When it comes to depicting the coronavirus infection on the cellular level,
you find the good, the ok, the bad and the ugly. But sometimes you also find the absolute
awesome. This painting (because yes, it was made with freaking watercolors), shows the complexity,
the scale and the organic nature of the molecular world, with a high degree of scientific accuracy.
The first time I saw David Goodsell’s painting I was delighted by the colors,
the incredible detail, and the purpose that every element seemed to have in the piece,
but I didn’t really know what I was looking at. To me it was kind of like seeing Tamil:
it looks really cool, there are incredible details and of course every element has a purpose,
but I really can't read it. And I really wanted, not only to read this David Goodsell painting,
but also understand what's going on with all of these other representations. So I
started to read about the coronavirus infection cycle, proteins, molecular representations and,
soon enough, I fell into a deep, deep rabbit hole. The good thing about this is that I now know
what’s going on and I’m going to explain it to you, but before that, we need to understand some
basics about cells, viruses and proteins. So, I present: The Coronavirus, Its Attachment and Entry
Compared to cells, viruses might seem pretty boring. Cells are huge and complex;
they move around, eat, breathe, grow, communicate and reproduce. Viruses, on the other hand,
are just bundles of genetic material, often surrounded by a protective membrane featuring
just the necessary tools for infection. Even after entering an organism, viruses outside a cell are
just inert particles; and the only reason they get from one place to another is because there are
*millions* of them being bounced around thanks to the power of diffusion. They’re like ink droplets:
they’re not alive and yet they slowly diffuse in still water. This is one of the reasons why
virologists generally don't like the idea of anthropomorphizing viruses (you know,
putting faces or assigning motivations to them), however I’m not a virologist and I like putting
faces on everything except stick figures, so allow me that artistic license. By the way,
virologists also refer to this as a “virion”, not a “virus”; but we don’t need to get into that
rabbit hole right now, so I’ll just use “virus”. The important thing to remember is that,
outside a cell, a virus is not alive; however as soon as it gets close to specific living cells,
this seemingly boring bundle triggers an impressive series of events that introduce
the viral genetic material inside the cell. The coronavirus responsible for the COVID-19
pandemic, for example, gets initially tethered to cells in the respiratory system thanks to a
sort of molecular fishing rod located in the forest-like exterior of the cell’s membrane.
This initial tethering allows some of the spike proteins on the virus to get
close and stick to another special protein also located on the cell’s membrane: the ACE2 receptor.
Now, none of these structures on the cell's membrane are here in order to catch viruses;
they all have normal jobs in areas like blood vessel formation, blood pressure regulation
and protein activation, to name a few. However, spike proteins have evolved to
take advantage of the cell's infrastructure. You see, once the virus is docked to the ACE2
receptor, some other cell structures are tricked into cutting the spike protein in very specific
locations, which releases a spring loaded harpoon that will pierce into the cell’s membrane and then
coil into itself, pulling the membranes of the cell and the virus close enough to fuse. This
is how the viral genetic material gets inside the cell, where it will take advantage of other
cellular structures to produce millions of viral parts, which will then self-assemble,
and exit the cell, starting the whole cycle again. An impressive process that will surely
keep my mind curious for a long time to come, but for now, this is all we need to know to review the
various depictions at the beginning of the video. This one, for example, has a very detailed virus,
that sharply contrasts with the smooth surface of the cell and the empty surroundings.
The attachment mechanism is unrealistic, and I can see how it would be friendlier to a casual viewer,
but the entry depiction is definitively very inaccurate. This other one does display the
fusion of the membranes of the cell and the virus, but the virus’ membrane is outside in and
the viral genetic material is released inside the membrane of the cell, which is completely wrong.
This other one isn’t really attempting an accurate representation on the molecular level,
and it’s just 20 seconds on a 25 minute episode about the coronavirus pandemic in general,
so I guess it’s ok. [Henry:] it's ok!?!?? Really??, after you nitpicked so much on the
other ones? [Ever:] Yeah, I think it’s… hmm... ok. Finally, David Goodsell’s amazing painting
displays a SARS-CoV-2 virion fusing with a cell: you can see Spike Proteins in several stages,
the cell membrane structures, the fusion between the membranes, the viral genetic material and
you can even see how the cell’s ribosomes are starting to produce viral proteins.
I’m not sure why the fishing rods are missing here, but the confirmation of their involvement
in the SARS-CoV-2 entry is very recent. Also, this painting has some degree of informed
speculation, since we don’t know everything about the coronavirus infection cycle.
For example, it’s February 2021 and we don’t know if the fusion happens at the attachment
site or after the virion is enveloped by the cell, and we don’t even know the exact shape
of some of the cellular structures involved. In any case, I, and now you, know a lot of
weird and specific stuff thanks to this amazing painting. I’m not sure if that knowledge will
be useful to you or if it will make you follow my steps, but I’m so glad and excited to be here...
at least while this lantern keeps working. Which reminds me: before you go climbing down rabbit
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I hope I don’t fall into that virion rabbit hole again.