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Canada Medicine News

Low Oxygen Cellular Protein Synthesis Mechanism Discovered 94

Posted by Unknown Lamer
from the live-forever dept.
New submitter _prime writes "Until recently the mechanism by which cells make proteins in low-oxygen environments has been unknown. As published in Nature (paywall) this week, the discovery of the mechanism by an Ottawa-based team of researchers potentially means it could be 'very easy to kill cancer cells' without harming normal cells because cancer cells leverage the same low-oxygen protein synthesis mechanism even in the presence of normal oxygen levels."
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Low Oxygen Cellular Protein Synthesis Mechanism Discovered

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  • by ColdWetDog (752185) on Monday May 07, 2012 @11:45PM (#39923725) Homepage

    Of note in the Nature article is that none of the breathless claims in the PR bit are even alluded to. The abstract (which is typically available):

    Protein synthesis involves the translation of ribonucleic acid information into proteins, the building blocks of life. The initial step of protein synthesis is the binding of the eukaryotic translation initiation factor 4E (eIF4E) to the 7-methylguanosine (m7-GpppG) 5cap of messenger RNAs1, 2. Low oxygen tension (hypoxia) represses cap-mediated translation by sequestering eIF4E through mammalian target of rapamycin (mTOR)-dependent mechanisms3, 4, 5, 6. Although the internal ribosome entry site is an alternative translation initiation mechanism, this pathway alone cannot account for the translational capacity of hypoxic cells7, 8. This raises a fundamental question in biology as to how proteins are synthesized in periods of oxygen scarcity and eIF4E inhibition9. Here we describe an oxygen-regulated translation initiation complex that mediates selective cap-dependent protein synthesis. We show that hypoxia stimulates the formation of a complex that includes the oxygen-regulated hypoxia-inducible factor 2 (HIF-2), the RNA-binding protein RBM4 and the cap-binding eIF4E2, an eIF4E homologue. Photoactivatable ribonucleoside-enhanced crosslinking and immunoprecipitation (PAR-CLIP)10 analysis identified an RNA hypoxia response element (rHRE) that recruits this complex to a wide array of mRNAs, including that encoding the epidermal growth factor receptor. Once assembled at the rHRE, the HIF-2–RBM4–eIF4E2 complex captures the 5cap and targets mRNAs to polysomes for active translation, thereby evading hypoxia-induced repression of protein synthesis. These findings demonstrate that cells have evolved a program by which oxygen tension switches the basic translation initiation machinery.

    Is certainly consistent with your thoughts on apoptosis but there is scant discussion in TFA.

  • by Ungrounded Lightning (62228) on Monday May 07, 2012 @11:48PM (#39923741) Journal

    One of the main problems cancer cells have is getting enough oxygen.

    Their continuous unregulated reproduction outgrows their blood supply - and while a typical tumor signals for more blood vessel growth (vascularization) into itself, the vessels themselves are organized so they can't really keep up. The result is that the bulk of a solid tumor is running on very low oxygen concentration, the main limit on its growth is its ability to obtain new vascularization, and a substantial fraction of the cancer cells may be dying off due to this oxygen shortage.

    So of course having essentially every low-oxygen hack available turned on is a reasonable thing to expect of dangerous tumor types. And turning them off, even through it might not completely kill the tumor, would knock it down enormously AND the remainder would be expected to be far more vulnerable to the body's immune system.

    (Of course if the tumor is a type that recognizes it should die but is evading apoptosis because that works on the normal but not the low-oxygen pathway, turning off the low-oxygen pathway means the cancer cells should just commit suicide, either completely killing the tumor or knocking it back to a miniscule number of cells with further mutations.)

  • by mirix (1649853) on Tuesday May 08, 2012 @04:53AM (#39925193)

    There's some info on texas department of public saftey's site [state.tx.us]

    You need a permit to buy/possess:

    (A) a condenser
    (B) a distilling apparatus
    (C) a vacuum drier
    (D) a three-neck or distilling flask
    (E) a tableting machine
    (F) an encapsulating machine
    (G) a filter, Buchner, or separatory funnel
    (H) an Erlenmeyer, two-neck, or single-neck flask
    (I) a round-bottom, Florence, thermometer, or filtering flask
    (J) a Soxhlet extractor
    (K) a transformer
    (L) a flask heater
    (M) a heating mantel or
    (N) an adaptor tube

    I didn't realise it was so broad. I suppose the condenser bit bans refrigeratiors and air-conditioning. 'Transformer' bans almost all electronics. Obviously it isn't enforced like this, but that's not really the point.

    Apparently glassware (and chemistry in general) is only useful for making bombs and drugs, right?
    Then they wonder why there is a shortage of scientists and engineers. It would be funnier if it wasn't so sad.

  • by Biotech_is_Godzilla (2634385) on Tuesday May 08, 2012 @06:58AM (#39925663)

    Mod parent up. I just signed up for an account to say exactly the same thing.

    To add to this, the major thing about Warburg metabolism is that not only does it allow cancer cells to survive in low-oxygen conditions; it actually produces the raw materials for making the protein needed to grow new cancer cells, so it allows cancer cells to grow faster than if they were using normal aerobic respiration. Here's James Watson talking about it in the NYT [nytimes.com]. So the low-oxygen conditions in a tumour are an evolutionary selection pressure for tumours to evolve towards dealing with low-oxygen conditions, but probably also for them to evolve towards growing faster and being more malignant too.

    In the study in the OP they already knew the normal gubbins that engages the services of the protein-making machinery doesn't work in low-oxygen conditions, so they went looking for something that does work under these conditions and found it. It normally exists in cells so that they can make proteins when starved of oxygen. What's not clear from the Nature abstract, and what will probably need more work to study, is whether this pathway is massively boosted in cancer cells. My guess is that it will be. The Warburg effect is interesting and unique to cancer cells, but it's difficult to turn into a treatment as it's a perversion of a pathway that's essential in all cells - if you drug the pathway itself you'll likely kill the patient. This study is different as it's a pathway that's specific to oxygen-starved cells, so it may well (in about 20 years) provide some exciting new 'universal' drug targets for solid tumours, that may not kill them dead but might at least slow them down. Don't take up smoking yet though...

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