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J Cell Sci. 2013 Jan 15;126(Pt 2):580-92. doi: 10.1242/jcs.114926. Epub 2012 Nov 23.

Ubiquitin-independent function of optineurin in autophagic clearance of protein aggregates.

Author information

1
Department of Immunology and Medical Genetics, School of Medicine, University of Split, Soltanska 2, 21000 Split, Croatia.

Abstract

Aggregation of misfolded proteins and the associated loss of neurons are considered a hallmark of numerous neurodegenerative diseases. Optineurin is present in protein inclusions observed in various neurodegenerative diseases including amyotrophic lateral sclerosis (ALS), Huntington's disease, Alzheimer's disease, Parkinson's disease, Creutzfeld-Jacob disease and Pick's disease. Optineurin deletion mutations have also been described in ALS patients. However, the role of optineurin in mechanisms of protein aggregation remains unclear. In this report, we demonstrate that optineurin recognizes various protein aggregates via its C-terminal coiled-coil domain in a ubiquitin-independent manner. We also show that optineurin depletion significantly increases protein aggregation in HeLa cells and that morpholino-silencing of the optineurin ortholog in zebrafish causes the motor axonopathy phenotype similar to a zebrafish model of ALS. A more severe phenotype is observed when optineurin is depleted in zebrafish carrying ALS mutations. Furthermore, TANK1 binding kinase 1 (TBK1) is colocalized with optineurin on protein aggregates and is important in clearance of protein aggregates through the autophagy-lysosome pathway. TBK1 phosphorylates optineurin at serine 177 and regulates its ability to interact with autophagy modifiers. This study provides evidence for a ubiquitin-independent function of optineurin in autophagic clearance of protein aggregates as well as additional relevance for TBK1 as an upstream regulator of the autophagic pathway.

PMID:
23178947
PMCID:
PMC3654196
DOI:
10.1242/jcs.114926
[Indexed for MEDLINE]
Free PMC Article

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