5b83 | pdb_00005b83
Crystal structure of Optineurin UBAN in complex with linear ubiquitin
Structural highlights
Disease[OPTN_HUMAN] Amyotrophic lateral sclerosis;Congenital glaucoma. Primary open angle glaucoma 1E (GLC1E) [MIM:137760]: A form of primary open angle glaucoma (POAG). POAG is characterized by a specific pattern of optic nerve and visual field defects. The angle of the anterior chamber of the eye is open, and usually the intraocular pressure is increased. The disease is asymptomatic until the late stages, by which time significant and irreversible optic nerve damage has already taken place. Note=The disease is caused by mutations affecting the gene represented in this entry.[1] [2] [3] [4] [5] [6] Normal pressure glaucoma (NPG) [MIM:606657]: A primary glaucoma characterized by intraocular pression consistently within the statistically normal population range. Note=Disease susceptibility is associated with variations affecting the gene represented in this entry.[7] Amyotrophic lateral sclerosis 12 (ALS12) [MIM:613435]: A neurodegenerative disorder affecting upper motor neurons in the brain and lower motor neurons in the brain stem and spinal cord, resulting in fatal paralysis. Sensory abnormalities are absent. The pathologic hallmarks of the disease include pallor of the corticospinal tract due to loss of motor neurons, presence of ubiquitin-positive inclusions within surviving motor neurons, and deposition of pathologic aggregates. The etiology of amyotrophic lateral sclerosis is likely to be multifactorial, involving both genetic and environmental factors. The disease is inherited in 5-10% of the cases. Note=The disease is caused by mutations affecting the gene represented in this entry.[8] Function[UBC_HUMAN] Ubiquitin exists either covalently attached to another protein, or free (unanchored). When covalently bound, it is conjugated to target proteins via an isopeptide bond either as a monomer (monoubiquitin), a polymer linked via different Lys residues of the ubiquitin (polyubiquitin chains) or a linear polymer linked via the initiator Met of the ubiquitin (linear polyubiquitin chains). Polyubiquitin chains, when attached to a target protein, have different functions depending on the Lys residue of the ubiquitin that is linked: Lys-6-linked may be involved in DNA repair; Lys-11-linked is involved in ERAD (endoplasmic reticulum-associated degradation) and in cell-cycle regulation; Lys-29-linked is involved in lysosomal degradation; Lys-33-linked is involved in kinase modification; Lys-48-linked is involved in protein degradation via the proteasome; Lys-63-linked is involved in endocytosis, DNA-damage responses as well as in signaling processes leading to activation of the transcription factor NF-kappa-B. Linear polymer chains formed via attachment by the initiator Met lead to cell signaling. Ubiquitin is usually conjugated to Lys residues of target proteins, however, in rare cases, conjugation to Cys or Ser residues has been observed. When polyubiquitin is free (unanchored-polyubiquitin), it also has distinct roles, such as in activation of protein kinases, and in signaling.[9] [10] [OPTN_HUMAN] Plays an important role in the maintenance of the Golgi complex, in membrane trafficking, in exocytosis, through its interaction with myosin VI and Rab8. Links myosin VI to the Golgi complex and plays an important role in Golgi ribbon formation. Negatively regulates the induction of IFNB in response to RNA virus infection. Plays a neuroprotective role in the eye and optic nerve. Probably part of the TNF-alpha signaling pathway that can shift the equilibrium toward induction of cell death. May act by regulating membrane trafficking and cellular morphogenesis via a complex that contains Rab8 and hungtingtin (HD). May constitute a cellular target for adenovirus E3 14.7, an inhibitor of TNF-alpha functions, thereby affecting cell death.[11] [12] [13] Publication Abstract from PubMedOptineurin (OPTN) mutations cause neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) and glaucoma. Although the ALS-associated E478G mutation in the UBAN domain of OPTN reportedly abolishes its NF-kappaB suppressive activity, the precise molecular basis in ALS pathogenesis still remains unclear. Here we report that the OPTN-UBAN domain is crucial for NF-kappaB suppression. Our crystal structure analysis reveals that OPTN-UBAN binds linear ubiquitin with homology to NEMO. TNF-alpha-mediated NF-kappaB activation is enhanced in OPTN-knockout cells, through increased ubiquitination and association of TNF receptor (TNFR) complex I components. Furthermore, OPTN binds caspase 8, and OPTN deficiency accelerates TNF-alpha-induced apoptosis by enhancing complex II formation. Immunohistochemical analyses of motor neurons from OPTN-associated ALS patients reveal that linear ubiquitin and activated NF-kappaB are partially co-localized with cytoplasmic inclusions, and that activation of caspases is elevated. Taken together, OPTN regulates both NF-kappaB activation and apoptosis via linear ubiquitin binding, and the loss of this ability may lead to ALS. Linear ubiquitination is involved in the pathogenesis of optineurin-associated amyotrophic lateral sclerosis.,Nakazawa S, Oikawa D, Ishii R, Ayaki T, Takahashi H, Takeda H, Ishitani R, Kamei K, Takeyoshi I, Kawakami H, Iwai K, Hatada I, Sawasaki T, Ito H, Nureki O, Tokunaga F Nat Commun. 2016 Aug 24;7:12547. doi: 10.1038/ncomms12547. PMID:27552911[14] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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