Rare Daily Staff

Researchers at the University of Cologne’s Cluster of Excellence for Aging Research said that they identified a system blocking the accumulation of toxin protein aggregates, which are responsible for neurodegeneration, an important step towards understanding the mechanisms that cause Huntington’s disease.

Huntington’s disease is a neurodegenerative disorder that results in the death of brain cells, leading to uncontrolled body movement, loss of speech and psychosis. Mutations in the huntingtin gene cause the disease, resulting in the toxic aggregation of the huntingtin protein. The accumulation of these aggregates causes neurodegeneration and usually leads to the patient’s death within twenty years after the onset of the disease.

To examine the mechanisms underlying Huntington’s disease, neuroscientist David Vilchez and his team at CECAD used induced pluripotent stem cells (iPSC) from Huntington’s disease patients, which can differentiate into any cell type, such as neurons. iPSCs derived from patients with Huntington’s disease exhibit an ability to avoid the accumulation of toxic protein aggregates, a hallmark of the disease. Even though iPSCs express the mutant gene responsible for Huntington’s disease, no aggregates were found.

The researchers identified a protein called UBR5 as a protective mechanism for the cells, promoting the degradation of mutant huntingtin. They said these findings can contribute to a better understanding of Huntington’s disease and could be a step toward developing further treatment in patients. The results were published in the journal Nature Communications.

The researchers found that huntingtin can be degraded by the cellular disposal system known as the proteasome. However, this system is defective in the neurons of Huntington’s disease patients, which leads to the aberrant aggregation of the mutant huntingtin protein. Vilchez and his team found that UBR5 is increased in pluripotent stem cells to accelerate the degradation of huntingtin in the cells.

To examine the role of UBR5 in the regulation of the mutant huntingtin gene, they reduced the levels of UBR5 and could immediately see an accumulation of aggregated proteins in iPSCs.

“This was striking to see,” said Vilchez. “From nothing, the cells went to huge amounts of aggregates.”

August 23, 2018
Photo: David Vilchez, neuroscientist at the University of Cologne’s Cluster of Excellence for Aging Research

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