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The Student News Site of Stony Brook University

The Statesman

The Student News Site of Stony Brook University

The Statesman

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    Wired Science: When the Poison Tastes Sweet

    This might get a little technical, so bear with me. A peptide (that long string from the good old 20 amino acids) could now turn out to be the miracle cure for cystic fibrosis (CF), a disorder that afflicts over 70,000 people in the world. The peptide, called GaTx1, has the ability to direct the flow of ions into and out of cells by using a chloride channel. The big ones, including the National Institutes of Health, the National Science Foundation and the Cystic Fibrosis Foundation are partaking in this endeavor.

    The peptide in question comes from scorpions, snakes and even spiders. But before you back out from revulsion, consider its implications. The toxins paralyze prey by essentially blocking the entry and exit of an ion. The only way an ion knows how to do this is through channels in the plasma membrane of a cell. GaTx1, in particular, is the first ever to selectively bind, and then reverse the normal flow of ions through a chloride channel. Now why chloride channels, you ask? Apart from having been studied very little, the channels have gained recognition because open to allow chloride ions among epithelial cells. They act like doormen for water to walk into and out of the cell.

    The movement of water is where the connection to cystic fibrosis becomes clearer. CF results a thick mucus (akin to the nasty phlegm that accompanied your last cold), which blocks major airways and glands in our bodies. It intensifies with the amount of water obstructed, which stems from the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) protein, a type of chloride channel. So, those who have CF, have a doormen who pretty much never shows up for work.

    If we wanted to get technical, the CFTR in these individuals has mutates due to amino acid deletions and has resultantly misfolded itself. Misfolding in proteins signifies a dead end, meaning it has denatured, and thus rendered non-functional. Interestingly, one type of deletion causes chaperone proteins to bind to the misfolded proteins and discard them from the cell. Chaperone proteins are sort of like the managers who fire the lazy doorman, our old friend CFTR. In this case, with no CFTR in sight, the airways get clogged with mucus and lead to CF.

    So, how do they do it? Scientists use reversed-phase high-performance liquid chromatography (HPLC), which is a fancy way of saying they shove liquids down a tube and separate its components based on polarity. HPLC is able to extract GaTx1 from Leiurus quinquestriatus hebraeus, which better translates into Giant Israeli Scorpion. Now that it has been isolated, the peptide can be used to study just how it is that the under-studied channels do their job.

    The implications of the study by the three big brothers are two-fold. One, it could potentially lead to a cure for CF. It can also serve as a proof of principle for curing other secretory disorders, such as secretory diarrhea (don’t laugh…it causes at least a thousand deaths every year), autosomal dominant polycystic kidney disease, diarrhea-predominant inflammatory bowel disease and possibly several others. On the flip side, the peptide could be used to inhibit the channels from opening and consequently decrease the excess water that often leads to fatal consequences in cases of cholera.

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