Autophagy, an evolutionarily conserved cellular degradation pathway of the lysosome, is associated with many physiological and pathological processes. The hallmark of autophagy is the formation of ...the autophagosome that engulfs and degrades cytosolic components via its fusion with the lysosome, in either a selective or a non-selective manner. Autophagy is tightly regulated by proteins encoded by autophagy-related (atg) genes. Among these proteins, ATG8/ LC3 is essential for autophagosome biogenesis/maturation and it also functions as an adaptor protein for selective autophagy. In mammalian cells, several homologs of yeast Atg8 such as MAP1LC3, GABARAP, and GABARAPL 1/2 have been identified. However, the biological relevance of this gene diversity in higher eukaryotes, and their specific roles, are largely unknown. In this review, we describe the mammalian ATG8/LC3 family and discuss recent advancements in understanding their roles in the autophagic process. BMB Reports 2016; 49(8): 424-430.
Abstract Mutations in fused in sarcoma (FUS), a DNA/RNA binding protein, have been associated with familial amyotrophic lateral sclerosis (fALS), which is a fatal neurodegenerative disease that ...causes progressive muscular weakness and has overlapping clinical and pathologic characteristics with frontotemporal lobar degeneration. However, the role of autophagy in regulation of FUS-positive stress granules (SGs) and aggregates remains unclear. We found that the ALS-linked FUS(R521C) mutation causes accumulation of FUS-positive SGs under oxidative stress, leading to a disruption in the release of FUS from SGs in cultured neurons. Autophagy controls the quality of proteins or organelles; therefore, we checked whether autophagy regulates FUS(R521C)-positive SGs. Interestingly, FUS(R521C)-positive SGs were colocalized to RFP-LC3-positive autophagosomes. Furthermore, FUS-positive SGs accumulated in atg5−/− mouse embryonic fibroblasts (MEFs) and in autophagy-deficient neurons. However, FUS(R521C) expression did not significantly impair autophagic degradation. Moreover, autophagy activation with rapamycin reduced the accumulation of FUS-positive SGs in an autophagy-dependent manner. Rapamycin further reduced neurite fragmentation and cell death in neurons expressing mutant FUS under oxidative stress. Overall, we provide a novel pathogenic mechanism of ALS associated with a FUS mutation under oxidative stress, as well as therapeutic insight regarding FUS pathology associated with excessive SGs.
Autophagy contributes to the selective degradation of liquid droplets, including the P-Granule, Ape1-complex and p62/SQSTM1-body, although the molecular mechanisms and physiological relevance of ...selective degradation remain unclear. In this report, we describe the properties of endogenous p62-bodies, the effect of autophagosome biogenesis on these bodies, and the in vivo significance of their turnover. p62-bodies are low-liquidity gels containing ubiquitin and core autophagy-related proteins. Multiple autophagosomes form on the p62-gels, and the interaction of autophagosome-localizing Atg8-proteins with p62 directs autophagosome formation toward the p62-gel. Keap1 also reversibly translocates to the p62-gels in a p62-binding dependent fashion to activate the transcription factor Nrf2. Mice deficient for Atg8-interaction-dependent selective autophagy show that impaired turnover of p62-gels leads to Nrf2 hyperactivation in vivo. These results indicate that p62-gels are not simple substrates for autophagy but serve as platforms for both autophagosome formation and anti-oxidative stress.
Objective To determine whether neurally adjusted ventilatory assist (NAVA), a new method of mechanical ventilation that delivers pressure assistance that is proportional to the electrical activity of ...the diaphragm (EAdi), could lower the inspiratory pressure and respiratory muscle load in preterm infants supported with ventilators. Study design Twenty-six mechanically ventilated preterm infants were randomized to crossover ventilation with NAVA and synchronized intermittent mandatory ventilation (SIMV) with pressure support (PS) for 4 hours each in a randomized order. A 1-hour interval for washout was provided between the 2 modes of ventilation. The ventilator settings were adjusted to maintain similar levels of end-tidal partial pressure of CO2 . The ventilator parameters, vital signs, and gas exchange effects under the 2 ventilatory modes were compared. Results Nineteen infants completed the 9-hour crossover comparison protocol. Peak inspiratory pressure (PIP), work of breathing, and peak EAdi with NAVA were lower than those in SIMV with PS. Calculated tidal volume to peak EAdi ratio and PIP to peak EAdi ratio were higher with NAVA. There were no significant differences in mean airway pressure, inspiratory oxygen fraction, and blood gas values. The measurements of vital signs did not differ significantly between the 2 modes. Conclusion NAVA lowered PIP and reduced respiratory muscle load in preterm infants at equivalent inspiratory oxygen fraction and partial pressure of CO2 of capillary blood in comparison with SIMV with PS.
Xenophagy is a selective lysosomal degradation pathway for invading pathogens in host cells. However, invading bacteria also develop survival mechanisms to inhibit host autophagy. RavZ is a protein ...secreted by Legionella that irreversibly delipidates mammalian autophagy-related protein 8 (mATG8) on autophagic membranes in host cells via efficient autophagic membrane targeting. In this study, we leveraged the autophagic membrane-targeting mechanism of RavZ and generated a new autophagosome probe by replacing the catalytic domain of RavZ with GFP. This probe is efficiently localized to mATG8-positive autophagic membranes via a synergistic combination between mATG8 protein-binding mediated by the LC3-interacting region (LIR) motifs and phosphoinositide-3-phosphate (PI3P) binding mediated by the membrane-targeting (MT) domain. Furthermore, the membrane association activity of this new probe with an MT domain was more efficient than that of probes with a hydrophobic domain that were previously used in LIR-based autophagosome sensors. Finally, by substituting the LIR motifs of RavZ with selective LIR motifs from Fyco1 or ULK2, we developed new probes for detecting LC3A/B- or GABARAP subfamily-positive autophagic membranes, respectively. We propose that these new RavZ-based sensors will be useful for monitoring and studying the function of mATG8-positive autophagic membranes in different cellular contexts for autophagy research.
Little is known about endogenous inhibitors of angiogenic growth factors. In this study, we identified a novel endogenous anti-angiogenic factor expressed in pericytes and clarified its underlying ...mechanism and clinical significance.
Herein, we found Kai1 knockout mice showed significantly enhanced angiogenesis. Then, we investigated the anti-angiogenic roll of Kai1 in vitro and in vivo.
KAI1 was mainly expressed in pericytes rather than in endothelial cells. It localized at the membrane surface after palmitoylation by zDHHC4 enzyme and induced LIF through the Src/p53 pathway. LIF released from pericytes in turn suppressed angiogenic factors in endothelial cells as well as in pericytes themselves, leading to inhibition of angiogenesis. Interestingly, KAI1 had another mechanism to inhibit angiogenesis: It directly bound to VEGF and PDGF and inhibited activation of their receptors. In the two different in vivo cancer models, KAI1 supplementation significantly inhibited tumor angiogenesis and growth. A peptide derived from the large extracellular loop of KAI1 has been shown to have anti-angiogenic effects to block the progression of breast cancer and retinal neovascularization in vivo.
KAI1 from PC is a novel molecular regulator that counterbalances the effect of angiogenic factors.
We compared the efficacy and safety of third‐standard‐dose triple and third‐standard‐dose dual antihypertensive combination therapies in patients with mild to moderate hypertension. This was a phase ...II multicenter, randomized, double‐blind, parallel‐group trial. After a 4‐week placebo run‐in period, 245 participants were randomized to the third‐dose triple combination (ALC group; amlodipine 1.67 mg + losartan potassium 16.67 mg + chlorthalidone 4.17 mg) or third‐dose dual combination (AL group; amlodipine 1.67 mg + losartan potassium 16.67 mg, LC group; losartan potassium 16.67 mg + chlorthalidone 4.17 mg, AC group; amlodipine 1.67 mg + chlorthalidone 4.17 mg) therapy groups and followed up for 8 weeks. The mean systolic blood pressure (BP) reduction was ‐18.3 ± 13.2, ‐13.0 ± 13.3, ‐16.3 ± 12.4, and ‐13.8 ± 13.2 mmHg in the ALC, AL, LC, and AC groups, respectively. The ALC group showed significant systolic BP reduction compared to the AL and AC groups at weeks 4 (P = .010 and P = .018, respectively) and 8 (P = .017 and P = .036, respectively). At week 4, the proportion of systolic BP responders was significantly higher in the ALC group (42.6%) than in the AL (22.0%), LC (23.3%), and AC (27.1%) groups (P = .013, P = .021, and P = .045, respectively). At week 8, the proportion of systolic and diastolic BP responders was significantly higher in the ALC group (59.7%) than in the AL (39.3%) and AC (42.4%) groups (P = .022 and P = .049, respectively) at week 8. Third‐standard‐dose triple antihypertensive combination therapy demonstrated early effective BP control compared to third‐standard‐dose dual combination therapies, without increasing adverse drug reactions in patients with mild‐to‐moderate hypertension.
Personality is an essential feature for creating socially interactive robots. Studies on this dimension will facilitate enhanced human–robot interaction (HRI). Using AIBO, a social robotic pet ...developed by Sony, we examined the issue of personality in HRI. In this gender‐balanced 2 (AIBO personality: introvert vs. extrovert) by 2 (participant personality: introvert vs. extrovert) between‐subject experiment (N = 48), we found that participants could accurately recognize a robot’s personality based on its verbal and nonverbal behaviors. In addition, various complementarity attraction effects were found in HRI. Participants enjoyed interacting with a robot more when the robot’s personality was complementary to their own personalities than when the robot’s personality was similar to their own personalities. The same complementarity attraction effect was found in participants’ evaluation of the robot’s intelligence and social attraction. Participants’ feelings of social presence during the interaction were a significant mediator for the complementarity attraction effects observed. Practical and theoretical implications of the current study for the design of social robots and the study of HRI were discussed.
In an experimental asthma model, the activation of TLR4 by bacterial LPS occasionally exacerbates allergic inflammation through the production of Th2 cytokines, and mast cells have been suggested to ...play a central role in this response. However, the detailed mechanism underlying how LPS/TLR4 stimulates the production of Th2 cytokines, especially IL-13, remains unclear in mast cells. In the current study, we observed that the expression levels of leukotriene B4 receptor-2 (BLT2) and the synthesis of its ligands were highly upregulated in LPS-stimulated bone marrow-derived mast cells and that BLT2 blockade with small interfering RNA or a pharmacological inhibitor completely abolished IL-13 production, suggesting a mediatory role of the BLT2 ligand-BLT2 axis in LPS/TLR4 signaling to IL-13 synthesis in mast cells. Moreover, we demonstrated that MyD88 lies upstream of the BLT2 ligand-BLT2 axis and that this MyD88-BLT2 cascade leads to the generation of reactive oxygen species through NADPH oxidase 1 and the subsequent activation of NF-κB, thereby mediating IL-13 synthesis. Interestingly, we observed that costimulation of LPS/TLR4 and IgE/FcεRI caused greatly enhanced IL-13 synthesis in mast cells, and blockading BLT2 abolished these effects. Similarly, in vivo, the IL-13 level was markedly enhanced by LPS administration in an OVA-induced asthma model, and injecting a BLT2 antagonist beforehand clearly attenuated this increase. Together, our findings suggest that a BLT2-linked cascade plays a pivotal role in LPS/TLR4 signaling for IL-13 synthesis in mast cells, thereby potentially exacerbating allergic response. Our findings may provide insight into the mechanisms underlying how bacterial infection worsens allergic inflammation under certain conditions.
There has been conflicting evidence for the association between antenatal factors and the development of symptomatic patent ductus arteriosus (PDA) or failure of pharmacologic treatment, especially ...for maternal pregnancy–induced hypertension (PIH) or chorioamnionitis. We assessed the perinatal risk factors of symptomatic PDA in preterm infants and those of secondary ligation in infants with pharmacologic treatment for symptomatic PDA using a national cohort.
A total of 2961 infants with 22–29 weeks of gestation with symptomatic PDA or no PDA were included from the Korean Neonatal Network database. To identify significant perinatal risk factors associated with symptomatic PDA or secondary ligation, all perinatal factors were included in the univariate and multivariate generalized estimating equation analysis and final model was selected using backward elimination method based on Quasi-likelihood Information Criterion.
Lower gestational age (GA), female gender, maternal PIH and surfactant use were significant risk factors of symptomatic PDA. Antenatal corticosteroid use decreased the risk of symptomatic PDA. For secondary ligation, lower GA and cesarean section were significant risk factors. Adjusted odds ratio (aOR) of PIH as a risk factor of symptomatic PDA was 1.56 95% confidence interval 1.17–2.08. In the subgroup analysis according to the GA, lower GA, female gender, multiple pregnancy, maternal PIH and surfactant use increased the risk of symptomatic PDA, and histologic chorioamnionitis and antenatal corticosteroid use decreased the risk of symptomatic PDA only in GA 26–29 weeks group.
Lower GA increased the risk of symptomatic PDA and secondary ligation. Maternal PIH and surfactant use increased the risk of symptomatic PDA; however, antenatal corticosteroid use decreased it. Close observation of the clinical symptoms of PDA is needed in preterm infants with maternal PIH.
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