Snapshot Issue 51 January 2009

Nav1.7

Though uncomfortable, the feeling of pain is necessary. It is like a sixth sense. If you break a leg, there’s a fair chance that you would call for help, rather than try to walk. And burning your hand once is warning enough to avoid it happening a second time. Pain exists for a purpose. When felt, our spontaneous reaction is to immobilise what hurts so that it can rest and restore itself. The memory of pain is just as crucial since it prevents us from repeating a prior painful experience which damaged a part of our body. It is for this precise reason that a young Pakistani boy spent a lot of his time in hospital. He was a busker who walked across red hot charcoal. Without ever feeling pain. How is this possible? Recently, scientists found a protein which seems to at the heart of insensitivity to pain: the Nav1.7 protein.

Nav1.7 was found in a number of Pakistani children. All lived – or still do – without ever feeling any kind of pain since they were born. However, to the scientists’ astonishment the children were able to discern between hot and cold for instance. The thing is the perception of pain does not use the same brain circuit. Pain begins at the end of specific neurons on our skin, for example, and then travels fast to our brain. Such neurons are particularly enriched with Nav1.7. Precisely.

Nav1.7 forms a channel in the cellular membrane. For pain to be felt, the channel has to open so as to let sodium ions pass. In the Pakistani children, the channel did not open because the protein had been altered. As a result, the sensation of pain is not transmitted.

The feeling of pain is singularly complex and yet one modified protein is enough to short-circuit the whole process. What is more, Nav1.7 is neither present in the heart nor the brain. The ideal painkiller would be a drug which stops Nav1.7 from functioning and which would offer minimal side effects. The discovery of Nav1.7 and its role in the sensation of pain offers hope for future therapies. But is it such a good thing never to feel pain?

Sodium channel protein type 9 subunit alpha (Nav1.7), Homo sapiens (Human): Q15858

L'édition française de cette chronique est disponible dans l'Instantanés du mois de Prolune.

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