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Protein aggregates have a strong correlation with the pathogenesis of multiple human pathologies represented by neurodegenerative diseases. One type of selective autophagy, known as aggrephagy, can selectively degrade protein aggregates. A recent study from Ge lab reported the TRiC subunit CCT2 (chaperonin containing TCP1 subunit 2) as the first identified specific aggrephagy receptor in mammals. The switch of CCT2's role from a chaperonin to a specific aggrephagy receptor is achieved by CCT2 monomer formation. CCT2 functions independently of ubiquitin and the TRiC complex to facilitate the autophagic clearance of solid protein aggregates. This study provides the intriguing possibility that CCT2, as a specific aggrephagy receptor, might be an important target for the treatment of various diseases associated with protein aggregation.

STX17 (syntaxin 17) mediates autophagosome-lysosome fusion, and the translocation of STX17 to autophagosomes is characteristic of this process. STX17 arrives at autophagosomes when they are closed, stays there for approximately 10 min to promote fusion with lysosomes, and leaves when the autolysosomes are mature. However, the mechanism of this transient visit remains largely unknown. Here, we summarize the current knowledge about this phenomenon, including a recently discovered retrieval mechanism, and discuss remaining questions. Abbreviations: MAM: mitochondria-associated membrane; SNX: sorting nexin; STX17: syntaxin 17.

In the preceding months, the novel SARS-CoV-2 pandemic has devastated global communities. The need for safe and effective prophylactic and therapeutic treatments to combat COVID-19 – the human disease resulting from SARS-CoV-2 infection – is clear. Here, we present recent developments in the effort to combat COVID-19 and consider whether SARS-CoV-2 may potentially interact with the host autophagy pathway. Abbreviations: ACE2, angiotensin converting enzyme II; βCoV, betacoronavirus; COVID-19, Coronavirus Disease 2019; CQ, chloroquine; DMV, double-membrane vesicle; GI, gastrointestinal; HCQ, hydroxychloroquine; IL, interleukin; MAP1LC3/LC3, microtubule associated protein 1 light chain 3; MEFs, mouse embryonic fibroblasts; MERS-CoV, Middle East respiratory syndrome coronavirus; MHV, murine hepatitis virus; PE, phosphatidylethanolamine; SARS-CoV, severe acute respiratory syndrome coronavirus; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; TMPRSS2, transmembrane serine protease 2; TNF, tumor necrosis factor; WHO, World Health Organization

RB1CC1/FIP200 is a subunit of the ULK1 complex in more complex eukaryotes. This large polypeptide was proposed to be a functional homolog of the Atg17 and Atg11 scaffolding proteins in yeast. Previous studies showed that RB1CC1 can bind to various proteins of the macroautophagy/autophagy machinery, where the RB1CC1 Claw domain directly interacts with a short linear segment of its interactors. A mechanistic insight into how the small globular RB1CC1 Claw domain can interact with such an array of structurally variable proteins has been elusive. The recent study by Zhou et al., discussed here, yields structural data that not only provide a unifying mechanistic explanation of these interactions, but also reveals previously unknown RB1CC1 interactors and opens a new field for exploration of autophagy regulation. Abbreviations: FIR: FIP200-interacting region; LIR: LC3-interacting region; pS/p-S: phosphorylated serine

There have been multiple inconsistencies in the manner the COVID-19 pandemic has been investigated and managed by countries. Population-based management (PBM) has been inconsistent, yet serves as a necessary first step in managing public health crises. Unfortunately, these have dominated the landscape within the United States and continue as of this writing. Political and economic influences have greatly influenced major public health management and control decisions. Responsibility for global public health crises and modeling for management are the responsibility of the World Health Organization (WHO) and the International Health Regulations Treaty (IHR). This review calls upon both to reassess their roles and responsibilities that must be markedly improved and better replicated world-wide in order to optimize the global public health protections and its PBM.“Ask a big enough question, and you need more than one discipline to answer it.”Liz Lerman, MacArthur “Genius” Fellow, Choreographer, Modern Dance legend, and 2011 Artist-in Residence, Harvard Music Department

The autophagy receptor for selective reticulophagy, RETREG1/FAM134B is essential for ER maintenance, and its dysfunction is associated with neuronal disorders, vascular dementia, or viral infections. The protein consists of the reticulon-homology domain (RHD) that is flanked at the N- and C-termini by an intrinsically disordered protein region (IDPR), where the C terminal IDPR carries the indispensable LC3-interacting region (LIR) motif for the interaction with LC3. The RHD of RETREG1 is presumed to play a role in membrane remodeling, but the absence of a known 3D structure of this domain so far prevented researchers from gaining mechanistic insights into how the RETREG1 RHD curves membranes, and thereby facilities reticulophagy. The recent study by Bhaskara et al., which is described in this editor’s corner article, used molecular dynamics (MD) simulations to create a structural model of the RETREG1 RHD. MD simulations along with in vitro liposome remodeling experiments reveal how the RHD domain acts on the ER membrane and, in concert with the C terminal IDPR, executes the function of RETREG1 in selective reticulophagy. Abbreviations: ER, endoplasmic reticulum; IDPR, intrinsically disordered protein region; LIR, LC3-interacting region; MD, molecular dynamics; RHD, reticulon-homology domain; TM, transmembrane

Mitophagy, a type of selective autophagy targeting damaged or superfluous mitochondria, is critical to maintain cell homeostasis. Besides the well-characterized PRKN-dependent mitophagy, PRKN-independent mitophagy also plays significant physiological roles. In a recent study, researchers from Anne Simonsen’s lab discovered two lipid binding kinases, GAK and PRKCD, as positive regulators of PRKN-independent mitophagy. The researchers further investigated how these two proteins regulate mitophagy and demonstrated their roles in vivo. Focusing on the less known PRKN-independent mitophagy regulators, these findings shed light on understanding the mechanism of mitophagy and its relation to diseases.

When I invite authors to submit a punctum to Autophagy, my e-mail includes the following: "Note for international authors: I would like to point out that I personally edit all the puncta for accuracy, but also for English grammar and spelling. I make this point to all international authors as I do not want you to worry extensively about the writing. As a native English speaker, it is easy for me to make small changes of this nature." I do not claim to be an expert in English grammar; however, I am indeed a native English speaker, I read a lot, and I am even fond of using the dictionary (both hard copy and online). Also, I do a lot of editing. Thus, I thought I would share some common mistakes to help reduce the required edits for papers that are submitted to Autophagy.

The unique cellular organization and metabolic demands of neurons pose a challenge in the maintenance of neuronal homeostasis. A critical element in maintaining neuronal health and homeostasis is mitochondrial quality control via replacement and rejuvenation at the axon. Dysregulation of mitochondrial quality control mechanisms such as mitophagy has been implicated in neurodegenerative diseases including Parkinson disease and amyotrophic lateral sclerosis. To sustain mitophagy at the axon, a continuous supply of PINK1 is required; however, how do neurons maintain a steady supply of this protein at the distal axons? In the study highlighted here, Harbauer et al. show that axonal mitophagy is supported by local translation of Pink1 mRNA that is co-transported with mitochondria to the distal ends of the neuron. This neuronal-specific pathway provides a continuous supply of PINK1 to sustain mitophagy.

It would be quite convenient if every protein had one distinct function, one distinct role in just a single cellular process. In the field of macroautophagy/autophagy, however, we are increasingly finding that this is not the case; several autophagy proteins have two or more roles within the process of autophagy and many even "moonlight" as functional members of entirely different cellular processes. This is perhaps best exemplified by the Atg8-family proteins. These dynamic proteins have already been reported to serve several functions both within autophagy (membrane tethering, membrane fusion, binding to cargo receptors, binding to autophagy machinery) and beyond (LC3-associated phagocytosis, formation of EDEMosomes, immune signaling) but as Maruyama and colleagues suggest in their recent report, this list of functions may not yet be complete.

Time-restricted feeding (TRF) has recently gained interest as a potential anti-aging treatment for organisms from Drosophila to humans.(1–5) TRF restricts food intake to specific hours of the day. Because TRF controls the timing of feeding, not nutrient or caloric content, TRF has been hypothesized to depend on circadian-regulated functions; the underlying molecular mechanisms remain unclear. To exploit the genetic tools and well-characterized aging markers of Drosophila, we developed an intermittent TRF (iTRF) dietary regimen that robustly extended fly lifespan and delayed onset of aging markers in muscles and gut. We found that iTRF enhanced circadian-regulated transcription and that iTRF-mediated lifespan extension required both circadian regulation and autophagy, a conserved longevity pathway. Night-specific induction of autophagy was both necessary and sufficient to extend lifespan on ad lib diet and also prevented further iTRF-mediated lifespan extension. In contrast, day-specific induction of autophagy did not extend lifespan. Thus, these results identify circadian-regulated autophagy as a critical contributor to iTRF-mediated health benefits in Drosophila. Because both circadian regulation and autophagy are highly conserved processes in human aging, this work highlights the possibility that behavioral or pharmaceutical interventions stimulating circadian-regulated autophagy may provide people with similar health benefits such as delayed aging and lifespan extension.

The Atg3 protein is highly homologous from yeast to human. Atg3 functions as an E2-like enzyme promoting conjugation of Atg8-family proteins to phosphatidylethanolamine (PE), a lipid molecule embedded in the growing phagophore membrane during stress-induced autophagy. Over the last decade, Atg3 became one of the most explored autophagy proteins, resulting in observations that provided specific insights into the structural mechanisms of its function. In this article, we describe a recent study by Ye et al. that reveals, using the human ATG3, how the membrane binding capability of the enzyme is tightly linked to its conjugation activity. We summarize the current knowledge on important mechanisms that involve protein-protein or protein-membrane interactions of Atg3 and that ultimately lead to efficient Atg8-PE conjugation.Abbreviations: AH: amphipathic helix; FR: flexible region; HR: handle region; NMR: nuclear magnetic resonance.

There have been a couple of times when we have reviewed papers that are essentially publishable as initially submitted; the "criticisms" were more along the lines of constructive suggestions that the authors might want to consider when they submitted a revised version of the paper, but those changes were not required. However, a much more common experience is for the authors to receive a series of comments from multiple reviewers. Most of those comments are critical for the authors to address, to ensure that the data in the paper are of sufficient quality and rigor, with adequate controls, to support the stated conclusions. That said, reviewers sometimes make requests, with the best of intentions, which might be reasonably considered as "beyond the scope of the present study". Thus, there needs to be a balance between addressing each and every comment of a review and completing a story even though there are additional avenues and questions that remain unexplored. Sometimes, even after a repeated round(s) of review, such questions linger and may impede acceptance of a worthy study.

In eukaryotes, ATG4/Atg4 is a critical regulator of macroautophagy/autophagy. The protease activity of Atg4/ATG4, involved in conjugation and deconjugation of Atg8-family proteins, was so far regarded as its sole functional contribution. However, the role of individual ATG4-family proteins during mammalian autophagy had previously not been examined in vivo. During their recent investigation, Nguyen et al. discovered a hitherto unexplored role for mammalian ATG4s during mitophagy - the recruitment of ATG9A-containing vesicles. Their article, highlighted here, discusses the finding, which uses a novel artificial intelligence (AI)-directed analysis technique for focused ion beam-scanning electron microscopy (FIB-SEM) imaging to demonstrate the role of ATG4s in promoting phagophore growth and establishing phagophore-ER contacts.

Although the aetiology of amyotrophic lateral sclerosis (ALS) remains poorly understood, impaired proteostasis is a common feature of different forms of ALS. Mutations in genes encoding ubiquilins, UBQLN2 and UBQLN4, cause familial ALS. The role of ubiquilins in proteasomal degradation is well established, but their role in autophagy-lysosomal clearance is poorly defined. Here, we describe a crosstalk between endoplasmic reticulum stress, mTOR signalling and autophagic flux in Drosophila and mammalian cells lacking ubiquilins. We found that loss of ubiquilins leads to endoplasmic reticulum stress, impairs mTORC1 activity, promotes autophagy and causes the demise of neurons. We show that ubiquilin mutants display defective autophagic flux due to reduced lysosome acidification. Ubiquilins are required to maintain proper levels of the V0a/V100 subunit of the vacuolar H+-ATPase and lysosomal pH. Feeding flies acidic nanoparticles alleviates defective autophagic flux in ubiquilin mutants. Hence, our studies reveal a conserved role for ubiquilins as regulators of autophagy by controlling vacuolar H+-ATPase activity and mTOR signalling.

VCP, a conserved ATPase, is involved in several cellular processes, and mutations in this protein are associated with various diseases. VCP also plays a role in autophagosome maturation. However, because a deficiency in autophagosome maturation presents a readily observable phenotype, other roles of VCP in autophagy regulation, in particular in the initial steps of autophagosome formation, may have been overlooked. In a recently published paper, using small-molecule inhibitors, Hill et al. showed that VCP regulates autophagy initiation through both stabilization of BECN1 and enhancement of phosphati-dylinositol 3-kinase (PtdIns3K) complex assembly.

Glucose deprivation induces macroautophagy/autophagy primarily through AMPK activation. However, little is known about the exact mechanism of this signaling. A recent study from Dr. David C. Rubinsztein's lab showed that ULK1 is activated by AMPK upon glucose starvation, resulting in the phosphorylation of the lipid kinase PIKFYVE on S1548. The activated PIKFYVE consequently enhances the formation of phosphatidylinositol-5-phosphate (PtdIns5P)-containing autophagosomes, and therefore drives autophagy upregulation. The novel discovery of how ULK1 regulates the non-canonical autophagy signaling (PtdIns5P-dependent autophagy), not only expands our knowledge of autophagy, but also sheds light on therapeutic strategies for curing human disorders, where glucose-induced starvation can play an important role.

It has been well established that Atg11 plays a critical role in selective macroautophagy/autophagy, but not in nonselective autophagy in the budding yeast Saccharomyces cerevisiae. However, its mammalian ortholog RB1CC1/FIP200 is indispensable for both types of autophagy, and the molecular mechanism behind its function is a mystery. Recently, Pan et al. showed that in the fission yeast Schizosaccharomyces pombe, Atg11 could also promote nonselective autophagy via activation of Atg1 kinase. These results prompt an interesting idea that Atg11 might have gained an additional ability to mediate nonselective autophagy through evolution.

Reticulophagy, a type of selective autophagy that specifically targets and degrades parts of the endoplasmic reticulum (ER) network (sheets or tubules), plays a crucial role in the responses to ER stress. The selectivity of the ER cargo recognition relies on the unique reticulophagy receptors, which tether and deliver cargos to phagophores, the precursors to autophagosomes. Various integral membrane proteins have been well characterized as reticulophagy receptors, including Atg39, Atg40, RETREG1/FAM134B, SEC62, RTN3L, CCPG1, TEX264, and ATL3, in both yeast and mammals in the past five years. In a recent paper, Zhao et al. discovered in fission yeast a novel reticulophagy receptor, Epr1, which bridges the ER and phagophore by binding to Atg8 and VAPs, a mechanism different from the aforementioned reticulophagy receptors.

This issue of N2 highlights the diversity of autoimmune disorders that affect the nervous system. Whether you are interested in T–cell- or B–cell-mediated disorders or prefer white matter or gray matter, you will likely find an article of interest. In addition for the medical sleuths among our readers, we have the likely resolution of a 190-year-old unresolved diagnosis.

Several studies have provided insight into the unique intracellular localization, dynamic trafficking and diverse repertoire of binding partners of Atg9/ATG9, but structural details of the protein have remained elusive. Guardia and colleagues now report the structure of human ATG9A to a resolution of 2.9 A, revealing, among other features, an elaborate system of tunnels permeating the ATG9A protein complex.

A key feature of macroautophagy (hereafter autophagy) is the formation of the phagophore, a double-membrane compartment sequestering cargos and finally maturing into a vesicle termed an autophagosome; however, where these membranes originate from is not clear. In a previous study, researchers from the Rubinsztein lab proposed a model in which the autophagosome can evolve from the RAB11A-positive recycling endosome. In their recent paper, they determine that DNM2 (dynamin 2) functions in scission of the recycling endosome, and the release of the autophagosome precursor. These findings explain how the centronuclear myopathy (CNM) mutation in DNM2 results in the accumulation of immature autophagic structures.

This has been a challenging spring, and we all hope that the summer will bring the needed relief. To help you unwind, the July issue of Neurology® Neuroimmunology & Neuroinflammation contains excellent articles on a wide variety of topics that should hold your interest and help charge your brain batteries. Here I highlight 4 studies that I choose for the common theme of dealing with rare inflammatory disorders. I took the liberty of including a study of pregnant and lactating women with MS/NMOSD because investigations of this cohort are relatively rare.

Classical macroautophagy/autophagy functions to maintain cell health during stressful conditions by targeting cytosolic components for degradation and recycling through the lysosomal pathway. In contrast, nondegradative secretory autophagy functions as an alternative autophagy mechanism to mediate extracellular secretion. A recent study published in Nature Cell Biology from the laboratory of Jayanta Debnath has identified components of the LC3-conjugation machinery as mediators in the selection of cargo for nonclassical secretion. Termed LC3-dependent extracellular vesicle loading and secretion (LDELS), this mechanism provides an additional link between secretory autophagy and the release of extracellular vesicles. ABBREVIATIONS: ATG, autophagy-related; BioID, proximity-dependent biotinylation; CM, conditioned medium; EV, extracellular vesicle; HNRNPK, heterogeneous nuclear ribonuclear protein K; ILVs, intralumenal vesicles; LDELS, LC3-dependent EV loading and secretion; LIR, LC3-interacting region; MAP1LC3/LC3, microtubule associated protein 1 light chain 3; MS, mass spectrometry; MVBs, multivesicular bodies; ncRNA, non-coding RNA; NSMAF/FAN, neutral sphingomyelinase activation associated factor; P-bodies, processing bodies; PE, phosphatidylethanolamine; RB1CC1/FIP200, RB1 inducible coiled-coil 1; RBP, RNA-binding protein; RNA-seq, RNA sequencing; SAFB, scaffold-attachment factor B; SILAC, stable isotope labeling of amino acids in cell culture; SMPD3/nSMase2, sphingomyelin phosphodiesterase 3; TEM, transmission electron microscopy; TMT, tandem mass tagging

During the past decade, the field of Neuroimmunology has expanded at a rapid pace. For some disorders, particularly those related to paraneoplastic and neuronal cell-surface antibodies, this growth has been accompanied by an increase in, and reliance on, the use of antibody testing. This testing does not come free of problems, and when it leads to the wrong direction, it slows our progress forward with important diagnostic and treatment implications. In this issue of N2, several articles revolve around this topic.

Hypoxia is a physiological stress that frequently occurs in solid tissues. Autophagy, a ubiquitous degradation/recycling system in eukaryotic cells, renders cells tolerant to multiple stressors. However, the mechanisms underlying autophagy initiation upon hypoxia remains unclear. Here we show that protein arginine methyltransferase 5 (PRMT5) catalyzes symmetrical dimethylation of the autophagy initiation protein ULK1 at arginine 170 (R170me2s), a modification removed by lysine demethylase 5C (KDM5C). Despite unchanged PRMT5-mediated methylation, low oxygen levels decrease KDM5C activity and cause accumulation of ULK1 R170me2s. Dimethylation of ULK1 promotes autophosphorylation at T180, a prerequisite for ULK1 activation, subsequently causing phosphorylation of Atg13 and Beclin 1, autophagosome formation, mitochondrial clearance and reduced oxygen consumption. Further, expression of a ULK1 R170K mutant impaired cell proliferation under hypoxia. This study identifies an oxygen-sensitive methylation of ULK1 with an important role in hypoxic stress adaptation by promoting autophagy induction.

Public health emergencies of international concern, in the form of infectious disease outbreaks, epidemics, and pandemics, represent an increasing risk to the worldʼs population. Management requires coordinated responses, across many disciplines and nations, and the capacity to muster proper national and global public health education, infrastructure, and prevention measures. Unfortunately, increasing numbers of nations are ruled by autocratic regimes which have characteristically failed to adopt investments in public health infrastructure, education, and prevention measures to keep pace with population growth and density. Autocratic leaders have a direct impact on health security, a direct negative impact on health, and create adverse political and economic conditions that only complicate the crisis further. This is most evident in autocratic regimes where health protections have been seriously and purposely curtailed. All autocratic regimes define public health along economic and political imperatives that are similar across borders and cultures. Autocratic regimes are seriously handicapped by sociopathic narcissistic leaders who are incapable of understanding the health consequences of infectious diseases or the impact on their population. A cross section of autocratic nations currently experiencing the impact of COVID-19 (coronavirus disease 2019) are reviewed to demonstrate the manner where self-serving regimes fail to manage health crises and place the rest of the world at increasing risk. It is time to re-address the pre-SARS (severe acute respiratory syndrome) global agendas calling for stronger strategic capacity, legal authority, support, and institutional status under World Health Organization (WHO) leadership granted by an International Health Regulations Treaty. Treaties remain the most successful means the world has in preventing, preparing for, and controlling epidemics in an increasingly globalized world.“Honesty is worth a lot more than hope…” The Economist, February 17, 2020.

In a recent issue of this journal I attempted to explain the purpose of macroautophagy/autophagy to a non-specialist audience through the use of cartoons. In the present article, I am continuing this approach by considering the topic of autophagy regulation-why does the cell need to modulate the autophagic response, and what are the basic morphological mechanisms that can be used to attain different levels of autophagy activity?

Beginning with this issue, we present answers to practical questions regarding autophagy from the lay public.