Effects of STAU1/staufen1 on autophagy in neurodegenerative diseases

The double-stranded RNA-binding protein, STAU1 (staufen double-stranded RNA binding protein 1) is a multifunctional protein that localizes to stress granules (SGs). We had previously found that STAU1 is overabundant in fibroblast cell lines from patients with spinocerebellar ataxia type 2 (SCA2) or amyotrophic lateral sclerosis (ALS)-frontotemporal dementia (FTD) as well as in animal models of these diseases. STAU1 overabundance is post-transcriptional and associated with MTOR hyperactivation and links SG formation with macroautophagy/autophagy. Reducing STAU1 levels in mice with ALS mutations normalizes MTOR activity and autophagy-related marker proteins. We also see increased STAU1 levels in HEK293 cells expressing C9orf72-relevant dipeptide repeats (DPRs), and DPRs are not observed in cells where STAU1 is targeted by RNAi. Overexpression of STAU1 in HEK293 cells increases MTOR translation by directly interacting with the MTOR mRNA 5'UTR, activating downstream targets and impairing autophagic flux. STAU1 may constitute a novel target to modulate MTOR activity and autophagy and for the treatment of neurodegenerative diseases.