A new study is bringing molecular precision to one of Parkinson’s disease’s most important biological puzzles: why changes in the GBA gene can sharply increase the risk of developing the disorder, and how those changes intersect with the protein abnormalities found in both inherited and apparently sporadic disease. Published in npj Parkinson’s Disease, the work by Morella, Teneketzi, Ferraro and colleagues examines post-mortem human brain tissue to build a quantitative biochemical picture of two closely connected features of Parkinson’s biology—glucocerebrosidase activity and the molecular forms of α-synuclein.
The study focuses on glucocerebrosidase, commonly abbreviated as GCase, an enzyme encoded by the GBA gene. GCase is located primarily inside lysosomes, the cell’s recycling compartments, where it helps break down specific fatty molecules known as glucosylceramides. Variants in GBA can reduce the enzyme’s efficiency and are among the most common genetic risk factors for Parkinson’s disease. Some variants cause Gaucher disease, a lysosomal storage disorder, while others produce subtler biochemical changes that increase Parkinson’s susceptibility without necessarily causing Gaucher disease.
Parkinson’s disease is also characterized by the accumulation of α-synuclein, a neuronal protein that can assemble into abnormal structures and contribute to Lewy bodies and Lewy neurites. However, α-synuclein is not a single, chemically uniform molecule. It exists in multiple “proteoforms,” meaning molecular variants created by differences in processing, chemical modification, truncation, aggregation state or interactions with other cellular components. These forms may behave differently in neurons, and distinguishing them could help explain why some types of α-synuclein are more toxic or more strongly associated with disease progression.
Morella and colleagues investigated these mechanisms in human brains collected after death from people with Parkinson’s disease linked to GBA alterations, people with idiopathic Parkinson’s disease, and comparison groups. The use of post-mortem tissue is crucial because it allows researchers to examine the molecular environment in the affected organ itself rather than relying only on blood, cerebrospinal fluid, cultured cells or experimental animals. At the same time, brain tissue collected after death presents analytical challenges, including differences in disease duration, medication history, tissue preservation, brain region and the extent of neuronal loss.
The central feature of the research is quantitative biochemical profiling. Rather than simply determining whether GCase or α-synuclein is present, this approach aims to measure how much enzymatic activity remains and which molecular forms of α-synuclein are present. Measuring GCase activity is particularly important because enzyme abundance alone does not necessarily indicate function. A neuron may contain detectable GCase protein while the enzyme is improperly folded, trapped in the wrong cellular compartment, chemically modified or otherwise less active.
The investigators’ examination of α-synuclein proteoforms adds another layer to the analysis. Standard laboratory tests can detect total α-synuclein, but total protein measurements may conceal biologically meaningful differences. For example, soluble α-synuclein, phosphorylated species, truncated fragments and aggregated forms may have distinct effects on synaptic function, cellular transport and lysosomal degradation. A detailed profile can therefore reveal whether GCase impairment is associated with a particular molecular signature rather than with a simple increase in the overall amount of α-synuclein.
The connection between GCase and α-synuclein is thought to operate in both directions. Reduced lysosomal GCase activity may interfere with the clearance of α-synuclein, allowing damaging species to accumulate. Conversely, α-synuclein aggregates may disrupt lysosomal trafficking or prevent GCase from reaching the compartment where it normally functions. This creates a potentially self-reinforcing cycle in which impaired cellular recycling promotes protein accumulation, while protein pathology further weakens the recycling system.
Comparing GBA-related Parkinson’s disease with idiopathic Parkinson’s disease is especially valuable because it can separate mechanisms that are specific to genetic risk from those shared across the broader Parkinson’s spectrum. If the two groups show similar biochemical patterns, that would support the idea that lysosomal dysfunction is a common pathway in Parkinson’s disease, even when no GBA mutation is identified. If they show distinct patterns, those differences could help explain variations in age of onset, clinical progression or treatment response and could guide the development of more targeted therapies.
The findings also have potential implications for drug development. Several experimental strategies are designed to increase GCase activity, improve its delivery to lysosomes, stabilize the enzyme or correct its trafficking. Other approaches aim to reduce harmful α-synuclein species or enhance their clearance. Quantitative measurements from human brain tissue can help determine whether these treatments are affecting the intended molecular targets. They may also help researchers identify biomarkers that reflect treatment response in living patients, although translating post-mortem biochemical signatures into clinical tests will require further validation.
By placing enzyme function and α-synuclein diversity in the same analytical framework, the study underscores a broader shift in Parkinson’s research. The disease is increasingly understood not as a single disorder with one uniform molecular cause, but as a collection of overlapping biological pathways that can converge on neuronal degeneration. Human-brain profiling cannot by itself establish causation, and post-mortem studies cannot fully capture the sequence of events that occurred during life. Yet by mapping the biochemical terrain with greater precision, this work may help reveal which molecular changes are drivers, which are consequences and which could serve as practical targets for the next generation of Parkinson’s therapies.
Subject of Research: Quantitative biochemical profiling of GCase activity and α-synuclein proteoforms in post-mortem human brains from GBA-related and idiopathic Parkinson’s disease.
Article Title: Quantitative biochemical profiling of GCase activity and α-synuclein proteoforms in post-mortem human brains from GBA-related and idiopathic Parkinson’s disease.
Article References: Morella, M.L., Teneketzi, M., Ferraro, F. et al. “Quantitative biochemical profiling of GCase activity and α-synuclein proteoforms in post-mortem human brains from GBA-related and idiopathic Parkinson’s disease.” npj Parkinson’s Disease (2026). https://doi.org/10.1038/s41531-026-01488-4
Image Credits: AI Generated
DOI: 10.1038/s41531-026-01488-4
Keywords: Parkinson’s disease, GBA, glucocerebrosidase, GCase, α-synuclein, proteoforms, lysosomes, neurodegeneration, post-mortem human brain, biochemical profiling
