ACE2: How researchers think coronavirus attacks cells
During our last session on April 27, 2020 we viewed a video on the different RNA structures that are present in a normal healthy cell. That helped us understand how the corona virus is used in the cells it invades.
The coronavirus infiltrates patients’ cells through spikes on the virus’s surface. These spikes use a protein receptor called ACE2, which sits on the surface of human cells. ACE2 reduces blood pressure and inflammation, but it also acts like a “door” to the cell for the virus which causes COVID-19.
A number of ACE2 variants, Expression level and pattern of ACE2 in different tissues might be critical for susceptibility and symptoms and the outcome of the novel corona virus infection.
“Angiotensin-converting enzyme 2 (ACE2), an enzyme attached to the outer surface (cell membranes) of cells in the lungs, arteries, heart, kidney, and intestines, could reduce the association between ACE2 and the spike protein.”
Corona virus is an RNA virus but it doesn't require translation into DNA. The RNA resembles mRNA structure and it is ready to go for the ribosomes. Corona doesn't have reverse transcriptase and other proteins used in retroviruses and therefore are classified as a separate group Corona. The viruse replicates its RNA and the host will donate a little of its membrane to produce its envelop with the spikes of the new viruses. There are RNA and DNA viruses which cause cancer. The cell undergoes transformation. A retrovirus has reverse transcriptase and integrase.
The genome of the virus is integrated into the host's genome and stays there. In humans 8% of the genome is retroviral genome or retroviral elements. The retroviral envelope gene is thought to be the basis for the creation of the placenta in animals. It started with a viral infection which created the placenta. Retroviruses are used for gene therapy. The idea is nice but it doesn't always produce the expected outcome which is a repaired gene. Instead, if the gene plus the retroviral vector is integrated near a proto-oncogene, it can turn into an oncogene, which might result in a cancer process.
Oncogenes were discovered as cancer causing viruses, but, they are also found in normal cells. The original unmutated wild type of an oncogene is known as proto-oncogene. The proto-oncogene promotes good cell growth and division. Nomal proto-oncogenes can become activated so that they become oncogenes. The process can begin with a carcinogen agent. Proto-oncogenes become cancerous when they mutate or when there are too many copies of them. There are proto-oncogenes and there are their retroviral counterparts. Proto-oncogenes encode regulatory proteins in the cell. They are important for growth and differentiation.