Parkinson’s disease is usually described through what it destroys: dopamine neurons in the substantia nigra, and with them the fine control of movement. But genetics keeps pointing somewhere less obvious. Alongside the familiar risk genes sits a gene almost nobody outside the field can pronounce, encoding a channel in the membrane of the lysosome – the cell’s recycling compartment. That gene is TMEM175, and the reason it keeps appearing in Parkinson’s studies is that the disease may begin as a failure of cellular housekeeping long before it looks like a movement disorder. In Canada, where the Public Health Agency tracks parkinsonism as a growing chronic disease burden, that distinction has practical stakes.
A channel that does not look like other channels
TMEM175 is the main potassium-conducting channel in the lysosomal membrane, and it is a genuine oddity. It shares almost no sequence similarity with the large, well-characterised families of potassium channels found at the cell surface, which means decades of accumulated pharmacology do not transfer to it. Researchers had to characterise it largely from scratch.
It is also unusual in what it carries. Depending on conditions, TMEM175 conducts either potassium or protons, and it does so as a channel rather than as an antiporter or exchanger. That dual behaviour matters because the lysosome is an acid compartment: it holds an internal pH near 4.5 to 5.0, and its digestive enzymes only work inside that narrow window. A channel that can move protons is not a bystander to lysosomal pH. It is part of the machinery that sets it.
What the genetics actually says
Large genome-wide association studies have repeatedly linked the TMEM175 locus to Parkinson’s risk. The more informative finding is that the direction of the effect tracks the direction of the channel’s activity. Variants that reduce channel function are associated with increased risk of Parkinson’s disease. Variants that increase channel function are associated with reduced risk. That is an unusually clean dose-response relationship for a complex disease, and it is the main reason TMEM175 is treated as a plausible drug target rather than a statistical curiosity.
| Direction of change | Effect on the lysosome | Association with Parkinson’s risk | Confidence |
|---|---|---|---|
| Loss of function | Impaired pH stability, reduced capacity to clear protein aggregates | Increased risk | Well replicated in human genetic studies |
| Gain of function | More stable lysosomal ion handling | Reduced risk – apparently protective | Well replicated |
| Complete knockout in cell and animal models | Lysosomes acidify abnormally, autophagy is impaired, alpha-synuclein accumulates | Not directly measurable in humans | Consistent across models |
| Acute pharmacological inhibition | Reported to increase lysosomal macromolecule catabolism | Unknown in humans | Preclinical only, and in apparent tension with the genetics |
The first selective compounds
For years the field had no way to interrogate TMEM175 directly, because there were no selective tools. That changed with the reported discovery of the first TMEM175-selective inhibitors, 2-phenylpyridin-4-ylamine, abbreviated 2-PPA, and a compound designated AP-6, published in the Journal of the American Chemical Society. Acute inhibition with either compound was reported to increase the rate at which lysosomes break down macromolecules, accelerating macropinocytosis and other digestive processes.
That result deserves to be read carefully rather than triumphantly. If loss-of-function variants raise Parkinson’s risk, the intuitive therapeutic move is to activate the channel, not block it. Yet acute blockade in cells appears to enhance degradative capacity. The two observations are not necessarily contradictory – a lifetime of reduced channel function is a different perturbation from a few hours of pharmacological block, and the lysosome compensates on different timescales – but the discrepancy is unresolved, and it means nobody can yet say with confidence whether a future TMEM175 drug should open the channel or close it.
Work published in 2025 added mechanistic detail on how the channel is gated by pH, identifying the histidine residue H57 as directly involved in gating and showing that it increases the channel’s proton conductance while leaving potassium conductance unaffected. That kind of residue-level resolution is what medicinal chemistry needs before it can design a molecule that pushes the channel in one specific direction.
Why this matters in Canada specifically
More than 100,000 Canadians currently live with Parkinson’s disease, with roughly 6,600 new diagnoses each year – more than 25 people every day. Modelling published in the BMJ projects Canadian cases rising about 69 per cent to roughly 259,000 by 2050, driven overwhelmingly by population ageing rather than by any change in underlying incidence.
That trajectory reframes what counts as a useful therapy. Existing treatment is symptomatic: levodopa and its successors replace dopamine but do not slow the underlying loss of neurons. A drug that acted on lysosomal function would be aiming at the disease process rather than its output. Even a modest delay in onset applied across a cohort that size changes the arithmetic of Canadian long-term care substantially.
Canada is not a bystander in this work. The Pacific Parkinson’s Research Centre at the University of British Columbia runs one of the largest peer-reviewed Parkinson’s research programmes in the country, and UBC’s Djavad Mowafaghian Centre for Brain Health has been among the groups publicising the 2050 projections. Canadian imaging and cohort work is a recognised part of the international evidence base on disease progression.
The honest state of play
There is no TMEM175 drug in clinical trials. There is a well-replicated genetic association with a clear directional logic, a structural and biophysical picture that is improving quickly, and a first generation of selective chemical tools whose effects do not yet line up neatly with the genetics. That is roughly where a target sits several years before anyone knows whether it will work in people, and it is worth saying plainly because lysosomal biology in Parkinson’s has been oversold before.
What makes TMEM175 worth watching is not that it is close to the clinic. It is that it is one of the few Parkinson’s targets where human genetics tells you not just that a protein matters but which way to push it – and the field now has molecules precise enough to test that.
Frequently asked questions
What is TMEM175?
TMEM175 is the principal potassium channel in the lysosomal membrane. Depending on conditions it conducts potassium or protons, and it helps maintain the acidic internal pH that lysosomal digestive enzymes require. It shares little sequence similarity with other potassium channel families.
How is TMEM175 linked to Parkinson’s disease?
Genome-wide studies associate the TMEM175 locus with Parkinson’s risk. Variants that reduce channel function increase risk; variants that increase function appear protective. In cell and animal models, losing the channel impairs autophagy and promotes accumulation of alpha-synuclein.
Are there drugs that target TMEM175?
Not in clinical use. The first selective inhibitors, 2-PPA and AP-6, were reported in the Journal of the American Chemical Society and are research tools. No TMEM175-targeting compound has entered clinical trials, and it is not yet settled whether a therapy should inhibit or activate the channel.
How many Canadians have Parkinson’s disease?
More than 100,000, with about 6,600 new diagnoses each year. Published projections put the figure near 259,000 by 2050, an increase of roughly 69 per cent driven mainly by population ageing.
What are lysosomal ion channels and why do they matter in disease?
Lysosomal ion channels control the flow of ions across the lysosomal membrane, setting the compartment’s internal pH and ionic balance. Because lysosomes clear damaged proteins and organelles, channel dysfunction is increasingly implicated in neurodegenerative conditions where protein aggregates accumulate, including Parkinson’s disease.
