OPTN (optineurin)-mediated selective autophagy prevents neurodegeneration due to herpesvirus infection

A cytoprotective role for optineurin during mycobacterial infection of macrophages

Autophagy has emerged as a critical innate immune mechanism for host elimination of intracellular pathogens, however, the role of the autophagy receptor Optineurin during mycobacterial infection is not fully understood. To address this lacuna, we infected bone marrow-derived macrophages (BMDMs) derived from Optn+/+ and Optn-/- mice with Mycobacterium smegmatis, and observed the infection outcome at sequential time points. While low multiplicity of infection (MOI) did not show any significant difference between BMDMs from the two groups, at high MOI Optn-/- mice-derived BMDMs showed significantly lower colony forming unit counts, as well as lower cell counts at 12 h and 24 h post-infection. Quantification of cell numbers and nuclear morphologies at various time points post-infection indicated a markedly higher cell death in the Optineurin-deficient macrophages. Optineurin-deficient BMDMs showed significantly lower levels of the autophagosomal protein LC3-II upon infection, indicating a potential role for Optineurin in regulating autophagy during mycobacterial infection. Moreover, when stimulated by bacterial LPS, Optineurin deficient macrophages, showed altered levels of the inflammatory cytokine pro-IL-1β. These observations taken together suggest a novel regulatory role for Optineurin during mycobacterial infection. Its deficiency leads to an impairment in macrophage responses, directly impacting the pathophysiology of infection.

From homeostasis to defense: Exploring the role of selective autophagy in innate immunity and viral infections

The process of autophagy, a conservative evolutionary mechanism, is responsible for the removal of surplus and undesirable cytoplasmic components, thereby ensuring cellular homeostasis. Autophagy exhibits a remarkable level of selectivity by employing a multitude of cargo receptors that possess the ability to bind both ubiquitinated cargoes and autophagosomes. In the context of viral infections, selective autophagy plays a crucial role in regulating the innate immune system. Notably, numerous viruses have developed strategies to counteract, evade, or exploit the antiviral effects of selective autophagy. This review encompasses the latest research progress of selective autophagy in regulating innate immunity and virus infectious.

Seneca Valley virus 3C protease cleaves OPTN (optineurin) to Impair selective autophagy and type I interferon signaling

Seneca Valley virus (SVV) causes vesicular disease in pigs, posing a threat to global pork production. OPTN (optineurin) is a macroautophagy/autophagy receptor that restricts microbial propagation by targeting specific viral or bacterial proteins for degradation. OPTN is degraded and cleaved at glutamine 513 following SVV infection via the activity of viral 3C protease (3C[pro]), resulting in N-terminal and a C-terminal OPTN fragments. Moreover, OPTN interacts with VP1 and targets VP1 for degradation to inhibit viral replication. The N-terminal cleaved OPTN sustained its interaction with VP1, whereas the degradation capacity targeting VP1 decreased. The inhibitory effect of N-terminal OPTN against SVV infection was significantly reduced, C-terminal OPTN failed to inhibit viral replication, and degradation of VP1 was blocked. The knockdown of OPTN resulted in reduced TBK1 activation and phosphorylation of IRF3, whereas overexpression of OPTN led to increased TBK1-IRF3 signaling. Additionally, the N-terminal OPTN diminished the activation of the type I IFN (interferon) pathway. These results show that SVV 3C[pro] targets OPTN because its cleavage impairs its function in selective autophagy and type I IFN production, revealing a novel model in which the virus develops diverse strategies for evading host autophagic machinery and type I IFN response for survival.Abbreviations: Co-IP: co-immunoprecipitation; GFP-green fluorescent protein; hpi: hours post-infection; HRP: horseradish peroxidase; IFN: interferon; IFNB/IFN-β: interferon beta; IRF3: interferon regulatory factor 3; LIR: LC3-interacting region; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MOI: multiplicity of infection; OPTN: optineurin; PBS: phosphate-buffered saline; SVV: Seneca Valley virus; SQSTM1: sequestosome 1; TAX1BP1: Tax1 binding protein 1; TBK1: TANK binding kinase 1; TCID50: 50% tissue culture infectious doses; UBAN: ubiquitin binding in TNIP/ABIN (TNFAIP3/A20 and inhibitor of NFKB/NF-kB) and IKBKG/NEMO; UBD: ubiquitin-binding domain; ZnF: zinc finger.

OPTN gene therapy increases autophagy and protects mitochondria in SOD1-G93A-expressing transgenic mice and cells

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by progressive motor neuron (MN) death. Mutation of the superoxide dismutase 1 (SOD1) gene, which results in abnormal protein aggregation, is one of the causes of familial ALS. Autophagic dysfunction occurs in SOD1-G93A mutant mice as the disease progresses, but the etiology of this disease is still unclear. Optineurin (OPTN) is an adaptor that is involved in autophagy and participates in aggrephagy and mitophagy. Previous studies have established that OPTN mutations contribute to diseases such as glaucoma and ALS. However, the function of OPTN in autophagy and mitophagy has not been intensively investigated in models of ALS. In this study, we assessed the beneficial effect of OPTN on autophagy and mitochondrial function by intrathecally injecting adeno-associated virus 9 (AAV9)-OPTN into SOD1-G93A transgenic mice and by administering lentivirus (LV)-OPTN to cells expressing the SOD1-G93A mutant protein. The expression of voltage-dependent anion channel 1 (VDAC1) was increased and autophagy was elevated after OPTN gene therapy, as shown by a lower level of p62 and a higher level of microtubule-associated protein 1A/1B-light chain 3 (LC3)-II. Moreover, using electron microscopy, we observed a hyperpolarized mitochondrial transmembrane potential and reversal of mitochondrial morphological abnormalities. Furthermore, the protein level of TANK-binding kinase 1 (TBK1) was increased, suggesting that mitophagy was increased. Our findings from both animal and cell line studies strongly suggest that OPTN gene therapy is a powerful strategy to increase autophagy and protect mitochondria to prevent the progression of ALS and could be effective in the treatment of ALS.

The Interplay of Genital Herpes with Cellular Processes: A Pathogenesis and Therapeutic Perspective

Genital herpes, primarily caused by herpes simplex virus-2 (HSV-2), remains a pressing global health concern. Its remarkable ability to intertwine with cellular processes, from harnessing host machinery for replication to subverting antiviral defenses like autophagy and programmed cell death, exemplifies the intricate interplay at the heart of its pathogenesis. While the biomedical community has extensively researched antiviral interventions, the efficiency of these strategies in managing HSV-2 remains suboptimal. Recognizing this, attention has shifted toward leveraging host cellular components to regulate HSV-2 replication and influence the cell cycle. Furthermore, innovative interventional strategies-including drug repurposing, microbivacs, connecting the host microbiome, and exploiting natural secondary metabolites-are emerging as potential game changers. This review summarizes the key steps in HSV-2 pathogenesis and newly discovered cellular interactions, presenting the latest developments in the field, highlighting existing challenges, and offering a fresh perspective on HSV-2's pathogenesis and the potential avenues for its treatment by targeting cellular proteins and pathways.

Optineurin in ocular herpes infection

Herpes Simplex Virus-1 (HSV-1) is a neurotropic virus that can infect humans in the eye and travel to the trigeminal ganglion to establish latency. HSV-1 causes various disease states in both the primary and secondary sites of infection including the eye and the nervous system. This DNA virus exploits various adaptive measures to infect host cells, hijack host cell proteins, evade host immune response and spread from cell-to-cell to avoid immune detection. Recent data suggest that Optineurin (OPTN), a host protein, is a key restriction factor that prevents cell-to-cell spread of HSV-1 and guards against serious damage to the nervous system during infection. In recent years OPTN has gained increased attention because of its involvement in cellular mechanisms that promote homeostasis and prevent neurodegeneration. At the center of it all is the role OPTN plays as a receptor for selective autophagy. This review summarizes our latest understanding of the viral lifecycle, disease pathologies, and OPTN-mediated protective mechanisms during HSV-1 infection of the eye and the nervous system. We specifically highlight recent discoveries that implicate OPTN as crucial in the prevention of ocular and neurodegenerative diseases.