Optineurin is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
[Optineurin[/proteins/optineurin (OPTN, optic neuropathy-inducing protein) is a multifunctional adaptor protein that plays essential roles in selective [autophagy[/entities/autophagy, vesicular trafficking, [NF-κB[/entities/nf-kb signaling regulation, and innate immune signaling. Encoded by the [OPTN[/genes/optn gene on chromosome 10p13, optineurin functions as a selective autophagy receptor for damaged [mitochondria[/entities/mitochondrial-dynamics, intracellular bacteria, and protein aggregates, working in close partnership with [TBK1[/proteins/TBK1 kinase.[1] Mutations in OPTN cause both familial [ALS[/diseases/als and primary open-angle glaucoma (POAG), establishing optineurin as a critical link between neurodegeneration and selective autophagy dysfunction.[2] The convergence of OPTN and [TBK1[/proteins/TBK1 mutations in ALS has illuminated the central importance of autophagy receptor-kinase signaling in [motor neuron[/cell-types/motor-neurons survival.
¶ Structure and Domains
Optineurin is a 577-amino acid, ~67 kDa cytoplasmic protein with multiple protein-protein interaction domains:[3]
| Property |
Details |
| Gene |
[OPTN[/genes/optn |
| UniProt ID |
Q96CV9 |
| Molecular Weight |
~67 kDa |
| Amino Acids |
577 |
| Subcellular Localization |
Cytoplasm, Golgi apparatus, autophagosomes, mitochondrial contact sites |
| Protein Family |
Selective autophagy receptors (SQSTM1-like) |
¶ Key Functional Domains
- Coiled-coil domains (CC1, CC2): Mediate self-dimerization and interactions with myosin VI, Rab8, and [huntingtin[/proteins/huntingtin. The CC1 domain (residues 78–185) contains the [TBK1[/proteins/TBK1-binding region essential for kinase recruitment. CC1 also mediates optineurin homo-oligomerization, which is important for forming multivalent autophagy receptor complexes
- LIR (LC3-interacting region) motif (residue 178): Contains the FEVI motif that binds LC3/GABARAP on autophagosomal membranes. TBK1-mediated phosphorylation at Ser177 dramatically enhances LIR-LC3 binding affinity, increasing it by ~20-fold[4]
- UBAN (ubiquitin-binding in ABIN and NEMO) domain (residues 412–520): Binds linear (M1-linked) and K63-linked polyubiquitin chains with high specificity. The UBAN domain forms a parallel coiled-coil dimer that creates a symmetric ubiquitin-binding interface. Critical for both [NF-κB[/entities/nf-kb signaling regulation and cargo recognition in selective autophagy[5]
- Zinc finger domain (C-terminal): Involved in protein-protein interactions and cargo recognition. Contains a C2H2-type zinc finger motif that contributes to ubiquitin binding cooperativity
- NEMO-like domain: Shares structural homology with NEMO ([NF-κB[/entities/nf-kb essential modulator), reflecting optineurin's evolutionary relationship and role in [NF-κB[/entities/nf-kb signaling
Optineurin function is extensively regulated by post-translational modifications:
| Modification |
Site |
Kinase/Enzyme |
Effect |
| Phosphorylation |
Ser177 |
[TBK1[/proteins/TBK1 |
Enhances LIR-LC3 binding (~20-fold) |
| Phosphorylation |
Ser473 |
TBK1 |
Enhances UBAN-ubiquitin binding |
| Phosphorylation |
Ser513 |
TBK1 |
Promotes IRF3 activation |
| Ubiquitination |
Multiple Lys |
HACE1, others |
Regulates protein stability and interactions |
| Deubiquitination |
Multiple Lys |
CYLD |
Negative regulation of [NF-κB[/entities/nf-kb signaling |
Optineurin functions as a selective autophagy receptor for multiple cargo types:[6]
[mitophagy[/mechanisms/mitophagy: Optineurin is recruited to damaged mitochondria following [PINK1[/proteins/pink1-protein/[Parkin[/proteins/parkin-mediated ubiquitination of outer mitochondrial membrane proteins. The UBAN domain recognizes ubiquitin chains on mitochondria, while the LIR motif recruits autophagosomes. [TBK1[/proteins/TBK1 phosphorylation amplifies this process, creating a feed-forward signaling cascade that ensures efficient engulfment of damaged mitochondria. Optineurin is considered the dominant autophagy receptor for Parkin-dependent mitophagy in several cell types, more important than [p62/SQSTM1[/proteins/p62-sqstm1 or NDP52 in this context.
Xenophagy: Optineurin is a primary receptor for antibacterial autophagy, targeting ubiquitinated intracellular bacteria (Salmonella, Mycobacterium) for autophagic destruction. TBK1-mediated phosphorylation at Ser177 is required for efficient xenophagy.
Aggrephagy: Optineurin participates in clearance of ubiquitinated protein aggregates, complementing [p62/SQSTM1[/proteins/p62-sqstm1 and NBR1 in the autophagic degradation of misfolded proteins. This is particularly relevant in [motor neurons[/cell-types/motor-neurons where [TDP-43[/proteins/tdp-43 and [SOD1[/proteins/sod1-protein aggregates accumulate in ALS.
The optineurin-TBK1 interaction is central to selective autophagy. A 2024 study in The EMBO Journal revealed that optineurin provides a physical mitophagy contact site for TBK1 activation:[7]
- Optineurin is recruited to ubiquitinated damaged mitochondria via its UBAN domain
- Optineurin simultaneously contacts pre-autophagosomal structures (PAS) via its LIR motif
- At this contact site between damaged mitochondria and autophagosome formation sites, TBK1 is activated via hetero-autophosphorylation
- Activated TBK1 phosphorylates optineurin at Ser177 and Ser473, dramatically enhancing both LC3 binding and ubiquitin binding
- This creates a positive feedback loop: more optineurin recruitment → more TBK1 activation → stronger optineurin-cargo binding → accelerated autophagosome formation
- TBK1 also phosphorylates other autophagy receptors ([p62/SQSTM1[/proteins/p62-sqstm1, NDP52), amplifying the autophagic response
This contact site model explains why both OPTN and TBK1 mutations cause ALS: disruption at either end of the optineurin-TBK1 axis impairs the mitophagy contact site and prevents efficient clearance of damaged mitochondria.
Optineurin participates in [liquid-liquid phase separation[/mechanisms/liquid-liquid-phase-separation (LLPS), forming dynamic biomolecular condensates that are critical for autophagy function. A 2024 study demonstrated that autophagy adaptors including optineurin form sheet-like liquid condensates on damaged mitochondria during Parkin-dependent mitophagy:[8]
- Optineurin-ubiquitin condensates are dynamic and liquid-like, undergoing fusion and fission
- The fluidity of these condensates is essential for mitophagy activity — reducing condensate fluidity suppresses ATG9 vesicle recruitment and impairs mitophagy
- ALS-associated mutations (E478G) in the UBAN domain disrupt condensate formation and dynamics
- TBK1 phosphorylation modulates condensate properties, potentially by altering multivalent interactions between optineurin, ubiquitin, and LC3
This connects optineurin dysfunction to the broader theme of pathological phase transitions in neurodegenerative diseases, where proteins like [TDP-43[/proteins/tdp-43 and [FUS[/proteins/fus-protein undergo aberrant phase separation and aggregation.
Optineurin negatively regulates [NF-κB[/entities/nf-kb signaling by competing with NEMO for ubiquitin chain binding. Through its UBAN domain, optineurin sequesters linear ubiquitin chains, preventing NEMO-mediated [NF-κB[/entities/nf-kb activation. Loss of optineurin function leads to enhanced [NF-kB[/entities/nf-kb-driven [neuroinflammation[/mechanisms/neuroinflammation, chronic inflammatory signaling, and increased production of pro-inflammatory cytokines including TNF-alpha, IL-1beta, and IL-6.
Optineurin interacts with Rab8, myosin VI, and [huntingtin[/proteins/huntingtin to regulate:
- Golgi maintenance and post-Golgi trafficking
- Secretory vesicle transport
- Receptor recycling and endosomal trafficking
- Exocytosis and membrane protein delivery
Beyond NF-kB, optineurin plays roles in type I interferon signaling through the [cGAS-STING] pathway. Optineurin promotes [STING[/entities/sting-pathway-mediated IRF3 activation via TBK1, contributing to antiviral defense and sterile inflammatory responses. Disruption of this function by ALS-causing mutations may contribute to dysregulated [interferon signaling] in Motor [Neuron[/entities/neurons Disease.[9]
OPTN mutations account for approximately 1–4% of familial [ALS[/diseases/als cases and some sporadic cases:[2]
Key ALS mutations:
- E478G: Located in the UBAN domain, abolishes ubiquitin binding. Causes aggressive ALS with [TDP-43[/proteins/tdp-43-positive inclusions. Disrupts condensate formation on damaged mitochondria
- Q398X: Truncation mutation removing the UBAN domain and zinc finger. Causes severe ALS
- E696K: Zinc finger mutation with reduced autophagy function
- R96L: Impairs optineurin self-dimerization and TBK1 interaction
- Homozygous deletions: Complete OPTN loss causes ALS, demonstrating that loss-of-function is sufficient for disease
Pathogenic mechanisms:
- Impaired [mitophagy[/mechanisms/mitophagy leading to accumulation of damaged mitochondria and [oxidative stress[/mechanisms/oxidative-stress
- Defective clearance of [TDP-43[/proteins/tdp-43 and [SOD1[/proteins/sod1-protein aggregates via aggrephagy
- Enhanced [neuroinflammation[/mechanisms/neuroinflammation through derepressed NF-kB signaling
- Disrupted vesicular trafficking and Golgi fragmentation in [motor neurons[/cell-types/motor-neurons
- Impaired phase separation dynamics at mitophagy contact sites
The convergence of OPTN, [TBK1[/proteins/TBK1, [p62/SQSTM1[/proteins/p62-sqstm1, and [VCP[/genes/vcp mutations in ALS establishes autophagy dysfunction as a central disease mechanism, defining a "selective autophagy" subtype of ALS.
OPTN mutations were first identified as a cause of normal-tension glaucoma (NTG), a neurodegenerative disease of retinal ganglion cells (RGCs):[10]
- E50K mutation: The most studied glaucoma-associated variant, causing enhanced TBK1 interaction and aberrant autophagosome formation. E50K OPTN induces RGC death through excessive autophagy activation and ER stress[11]
- M98K mutation: Risk factor for NTG, activating TBK1-dependent autophagy and retinal cell death
- Shared ALS-glaucoma mechanisms: Both conditions involve autophagy dysregulation, mitochondrial dysfunction, and selective neuronal death, suggesting a shared neurodegenerative mechanism linking long-projecting [neurons[/entities/neurons (motor [neurons[/entities/neurons and retinal ganglion cells)
- [Huntington's disease[/mechanisms/huntington-pathway: Optineurin interacts directly with [huntingtin[/proteins/huntingtin protein; mutant [huntingtin[/proteins/huntingtin disrupts optineurin-mediated vesicular trafficking and Golgi maintenance
- [Alzheimer's disease[/diseases/alzheimers: Optineurin is found in neurofibrillary tangles and dystrophic neurites in AD brain, suggesting involvement in tau]/proteins/tau] pathology. Optineurin-mediated mitophagy may be impaired in AD [neurons[/entities/neurons
- [Parkinson's disease[/diseases/parkinsons: OPTN participates in [PINK1[/proteins/pink1-protein/[Parkin[/proteins/parkin-dependent [mitophagy[/mechanisms/mitophagy, and OPTN deficiency may contribute to [dopaminergic neuron[/cell-types/dopaminergic-neurons vulnerability in PD
- [Paget's disease of bone[/diseases: OPTN mutations (D474N) are associated with Paget's disease, linking optineurin to osteoclast NF-kB signaling
- Crohn's disease: Rare OPTN variants are associated with inflammatory bowel disease, consistent with its role in xenophagy and immune regulation
- OPTN-null mice develop late-onset motor axon degeneration, gliosis, and neurofilament abnormalities, but with slower progression than human ALS[12]
- Conditional deletion of OPTN in [neurons[/entities/neurons causes accumulation of damaged mitochondria, increased [oxidative stress[/mechanisms/oxidative-stress, and progressive motor dysfunction
- OPTN knockout mice crossed with SOD1-G93A mice show accelerated disease progression, demonstrating genetic interaction
- E50K OPTN knock-in mice develop progressive retinal ganglion cell loss resembling normal-tension glaucoma
- Enhanced TBK1 activation and autophagosome accumulation are observed in RGCs
- These mice have been used to test TBK1 inhibitors and autophagy modulators as potential glaucoma therapies
- Loss of OPTN in mice leads to accumulation of [TDP-43[/proteins/tdp-43-positive cytoplasmic inclusions in spinal motor [neurons[/entities/neurons
- This demonstrates that OPTN-dependent autophagy is required for [TDP-43[/entities/tdp-43 clearance, connecting the two most common pathological hallmarks of ALS
- TBK1 activators: Small molecules enhancing TBK1-OPTN signaling to boost selective autophagy and mitophagy. AZVS-1811 is a TBK1 activator in preclinical development
- Gene therapy: AAV-mediated OPTN overexpression in preclinical glaucoma and ALS models has shown neuroprotective effects in retinal ganglion cells and motor [neurons[/entities/neurons
- [autophagy[/entities/autophagy modulators: Compounds enhancing OPTN-dependent mitophagy for neuroprotection, including rapamycin analogs and [TFEB[/entities/tfeb activators
- Anti-inflammatory strategies: Targeting OPTN-NF-kB axis to reduce neuroinflammation while preserving autophagy function
- Condensate modulators: Emerging approaches to restore normal phase separation dynamics at mitophagy contact sites
- [STING[/entities/sting-pathway pathway modulation: Targeting the OPTN–TBK1–[STING[/entities/sting-pathway axis to reduce [neuroinflammation[/mechanisms/neuroinflammation while maintaining autophagy
The study of Optineurin has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
- [Wild et al., Phosphorylation of the autophagy receptor optineurin restricts Salmonella growth, Science (2011)]https://pubmed.ncbi.nlm.nih.gov/21617041/)
- [Maruyama et al., Mutations of optineurin in amyotrophic lateral sclerosis, Nature (2010)]https://pubmed.ncbi.nlm.nih.gov/20428114/)
- [Ying & Bhatt, Optineurin — multifunctional roles in diseases and gene therapy, Trends in Molecular Medicine (2016)]https://pubmed.ncbi.nlm.nih.gov/27693724/)
- [Richter et al., Phosphorylation of OPTN by TBK1 enhances its binding to Ub chains, PNAS (2016)]https://doi.org/10.1073/pnas.1523926113)
- [Li et al., Structural insights into the ubiquitin recognition by OPTN and its regulation by TBK1, Autophagy (2018)]https://pubmed.ncbi.nlm.nih.gov/29130380/)
- [Lazarou et al., The ubiquitin kinase PINK1 recruits autophagy receptors to induce mitophagy, Nature (2015)]https://pubmed.ncbi.nlm.nih.gov/25417166/)
- [Yamano et al., Optineurin provides a mitophagy contact site for TBK1 activation, The EMBO Journal (2024)]https://doi.org/10.1038/s44318-024-00036-1)
- [Yamano et al., Autophagy adaptors mediate Parkin-dependent mitophagy by forming sheet-like liquid condensates, The EMBO Journal (2024)]https://doi.org/10.1038/s44318-024-00272-5)
- [Bakshi et al., Structural and functional perspectives of optineurin in autophagy, immune signaling, and cancer, Cells (2025)]https://doi.org/10.3390/cells14221746)
- [Rezaie et al., Adult-onset primary open-angle glaucoma caused by mutations in optineurin, Science (2002)]https://pubmed.ncbi.nlm.nih.gov/11834836/)
- [Minegishi et al., Enhanced optineurin E50K-TBK1 interaction evokes protein insolubility and initiates POAG, Human Molecular Genetics (2013)]https://pubmed.ncbi.nlm.nih.gov/23918786/)
- [Ito et al., RIPK1 mediates axonal degeneration by promoting inflammation and necroptosis in ALS, Science (2016)]https://pubmed.ncbi.nlm.nih.gov/27576665/)
- [Nakazawa et al., Linear ubiquitination is involved in the pathogenesis of optineurin-associated ALS, Nature Communications (2016)]https://pubmed.ncbi.nlm.nih.gov/27035970/)
- [Li et al., Structural insights into the interaction of optineurin and TBK1, Nature Communications (2016)]https://doi.org/10.1038/ncomms12708)