Optineurin Is Required for CYLD-Dependent Inhibition of TNFα-Induced NF-κB Activation

Abstract

The nuclear factor kappa B (NF-κB) regulates genes that function in diverse cellular processes like inflammation, immunity and cell survival. The activation of NF-κB is tightly controlled and the deubiquitinase CYLD has emerged as a key negative regulator of NF-κB signalling. Optineurin, mutated in certain glaucomas and amyotrophic lateral sclerosis, is also a negative regulator of NF-κB activation. It competes with NEMO (NF-κB essential modulator) for binding to ubiquitinated RIP (receptor interacting protein) to prevent NF-κB activation. Recently we identified CYLD as optineurin-interacting protein. Here we have analysed the functional significance of interaction of optineurin with CYLD. Our results show that a glaucoma-associated mutant of optineurin, H486R, is altered in its interaction with CYLD. Unlike wild-type optineurin, the H486R mutant did not inhibit tumour necrosis factor α (TNFα)-induced NF-κB activation. CYLD mediated inhibition of TNFα-induced NF-κB activation was abrogated by expression of the H486R mutant. Upon knockdown of optineurin, CYLD was unable to inhibit TNFα-induced NF-κB activation and showed drastically reduced interaction with ubiquitinated RIP. The level of ubiquitinated RIP was increased in optineurin knockdown cells. Deubiquitination of RIP by over-expressed CYLD was abrogated in optineurin knockdown cells. These results suggest that optineurin regulates NF-κB activation by mediating interaction of CYLD with ubiquitinated RIP thus facilitating deubiquitination of RIP.

Optineurin mediates negative regulation of Rab8 function by TBC1D17, a GTPase activating protein

“…The N-terminal non-catalytic domain of TBC1D17 is involved in direct interaction with optineurin. Recent studies suggest that optineurin can act as an adaptor protein facilitating assembly of multimolecular signaling complexes (del Toro et al, 2009;Nagabhushana et al, 2011;Sahlender et al, 2005;Wild et al, 2011). In accordance with its emerging role as an adaptor protein, our results show that the binding site of TBC1D17 for optineurin (aa 209-411) is close to the Rab8-binding site (aa 141-209) reported earlier (Hattula and Peranen, 2000).…”

“…It is involved in regulating many cellular functions such as vesicular trafficking from the Golgi to plasma membrane (Sahlender et al, 2005), endocytic trafficking (Au et al, 2007;Nagabhushana et al, 2010) and signaling leading to NF-kB activation (Nagabhushana et al, 2011;Zhu et al, 2007). Mutations in optineurin are associated with certain glaucomas and amyotrophic lateral sclerosis (Maruyama et al, 2010;Rezaie et al, 2002).…”

Toward an integrative view of Optineurin functions

“…Through its interaction with TAX1BP1, A20 or CYLD, Optn may therefore act as an inhibitor of the antiviral signaling pathway by targeting component of this pathway (such as TBK1) to deubiquitinase enzymes. 10,14,15 Optn function in the host defense to bacterial infection. Connection between the antiviral immune system and host defense mechanisms against bacteria has been demonstrated by the inability of cells deficient in TBK1 to restrict Salmonella enterica proliferation compared with wild-type cells.…”

From the Cover: Alterations in Optineurin Expression and Localization in Pre-clinical Parkinson’s Disease Models

“…OPTN expression is known to be regulated by the autophagy regulator transcription factor EB (TFEB) and the inflammatory cytokine TNF-alpha (Nagabhushana et al, 2011;Visvikis et al, 2014). Both autophagic dysfunction and neuroinflammation occur in PD and are linked to pathogenesis (Macchi et al, 2015;Tan et al, 2014).…”