Snapshot Issue 32 March 2007
Sodium channel protein type 9 subunit alpha
Pain is not pointless. Deprived of the capacity to sense the red hot of metal, the cut of a sharp blade, or even the breaking of a bone, our bodies would be in very poor shape indeed. A child has to learn very fast what is too hot, and what can bruise. Without the perception of pain, there is little chance of survival. We need to learn to shun what could hurt us and rest when part of us needs to repair.
Since the beginning of the 20th century, there have been reports of people who are either indifferent to pain, or simply don’t feel it. Recently, a young Pakistani street performer made use of his oddity by pushing knives through his arms or walking on scalding coal until – at the early age of 14 – he killed himself by jumping off a roof. Doctors discovered that members of his family suffered from the same condition, indicating that their lack of pain sensation might be hereditary.
Besides being otherwise perfectly healthy and functional in every way, three members of the family carry mutations in a gene which codes for the type 9 alpha-subunit of a voltage-gated sodium channel. This particular sodium channel is expressed at high levels in sensory neurons. Its precise role is still unknown but it is clearly involved in the perception of pain and making it known to the brain. When it is deficient, as is the case in the Pakistani family, the individuals carrying the mutation sense no pain whatsoever.
The molecular pathways involved in pain perception are many and complex, so it was surprising to discover that a mutation in only one protein could have such a drastic effect. The finding is of great interest though because not only could small changes within this particular sodium channel explain pain thresholds between individuals but it is also a prime target for the design of novel and safe analgesics.
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