Involvement of ubiquilin-1 transcript variants in protein degradation and accumulation.

Controlled management of protein levels and quality is essential for normal cellular function. Specific molecular chaperones and foldases monitor the levels and assist correct folding of proteins. The ubiquitin-proteasome system recognizes and degrades misfolded proteins that can otherwise be harmful to cells. However, when misfolded or aggregated proteins excessively accumulate, they may be sequestered to the microtubule-organizing center to form aggresomes. These may then be removed from cells by autophagocytosis. Abnormal protein accumulation and aggregation is a common hallmark of many neurodegenerative diseases. In a recent study, we provide evidence that specific transcript variants (TVs) of ubiquilin-1, which are genetically and functionally associated to Alzheimer's disease (AD), regulate proteasomal and aggresomal targeting of presenilin-1 (PS1), a key player in AD pathogenesis. Our study together with current data provide interesting implications for ubiquilin-1 and its TVs in the pathogenesis of AD and other neurodegenerative diseases involving abnormal protein aggregation.