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Welcome to the deep diff um our mission today is to unpack this like totally paradigm shifting twenty twenty five paper from the journal cell by woo and colleagues
Yeah
It's a fascinating
When we're looking at a really fundamental biological paradoxes
Right
It's all about how our immune system manages this um h raisor or thin line between fighting often infection and uh fascdently just pustroying our own tissues in the process
Exactly we're basically looking at the fail saace of information
Because um in in of of iminletion that um h fasicicly puzzled researarchfor decades es because i mean information is non negotiable for survival right like you get to cut
You gets read
Inflamed you need that
You absolutely need it
But uncheck systemic information which is uh what we see often excepthis is often what actually kills the patient right
The pamagine starts the fire
But the immune system just like burns down a whole house
Yes
Exactly
And the assumption is long been that chemical signalling pathways just sort of um peter out over time
Or that in in the atory cytykineeventually override the flammory ones
But this cell paper just throws a massive curve ball into all of that thinking the others discovered that the overriding switch isn't a chemical time
Or at all no
It's the physical environment of the tissue
Itself specifically a radical drop in ph accidity acciity combined with the shape shifting protein acting as like an internal cellular thermostad
Which is wild
Because let's set the baseline for you listening here
Blood ph is usually locked in this really rigid window right
Hovering right tween
Seven point three five and seven point four five
Always it's the researchers um they focused on the local microenvironment during an infection
They used a bacterial trigger called lps lepal polysactary ah lps right
Which effectively simulate a really severe systemic infection in mice
And while the blood ph does drop information during a bicsysevere information what happens locally ly just drased with the drastic a retalk in in flame tissues with lymphnodes and even inside solid in ph course
The local microenvironment becomes intensely acacthetic
We are talking about aph pluminting all the way down to six point five ow and keep in mind
You know ph is lotterorismic so a drop from seven point four to point five
If an enormous shift in protoin concentration massive
Which brings up in a media question
I think if the tissue environment drops to a ph of six point five
How is that a controlled biological response right wouldn't bathing a macrophages in that much assajust in didiscriminadee nature
It's protein exactly just melt the cell
And caused a total failure
You would think so and honestly that's precisely why this mechanism would undiscovered for so long
Because we've known cells have these surface receptors designed to monitor envivionmental acacity sort of little smoke detectors on the outside of the cell perfectly said proteins like agpr sixty five or gpr sixty eight
And even transcription factors link to hypoxia like hima
They sit right on the cell
Membranin effectively acting as external sensors
So the prevailing theory was just that the macrophage detextiasstic environment using the specific surface receptors
Right Yeah
It smells the acid outside signals
The nucleus and trigers
The controlled shut down
Before the acid causes permanent damage
That was the standard hypothesis
But the researchers did the definitive test
Then ah they did they utilize macrophages from knock out mice
These are mice genetically engineers red completely like act those specific sensor
So they deleted gpr sixty five
Gpr sixty eight hif one a
Exactly they made the cells essentially blind to external acitity through all the known traditional recept pathways
But the twist in the papapis that it didn't matter
Or but the nogw macrophages still successfully detected the acidic environment
Yes
They still actively dial back their in ffmmory response se external sensors
The completely irrelevant to the specific fael safe
The calls coming from inside the house
Exactly
The regulatory signal wasn't coming from a recepter on the cell membre
The sensor had to be interinternal
The acethetic environment was somehow penetrating the cellular machinatory itself okay
But before we track down that internnal sensor we need to clarifall
The acsor is actually doing to the macrofages programming
Because looking at the source material
The acidic ph doesn't just broadly suppress the cell
No
Not at all
It's not a master volume
Not turning down the immune functions equally right and to figure out
Exactly what was happening the researchers applied something called a linear deconvolution model to the geneic pression data
Yeah lepausim that because the methodology es really crucial to understand here
When a macrophage just hit with lps and an acidic ph simultaneously the resulting data is just incredibly noisy
Just a massive data
Just a regulated down llaneted gene
Exactly so how do you isolate the specific effect of the acid a linear deconvolution model essentially allows you to untangle interacting variables mathematically so if you know how this so reacts to ls alone one
And how it acts to isalalone the model a filter those out
Exactly a filter amout to reveal the interaction effect
It shows how the acid specifically altors or uh hijax the lps response
It isolates the delta
And when they ran this analysis the gene responses fell into three really distant categories with walk through those sure
So the first group of genes prove completely insensitive to the ph drop
These are the fggintal genline ananemicrobial defence genans like tnf and nfkbm
The reresponders right
Whether the ph is seven point four
Six point five
They fire full capacity
But that makes perfect evolutionary sense
You know
Because you can't compromise your immediate defence agaagainst the pathogenjust
Because
Because the enenvironment change of it exactly the cell maintains its core anti microbial integrity
But the second category the ph repressed genes
Yes
The the thirilsafer really kicks in
Yeah
These are the heavy artillery
The systemic drivers of information genes like iosiics and ad one right
These are the systemic lelecujust
Just the the the asassiof adaptive immune damage
These the the heavere swelling
And they cause massive collateral tissue damage and the researchers found that the acysic environment sharply and specifitely shuts these heavy hitters down and completely turns them off
But the third category is what genuinely surprise me in reading this the ph cenrogistic genes
The surprises
Yes
The acid doesn't just ignore or suppress them
It literally high prohectiates them genes governing anti varreal response and tissue repair
Like if mb one in adam
They spiked by an average of twenty fold
That twenfold increase is staggering
And is highlights a remarkable biological pivot
Look closely at this two geniny mention ed one and adam
So this is such a cool contradiction
So adin one promotes vezzo construction right it restricts blood flow
Which is a classic early ffmmmatory ory response to like isolaal ininfection and and adm verversepropromotes vezzal dillation
It opens the blood vessels up
Which is crucial for tissue repair and clearing out cellular debris so undnormal phphyological ph and ininfection triggthe conconstruor edden one
But as the tissue gets inflamed in the ph drops to six point five
The acid physically suppresses the constructor and massively boosts the didiatator add one
It is a physictal tal programming of the macrophages in entier operational strategy
Okay
This is to a quick many recaat for you listening to sympticize this
So the city city envesezment it n't acting like a simple vogical nob
Which is a promote contrarophtion no it that's more like a precise railway switch right right reverting the train away from the tissue derawing systemic information and forcing it under the tracks of tissue repair and resolution
That's a perfect analogy
And to understand how that railway spech is actually thrown the researchers had to look at the internal ph of the macrophs right using specialized ph sensitive forust and die
Yeah they track the interest cellular environment
And they discovered that as the external tisue pitch drops the inside of the macrofish also accitified it settles right around aph of six point six
Exactly so the site applazthat itself become citifitic
Which means whatever throwing that swhich has to be a protein sitting inside the cell
That physically authors its behavior at exactly ph six point six
And finding that specific protein is no small task
Yeah they sisithrough the entire proteum
Yeah they utilized a massive bioinmamatic scan analyzed over fifty thousand most protein
And they searching for a very particular molecular architecture
They needed a protein that undergoes a massive shift
It's electrical charge precisely at that ph drop and the scan flight of protein called brd for right now if you follow geneticics brd four is a very familiar player
It's a classic epigenetic creator
Its primary job is to bind to a setellated ststes and facfacility transcription
But a trtrscription factor doesn't tificicffunction as an environmental sensor
So how was brd dedetecting acid
It secret lies in a specific structural anommally
Within brd for it contains an intrinically deforred progion or an idr right
An idr so we usually concepalized proteins is having these rigid highly specific three d structures like a classic lock and key model
Exactly
But an idr defies that completely it's a sequence of a mino acseds
That lacks a fixed stable conrimation
But i was seegive it like a floppy unstructure piece of wet spaeti just come loose and shifting shape red speaeti is a great waia picture and the biochemical composition of that flexible spegetii chain is the key
The iddr brd four is highly enrichwith three specific ammino assets
Histedeine prolin and gluedemeine the hpq sequence right and out of those three histedeine is the true environmental sensor
Let's it into the chemistry of histedeine
Why is a uniquely position to sense of ph drop it comes down to its pki of value
That the specific age at which a molecule gains are loses a protom histedy is unique among a mino acseds
Because its pki is right right around six point zero to six point five
Oh wow
Right the sweets by exactly in a normally sayillar environment at ph seven point four hististeine is largely uncharged it's neutral
But the exact moment
The interecellular ph drops into that six point five range
The images or ring on the hiyitan molecule acthdn chemical al sponge
It is suddenly soaks up all those lose proteins in the acyditic environment
Yes
A rapidly buds to them
And because protoons carry a positive charge
This normally floppy neutral chain of wet begeti is suddenly just bombarded with positive electrical charges
You've got it the local acidification physically alters the electricthetic landscape
Because its brd for protein in an inciant okay
So a drop in ph gives the flexible region of brd for a sudden popotive charge ge
Oh is that electrical shift actually translate to shutting down the heavy artile regions like i osix
While leaving the front line defence like like nf alone
Right
How does it regulate specific transcription
This brings us to the underline mechanics of face separation biommolecular concondentes tes
Yes
This is arguably one of the most critical discoveries in modern biophysics for those following the recent shift in secular biology
You know the old model of the nucleus was basically a soup
Great just a soup
Where proteins fluat around and renomomly bumped the dna they need to read
But face seication proves it's much more organize than that under healthy normal ph conditions
Brd four and utizes that flexible wet spageti iar to physically link up with another protein called med one
Yes because
Because of those intrinically nucleded regions
When brd four and med one reach ach critical concentrates
Yes
This go liquid
Liquid face separation they demix from the surrounding nuclecleoplasm m of like oil separating from water
While leatly like organzthan that form these highly concentrated localized liquid droplets directly on specific regions of the chromaton transcriptional condentes tes
I love comparing these condensates tes a flash mob or like an exclusive vip laounge
They create this isolated highly concentrtraenvirononthat just pulls in arna pollumorrtes and all the necessary machinery to transcribe genes at massive volumes
A vip laounge is perfect
And here's where it can expect to those dangerinflammatory genes 对genes like eyle six aren't driven by standard simple promoters
They are driven by superenhancers
Right
Superenhancers let's explain that they are massive clusters of regulatory dna elements
But they can be located thousands of basepayers away from the actual gene
They control exactly
And because the dna is linear to read a superenhcer
The d na strain literally has to loop back on itself in three d space
And the brd four conconsates tes the vip lounch flash mob are basically
The glue holding that three loop together
Exactly they bridge the massive gap between the distant superenhcer and the gene promoter
If you don't have the physical liquid drop at there
The dna loopp just falls apart machinatory defuses
And the superenhancer cannot activate the gene
Which perfectly explains the fell safe
Think about what happens
When the intecillar lar ph drops six poinsix the histteans ans on the rr four protein absorort proteins
They act like that spunge right
And they become positively charged
And when you pack at dense cluster of positive charges into a microscopic liquid droplet fundamental physics takes over like charges repel
Yes
The elecrosthetic repulsion violently overcomes the weak interactions that hold the condensates together
The vip laounch just explodes
It dissolves the liquid dropped violently dissolves and the protein scatter back into the nuclear plasm
The flash mob scatter and without the conenciate acting is the glue
The three d loop of the superhancer collapses
The heavy and fmmmatory genes like il six are just instantly disconnected from their activation machinery silcing the systemic mlammatory response entirely exactly
The defence genes like tnf don't rely on massive superenhances or or br deit condentes tes tes function
Which is why they keep firing perfectly fine in the acithetic environment
They ilcthe the ip launge exactly
And the proof of this is just gorgeous
They didn't rely on circumstantial genetic data
The utilized s stead microscope y stimulathe emission depleletion micrococope y the amazing because
Because biypasses the traditional defraction limits of light right
It lets them visualize these these condensates in living cells at the nano scale
They literally watched the process unfold in real time
Within ten minutes of exposing the live micropages to an acidic environment
The glowing brd four concondentes tes physically melted away on the imaging monitor h just poably bubble
Just melted
And when they restored the ph to seven point for the condendentes ble reformed
The face operation is highly dynamic
Is completely imversible
But the most compelling evidence comes from their bioengineering
Because they needed to prove that the hiydine prode ination was the exclusive trigger dissolving these conindentes tes right
So they engineered a mutton variant of the brd four protein
They systematically targeted the flexible region and swapped out thirty three of those histedine ammino assets
And they replaced him with alony
Exactly because alony lacks that proton absorbing ring
It's charge remain stable regardless of the ph
So it's basically immune to the acid
And the result was exactly what the physics predict when they beides cells containing this mute brd four in the ph six point five acid
The concondentes tes never dissolved
Right because the onion couldn't absorb the protoons
The protein never gained the positive charge
The repulsion never happened
And the inflammatory superenhancers just kept firing indefinitely they even at the reverse again a function experiment using a completely unrelated protein called fusfus is an arne binding protein known deform its own condentes tes
But it is totally insensitive to asset
Until they glued a sequentwtwelve histidienes onto it right
Exactly they synthetically grarafted a histediine tag onto fus and magally ineninered it to behave just like brd four at ph six point five
The newly added ded histedies absorbed prosons and the fus condensates shattered
That is just incredibly definitively isolate that syythetic ally rinenences the delly programmable ph sensor
Okay
Let's do a quick bullet rek for you listening to cemet this whole pathway
Good Okay
Step one and infection starts
Step two
The interior of the mcrophage drops to in nacidic ph of six point six
Step three
The histidienes on the floppy drd for protein ethlex psues absorbing protoons and gaining a positive charge
Step four
Because like charges repel that positive charge causes the liquid condensates
The the ip launches to violent pop and step five
Without the concondentes tes the dna loops collapse
But the most dangerous and flamatory genes are instantly tly connenected
It is a floless memeical ism yes
But to fully understand as biological circuit
We have to answer the originating colvabable
What initiates the drop in intrillular ph in the first place
Right because it's not just passive acid leaking in from the tissue is it
No
It's not passive diffusion at all the microfish actively drives it's on a sigtification
This was the final piece of the puzzle
Right because when the lps signal hits the macrophage
It obviously triggers the inffmmtory cisades
But it's simultaneously triggers of puzzle shift and celsive metabolim m the macrorofige rapidly upregulates pichossis
Fifight infefection
Csel demands and immediate massive influx of atp energy
So it is choese this by basically burning through glue cose using enzs called hexicinysis exacthe and the inevitable metablic byproduct of that hyperactive like iclosis is the rapid accumulation of lactic acid and free proons
Within the sisytoplasm wait
So the the metaoblic engine that powers the ffmmmatory response is it tively generating the exact acid that will eventually shut it down
Exactly it is the ultimate negative feedback loop the mcrophage effectively sets its own chemical timer the moment
It engages the pathogen that is brilliant
And what truly makes this master class and genetic regulation is that brd four itself actually controls the exexcinacsyes yes
It regulates the transscription
If it exact metaablic ganzzthe brd four turns on the metaaboligzine
The engine mediasasassed the acid dissolves the brd for concondentes tes and the whole system powers down
It is a literal thermos
That if it gets too hot to inflame
If it relates tes the brd for switch breaking the circuit before the tissue is completely destroyed
It perfectly self contained
If they verified this entirely in vivo
对
They tracked partonial mcrophages in living mice during a severe bacteria infection
So they actually watch this happenin a living organism
They did they document ted the whole thing
The metabolic surge
The corresponding drop in intercellular ph and dissolution of the brd for single sesetes
And the precious recalibration of the immunal response
We happening life to prevent fatal supcess
Right is fundamenally respped
How we understand the nucleus
I mean the dna isn't sealed off and evolved fensively waiting for chemical messenges
Not at all the robbiopphysics of the cellular environment
The actual acyslation of protoons from the taboism
The directly reaching into the genome and physically resmantling the three d structures required to read it
We zooed all the way from red and flame tissue down into the nucleus of a single cell
Watching these microscopic droplets pop
Just to keep us safe
It's incredible
And it presents some profound therapeuuc implications particularly in oncology
Right because this is just cool biology
It's the future of medicine
Yeah
Watming these highliacitic environments extremely acitic
And this research provides a direct mechanical explanation for how tumors suppress the immune system
The tumor is literally weaponizing the fail safe
Because the flootting the local environment with acid
The tumor premature ally triggers the protennation
The brd four inside the invading macroficies
Exactly the condenciate shatter and the immunent cells are forced to shut down their inflammatory ory tack before they can clear the cancer
The tumor hijacks the thermostep
Well 好的
对的
But understanding that exact biophyical ical mechanism that relied specifically on historimimprotnation descripting the face operation that opens up entirely new avoites for reprevention right
Absolutely think about that muton bard for architecture ture discucuss the alionine swap ols right
If we could utilize that we could theoretically engineer cararity cells or specialized macroceles with condensates that are totally immune to acid induced repulsion
We could create immune cells that simply refuse to shut down in the acidic tumor microenvirrment or on the flipside
We could apply this to automomum bipology like romitote our thoriorities or inflammatory boudisease
Where the infmmmatory ory ircuit basically fails to deactivate
Exactly if we can design small molecules that selectively target the intrinically disdisorder region of brd for and basically mimic the electorsthetic repulsion of the proteon
We could intentionally shater those condensates
We could physically disconnect the inflamatory superinhltions without relying on like broad spectrmumuoprepresthat that welutely aliwe can all the immune system precisely we are looking at the future
Where we don't just block recepters
We actively modulate the face separation physics of the genome
Itself it leaves you with this profound realization about how deeply integrated our biology is with the physical environment
It really does i mean
If you think about if our immunsystem relies on the raw electrrostatic charge of accumulatic charton to physically assemble and dissolve these temporary local structures on our dn a what other invisible physical forces are currently dictating your gene expression right now it's a huge question right could defluctuating physical pressure within your joints
Or even the exact internal thermal shift during a fever possestheir own intrinsically disted censors are there entirely undiscovered condensates
Tes forming and melting inside yourselves based clerely on physical tension or temperature gradients
Something to think about the next time
You get a fever
The architecture of your dna is listening the physics of your body
A lot cloer than we ever imagined
