For everybody looking for a break from #coronaviruses check out our @virusfusion007 recent results on a #herpesvirus known as #HHV8 or #KSHV.

The preprint is available at @biorxivpreprint bit.ly/39mvx9I.

The main findings are discussed in the 🧵 that follows (1/n) Image
KSHV and its cousin EBV use an envelope glycoprotein complex called gH/gL to bind to #EphA2 receptor tyrosine kinase to gain access to host cells. We set to determine the structure of the KSHV gH/gL-EphA2 complex and perform functional studies to understand the mechanism (2/n)
While we were gathering the functional data Su et al. published the 3.2 A structure and provided some interesting insights few months ago.
But under our 'no scoop good enough' mantra we kept working and obtained some cool data that we can now share (3/n)

go.nature.com/3sIbQRL
First, we show that in addition to gL N-terminus, a single residue E52 on KSHV gH provides essential contacts for EphA2 binding, which we measured to be below 1nM. This validates several mutagenesis studies that implicated gH in binding (4/n) Image
But the most interesting part came from revealing key and novel structural details (thanks to 2.7 A resolution and analyzing the structure to death) that established clear structural mimicry between gH/gL and the physiological ligands of #EphA2 called #ephrins (5/n) Image
Being so intrigued by the similarity we went to determine if this translated into functional mimicry. Does binding of gH/gL to EphA2 receptor induce the same kind of changes at the membrane and cellular level as ephrin ligands do? (6/n)
So we started a collaboration with the masters of measuring protein-protein interactions in live cell membranes 😎, the Twitterless Kalina Hristova and her talented student Taylor Light @JohnsHopkins (7/n)
Like other tyrosine receptor kinases, EphA2 molecules cluster into oligomers of different sizes upon ligand binding. This is important for the downstream signalling, and especially interesting since EphA2 signalling can in some cases ⬆️ the oncogenic potential of the cell (8/n)
And KSHV is an oncogenic hepresvirus ...

Kalina and her team had developed an FSI-FRET assay with which they can follow EphA2 oligomerization state in membranes (very cool imho), so we asked - can soluble gH/gL induce clustering of EphA2 like ephrin ligands do? (9/n) Image
And the answer is - yes. Soluble KSHV gH/gL induced formation of EphA2 dimers, mimicking the early steps of ephrin-induced oligomerization. Further more, the gH/gL mutant with a change in that single important gH residue - E52 - was defective. So gH indeed matters (10/n) Image
Then we show that the functional mimicry between ephrin ligands and gH/gL exists at the cellular level too: both cause the cytoskeletal rearrangements that lead to cell contraction (and the gH E52R mutant is functionally deficient, as expected) (11/n) Image
While we have provided the insight into what emulates the early steps of KSHV infection i.e. virus binding via gH/gL and inducing EphA2 to dimerize (or possibly further aggregate - but we don't know that yet) many interesting questions remain to be answered (12/n)
For example, some fundamental questions related to EphA2 mechanism - how are the EphA2 dimers we observe stabilized by gH/gL? How is the binding transmitted across the membrane to induce phosphorylation and signalling? How does the signalling ⬆️ endocytosis of the virus?(13/n)
Ephrin ligands can ⬆️ or ⬇️ oncogenic signalling in cells, depending on the cell type, distribution of the ligands/receptors on cells etc. So does KSHV use EphA2 to merely enter the cells, or does it take advantage to drive oncogenic transformation of the cell ... (14/n)
... later on during the latent phase of infection. Are the EphA2 dimers sufficient to stimulate endocytosis and facilitate viral entry, or larger clusters form / need to form when the virus is present (we looked only at the soluble protein) (15/n)
And finally if gH/gL simulation of EphA2 can contribute to oncogenesis, can we use EphA2 inhibitors to block the spread of KSHV?

So this will keep #KSHV and #Eph receptor enthusiasts busy for some time 😀(16/n)
This work was done with the support of @institutpasteur and thanks to the amazing collaboration with Kalina and people @virusfusion007 - @Guardado_Calvo, Delphine, Riccardo, Felix; Ahmed Haouz from the crystallization platform at IP and staff @PROXIMA_1 @Proxima2A (17/n)
Go check our paper and leave comments. Thanks for reading!

(the end)

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More from @marija_backovic

3 Apr
Thanks to the @CEPIvaccines @WHO @EuWHOEurope #Covax and others, 24,000 doses of #AstraZeneca vaccines arrived in 🇲🇪 last week, and this is just fantastic! But as in other European countries, there is a lot of hesitancy and fear related to this vaccine. 👇🏻 (🧵)
The ministry of health @MinZdravlja made the #AstraZeneca vaccine available to all 65+ old citizens, and this is great news as they are the most vulnerable group that was not eligible for @sputnikvaccine and #Sinopharm vaccines given in previous weeks to people 70+ 👇🏻
The main fear from what I understand is related to the inconsistent recommendations about the appropriate target groups and recent reports of #thrombotic events recorded in several EU countries now. Let’s address the issues one by one 👇🏻
Read 18 tweets
3 Apr
Following some hoopla that my tweet 👇🏻 caused…

1. I want to applaud all the medical workers in #Montenegro - epidemiologists, support staff, technicians, nurses, doctors - who are at the front line, caring for the many sick people in the hospitals around the country (🧵1/10)
You are the unsung heroes!

I want to make sure that what I’ll say is #not meant to indicate that the #services you provide in 🇲🇪 are not good - I know that you are doing your very best, and I thank you from the bottom of my heart (2/10)
*reminder: health services is not a synonym for health system

My comment that it doesn’t make sense to use #CFR (or as was referred to ‘lethality’) for comparisons between countries, and as a mirror of the quality of health system quality is based on the following facts (3/10)
Read 11 tweets
28 Mar
Seemingly good news are coming from 🇲🇪 and this makes me happy, but I implore @VladaCG not to give false idea of security to its citizens. The number of detected cases dropped by 50% as their graph shows, but that is largely due to the ⬇️ numbers of tested performed daily. (1/4)
If you look at the incidence rate, it shows a very small decrease that cannot be reliably attributed to 'a better situation' in #Montenegro (2/4)
Don't be fooled that the situation will get better until most people are vaccinated. The B.1.1.7 (UK) strain that is wracking havoc around Europe now is growing in Montenegro too, it's just that we don't know which % it is at now because of the lack of sequencing (3/4)
Read 4 tweets

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