February 22, 2010 Leave a comment
The most painful egg-laying mammal: the platypus
The duckbill platypus is an impossible-looking, risible creature that we don’t typically associate with horrific pain. In fact, besides its odd looks, its greatest claim to fame is that it’s a mammal that lays eggs. But that’s just because you’re not paying close enough attention. On the hind legs of the male platypus are two spurs that inject a venom so painful, the recipient human writhes for weeks after the encounter. In spite of the fact that platypuses (platypi?) and humans don’t hang out together much, platypus venom contains a specific peptide–a short protein strand–that can directly bind to receptors on our nerve cells that then send signals of screeching pain to our brains. Ouch.
Hurting? Reach for a scorpion
If you’ve ever experienced platypus-level pain and taken pain killers for it, you know that they have…well…side effects. It’s because they affect more than the pain pathways of the body. The search for pharmaceuticals that target only the pain pathway–and, unlike platypus venom, inhibit it–forms a large part of the “rational design” approach to drug development. In other words, you rationally try to design things that target only the pathway of interest. In this case, researchers reached for the scorpion.
Their decision has precedent. In ancient Chinese medical practice, scorpion venom has been used as a pain reliever, or analgesic. But as developed as the culture was, the ancient Chinese didn’t have modern protein analysis techniques to identify the very proteins that bind only to the pain receptors and inhibit their activity. Now, a team from Israel is doing exactly that: teasing apart the various proteins in scorpion venom and testing their ability to bind pain receptors in human nerve cells.
The next step? Mimicry
With proteins in-hand, the next step will be to create a synthetic mimic that influences only the receptors of interest. It’s a brave new world out there, one where we wrestle proteins from scorpion venom and then make copycat molecules to ease our pain.
For your consideration
Why do you think the platypus makes proteins in its venom that human pain receptors can recognize if humans generally haven’t targeted platypuses (platypi?) as prey over its evolution?
In the human body, a receptor may be able to bind each of two closely related molecules–as a hormone receptor does with closely related hormones–but one of the molecules activates the receptor, while the other molecule inhibits it. Taking this as a starting point, why do you think some proteins in scorpion venom–which often causes intense pain–have the potential effect of alleviating pain?