By causing mitochondria to collapse, clumps of these proteins may lead to nerve death.
Misfolded protein clumps cause brain cell traffic jams. In neurodegenerative diseases, these jams may have deadly consequences.
Clusters of prions block passage of crucial cargo along intracellular roadways in brain cells, Cell biologist Tai Chaiamarit of the Scripps Research Institute in La Jolla, California, reported at the joint annual meeting of the American Cell Biology Society and the European Molecular Biology Organization on 10 December.
Prions, abnormal versions of a normal brain protein, clump together in large aggregates that are ensign of degenerative brain diseases, such as mad cow disease in cattle, chronic deer disease and Creutzfeldt-Jakob disease in humans.
It’s uncertain why nerve cells called neurons are so deadly to these clumpy proteins, but the new research may provide hints as to what’s wrong with these diseases.
Axons, long stringy nerve cell projections carrying electrical signals to other nerves, are the sites of prion traffic jams, Chaiamarit and colleagues found.
As more prions clump together, they cause the axon to look like a snake that has just swallowed a large meal.
Through a microscope, Chaiamarit and colleagues have seen mitochondria transported at the bulges to the furthest reaches of the cell.
Mitochondria, the energy-generating organels of the cells, are carried out by a motor protein called kinesin-1 from the cell’s main body.
Protein motors are called microtubules along molecular rails. Another motor protein, dynein, carries mitochondria back along those same rails to the cell body.
Chaiamarit said. Prion clumps disrupt outbound traffic, causing kinesin-1 and mitochondria to jump the microtubule tracks in the swollen sections, the researchers discovered. Microtubules may be bent or broken in those spots.
Mitochondria movement back toward the cell body wasn’t impaired, perhaps because dynein is better at avoiding obstacles than kinesin-1, Chaiamarit added
When the traffic jams start, brain cells are alive, but the researchers believe that the jams later contribute to cell death..


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