Efficacy, Safety, and Tolerability of Inclisiran in Patients With Homozygous Familial Hypercholesterolemia: Results From the ORION-5 Randomized Clinical Trial.

BACKGROUND: Homozygous familial hypercholesterolemia is a genetic disease characterized by extremely high levels of low-density lipoprotein cholesterol (LDL-C) and a high risk of premature cardiovascular events. The proof-of-concept study ORION-2 (A Study of Inclisiran in Participants With Homozygous Familial Hypercholesterolemia) showed that inclisiran, a small interfering RNA that prevents production of the hepatic PCSK9 protein (proprotein convertase subtilisin/kexin type 9), could lead to durable reductions in LDL-C levels when added to statins and ezetimibe in patients with homozygous familial hypercholesterolemia. METHODS: ORION-5 was a phase 3, 2-part, multicenter study in 56 patients with homozygous familial hypercholesterolemia and elevated LDL-C levels despite maximum tolerated doses of LDL-C-lowering therapies with or without lipoprotein apheresis. Patients eligible for part 1 (double-blind, 6 months) were randomized 2:1 to receive either 300 mg of inclisiran sodium (equivalent to 284 mg of inclisiran) or placebo. Placebo-treated patients from part 1 were transitioned to inclisiran in part 2 (open-label, 18 months). The primary end point was the percentage change in LDL-C levels from baseline to day 150. RESULTS: The mean age of the patients was 42.7 years, and 60.7% were women. The mean baseline LDL-C levels were 294.0 mg/dL and 356.7 mg/dL in the inclisiran and placebo groups, respectively. The placebo-corrected percentage change in LDL-C level from baseline to day 150 was -1.68% (95% CI, -29.19% to 25.83%; P=0.90), and the difference was not statistically significant between the inclisiran and placebo groups. The placebo-corrected percentage change in PCSK9 levels from baseline to day 150 was -60.6% with inclisiran treatment (P<0.0001); this was sustained throughout the study, confirming the effect of inclisiran on its biological target of PCSK9. No statistically significant differences between the inclisiran and placebo groups were observed in the levels of other lipids and lipoproteins (apolipoprotein B, total cholesterol, and non-high-density lipoprotein cholesterol). Adverse events and serious adverse events did not differ between the inclisiran and placebo groups throughout the study. CONCLUSIONS: Inclisiran treatment did not reduce LDL-C levels in patients with homozygous familial hypercholesterolemia despite substantial lowering of PCSK9 levels. Inclisiran was well-tolerated, and the safety findings were consistent with previously reported studies and the overall safety profile. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03851705.

Nonsteroidal anti-inflammatory drug-sparing effect of secukinumab in patients with radiographic axial spondyloarthritis: 4-year results from the MEASURE 2, 3 and 4 phase III trials.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used to reduce pain and inflammation, and are considered the cornerstone of pharmacological intervention in patients with radiographic axial spondyloarthritis (r-axSpA); however, the long-term use of NSAIDs is debatable due to their restricted therapeutic potential and the risk of side effects and complications. Therefore, reduction in NSAID intake is desirable in r-axSpA patients. Here, we report the long-term NSAID-sparing effect of secukinumab over 4 years in patients with r-axSpA. This post hoc analysis pooled data from 3 secukinumab trials (MEASURE 2-4) for each secukinumab maintenance dose of 150 and 300 mg, regardless of the loading dose regimen being i.v. or s.c. NSAID intake was evaluated prospectively using the Assessment of SpondyloArthritis International Society (ASAS)-NSAID score. Patients with an ASAS-NSAID score > 0 at baseline were analysed. NSAID-sparing endpoints included the mean change in the ASAS-NSAID score, the proportion of patients achieving 50% reduction, and the proportion of patients with an ASAS-NSAID score < 10. Percentages of patients who achieved BASDAI ≤ 2 were also assessed. Overall, 562 patients were included in this pooled analysis (secukinumab: 150 mg, N = 467; 300 mg, N = 95). The mean ASAS-NSAID score decreased with time in both the secukinumab 150 mg and 300 mg dose groups. The proportion of patients who achieved 50% reduction in the ASAS-NSAID score and clinically meaningful reduction of ASAS-NSAID score < 10 increased with time in both dose groups and in both low and high NSAID intake patients. The percentage of patients with a clinically relevant improvement (BASDAI ≤ 2) was consistently higher in patients with an ASAS-NSAID score < 10 than in patients with an ASAS-NSAID score ≥ 10. Secukinumab provided sustained, long-term NSAID-sparing effects in patients with r-axSpA for up to 4 years of treatment, as measured using the ASAS-NSAID score. Trial registered at clinicaltrials.gov: NCT01649375 ( https://clinicaltrials.gov/ct2/show/NCT01649375 ); NCT02008916 ( https://clinicaltrials.gov/ct2/show/NCT02008916 ); NCT02159053 ( https://clinicaltrials.gov/ct2/show/NCT02159053 ).

Secukinumab shows sustained efficacy and low structural progression in ankylosing spondylitis: 4-year results from the MEASURE 1 study.

OBJECTIVE: To evaluate the effect of secukinumab, a fully human anti-interleukin-17A monoclonal antibody, on efficacy, imaging outcomes, and safety through 4 years (208 weeks) in patients with ankylosing spondylitis. METHODS: Patients opting to enrol had completed 2 years' treatment in the MEASURE 1 core study with subcutaneous secukinumab 150 or 75 mg every 4 weeks (q4Wk), following intravenous loading to Week (Wk) 4, or placebo treatment to Wk16/24. Up-titration from secukinumab 75-150 mg q4Wk was permitted following a protocol amendment. Efficacy is reported for patients originally randomized to secukinumab. Radiographic changes were assessed using the modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) and changes in MRI measures of inflammation using the Berlin scoring method. Safety and tolerability were evaluated. RESULTS: Among 274 extension study participants, 89.7% (78/87) and 93.0% (93/100) originally randomized to secukinumab 150 and 75 mg, respectively, completed 208Wk. Through Wk208, Assessment of Spondyloarthritis International Society 20/40 (observed) were 79.7%/60.8% (150 mg), 71.0%/43.5% (75 mg) and 80.0%/76% (up-titrators; n = 25). Mean (s.d.) changes in mSASSS were 1.2 (3.91) (150 mg), 1.8 (4.32) (75 mg) and 1.6 (5.67) (up-titrators). No radiographic progression (mSASSS change from Baseline < 2) was observed in 79% of patients receiving either secukinumab dose. Exposure-adjusted incidence rates per 100 patient-years were: serious infections (1.0), Candida infections (0.4), Crohn's disease (0.6), ulcerative colitis (0.2), and malignant/unspecified tumours (0.5), with no new safety signals. CONCLUSION: Through 4 years, secukinumab provided sustained efficacy on signs and symptoms, and MRI outcomes, a low rate of radiographic progression and a consistent safety profile. TRIAL REGISTRATION: NCT01863732.

Long-term effects of interleukin-17A inhibition with secukinumab in active ankylosing spondylitis: 3-year efficacy and safety results from an extension of the Phase 3 MEASURE 1 trial.

OBJECTIVES: Secukinumab, a fully human anti-IL-17A monoclonal antibody, provided rapid and sustained improvements in signs and symptoms of ankylosing spondylitis (AS) over 2 years in the Phase 3 MEASURE 1 trial. Here, we report efficacy and safety after 3 years of treatment. METHODS: AS subjects completing 2 years of treatment every 4 weeks with subcutaneous secukinumab 150 or 75 mg (following intravenous loading or initial placebo treatment to 16/24 weeks) entered a separate 3-year extension study (NCT01863732). Assessments included ASAS20/40, ASAS5/6, BASDAI, BASDAI 50, BASFI, BASMI, SF-36 physical component summary, ASAS partial remission and ASDAS-CRP. Results were also analysed by prior anti-TNF treatment status. RESULTS: Among 290 subjects completing the core trial, 274 entered the extension study, with 260 subjects (94.9%) completing 156 weeks of treatment. ASAS20/40 response (observed) was 80.2%/61.6% in the IV→150 mg group and 75.5%/50.0% in the IV→75 mg group after 156 weeks. Sustained improvements were also seen in BASDAI, BASFI, BASMI and across all other endpoints regardless of previous exposure to anti-TNF agents. Mean secukinumab exposure was 964.3 days (137.8 weeks). Discontinuation rates were low, and secukinumab had a favourable safety profile, consistent with previous reports. Exposure-adjusted incidence rates for serious infections, Candida infections, Crohn's disease, ulcerative colitis, malignant/unspecified tumours, and adjudicated major adverse cardiac events were 1.1, 0.4, 0.5, 0.1, 0.5 and 0.7 per 100 subject-years, respectively. CONCLUSIONS: Secukinumab provided sustained efficacy in signs, symptoms and physical function in subjects with AS over 3 years. No new safety signals were observed.

Inclisiran administration potently and durably lowers LDL-C over an extended-term follow-up: the ORION-8 trial.

AIMS: Data describing the long-term efficacy and tolerability of inclisiran are limited. This was explored in ORION-8, an open-label extension of preceding Phase 2 and Phase 3 placebo-controlled and open-label extension trials. METHODS AND RESULTS: Following completion of the parent trial, adult patients with atherosclerotic cardiovascular disease (ASCVD), ASCVD risk equivalent, or heterozygous familial hypercholesterolaemia received open-label inclisiran twice yearly (after initial and 3-month doses) until Day 990, followed by an end-of-study visit at Day 1080 or ≥ 90 days after the last dose. The study endpoints included the proportion of patients achieving pre-specified low-density lipoprotein cholesterol (LDL-C) goals [ASCVD: < 1.8 mmol/L (< 70 mg/dL); ASCVD risk equivalent: < 2.6 mmol/L (< 100 mg/dL)], percentage and absolute changes in LDL-C at end-of-study, and safety of inclisiran. Of 3274 patients, 2446 (74.7%) were followed until end-of-study. Mean age was 64.9 ± 9.9 years, 82.7% (n = 2709) had ASCVD, and mean baseline LDL-C was 2.9 ± 1.2 mmol/L. Mean cumulative exposure to inclisiran (including parent trials) was 3.7 years; maximum exposure was 6.8 years. With inclisiran, 78.4% [95% confidence interval (CI): 76.8, 80.0] of patients achieved pre-specified LDL-C goals and mean percentage change in LDL-C was -49.4% (95% CI: -50.4, -48.3). No attenuation of LDL-C lowering over time was observed. Treatment-emergent adverse events at injection site (all mild/moderate) occurred in 5.9% of the patients. Inclisiran-associated anti-drug antibodies were infrequent (5.5%) and had no impact on the efficacy or safety of inclisiran. No new safety signals were identified. CONCLUSION: In the largest and longest follow-up to date with >12 000 patient-years exposure, inclisiran demonstrated consistent and effective LDL-C lowering with a favourable long-term safety and tolerability profile. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov identifier: NCT03814187.

Long-term efficacy and safety of inclisiran in patients with high cardiovascular risk and elevated LDL cholesterol (ORION-3): results from the 4-year open-label extension of the ORION-1 trial.

INTRODUCTION: Whether long-term treatment with the twice-yearly, siRNA therapeutic inclisiran, which reduces hepatic production of proprotein convertase subtilisin/kexin type 9 (PCSK9), results in sustained reductions in LDL cholesterol with an acceptable safety profile is not known. The aim of this study was to assess the effect of long-term dosing of inclisiran in patients with high cardiovascular risk and elevated LDL cholesterol. METHODS: ORION-3 was a 4-year open-label extension study of the placebo-controlled, phase 2 ORION-1 trial, conducted at 52 sites across five countries. Patients with prevalent atherosclerotic cardiovascular disease or high-risk primary prevention and elevated LDL cholesterol despite maximally tolerated statins or other LDL-lowering treatments, or with documented statin intolerance, who had completed the ORION-1 trial were eligible. Patients receiving inclisiran in ORION-1 received twice-yearly 300 mg subcutaneous inclisiran sodium throughout ORION-3 (inclisiran-only arm), whereas patients receiving placebo in ORION-1 first received subcutaneous evolocumab 140 mg every 2 weeks until day 360 thereafter transitioning to inclisiran twice-yearly for the remainder of ORION-3 study (switching arm). The primary efficacy endpoint was the percentage change in LDL cholesterol with inclisiran from the start of ORION-1 through to day 210 of the open label extension phase in the inclisiran-only arm (approximately 570 days of total inclisiran exposure in the modified intention-to-treat population). Secondary and exploratory endpoints included changes in LDL-C cholesterol and PCSK9 concentrations levels up to day 1440 (4 years) in each arm, and safety. ORION-3 is registered with ClinicalTrials.gov, NCT03060577. FINDINGS: Of the original ORION-1 cohort of 497 patients, 290 of 370 patients allocated to drug continued into the inclisiran-only arm and 92 of 127 patients allocated to placebo entered the switching-arm in the ORION-3 extension study conducted between March 24, 2017, and Dec 17, 2021. In the inclisiran-only arm, LDL cholesterol was reduced by 47·5% (95% CI 50·7-44·3) at day 210 and sustained over 1440 days. The 4-year averaged mean reduction of LDL-C cholesterol was 44·2% (95% CI: 47·1-41·4), with reductions in PCSK9 ranging from 62·2% to 77·8%. Adverse events at the injection site were reported in 39 (14%) of 284 patients in the inclisiran-only arm and 12 (14%) of 87 patients in the switching arm. The incidence of treatment-emergent serious adverse events possibly related to the study drug was 1% (three of 284) in the inclisiran-only arm and 1% (one of 87) in the switching arm. INTERPRETATION: Twice-yearly inclisiran provided sustained reductions in LDL cholesterol and PCSK9 concentrations and was well tolerated over 4 years in the extension study. This is the first prospective long-term study to assess repeat hepatic exposure to inclisiran. FUNDING: Novartis Pharma.

Akt suppresses retrograde degeneration of dopaminergic axons by inhibition of macroautophagy.

Axon degeneration is a hallmark of neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease. Such degeneration is not a passive event but rather an active process mediated by mechanisms that are distinct from the canonical pathways of programmed cell death that mediate destruction of the cell soma. Little is known of the diverse mechanisms involved, particularly those of retrograde axon degeneration. We have previously observed in living animal models of degeneration in the nigrostriatal projection that a constitutively active form of the kinase, myristoylated Akt (Myr-Akt), demonstrates an ability to suppress programmed cell death and preserve the soma of dopamine neurons. Here, we show in both neurotoxin and physical injury (axotomy) models that Myr-Akt is also able to preserve dopaminergic axons due to suppression of acute retrograde axon degeneration. This cellular phenotype is associated with increased mammalian target of rapamycin (mTor) activity and can be recapitulated by a constitutively active form of the small GTPase Rheb, an upstream activator of mTor. Axon degeneration in these models is accompanied by the occurrence of macroautophagy, which is suppressed by Myr-Akt. Conditional deletion of the essential autophagy mediator Atg7 in adult mice also achieves striking axon protection in these acute models of retrograde degeneration. The protection afforded by both Myr-Akt and Atg7 deletion is robust and lasting, because it is still observed as protection of both axons and dopaminergic striatal innervation weeks after injury. We conclude that acute retrograde axon degeneration is regulated by Akt/Rheb/mTor signaling pathways.

Dopamine-modified alpha-synuclein blocks chaperone-mediated autophagy.

Altered degradation of alpha-synuclein (alpha-syn) has been implicated in the pathogenesis of Parkinson disease (PD). We have shown that alpha-syn can be degraded via chaperone-mediated autophagy (CMA), a selective lysosomal mechanism for degradation of cytosolic proteins. Pathogenic mutants of alpha-syn block lysosomal translocation, impairing their own degradation along with that of other CMA substrates. While pathogenic alpha-syn mutations are rare, alpha-syn undergoes posttranslational modifications, which may underlie its accumulation in cytosolic aggregates in most forms of PD. Using mouse ventral medial neuron cultures, SH-SY5Y cells in culture, and isolated mouse lysosomes, we have found that most of these posttranslational modifications of alpha-syn impair degradation of this protein by CMA but do not affect degradation of other substrates. Dopamine-modified alpha-syn, however, is not only poorly degraded by CMA but also blocks degradation of other substrates by this pathway. As blockage of CMA increases cellular vulnerability to stressors, we propose that dopamine-induced autophagic inhibition could explain the selective degeneration of PD dopaminergic neurons.

Autophagy induced by Alexander disease-mutant GFAP accumulation is regulated by p38/MAPK and mTOR signaling pathways.

Glial fibrillary acidic protein (GFAP) is the principle intermediate filament (IF) protein in astrocytes. Mutations in the GFAP gene lead to Alexander disease (AxD), a rare, fatal neurological disorder characterized by the presence of abnormal astrocytes that contain GFAP protein aggregates, termed Rosenthal fibers (RFs), and the loss of myelin. All GFAP mutations cause the same histopathological defect, i.e. RFs, though little is known how the mutations affect protein accumulation as well as astrocyte function. In this study, we found that GFAP accumulation induces macroautophagy, a key clearance mechanism for prevention of aggregated proteins. This autophagic response is negatively regulated by mammalian target of rapamycin (mTOR). The activation of p38 MAPK by GFAP accumulation is in part responsible for the down-regulation of phosphorylated-mTOR and the subsequent activation of autophagy. Our study suggests that AxD mutant GFAP accumulation stimulates autophagy, in a manner regulated by p38 MAPK and mTOR signaling pathways. Autophagy, in turn, serves as a mechanism to reduce GFAP levels.

Methamphetamine inhibits antigen processing, presentation, and phagocytosis.

Methamphetamine (Meth) is abused by over 35 million people worldwide. Chronic Meth abuse may be particularly devastating in individuals who engage in unprotected sex with multiple partners because it is associated with a 2-fold higher risk for obtaining HIV and associated secondary infections. We report the first specific evidence that Meth at pharmacological concentrations exerts a direct immunosuppressive effect on dendritic cells and macrophages. As a weak base, Meth collapses the pH gradient across acidic organelles, including lysosomes and associated autophagic organelles. This in turn inhibits receptor-mediated phagocytosis of antibody-coated particles, MHC class II antigen processing by the endosomal-lysosomal pathway, and antigen presentation to splenic T cells by dendritic cells. More importantly Meth facilitates intracellular replication and inhibits intracellular killing of Candida albicans and Cryptococcus neoformans, two major AIDS-related pathogens. Meth exerts previously unreported direct immunosuppressive effects that contribute to increased risk of infection and exacerbate AIDS pathology.

Secukinumab Demonstrates Sustained Efficacy and Safety in a Taiwanese Subpopulation With Active Ankylosing Spondylitis: Four-Year Results From a Phase 3 Study, MEASURE 1.

Objectives: To present the long-term (4-year) efficacy and safety of secukinumab in Taiwanese patients with active AS in the MEASURE 1 extension study. Methods: This post hoc analysis reports data from Taiwanese patients originally randomized to subcutaneous secukinumab 150 or 75mg or placebo every 4 weeks (following intravenous loading dose) who were invited to enter the 3-year extension study. Assessments at Week 208 included ASAS20/40 responses and other clinically relevant endpoints. Efficacy data are presented as observed. Safety analyses included all patients who received ≥1 dose of secukinumab. Results: Of the 57 Taiwanese patients in the core trial, 48 entered the extension study and 87.5% patients (42/48) completed 4 years of treatment. Thirteen Taiwanese patients (including placebo-switchers) were escalated from 75 to 150mg (approved dose) at some point starting from Week 172. ASAS20/40 responses were sustained through 4 years in the Taiwanese patients who were originally randomized to secukinumab 150mg. Clinical responses were improved in those patients who received dose-escalation from 75 to 150mg during the study. No unexpected safety signals were reported. Conclusion: Secukinumab 150mg demonstrated sustained efficacy over 4 years in Taiwanese patients with active ankylosing spondylitis. The safety profile of secukinumab was consistent with previous reports. ClinicalTrialsgov identifier: NCT01863732.

Long-term efficacy and safety of secukinumab 150 mg in ankylosing spondylitis: 5-year results from the phase III MEASURE 1 extension study.

Objective: This study aimed to report end-of-study results on efficacy and safety of secukinumab 150 mg through 5 years in patients with ankylosing spondylitis (AS; MEASURE 1 extension trial (NCT01863732)). Methods: After the 2-year core trial, 274 patients receiving subcutaneous secukinumab 150 or 75 mg (following intravenous loading or initial placebo treatment to 16/24 weeks) every 4 weeks were invited to enter the 3-year extension study. Dose escalation from 75 to 150 mg (approved dose) was allowed at or after week 156 based on the judgement of the treating physician. Assessments at week 260 (5 years) included Assessment of SpondyloArthritis international Society (ASAS) 20/40 and other efficacy outcomes. Data are presented as observed. Safety assessment included all patients who received ≥1 dose of study treatment. Results: Of the 274 patients who entered the extension study, 84% (230/274) completed 5 years of treatment. ASAS20/40 responses were 78.6/65.2%, Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) 50 response was 63.4% and mean (±SD) BASDAI total score was 2.6±1.76 with secukinumab 150 mg at 5 years. Improvements in efficacy outcomes were sustained through 5 years. A total of 82 patients on secukinumab 75 mg (56.2%) had their dose escalated to 150 mg after week 168; ASAS40, ASAS-PR, ASAS 5/6 and BASDAI50 responses were improved in patients whose dose was escalated from secukinumab 75 to 150 mg. Secukinumab was well tolerated with a safety profile consistent over the course of the study. Conclusions: Secukinumab 150 mg provided sustained efficacy across multiple domains of AS with a favourable and consistent safety profile through 5-year treatment. Over 50% of patients required dose escalation from 75 to 150 mg and efficacy improved in these patients.

Neuronal pigmented autophagic vacuoles: lipofuscin, neuromelanin, and ceroid as macroautophagic responses during aging and disease.

The most striking morphologic change in neurons during normal aging is the accumulation of autophagic vacuoles filled with lipofuscin or neuromelanin pigments. These organelles are similar to those containing the ceroid pigments associated with neurologic disorders, particularly in diseases caused by lysosomal dysfunction. The pigments arise from incompletely degraded proteins and lipids principally derived from the breakdown of mitochondria or products of oxidized catecholamines. Pigmented autophagic vacuoles may eventually occupy a major portion of the neuronal cell body volume because of resistance of the pigments to lysosomal degradation and/or inadequate fusion of the vacuoles with lysosomes. Although the formation of autophagic vacuoles via macroautophagy protects the neuron from cellular stress, accumulation of pigmented autophagic vacuoles may eventually interfere with normal degradative pathways and endocytic/secretory tasks such as appropriate response to growth factors.

Efficacy and Safety of Secukinumab 150 mg with and Without Loading Regimen in Ankylosing Spondylitis: 104-week Results from MEASURE 4 Study.

INTRODUCTION: To evaluate the efficacy and safety of secukinumab 150 mg, with or without a loading regimen, using a self-administered prefilled syringe in patients with ankylosing spondylitis (AS) over 104 weeks from the MEASURE 4 study. METHODS: Patients (N = 350) with active AS were randomized (1:1:1) to receive subcutaneous secukinumab 150 mg with loading dose (150 mg), without loading dose (150 mg no load), or placebo. All patients received secukinumab or placebo at baseline, weeks 1, 2, and 3 and every 4 weeks starting at week 4. The primary endpoint was the Assessment of SpondyloArthritis international Society criteria for 20% improvement (ASAS20) at week 16. RESULTS: A total of 96.9% of patients (339/350) completed 16 weeks and 82.6% (289/350) completed 104 weeks of treatment. The ASAS20 response rate at week 16 was 59.5% and 61.5% with 150 and 150 mg no load groups, respectively, versus placebo (47%; P = 0.057 and 0.054, respectively); the primary endpoint was not met. Increases in response rates achieved with secukinumab for ASAS20 at week 16 were sustained through week 104. The safety profile of secukinumab 150 mg, with or without a loading regimen, showed no new or unexpected safety signals. CONCLUSIONS: Secukinumab 150 mg, with or without loading regimen, provided rapid and sustained decreases in the signs and symptoms of patients with AS, but the differences were not statistically significant at week 16 due to higher than expected placebo responses. The responses and safety profile were consistent with previous phase 3 studies and sustained through 2 years. TRIAL REGISTRATION: ClinicalTrials.gov identifier, NCT02159053. FUNDING: Novartis Pharma AG, Basel, Switzerland.

Autophagy protects against Sindbis virus infection of the central nervous system.

Autophagy functions in antiviral immunity. However, the ability of endogenous autophagy genes to protect against viral disease in vertebrates remains to be causally established. Here, we report that the autophagy gene Atg5 function is critical for protection against lethal Sindbis virus (SIN) infection of the mouse central nervous system. Inactivating Atg5 in SIN-infected neurons results in delayed clearance of viral proteins, increased accumulation of the cellular p62 adaptor protein, and increased cell death in neurons, but the levels of viral replication remain unaltered. In vitro, p62 interacts with SIN capsid protein, and genetic knockdown of p62 blocks the targeting of viral capsid to autophagosomes. Moreover, p62 or autophagy gene knockdown increases viral capsid accumulation and accelerates virus-induced cell death without affecting virus replication. These results suggest a function for autophagy in mammalian antiviral defense: a cell-autonomous mechanism in which p62 adaptor-mediated autophagic viral protein clearance promotes cell survival.

Cargo recognition failure is responsible for inefficient autophagy in Huntington's disease.

Continuous turnover of intracellular components by autophagy is necessary to preserve cellular homeostasis in all tissues. Alterations in macroautophagy, the main process responsible for bulk autophagic degradation, have been proposed to contribute to pathogenesis in Huntington's disease (HD), a genetic neurodegenerative disorder caused by an expanded polyglutamine tract in the huntingtin protein. However, the precise mechanism behind macroautophagy malfunction in HD is poorly understood. In this work, using cellular and mouse models of HD and cells from humans with HD, we have identified a primary defect in the ability of autophagic vacuoles to recognize cytosolic cargo in HD cells. Autophagic vacuoles form at normal or even enhanced rates in HD cells and are adequately eliminated by lysosomes, but they fail to efficiently trap cytosolic cargo in their lumen. We propose that inefficient engulfment of cytosolic components by autophagosomes is responsible for their slower turnover, functional decay and accumulation inside HD cells.

Adaptive autophagy in Alexander disease-affected astrocytes.

The ubiquitin-proteasome and autophagy-lysosomal pathways are the two main routes of protein and organelle clearance in eukaryotic cells. The proteasome system is responsible for unfolded, short-lived proteins, which precludes the clearance of oligomeric and aggregated proteins, whereas macroautophagy, a process generally referred to as autophagy, mediates mainly the bulk degradation of long-lived cytoplasmic proteins, large protein complexes or organelles.(1) Recently, the autophagy-lysosomal pathway has been implicated in neurodegenerative disorders as an important pathway for the clearance of abnormally accumulated intracellular proteins, such as huntingtin, tau and mutant and modified alpha-synuclein.(1-6) Our recent study illustrated the induction of adaptive autophagy in response to mutant glial fibrillary acidic protein (GFAP) accumulation in astrocytes, in the brains of patients with Alexander disease (AxD), and in mutant GFAP knock-in mouse brains.(7) This autophagic response is negatively regulated by mammalian target of rapamycin (mTOR). The activation of p38 MAPK by GFAP accumulation is responsible for mTOR inactivation and the induction of autophagy. We also found that the accumulation of GFAP impairs proteasome activity.(8) In this commentary we discuss the potential compensatory relationship between an impaired proteasome and activated autophagy, and propose that the MLK-MAPK (mixed lineage kinase-mitogen-activated protein kinase) cascade is a regulator of this crosstalk.

Adaptive autophagy in Alexander disease-affected astrocytes.

The ubiquitin-proteasome and autophagy-lysosomal pathways are the two main routes of protein and organelle clearance in eukaryotic cells. The proteasome system is responsible for unfolded, short-lived proteins, which precludes the clearance of oligomeric and aggregated proteins, whereas macroautophagy, a process generally referred to as autophagy, mediates mainly the bulk degradation of long-lived cytoplasmic proteins, large protein complexes or organelles.1 Recently, the autophagy-lysosomal pathway has been implicated in neurodegenerative disorders as an important pathway for the clearance of abnormally accumulated intracellular proteins, such as huntingtin, tau, and mutant and modified α-synuclein.1-6 Our recent study illustrated the induction of adaptive autophagy in response to mutant glial fibrillary acidic protein (GFAP) accumulation in astrocytes, in the brains of patients with Alexander disease (AxD), and in mutant GFAP knock-in mouse brains.7 This autophagic response is negatively regulated by mammalian target of rapamycin (mTOR). The activation of p38 MAPK by GFAP accumulation is responsible for mTOR inactivation and the induction of autophagy. We also found that the accumulation of GFAP impairs proteasome activity.8 In this commentary we discuss the potential compensatory relationship between an impaired proteasome and activated autophagy, and propose that the MLK-MAPK (mixed lineage kinase-mitogen-activated protein kinase) cascade is a regulator of this crosstalk. Addendum to: Tang G, Yue Z, Talloczy, Z, Hagemann T, Cho W, Sulzer D, Messing A, Goldman JE. Alexander disease-mutant GFAP accumulation stimulates autophagy through p38 MAPK and mTOR signaling pathways. Hum Mol Genetics 2008; In press.

HSV-1 ICP34.5 confers neurovirulence by targeting the Beclin 1 autophagy protein.

Autophagy is postulated to play a role in antiviral innate immunity. However, it is unknown whether viral evasion of autophagy is important in disease pathogenesis. Here we show that the herpes simplex virus type 1 (HSV-1)-encoded neurovirulence protein ICP34.5 binds to the mammalian autophagy protein Beclin 1 and inhibits its autophagy function. A mutant HSV-1 virus lacking the Beclin 1-binding domain of ICP34.5 fails to inhibit autophagy in neurons and demonstrates impaired ability to cause lethal encephalitis in mice. The neurovirulence of this Beclin 1-binding mutant virus is restored in pkr(-/-) mice. Thus, ICP34.5-mediated antagonism of the autophagy function of Beclin 1 is essential for viral neurovirulence, and the antiviral signaling molecule PKR lies genetically upstream of Beclin 1 in host defense against HSV-1. Our findings suggest that autophagy inhibition is a novel molecular mechanism by which viruses evade innate immunity and cause fatal disease.

PKR-dependent autophagic degradation of herpes simplex virus type 1.

The lysosomal pathway of autophagy is the major catabolic mechanism for degrading long-lived cellular proteins and cytoplasmic organelles. Recent studies have also shown that autophagy (xenophagy) may be used to degrade bacterial pathogens that invade intracellularly. However, it is not yet known whether xenophagy is a mechanism for degrading viruses. Previously, we showed that autophagy induction requires the antiviral eIF2alpha kinase signaling pathway (including PKR and eIF2alpha) and that this function of eIF2alpha kinase signaling is antagonized by the herpes simplex virus (HSV-1) neurovirulence gene product, ICP34.5. Here, we show quantitative morphologic evidence of PKR-dependent xenophagic degradation of herpes simplex virions and biochemical evidence of PKR and eIF2alpha-dependent degradation of HSV-1 proteins, both of which are blocked by ICP34.5. Together, these findings indicate that xenophagy degrades HSV-1 and that this cellular function is antagonized by the HSV-1 neurovirulence gene product, ICP34.5. Thus, autophagy-related pathways are involved in degrading not only cellular constituents and intracellular bacteria, but also viruses.