In patients with a severe or long form of Covid-19 disease, bleeding disorders have often been observed. The patient’s immune system could be involved in the mechanisms leading to this type of symptom.
It is now something well known to all: the Covid-19 is a systemic disease and affects many organs. The virus SARS-CoV-2 is not limited to lungs and can last a long time. The list of organs that can be affected is only growing: heart, kidneys, eyes, nose, brain… and blood clotting. Why the virus affects so many organs? A team may have found some answers. Their work has been published in the journal Journal of American Chemical Society.
Spike protein can form amyloid
The research theme of this team door on abnormally folded proteins, responsible for various diseases including Alzheimer’s disease. They observed similarities between symptoms misfolded protein diseases and Covid-19 disease. Indeed, the folding of proteins and their 3D structure in space are essential to their function. A particular type of folding, called amyloid, promotes the aggregation of proteins into plaques. Symptoms depend on where they are located.
The protein Spike is the key protein in coronavirus : it is the one that allows it to bind and penetrate human cells. Using a computer simulationthe authors found that it has the ability to fold and form amyloid.
How is amyloid formed?
In Alzheimer’s disease, the formation of amyloid is preceded by a stage during which our body cuts large proteins into smaller ones. In this study, the authors show that a enzyme of our immune system has the ability to cut the Spike protein of the coronavirus into several pieces. One of the fragments obtained corresponds exactly to the part of the protein most likely to form amyloid.
At the onset of a Covid-19 infection, polynuclear neutrophils are produced in large quantities. It is precisely this type of cell that releases the enzyme capable of cutting the Spike protein. The authors brought together pure whole Spike proteins and the enzyme of interest: fibrils amyloid formed.
What is the link with bleeding disorders?
Fibrin is a protein that circulates in the blood. Its role is to allow coagulation. In case of lesions of a vessel, it facilitates the filling of the hole. When the healing is made, it is the plasmin which breaks the plug. The authors found that in the presence of amyloid from the Spike protein, plasmin could not play its role. This could explain why SARS-CoV-2 leads to the formation of clots blood. Moreover, this type of disorder is commonly observed in diseases related to the formation of amyloid.
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