AP Biology class blog for discussing current research in Biology

COVID-19: Multiple Doors and Multiple Species

An article published in August of this year identifies how the Coronavirus is able to jump from one species to another. Since the discovery of the COVID-19, the disease caused by the virus SARS-CoV-2, in 2019, many scientists have wondered how SARS-CoV-2 infiltrates cells by hijacking a protein called ACE2 which is found on human cells. At first, many believed that the ACE2 protein was required for infection, but recent discovery from the Virginia School of Medicine reveals that SARS-CoV-2 can use multiple pathways to enter cells. A good example to describe this discovery is a house. To the virus, ACE2 is the front door, but if the front door is blocked, the virus can use other proteins to enter the cells which can serve as a back door or windows in the “house.” This is concerning as SARS-CoV-2 is able to adapt to different proteins that serve as the doors into cells of other species. 

Coronavirus. SARS-CoV-2

After discovering that SARS-CoV-2 has the ability to enter cells using proteins other than ACE2, scientists conducted further research to determine the necessity of ACE2 in the infiltration fo healthy cells. As a result, it was revealed that SARS-CoV-2 can bind to and infect cells without ACE2 being present at all. You may be wondering what proteins besides ACE2 COVID-19 and SARS-CoV-2 use to enter and infect cells. Here is one example. 

An article published in the same month identifies TMPRSS2 as an endothelial cell surface protein that allows the spread of COVID-19 and SARS-CoV-2. The definition is similar to that of ACE2 as TMPRSS2 is simply another door or window that SARS-CoV-2 can use to enter healthy cells and infect them. TMPRSS2 is commonly found in the respiratory and digestive tracts which is a supporting factor to why the Coronavirus may encounter this protein. For example, someone infected with COVID-19 may sneeze near you resulting in you breathing the virus into your respiratory tract. 

In addition, an article published in the summer of 2022 explains an experiment done in order to determine the structure of the TMPRSS2 protein. The results section of the article confirms that TMPRSS2 is composed of three domains and three subdomains. An image of the protein shows tertiary protein structure surrounding the protein which is integrated into the membrane. The experiment allows us to see how similar TMPRSS2 is to ACE2 and how an antigen is able to bind to either protein and enter the membrane, but, how can this be prevented?

Although SARS-CoV-2 can enter cells in our body and infect them by entering protein channels such as ACE2 on the cell membrane, cells can create antibodies that attach to their cell membranes. In AP Bio class, we learned that in adaptive immunity, B-cell antibodies bind to foreign antigens while also inhibiting B cells to divide. B cells are then able to create B Memory Cells which recognize a foreign disease such as COVID-19 if it enters the body multiple times. B cells which are activated by B-Cell antigens, can protect our cells and prevent SARS-CoV-2 from infecting our cells by entering through ACE2 channels. 

I agree that these new findings have helped us understand how SARS-CoV-2 enter healthy cells allowing them to jump species, but I also believe there is more to discover about both of these diseases such as the question of whether or not a variant of SARS-CoV-2 can be created that is able to bi pass antibodies and enter cells at the same rate it would before vaccination or first infection. ACE2 and TMPRSS2 have been around for a while but we are just now discovering how proteins like them allow diseases to jump species. What do you think?


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1 Comment

  1. lagoon1

    Atomicmass, I enjoyed reading your post about proteins and infection. I found it interesting how specific proteins like ACE2 and TMPRSS2 allow entry to cells. I also liked your analogy comparing these proteins to multiple entry points in a house. This helped clarify the concept. These viruses are very complex and there is so much behind the virus’s strategies to infiltrate cells. The overall connection to the immune system and its role in combating the virus, particularly through B-cell antigen receptors and antibodies, brought the whole idea together. Now that we know that SARS-CoV-2 has various entry points beyond ACE2 for cell infection, scientists must be vigilant against potential mutations that might find different cellular entry pathways that we don’t have immunity to It is also interesting how these proteins now reveal new insights into how diseases can jump species, which is something I would like to know more about. Great job describing this topic and hinting about diseases jumping species.

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