Certain viral molecules would facilitate the propagation of protein aggregates, characteristic of neurodegenerative diseases, such as Alzheimer’s disease.
- Chronic or acute viral infections could facilitate neurodegeneration.
- Extracellular vesicles are secreted specifically for communication between cells.
- Viral infections increase the spread of protein aggregates between cells, both by direct cell contact or via these extracellular vesicles.
Proteins are involved in neurodegenerative diseases. In the case of Alzheimer’s disease, the Tau protein and A-beta accumulate abnormally in the brain. This forms plaques, called amyloid. If the process is known, its causes are still uncertain. In Nature Communicationsresearchers bring new knowledge on this subject: they note that viral infections accelerate the phenomenon.
Previously studied links
This is not the first time that the links between viruses and the brain have been studied. “The brains of patients with neurodegenerative diseases sometimes contain certain virusesexplains Ina Vorberg, author of the study. They are suspected of causing inflammation or having a toxic effect, thereby accelerating neurodegeneration.e.” In this research, scientists were interested in the effects of viruses on the proteins responsible for these pathologies. Protein aggregates, which are present in prion diseases such as Creutzfeldt-Jakob disease, have the ability to move from one cell to another, where they transfer their abnormal shape to proteins of the same type.Thus, the disease spreads through the brain.The same processes are involved in Alzheimer’s disease and Parkinson’s disease. “The precise mechanisms of transmission are unknown“, clarifies Ina Vorberg. “However, the membranes must make contact and fuse together. This is facilitated when ligands are present that bind to receptors on the cell surface and then cause the two membranes to fuse.” Ligands are molecules capable of binding to other molecules.
To find out more, the research team carried out different cell culture experiments. They observed the transfer of molecules and the formation of aggregates in neurodegenerative diseases. Mimicking what happens following a viral infection, the researchers stimulated cells to produce viral proteins that mediate cell binding and membrane fusion. Two proteins were chosen as prime examples: the SARS-CoV-2 protein, and the vesicular stomatitis virus glycoprotein VSV-G, produced by a pathogen that infects livestock and other animals.
Molecules that act as keys
The researchers found that the viral proteins are present in the cell membrane and in the extracellular vesicles. “Their presence increased the spread of protein aggregates between cells, both by direct cell contact or by extracellular vesicles.”, say the authors. The ligands facilitated the transmission of protein aggregates and the creation of new aggregates. “Ligands act like keys that unlock receptor cells and sneak in dangerous cargo“, compares Ina Vorberg. She points out that other work will be necessary, because the cells present in the brain are numerous and specific, but for her it is a “unprecedented discovery“.
.
