized aberrant mitochondria through mitophagy. Our findings also demonstrate that SH-SY5Y neuron-like cells expressing the SARS-CoV-2 spike protein were more susceptible to MPTP induced necrosis, likely necroptosis.

Together, these results reveal novel mechanisms that may contribute to SARS-CoV-2-induced neurodegeneration.

Link | PDF (Current Research in Neurobiology)

 

[SNT Gatchaman]

Emerging evidence suggests that SARS-CoV-2 may also be linked to post-encephalitic Parkinsonism, however, the molecular mechanisms are poorly elucidated. Persistent circulating S protein is associated with post-acute COVID-19, and the spike glycoprotein can elicit alterations in cellular metabolism that may contribute to neurodegeneration. Here, we show that the S protein can interact with, and increase activity of MAO-B. We also demonstrate that the spike glycoprotein can impair mitochondrial bioenergetics, induce oxidative stress, perturb the degradation of depolarized aberrant mitochondria, and increase sensitivity to MPTP-induced cell death, which are common pathophysiological mechanisms shared with neurodegenerative diseases.

Progressive loss of nigrostriatal dopaminergic neurons in the substantia nigra pars compacta, and the accumulation of misfolded α-synuclein leading to Lewy body pathology are the hallmark features of Parkinson’s disease. MAO-B activity is elevated in patients with Parkinson’s disease, and the high MAO-B activity results in increased dopamine catabolism and the formation of DOPAL, which plays a role in the aggregation of α-synuclein.

Substantial brain invasion of SARS-CoV-2 is relatively uncommon, likely due to low ACE2 receptor expression in the brain; however, spatial distribution analysis [...] revealed that ACE2 expression is relatively high in specific brain regions, including the substantia nigra. [...] The SARS-CoV-2 S 1 subunit can readily cross the BBB, resulting in widespread brain regional distribution. The new onset of Parkinsonism following SARS-CoV-2 infection has been reported in case studies along with presynaptic nigrostriatal dopamine disturbance and depigmentation of the substantia nigra. Patients with existing Parkinson’s disease often need to increase the dosing of levodopa following SARS-CoV-2 infection

Our findings of elevated mitochondrial content without an increase in mitochondrial biogenesis support our conclusion that mitochondrial clearance is perturbed, leading to the accumulation of aberrant mitochondria.

spike glycoprotein may contribute to impaired mitophagy through decreased parkin-mediated ubiquitination of mitochondrial outer membrane proteins. The observed decrease in parkin expression may also contribute to enhanced MAO-B activity, as parkin can suppress the expression of MAO-B. The drastic reduction of p53 in cells expressing the S protein may contribute to impaired mitophagy and elicit the Warburg effect by decreasing parkin expression, which is supported by our findings of increased LDH activity and extracellular lactate. Computational modelling suggests that the SARS-CoV-2 S 2 subunit can interact with p53 and modulate its expression, which may be a mechanism to suppress type I interferon antiviral responses

 

[rapidboson]

Have there been any updates on this? Any opinions?

 

[rapidboson]

This paper seems related?

Background
After acute COVID-19, 5% of people experience persistent depressive symptoms and reduced cognitive function (COVID-DC). Theoretical models propose that astrogliosis is important in long COVID, but measures primarily indicative of astrogliosis have not been studied in the brain of long COVID or COVID-DC. The objective of the current study was to measure [11C]SL25.1188 total distribution volume ([11C]SL25.1188 VT), an index of monoamine oxidase B density and a marker of astrogliosis, with positron emission tomography in participants with COVID-DC and compare with healthy control participants.

Methods
In 21 COVID-DC cases and 21 healthy control participants, [11C]SL25.1188 VT was measured in the prefrontal cortex, anterior cingulate cortex, hippocampus, dorsal putamen, and ventral striatum. Depressive symptoms were measured with the Beck Depression Inventory-II, and cognitive symptoms were measured with neuropsychological tests.

Results
[11C]SL25.1188 VT was higher in participants with COVID-DC in the prefrontal cortex, anterior cingulate cortex, hippocampus, dorsal putamen, and ventral striatum than in healthy control participants. Depressive symptom severity negatively correlated with [11C]SL25.1188 VT across prioritized brain regions. More recent acute COVID-19 positively correlated with [11C]SL25.1188 VT, reflecting higher values since predominance of the Omicron variant. Exploratory analyses found greater [11C]SL25.1188 VT in the hippocampus, dorsal putamen, and ventral striatum of COVID-DC participants than control participants with a major depressive episode with no history of COVID-19, and there was no relationship to cognitive testing in prioritized regions.

Conclusions
Results strongly support the presence of monoamine oxidase B–labeled astrogliosis in COVID-DC throughout the regions assessed, although the association of greater astrogliosis with fewer symptoms raises the possibility of a protective role. The magnitude of astrogliosis in COVID-DC is greater since the emergence of the Omicron variant.

Does this potentially shed and light on disease etiology or at least potential downstream treatment?
Is anybody aware of trials or clinical experience with people with Parkinson's (or others taking MAO-B inhibitors) and Long COVID (or others with cognitive dysfunction)? Too much brain fog myself to dig deep.

What else could these results point towards if not astrogliosis/neuroinflammation?

@Jonathan Edwards do you have any insights?

 

[rapidboson]

Is there nobody here that can discuss this a bit?

 

[Utsikt]

Is there nobody here that can discuss this a bit?

This seems to be pretty niche and technical, so most people are probably not able to discuss it, including myself.

The authors of the paper you posted have substantial financial interests in MAO-B, so they will probably push for studies and trials if it’s worthwhile.

 

[rapidboson]

This seems to be pretty niche and technical, so most people are probably not able to discuss it, including myself.

I figured, but thank you for your assessment in any case
I am wondering - as I lack knowledge/education in this field - why this line of thought linking MAO-B and LC (and mitochondrial energetics) is not looked into more.

The authors of the paper you posted have substantial financial interests in MAO-B, so they will probably push for studies and trials if it’s worthwhile.

Well spotted!

 

[Utsikt]

I am wondering - as I lack knowledge/education in this field - why this line of thought linking MAO-B and LC (and mitochondrial energetics) is not looked into more.

Most research is quite disjointed and some just work on their pet theories regardless of the merit of the theories. And most of academia is completely broken, it’s all about citations, publications, grants, power and status. I have no way of knowing if this is a part of that or not.

 

[jnmaciuch]

I am wondering - as I lack knowledge/education in this field - why this line of thought linking MAO-B and LC (and mitochondrial energetics) is not looked into more.

There seems to only be a handful of papers thus far examining SARS-CoV-2 interactions with mitochondria at all, so brain-specific mitochondrial interactions probably just weren't on the radar until now. Measuring that in the context of LC would be extremely challenging without good mouse models.

 

[jnmaciuch]

I'll preface this by saying that I'm by no means an expert on the topic here--my experience comes from spending time discussing similar cell bio papers in grad school journals clubs. So I can probably do a decent job of "translating" and can generally follow the logic, but I cannot comment on the finer details of the methodology.

Our group has recently shown that the substrate binding region of monoamine oxidase B (MAO-B) has 95–100% structural homology with the ACE2 receptor binding region (Cuperlovic-Culf et al., 2021).

Previous computational modeling has shown that the active domain of the MAO-B protein is very structurally similar to the active domain on ACE2 where SARS-CoV-2 is known to interact and use it to gain entry into cells. This made the authors think that there was a possibility of SARS-CoV-2 directly interacting with MAO-B.

Fig1 shows in-vitro (i.e. in a cell line) evidence of direct interactions between SARS-CoV-2 spike proteins and MAO-B.

For Fig2, they took a neuronal cell line and caused it to internally generate the SARS-CoV-2 spike protein. They used a particular labeling technique to measure the specific products of MAO-B enzymatic activity (14C labeling of phenylethylamine that would end up in the aldehyde product of MAO-B reactions) and found that in cells expressing the spike protein, MAO-B activity was much higher.

Fig3: Neuronal cells expressing the SARS-CoV-2 spike protein show other abnormalities in various measurements of mitochondrial function. From the text:

However, upon normalisation to citrate synthase to account for elevations in mitochondrial content, we observed lower resting respiration of intact cells (i.e., prior to permeabilization), as well as lower Complex I + II-driven OXPHOS, Complex I + II-driven leak respiration, and FCCP-induced maximal respiration in permeabilized SH-SY5Y cells (Fig. 3d), consistent with the conclusion that the S protein impairs intrinsic mitochondrial bioenergetic functions.

Moreover, fluorometric-based analysis of mitochondrial membrane potential with TMRM revealed that mitochondria in SH-Spike cells were depolarized across different respiratory states (Fig. 3e), again consistent with impaired mitochondrial bioenergetic functions.

Consistent with a shift in oxidative to glycolytic metabolism, SH-SY5Y-Spike cells demonstrated increased LDH activity and higher lactate concentrations in cultured medium compared to SH-EV cells (Fig. 3f and g).

That last part is particularly interesting to me, since I've been investigating impaired OxPhos and compensatory glycolytic increase in ME/CFS. So this provides more evidence to existing literature potentially linking SARS-CoV-2 infection to the eventual development of bioenergetic differences associated with ME/CFS.

My main note here is that these differences in mitochondrial function cannot be solely attributed to the interaction of the spike protein with MAO-B. There could be other interactions that drive the changes beyond what was observed in Fig2. Figures 4 and 5 are a similar story--there are differences in other measures of mitochondrial function when you cause neuronal cells to express spike protein. Those changes may mediated by SARS-CoV-2 interaction with MAO-B, but they haven't proved that definitively at this step.

Fig6: Neuronal cells expressing SARS-CoV-2 spike proteins are differentially affected by MPTP in terms of cell death pathways:

MPTP is a potent neurotoxin that is oxidized to MPP+ by MAO-B in a two-step process in astrocytes and serotonergic neurons. MPP+ is the active neurotoxin that is transported into dopaminergic neurons, which accumulates within the inner mitochondrial membrane and inhibits complex I of the electron transport chain (Heikkila et al., 1984; Javitch et al., 1985; Ramsay and Singer, 1986).

The cells expressing spike protein seemed to be skewed towards necrotic cell death rather than apoptopic cell death, the latter of which tends to be mediated by mitochondria as a purposeful response (i.e. cell recognizes infection, ends up using mitochondria to kill itself instead of allowing the virus to use its machinery to replicate). This experiment is the closest that the paper comes towards showing a direct MAO-B mediated phenotypic effect since MPTP is known to be converted into neurotoxic form by MAO-B. But again, it's somewhat indirect and might be circumstantial.

My overall impression of this paper is that it provides strong evidence (with appropriate controls and other checks) to prove that:
1) the spike protein interacts with MAO-B
and
2) presence of the spike protein results in bioenergetic changes

but does not provide strong evidence that these bioenergetic changes are mediated by spike protein interaction with MAO-B. Considering that similar findings of mitochondrial dysfunction were found in other cell lines with low or non-existent MAO-B activity (which they cite), I think MAO-B likely only plays a small part of the puzzle.

Furthermore, they're using only the spike protein, not the whole virus. There's a reason for doing this (if they used the whole virus, they'd probably just see a lot of cell death). This study, along with others, provides evidence that just the spike protein is enough to cause (at least short term) changes in mitochondrial function, but there might be more to the story mediated by the rest of the virus (e.g. other viruses are known to produce additional proteins that directly interact with host proteins, so you'd only see that interaction if you were infecting cells with more than the spike protein).

 

[Utsikt]

The cells expressing spike protein seemed to be skewed towards necrotic cell death rather than apoptopic cell death, the latter of which tends to be mediated by mitochondria as a purposeful response (i.e. cell recognizes infection, ends up using mitochondria to kill itself instead of allowing the virus to use it's machinery to spread).

So in blunt terms, the cells are murdered rather than committing suicide?

 

[jnmaciuch]

So in blunt terms, the cells are murdered rather than committing suicide?

Kind of--it's less murder and more death by neglect, since it wouldn't be good for the virus if the cell dies prematurely by suicide or murder. Necrotic death usually comes from an accumulation of toxins when the cell can't function properly. It's more like the virus prevents the cell from using its own kill switch, keeps it alive long enough to co-opt all the machinery for its own purposes, and then leaves it for dead (assuming that the cell wouldn't just die anyways when the virus replicates and blows a hole in the cell membrane to spread further).

Something like the Alien movies I suppose. Which I guess could be viewed as murder, but that's more of a semantic distinction haha

 

[Utsikt]

Kind of--it's less murder and more death by neglect, since it wouldn't be good for the virus if the cell dies prematurely by suicide or murder. Necrotic death usually comes from an accumulation of toxins when the cell can't function properly. It's more like the virus prevents the cell from using its own kill switch, keeps it alive long enough to co-opt all the machinery for its own purposes, and then leaves it for dead (assuming that the cell wouldn't just die anyways when the virus replicates and blows a hole in the cell membrane to spread further).

Something like the Alien movies I suppose. Which I guess could be viewed as murder, but that's more of a semantic distinction haha

Thank you for explaining, that makes sense to me!

 

[jnmaciuch]

One way this paper could have been improved is by knocking down MAO-B in the cells and seeing if the observed bioenergetic changes still occur when spike protein is expressed. If you only see the mitochondrial changes in the presence of MAO-B + spike protein, this would provide evidence that all the changes are directly mediated by MAO-B and not by some other interaction between the spike protein and mitochondria. From looking at the literature, it seems like MAO-B is not vital to neuronal cell survival, so knocking it down would be viable.

 

[Utsikt]

One way this paper could have been improved is by knocking down MAO-B in the cells and seeing if the observed bioenergetic changes still occur when spike protein is expressed. If you only see the mitochondrial changes in the presence of MAO-B + spike protein, this would provide evidence that all the changes are directly mediated by MAO-B and not by some other interaction between the spike protein and mitochondria. From looking at the literature, it seems like MAO-B is not vital to neuronal cell survival, so knocking it down would be viable.

The cynic in me wonders if this was not done on purpose. You wouldn’t run the risk of disproving your pet theory, especially when you have a financial interest.

 

[Jonathan Edwards]

What else could these results point towards if not astrogliosis/neuroinflammation?

@Jonathan Edwards do you have any insights?

Sorry I missed this.
I cannot get excited about any of this being of any relevance to ME/CFS or Long Covid much. We see similar illness following lots of infections so individual antigens and their similarity to human proteins are likely to be irrelevant, in my view.

This looks to me like the typical tunnel vision of much biomedical science these days. Measure anything you can measure and forget the fact that there are a lot of context factors that make most theories implausible before you even start.

Neurons may well die in people on intensive care during acute Covid but I doubt neuronal death has anything to do with LC - or astrogliosis.

 

[forestglip]

My overall impression of this paper is that it provides strong evidence (with appropriate controls and other checks) to prove that:
1) the spike protein interacts with MAO-B
and
2) presence of the spike protein results in bioenergetic changes

Did they show that it's something specific to spike? I mean maybe if they made the cell produce any other random foreign protein, like a piece of influenza, the same changes might happen, right?

 

[jnmaciuch]

Did they show that it's something specific to spike? I mean maybe if they made the cell produce any other random foreign protein, like a piece of influenza, the same changes might happen, right?

They only tested SARS-CoV-2 spike so it absolutely could be something that other viruses can also do.

 

[rapidboson]

This looks to me like the typical tunnel vision of much biomedical science these days. Measure anything you can measure and forget the fact that there are a lot of context factors that make most theories implausible before you even start.

Neurons may well die in people on intensive care during acute Covid but I doubt neuronal death has anything to do with LC - or astrogliosis.

Interesting. It does seem though, that MAO-B is more active in both papers, one being a human trial? I'm not very familiar with this though, so I'm wondering what else (besides their ideas about astrogliosis) could be reason for getting such a result (methodologically or pathophysiologically)?
In this case, what context factors make this theory implausible?