Coupling of SARS-CoV-2 to Amyloid Fibrils and Liquid-Liquid Phase Separation

COVID-19 is a respiratory disease caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), but because the receptor protein of this virus can appear not only in the lungs and throat but also in various parts of the host's body, it causes different diseases. Recent observations have suggested that SARS-CoV-2 damages the central nervous system of patients in a manner similar to amyloid-associated neurodegenerative diseases such as Alzheimer's and Parkinson's. Neurodegenerative diseases are believed to be associated with the self-assembly of amyloid proteins and peptides. On the other hand, whole proteins or parts of them encoded by SARS-CoV-2 can form amyloid fibrils, which may play an important role in amyloid-related diseases. Motivated by this evidence, this mini-review discusses experimental and computational studies of SARS-CoV-2 proteins that can form amyloid aggregates. Liquid-Liquid Phase Separation (LLPS) is a dynamic and reversible process leading to the creation of membrane-less organelles within the cytoplasm, which is not bound by a membrane that concentrates specific types of biomolecules. These organelles play pivotal roles in cellular signaling, stress response, and the regulation of biomolecular condensates. Recently, LLPS of the Nucleocapsid (N) protein and SARS-CoV-2 RNA has been disclosed, but many questions about the phase separation mechanism and the formation of the virion core are still unclear. We summarize the results of this phenomenon and suggest potentially intriguing issues for future research.