Coiled-Coil Structures Mediate the Intercellular Propagation of Huntingtin

Huntington's Disease (HD) originates from the expansion of a polyglutamine (PolyQ) tract in the huntingtin protein (Htt), which can assume a coiled-coil fold (Cc). We previously found that Cc structures mediate the aggregation and toxicity of polyQ Htt. Since polyQ Htt aggregates were previously found to be internalized by cells, here we hypothesize that Cc structures might be implicated in the intercellular propagation of Htt aggregates. To test this hypothesis, we performed experiments using human cell lines expressing Htt proteins with different probabilities to acquire a Cc fold. We found that Htt with reduced Cc structures were released significantly less compared to Htt with intact Cc structures. We also found that Cc structures mediate the internalization of Htt proteins in recipient cells. Together, these results underline the importance of the Cc structure in the process of intercellular propagation of Htt polyQ aggregates and suggest that interfering with Cc formation might be a therapeutic strategy for HD.