A truncated PACT protein resulting from a frameshift mutation reported in movement disorder DYT16 triggers caspase...

Area of Science:

• Molecular Biology
• Cellular Stress Response
• Neurodegenerative Diseases

Background:

• Protein Activator (PACT) typically activates the PKR pathway in response to cellular stress.
• Dysfunctional PACT, due to mutations, is implicated in neurological disorders like dystonia.
• The interferon (IFN)-induced double-stranded (ds) RNA-activated protein kinase (PKR) pathway is crucial in cellular defense and can be dysregulated in disease.

Purpose of the Study:

• To investigate the biochemical properties and cellular effects of a frameshift (FS) mutant PACT protein found in early-onset dystonia 16 (DYT16).
• To elucidate the mechanism by which the FS mutant PACT protein impacts the PKR pathway and induces apoptosis.

Main Methods:

• Biochemical analysis of the FS mutant PACT protein's binding affinities (dsRNA, PKR, TRBP).
• Expression of fluorescently tagged FS mutant PACT in mammalian cells to observe aggregation and cellular effects.
• Assessment of caspase activation and dependence on PKR and PACT pathways.

Main Results:

• The FS mutant PACT protein fails to bind dsRNA or interact with PKR but retains binding to PACT and TRBP.
• Expressed FS mutant PACT protein forms aggregates in mammalian cells, inducing apoptosis.
• Apoptosis occurs through caspase activation, partly dependent on PKR and PACT, and also via PKR- and PACT-independent mechanisms.

Conclusions:

• The FS mutant PACT protein disrupts normal PACT function and can trigger apoptosis through mechanisms involving PKR pathway dysregulation.
• Interaction of the FS mutant PACT with TRBP can lead to PACT dissociation, PKR activation, and subsequent cell death.
• These findings highlight the role of protein aggregation and PKR activation in neurodegenerative conditions and suggest therapeutic targets.