Journal of Molecular Pathology and Biochemistry
Open Access

Protein Misfolding and Aggregation in Neurodegenerative Diseases

Laura Müller^{* *}Correspondence: Laura Müller, Department of Molecular Biology, University of Munich, Munich, Germany, Email:

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Above the Study

Protein misfolding and aggregation lie at the heart of many neurodegenerative diseases, and in my view, they represent one of the most compelling yet still incompletely understood mechanisms of progressive neuronal dysfunction. Disorders such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and amyotrophic lateral sclerosis all share a common pathological feature: the accumulation of misfolded proteins that disrupt cellular homeostasis. While each disease is characterized by distinct protein species, the underlying principle of proteotoxic stress is remarkably conserved.

At a fundamental level, proteins must adopt precise three-dimensional structures to function correctly. Cellular quality control systems, including molecular chaperones, the ubiquitin–proteasome system, and autophagy-lysosomal pathways, ensure that misfolded proteins are either refolded or degraded. However, in neurodegenerative conditions, these systems become overwhelmed or impaired. As a result, misfolded proteins escape normal surveillance and begin to aggregate, forming oligomers, fibrils, and ultimately insoluble inclusions. In my opinion, the most toxic species are not necessarily the large aggregates themselves, but the smaller soluble oligomers that interfere with synaptic function and cellular signaling.

A critical aspect of protein aggregation is its prion-like behavior. Misfolded proteins can act as templates, inducing conformational changes in normally folded proteins and propagating pathological states from cell to cell. This concept has significantly reshaped how we think about neurodegeneration, shifting the focus from isolated cellular events to spreading molecular pathology across neural networks. For example, tau pathology in Alzheimer’s disease appears to spread in a predictable anatomical pattern, suggesting a self-propagating mechanism of misfolded protein transmission.

Another important consideration is the role of cellular stress in promoting protein misfolding. Oxidative stress, mitochondrial dysfunction, and impaired calcium homeostasis all contribute to an environment that favors protein instability. Neurons are particularly vulnerable due to their high metabolic demands and long lifespan. Unlike other cell types, neurons must maintain proteostasis over decades, making them especially susceptible to cumulative damage. In my view, this long-term vulnerability is a key reason why neurodegenerative diseases are primarily age-associated.

Genetic mutations further exacerbate protein misfolding. In familial forms of neurodegenerative disease, mutations in genes encoding proteins such as Amyloid Precursor Protein (APP), presenilin, alpha-synuclein, or superoxide dismutase can directly alter protein structure, stability, or processing. However, even in sporadic cases, subtle genetic variations may influence protein folding efficiency or clearance capacity. This suggests that protein aggregation is not solely a consequence of rare mutations but also of broader genetic susceptibility combined with environmental stressors.

The cellular response to misfolded proteins is another area of intense interest. The Unfolded Protein Response (UPR) in the endoplasmic reticulum and the heat shock response are activated to restore proteostasis. While these pathways are initially protective, chronic activation can become maladaptive, leading to inflammation and cell death. I believe this dual nature of stress responses protective in the short term but damaging when persistent is central to disease progression.

From a therapeutic perspective, targeting protein aggregation has proven challenging. Strategies aimed at reducing aggregate formation, enhancing clearance, or stabilizing native protein conformations have shown limited success in clinical settings so far. One limitation is that aggregation is often a downstream event, meaning that by the time it is detectable, significant neuronal damage has already occurred. This raises the important question of whether interventions should focus earlier in the disease cascade, perhaps at the level of protein synthesis, folding efficiency, or cellular stress regulation.

Another promising direction involves immunotherapy, where antibodies are used to target misfolded protein species for clearance. While this approach has shown some benefit in clinical trials, its efficacy varies and is often modest. This variability suggests that protein aggregation is only one part of a much broader pathological network involving inflammation, synaptic dysfunction, and metabolic failure.

In conclusion, protein misfolding and aggregation are central to the pathogenesis of neurodegenerative diseases, but they should not be viewed in isolation. Instead, they represent one component of a complex, interconnected system of cellular dysfunction. In my opinion, future progress in this field will depend on integrating protein biology with systems neuroscience, aging research, and cellular stress pathways to develop more comprehensive and effective therapeutic strategies.