Emerging Drug Targets in Parkinson's Disease with Joe Mazzulli, PhD

“People don't really study nuclear dysfunction in Parkinson's disease. There are certainly labs out there that do it, but it's not one of the major fields of study. So that we found this new pathology I think is exciting in the sense that it could indicate how gene dysregulation may occur in Parkinson's disease.” — Joseph Mazzulli, PhD 

• Associate Professor, Ken and Ruth Davee Department of Neurology, Division of Movement Disorders 
• Member of the Simpson Querrey Center for Neurogenetics

Mazzulli shares details from his two recent studies, discussing their implications for the future of Parkinson's disease treatments, including the possibility of new multi-pathway therapies. His research offers new insights into alpha-synuclein protein misfolding, the role of RNA-binding proteins and breakthroughs in understanding lysosomal dysfunction. 

• In Mazzulli’s lab, ​​the overall goal is to determine how the misfolding and aggregation of a protein called alpha-synuclein leads to neurodegeneration in age-related neurodegenerative disorders, such as Parkinson's disease and dementia with Lewy bodies.  
• Mazzulli was first captivated by protein aggregation in graduate school, particularly by the notion that metamorphic proteins can transform from one conformation to another. This combined with the promise of helping others through scientific research catapulted his career.  
• While the field of Parkinson’s has been dominated by alpha-synuclein research,  Mazzulli’s recent study in Neuron shows that RNA-binding proteins like NONO and SFPQ also accumulate and form pathological inclusions. 
• The study in Neuron, which used patient-derived stem cells from patients with Parkinson’s disease, also shows that RNA editing occurs too often in diseased neurons and may also be linked to neurodegeneration. 
• Mazzulli and his team are looking into therapeutic targets for reducing excessive RNA editing, specifically enzymatic targets.  
• In their induced pluripotent stem cell (IPSC) model, the team simulated neuronal maturation, and over 120 days, observed a detailed progression of Parkinson’s disease in a concentrated model. 
• In a second study published in Nature Communications, Mazzulli investigated mechanisms that link protein misfolding in neurons to glucose metabolism, a topic that has remained largely unexplored. 
• Investigating lysosomal dysfunction, the study in Nature Communications revealed that a glucose-based process called N-glycosylation is impaired in patients with Parkinson’s, which leads to protein misfolding. The team found that by boosting glycans, they could mitigate misfolding. 
• Mazzulli has two patents related to the development of new small molecules that positively impact protein folding and lysosomal function. They are currently testing some of these in patient-derived cultures and other cell models. They are also beginning to move into in vivo models. 
• While other preclinical and clinical trials for Parkinson's are currently only targeting a single therapeutic pathway, Mazzulli’s studies show potential for multi-pathway approaches, potentially accelerating new treatments for Parkinson’s. 
• Mazzulli cites two main challenges for the future of Parkinson’s research: the need for clear biomarkers that could indicate the onset of Parkinson’s much earlier and the development of small molecules that are potent enough to impact protein clearance in the brain.  

Recorded on October 10, 2024 

Additional Reading 

• Read a feature of Mazzulli's work in Breakthroughs newsletter
• Learn more about the Mazzulli lab
• Mazzulli outlines more about alpha synuclein in a review in Neuroscientist

Target Audience

Academic/Research, Multiple specialties

Learning Objectives

At the conclusion of this activity, participants will be able to:

1. Identify the research interests and initiatives of Feinberg faculty.
2. Discuss new updates in clinical and translational research.

Accreditation Statement

The Northwestern University Feinberg School of Medicine is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians.

Credit Designation Statement

The Northwestern University Feinberg School of Medicine designates this Enduring Material for a maximum of 0.50 AMA PRA Category 1 Credit(s)™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

American Board of Surgery Continuous Certification Program

Successful completion of this CME activity enables the learner to earn credit toward the CME requirement(s) of the American Board of Surgery’s Continuous Certification program. It is the CME activity provider's responsibility to submit learner completion information to ACCME for the purpose of granting ABS credit.

Disclosure Statement

Joe Mazzulli, PhD, has nothing to disclose. Course director, Robert Rosa, MD, has nothing to disclose. Planning committee member, Erin Spain, has nothing to disclose. FSM’s CME Leadership, Review Committee, and Staff have no relevant financial relationships with ineligible companies to disclose.

All the relevant financial relationships for these individuals have been mitigated.

[00:00:00] Erin Spain, MS: This is Breakthroughs, a podcast from Northwestern University Feinberg School of Medicine. I'm Erin Spain, host of the show. Nearly 1 million people in the US are living with Parkinson's disease, a condition for which there is still no known cause or cure. However, Northwestern medicine investigators have made an exciting breakthrough in Parkinson's research, uncovering previously unknown cellular mechanisms driving the disease. Northwestern's Joe Mazzulli led two recent studies published in Neuron and Nature Communications. The studies highlight the potential for new therapeutic targets, including restoring neuronal function for patients with Parkinson's and other neurodegenerative diseases. He is an associate professor in the Ken and Ruth Davee Department of Neurology's Division of Movement Disorders. He joins me today with details of these studies and he shares their implications in the future of Parkinson's disease treatments. Welcome to the show. Thank you so much for being here. 

[00:01:12] Joseph Mazzulli, PhD: Thanks so much for having me. 

[00:01:14] Erin Spain, MS: So you have been dedicated to studying Parkinson's disease for quite some time. Explain your research broadly to me and what you're presently studying in your lab. 

[00:01:23] Joseph Mazzulli, PhD: Sure. So, the overall goal of our research is to determine how protein misfolding and aggregation leads to neurodegeneration in age-related neurodegenerative disorders like dementia with Lewy bodies, Parkinson's Disease. We're focused on a class of diseases called synuclein neuropathies, where a protein called alpha synuclein accumulates in the brain and somehow causes cell death. Our lab is really focused on two main branches for this. The first branch is to determine the mechanisms of how this protein, alpha synuclein, is triggered into its aggregated form. It's normally a soluble protein, and for some reason, it builds up, it accumulates and it forms these insoluble fibrils in the brain. So we're looking at the mechanisms of how those aggregates form. And then the second thing is looking at once those aggregates are formed, what downstream essential cellular pathways are they disrupting? How do they actually induce cell death? And that's been a major question for a lot of labs since the discovery of alpha synuclein a long time ago. That's one of our main focuses. So regarding that pathway, what we're looking at mostly is protein trafficking, from one cellular compartment to another, how synuclein aggregates influence the movement of proteins and how lysosomes are affected. And lysosomes are organelles that are responsible for degrading proteins, lipids, and other macromolecules in the cell. 

[00:02:48] Erin Spain, MS: What motivated you to begin studying this field and Parkinson's disease in particular. What made you interested in really dedicating your life's work to this particular disease and group of diseases? 

[00:03:01] Joseph Mazzulli, PhD: I started studying protein aggregation in grad school, and that was over 20 years ago. It was the first thing that I was ever interested in. I was always interested in neuroscience in general as an undergrad. The fascinating part for me was this question of how a protein that is normally soluble, what allows it to change shape and convert into this pathological confirmation. So it's more of a basic biochemistry question on what dictates protein folding and it's so complex, so many mysteries in that process. Even though we do understand a lot about how proteins fold, the fact that there's these metamorphic proteins out there like alpha synuclein, that they're made to go from one conformation to the other. So that flexibility, I think, was the thing that sort of started me off on this path. And obviously the benefit of solving a problem like this that can help so many people that are suffering from these diseases would be very rewarding.  

[00:03:58] Erin Spain, MS: You mentioned that for quite some time it's been known that alpha-synuclein is responsible for the inflammation and dysfunction, which is a hallmark of a lot of these diseases. But you are also realizing that there are other proteins involved, specifically in Parkinson's pathogenesis, that haven't been studied before, and that was part of your recent publication in the journal Neuron. Can you tell me about this in the recent study? 

[00:04:24] Joseph Mazzulli, PhD: First of all, you know, starting from synuclein, as you mentioned, it's been known for 25, almost 30 years the link of alpha synuclein to disease. It started out as a discovery in genetics, rare familial forms of Parkinson's disease were found to harbor mutations in the alpha synuclein gene. It was then discovered that the alpha synuclein protein was a major component of Lewy body inclusions that histopathologically characterize the disease. These are intracellular, cytoplasmic aggregates. And, from that time, so those discoveries occurred in the late nineties, people have been really focused on synuclein and how it aggregates and how it causes disease.  So what we were looking at was how other proteins are actually affected in this disease. And one of the main reasons was genetics of Parkinson's disease and dementia with Lewy bodies has indicated that disruptions in protein clearance pathways play a major role in disease. So there's a lot of associations of variants and components that encode for enzymes that degrade proteins or enzymes that degrade lipids that they're associated with disease. So what we did was we asked the question if these pathways are disrupted in idiopathic Parkinson's disease and they are responsible for actually degrading many proteins, alpha synuclein isn't the only protein that is going through this pathway. Many proteins are. So we hypothesized that other proteins would be aggregating beyond alpha synuclein. And the reason for that was because we know that the proteome has a lot of proteins that are sort of considered, I would say, meta stable or they're flexible. They're made to go in and out of different conformations. That makes them susceptible to forming these aggregates under the wrong conditions. For example, if there's too much of the protein, it somehow builds up in the cell. It can trigger the formation of a pathological inclusion in an insoluble aggregate. So knowing this basic information, what we did was we used patient derived induced pluripotent stem cell models, directly derived from patients that have Parkinson's disease and dementia with Lewy bodies. We differentiated those cells into dopamine neurons, allowed them to age and mature in vitro. And then we asked the question, what proteins are turning insoluble? We did a proteomic study, an unbiased screen to see, quantify proteins that were going up and down and which ones were turning into these insoluble inclusions. And to the proteins that came up as the biggest hits that were accumulating were actually very surprising to us. They were accumulating in the nucleus of these cells, and they're called NONO and SFPQ. They're RNA binding proteins. And as I said, these are actually metastable proteins. They're prion- like in the sense that they can go in and out of aggregated states They're actually made to do that under physiological conditions. But as I said, that's one of the features that makes proteins like this susceptible to aggregation. Those were two the biggest hits that we found. And that's sort of how we got into the question in the first place was to look at specificity and ask the question, is synuclein really the only protein that is turning insoluble here? And, and the answer is no. We think there's other proteins involved and NONO and SFPQ are our top hits. 

[00:07:48] Erin Spain, MS: I mean, this is a major finding. It has the potential to change our understanding of Parkinson's in a very fundamental way. Tell me about the broader implications of this finding in the field of Parkinson's research. 

[00:08:00] Joseph Mazzulli, PhD: So we're excited about this because it sort of opens up a new pathway. People don't really study nuclear dysfunction in Parkinson's disease. There are certainly labs out there that do it, but it's not one of the major fields of study. So that we found this new pathology, I think is exciting in the sense that it could indicate how gene dysregulation may occur in Parkinson's disease. Now downstream of when these aggregates form, another exciting finding was that we found that it affects the RNA editing pathway. This is a process where adenosines and RNA are converted to inosines by an enzymatic reaction. And this could have many effects on transcription and translation. It could change the function of a protein if it's within a coding region or an axon. It can also affect the translation of the protein how well is it made in the cytoplasm, if it's in non-coding regions that regulate nuclear retention and export. It could affect RNA splicing as well if it alters a splicing site. Where an RNA spliceosome can no longer bind to it. Maybe it changes the affinity of that binding. It can turn into alternative splicing isoforms. So, RNA editing from a physiological standpoint is we think in place to sort of diversify the genome even more. It's a way of regulating protein levels in a more sensitive way. And also has the potential to alter protein function. So what we found was that this process of editing was actually happening too much. When we did an RNA sequencing study, we just did an unbiased screen to look at all the RNAs that are edited and what their levels were in patient neurons. We found that a lot of these edit sites were increased. And in turn, we're still studying this, but one of the things that we found was that these edited transcripts are actually sticking in the nucleus inappropriately. They're supposed to get out into the cytoplasm to be translated in the protein, but these were transcripts that encode essential cellular proteins, things that encode mitochondrial components. They encode axon and synaptic components. These are proteins, survival proteins that you need for the neuron to undergo normal maintenance and things like that. And so they were sticking in the nucleus not being translated, and that's what we think was causing the neurodegeneration as a consequence of these aggregates. So this is actually a lot different in terms of a pathology. It's a lot different from Lewy bodies because Lewy bodies, we've known they existed for over a hundred years. We still don't really know what they're doing. We don't know if they're causing toxicity. That's what most people think, but it's possible that they could be protective. Now, in this case, for NONO and SFPQ and nuclear aggregates, we have a better, more clear understanding of the pathological mechanisms. We think that as I described, that they're sequestering inappropriately sequestering these survival mRNAs and reducing their protein expression. 

[00:10:57] Erin Spain, MS: I know you said you're still studying this in your lab, and this was the first paper that you published on this, but what do you envision potentially for new therapeutic targets focused on this new RNA editing pathway? 

[00:11:09] Joseph Mazzulli, PhD: Because editing is overall increased, we're looking at ways of reducing that. And there are some enzymatic targets that we can use to try to either reduce them by knocking them down in cells and measuring the effect on patient derived cultures in vitro. See if they survive better. And there's also some small molecules out there that can inhibit the pathway. They're not very good small molecules. They're non-specific and toxic at some level. So we're looking at ways of developing better ones that inhibit this pathway. The idea would be to, if we reduce RNA editing, that we could have a chance at breaking up and dissolving those nuclear aggregates. This should restore normal protein translation of those essential axon and synaptic and mitochondrial proteins. And that should in turn, help neurons survive and reverse the whole thing. The other thing is that, you know, these are phenotypes that we discovered that happen very early in the stages of pathology. So we have that advantage using the IPSC model because we can look at different timeframes. We have the pathological cascade pretty well characterized. We've been working on this model for 10 to 15 years. We know when synuclein aggregates occur, we know when lysosomes start to become dysfunctional, and we know what time the neurites start to degenerate. So we could look at different phenotypes before and after those events. 

[00:12:38] Erin Spain, MS: I mean, if you could explain that a little more to me, what is that timeline like?  

[00:12:41] Joseph Mazzulli, PhD: You know, the model is set up so that when we initially differentiate IPSCs with different factors that push them towards dopaminergic phenotypes, that happens within about the first 30 days. They're already starting to turn into neurons, but they're more, I would say, immature neurons. Over the next months, so this is two months total, we start to see signs of maturity. We cannot say that they're adult or that they're aged neurons, but there are certain biochemical phenotypes that we can look at to say this is a mature neuron. One of the things that we look at is the synaptic localization of synuclein. We know that in young, very young neurons, synuclein sort of everywhere. But then it, as they mature, it becomes concentrated in synapses. So that's one of the things that we look at, and that happens by about day 60 in this model. After that we start to see problems and the models that we use are familial forms of Parkinson's, so it's a little easier to identify phenotypes as compared to sporadic forms or sporadic models that we have. In the sporadic cases, we're not sure what is going on? What mutated proteins that are there? So it's a little easier to use these familial forms. And so day 60 to day 90 is when the aggregation occurs and cellular dysfunction starts happening, and then it takes about another month after that for neurites to start to degenerate. So at that point, we're at about day 120, and that's about the length of an experiment for us. 

[00:14:14] Erin Spain, MS: Tell me about the importance of having access to these patient samples. 

[00:14:18] Joseph Mazzulli, PhD: It's really important to be able to have access to these rare, familial forms of the cells from these patients that harbor mutations in the synuclein gene. We get them oftentimes from cellular repositories. What we do is we reprogram them in the lab into induced pluripotent stem cells using pretty standardized techniques at this point. So it's valuable because these are patient cells that because they have the naturally occurring disease causing mutations, we don't actually have to do anything to the cells to model the disease. Now, before this, what we would have to do in the case of synucleinopathies, people were over-expressing in an artificial way, and we still do this because it's feasible and it's easy to do. But there's limitations because we're artificially over-expressing the protein sometimes 100 fold times what it would normally be to try to induce a phenotype in a time scale we can study, something that doesn't take 40 years. So that was the older way. Now what we're doing is we're taking advantage of these naturally occurring mutations that will more naturally accumulate the protein. So we think that's a better model because it's more accurately recapitulating what happens in the patient brain. 

[00:15:36] Erin Spain, MS: I'm going to shift gears to talk about the second study published in Nature Communications. So in this one, you were trying to better understand the mechanisms that link this protein misfolding and neurons glucose metabolism. These two things happen concurrently, but how they're linked has remained largely unexplored. So explain why this was the leading question behind this particular study. 

[00:15:58] Joseph Mazzulli, PhD: This was something that we started probably about 10 years ago, and it was really focused on this question of how protein misfolding and maturation is perturbed in Parkinson's disease. So a few studies published in the 2000s indicated that synuclein, when it accumulates, it impedes the movement of proteins between the endoplasmic reticulum and the Golgi. And we've looked at a few protein targets that were linked to cellular clearance pathways, glucocerebrosidase is one of them. And found that alpha synuclein impedes the trafficking of this protein glucocerebrosides. So the idea was based off of that, how does alpha synuclein inhibit the maturation of the protein? We looked at the very initial stages of how these proteins, like glucocerebrosidase are synthesized and trafficked into lysosomes. That happens in the endoplasmic reticulum. Once the mRNA is made, it gets translated in the endoplasmic reticulum and what a lot of proteins require are glycans that help them fold. And so this is something that comes from glucose. Glucose, most of it goes through glycolysis and it is required for energy production in cells. A small part of it actually goes into the endoplasmic reticulum in the form of N-glycosylation. And what this is, is a glucose attachment to proteins. And there's chaperones in the endoplasmic reticulum that interact with these glycans and help them to fold. So because we knew that folding was perturbed in Parkinson's, we wanted to look at this pathway and how glucose was involved. And so what we found was that N-glycosylation was decreased in Parkinson's disease and a pathway called the hexosamine pathway that is responsible for generating the essential precursors for these glycans was perturbed. So that was sort of how we got into it. It was like I said, over 10 years ago when we started it, and it was based off of the trafficking disruption that we found. The exciting part of this study is that we found a way to replace the glycans in the endoplasmic reticulum so that we could partially restore the folding of some of these proteins. We were mainly looking at lysosomal proteins like glucocerebrosidase, because it's a really important target for Parkinson's disease. It's the strongest genetic risk factor for Parkinson's as well as dementia with Lewy bodies. So we think if we could enhance the activity of this enzyme, that that would be very important for as a treatment strategy. So these N-glycans were able to actually do that. They improved the folding of glucocerebrosides in the endoplasmic reticulum and actually allowed it to traffic into lysosomes and degrade substrates much better. 

[00:18:44] Erin Spain, MS: This was a pharmaceutical approach that you use then to restore the proper protein folding? 

[00:18:49] Joseph Mazzulli, PhD: That's a good point. Yeah, we used both. We used pharmacology and we also used a genetic approach where there's a rate limiting enzyme. It's called GFPT-2. It's the most important enzyme that mediates the hexosamine pathway. So when we put that protein, overexpress that in the cell, we were able to boost glycans and improve folding. The other way we did it was by using N-Acetylglucosamine which was something that was shown by other labs to boost the hexosamine pathway. So it sort of intervenes in a middle stage of the metabolic pathway. And so when we added that to cultures, we found that pretty much the same thing as with GFPT-2 over expression is that lysosomal function was restored. What we're trying to do now is see if that is working in vivo by using in vivo mouse models to see if it happens in the brain. 

[00:19:39] Erin Spain, MS: So there is work being done right now to really hopefully translate these recently discovered mechanisms into potential therapies. I understand you even have patents that are attached to and associated with the two studies we just discussed. Can you tell me a little bit about that? 

[00:19:53] Joseph Mazzulli, PhD: What we're trying to do is develop new ways of enhancing protein folding and lysosomal function. And we think this could be applicable to Parkinson's disease, dementia with Lewy bodies, but also a lot of other diseases that are characterized by protein accumulation. Alzheimer's disease is one of them where we have a beta and tau accumulating. So there's potential there that this could be the strategy could be widely used because it's targeting an essential part of the cell that's responsible for degrading a lot of proteins and damaged organelles. So what we're trying to do is, and what the patents are related to, are new small molecules that we found using in silico screening. Found small molecules that can modulate the lysosomal pathway. We're currently testing some of these in patient derived cultures and other cell models. We're starting to move into in vivo models. We don't do a lot of mouse work. A lot of our initial discovery is done in human cells. But what we go to mouse models just for asking the question, does a small molecule get into the brain? A lot of times if you orally administer a small molecule, it will not get into the brain at sufficient amounts to engage its target. So that's why we use mouse models to treat the mice in a way that a patient would get it. It's usually that's through drinking water or through the food. Some oral method. Measure its levels in the brain. And then we have a lot of activity assays that we do usually in brain lysates or in fixed tissue where we can actually detect, has that small molecule engaged its target and has it sufficiently boosted enzymatic activity at levels that we think may be therapeutic for patients. If we find something like that, then we would go on and do toxicology studies to see how it's metabolized and how long can we treat this? How high of a dose can we go? And basic questions like that before we go into trying to start a clinical trial in humans. 

[00:21:58] Erin Spain, MS: Something that's really interesting about this work is that other preclinical or clinical trials for Parkinson's are currently only targeting one pathway, but these studies show potential for multi pathway approaches. Tell me how this could potentially accelerate treatments for the disease. 

[00:22:15] Joseph Mazzulli, PhD: What we know about what synuclein is doing to the cell, it's actually attacking multiple branches of the protein homeostasis pathway. It's attacking a lot of different organelles. There's many things that are happening. So we think that if you were to target simultaneously two or three pathways, that would provide more effective therapeutic treatment as opposed to just treating one. So one of the things that we're looking into is activating lysosomal enzymes and at the same time also trying to stimulate protein folding in the endoplasmic reticulum. So that could be through n- acetylglucosamine, which is the compound I mentioned before that enhances the hexosamine pathway. We're looking at a small molecule that can enhance the movement of proteins between the endoplasmic reticulum and the Golgi. So that will improve one major problem that we think is happening in Parkinson's. A simultaneous induction of both of those pathways at the same time, we think, would be stimulating lysosomes more effectively and able to reduce protein aggregates even better than just one compound alone. Another advantage of using combination therapies, sometimes, you know, you have to use, if you're just treating with one small molecule, you may have to use a very high dose and it could be hitting off targets. it could be causing nonspecific cellular toxicity. So when you add in another compound, you have the potential that you can actually increase the potency of it and reduce the dose. And so that would be very important for limiting toxicity of some of these drugs that have side effects. 

[00:23:52] Erin Spain, MS: The Parkinson's disease community, which includes patients and advocates. I know that you have some funding from the Michael J. Fox Foundation, for example. There's a lot of interested parties out there who are excited about your research. What has the response been from both the patient and advocate side and then as well as your colleagues and peers? 

[00:24:12] Joseph Mazzulli, PhD: I think it's been overall positive and the exciting part of it has been around some of the basic pathological mechanisms, identifying this new pathway related to RNA editing. It really opens up a lot of possibilities for treatments and new targets. It is consistent with some more recent papers that have been published that have shown that synuclein affects RNA metabolism. And so these papers are just starting to come out now. I think that there's excitement around that pathway. The other thing is that there is a potential for stimulating lysosomes in the brain and we're getting closer than we ever have before, and finding small molecules that are brain penetrant that can boost the activity of lysosomes in the brain that could eventually degrade these toxic protein aggregates. And so I think the translational part of that is particularly exciting and we're hoping in the next five to 10 years to have something that we could take to the clinic. These processes are very long and they take a while, but we're getting closer and closer every day. 

[00:25:15] Erin Spain, MS: Looking to the future, what do you think are the biggest challenges facing Parkinson's research today? And do you think these findings you were talking about and that other papers are now releasing, do you think they sort of chip away at any of those challenges? 

[00:25:29] Joseph Mazzulli, PhD: They start to, I mean, one of the biggest things for Parkinson's field is being able to predict the disease before you see a movement disorder. There are a few ways of doing that, but there's nothing that's a hundred percent accurate. What we would like is a biomarker that we can get from accessible fluids like blood or cerebrospinal fluid that we can measure and say with some certainty, you will probably get Parkinson's disease in 10 years. We know it's a slowly moving disease. It takes a long time to start to see this degeneration of dopamine neurons that's translating to a movement problem. By the time the movement disorder is apparent in patients and what brings them to the clinic in the first place, most of their dopamine neurons are already gone. We think that by that point it may be too late because inflammation has already kicked into gear, and those are things that are hard to reverse. Some of the things that we found, like the, in the RNA editing pathway may be future biomarkers. That's something that we're starting to look into, but it's possible that measuring the level of edited RNA, for example, may indicate at what stage in disease they are. I think the other major challenge is we've got sufficient biological targets. I think it's hard to find small molecules that are potent enough to stimulate lysosomes in the brain. And that goes back to the combination therapies that we were talking about as a way of enhancing the potency of some of those drugs. If you had those two things taken care of, accurate biomarkers, accurate ways of predicting disease, and a small molecule that was very effective at enhancing protein clearance in the brain, I think those would be two very important challenges for the future. 

[00:27:09] Erin Spain, MS: Well, thank you so much for explaining this research and what you're working on now towards the future. This is very exciting and this basic science is critical to understanding these diseases. So thank you so much for all the work that you've done here, and thank you for being on the show. 

[00:27:26] Joseph Mazzulli, PhD: Thanks for having me. 

[00:27:27] Erin Spain, MS: Thanks for listening, and be sure to subscribe to this show on Apple Podcasts or wherever you listen to podcasts. And rate and review us also for medical professionals. This episode of Breakthroughs is available for CME Credit. Go to our website, feinberg northwestern edu, and search CME.