BLOCKED transport systems may be what kills brain cells in people with Huntington鈥檚. The disease is caused by mutations in the gene that codes for the huntingtin protein, and two teams have now shown that the abnormal protein can block the transport of molecules within axons, the long finger-like extensions of nerve cells. Axons鈥� main function is to transmit nerve impulses but to keep them working, molecules such as proteins must be able to travel to and from the main body of the cell.
鈥淢utant huntingtin deals a double blow,鈥� says Lawrence Goldstein of the University of California, San Diego. 鈥淚t steals parts of the cell transport machinery, slowing traffic, and then it aggregates, clogging the pipeline like a clump of toilet paper.鈥� Goldstein鈥檚 group has shown this can happen in the neurons of living fruit flies, while Scott Brady at the University of Illinois in Chicago and his colleagues have demonstrated the same effect in giant squid axons (Neuron, vol 40, p 25 and p 41).
Until now the build-up of mutant huntingtin in the nucleus was thought to kill cells. But this work raises the question of whether huntingtin鈥檚 role in axons is actually the primary event that causes the disease.
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