Trying to LIMP-2 the lysosome

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Lysosomes are small bags of enzymes that are used to break down material inside of cells – digesting newly absorbed food or recycling old/used proteins and rubbish. Recently researchers have been discovering increasing evidence that points towards dysfunction in lysosomes as a key influential player in neurodegenerative conditions, like Parkinson’s.

There are several Parkinson’s genetic risk factors associated with lysosomal function (GBA being the obvious one), that can increase one’s risk of developing Parkinson’s.

But there is also data indicating that individuals without any of these risk factors may also have reduced lysosomal activity. And recently researchers have identified one possible explanation.

In today’s post, we will explore what lysosomes are, investigate how they maybe involved with Parkinson’s, review what the new data reports, and discuss how this information might be useful.

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Type of endocytosis. Source: Slidemodel

On a continual basis, cells inside your body are absorbing material from the world around them with the aim of collecting all that they need to survive. They do this predominantly via a process called endocytosis, in which a small part of the cell membrane envelopes around an object (or objects) and it is brought inside the cell.

As the section of cell membrane enters the interior of the cell, it detaches from the membranes and forms what is called an endosomes (sometimes it is also called a vacuole). Once inside, the endosome transported deeper into the interior of the cells where it will bind to another small bag that is full of digestive enzymes that help to break down the contents of the endosome.

This second bag is called a lysosome.


How lysosomes work. Source: Prezi

Once bound, the lysosome and the endosome/vacuole will fuse together and the enzymes from the lysosome will be unleashed on the material contained in the vacuole. The digestion that follows will break down the material into more manageable components that the cell needs to function and survive.

This enzymatic process works in a very similar fashion to the commercial products that you use for washing your clothes.

Enzymatic degradation. Source: Samvirke

The reagents that you put into the washing machine with your clothes contain a multitude of enzymes, each of which help to break down the dirty, bacteria, flakes of skin, etc that cling to your clothes. Each enzyme breaks down a particular protein, fat or such like. And this situation is very similar to the collection of enzymes in the lysosome. Each enzyme has a particular task and all of them are needed to break down the contents of the endosome.

Interesting, but what does this have to do with Parkinson’s?

Continue reading “Trying to LIMP-2 the lysosome”

The Ambroxol Results


The new year has started with some pleasing clinical trial news for the Parkinson’s community: The results of the “Ambroxol in Disease Modification in Parkinson Disease” (AiM-PD study) have been published.

This is a clinically available drug that is used for the treatment of respiratory issues, which researchers are re-purposing for Parkinson’s based on some interesting properties the drug has.

The results of the clinical trial suggest that ambroxol was safe and well tolerated in people with Parkinson’s for the length of the 6 month study. It accessed the brain and increased levels of target proteins while there.

In today’s post, we will discuss what ambroxol is, what research has been conducted on it, and what the results of this study suggest.


The author of this blog is the deputy director of research at The Cure Parkinson’s Trust, and as such he feels that it is necessary to start this post with a very clear declaration –  FULL DISCLOSURE: The Cure Parkinson’s Trust (in partnership with the Van Andel Institute) was a funder of the ambroxol clinical trial which is going to be discussed in this post.

Right. That said, let’s try and do a completely unbiased review of the ambroxol trial results 🙂

In one particular SoPD post last year we discussed the Linked Clinical Trials initiative, which is an international program that was set up 8 years ago with the goal of rapidly repurposing clinically available drugs exhibiting disease modifying potential in models of Parkinson’s (Click here to read the previous SoPD post on this topic).

What is meant by repurposing?

Drug repurposing (repositioning, reprofiling or re-tasking) is a strategy of identifying novel uses for clinically approved drugs that fall outside the scope of the original medical indication.

An example of this is “Viagra”.

It was originally developed as an anti-hypertensive medication, but was hugely more successful in the treatment of erectile dysfunction.

The strategy has been adopted and applied by many organisations because it allows for the by-passing of large parts of the drug discovery process, saving time and resources in getting new treatments to the clinic.

Source: Austinpublishinggroup

By repurposing a clinically approved drug – for which we may know a great deal about already in terms of safety, tolerability and dose range – we can skip large parts of the clinical trial process and jump straight to testing the drug in our population of interest (in this case people with Parkinson’s).

And this is what the Linked Clinical Trials (or LCT) program was set up to do in Parkinson’s.

The first drug that was prioritised by the LCT committee for repurposing was a diabetes drug called exenatide (also known as Bydureon).

It is fair to say this LCT-initiated clinical trial program has provided interesting results thus far (Click here and here to read a SoPD post on this) and the exenatide program is now entering Phase III testing in Parkinson’s (Click here to read more about the Phase III trial).

In late 2014, the LCT committee prioritised another clinically available drug for repurposing to Parkinson’s.

That drug is called ambroxol.

What is ambroxol?

Continue reading “The Ambroxol Results”