Feed-forward Mechanism Research Articles

Disturbance‐observer‐based speed control for SPMSM drives using modified super‐twisting algorithm and extended state observer

AbstractTo address the robust speed control problem of the surface‐mounted permanent‐magnet synchronous motor (SPMSM) drive, a novel composite speed controller (CSC) is proposed, which consists of the modified super‐twisting sliding‐mode SC (STSM‐SC) and the extended state observer (ESO). Regarding the motion dynamics of the SPMSM drive, the unmodeled dynamics, endogenous, and exogenous disturbances are lumped together as the total disturbance. The ESO‐based feedforward compensation mechanism is used to deal with the total disturbance for the robustness improvement of the speed control achieved by the modified STSM‐SC‐based feedback regulation mechanism. On the basis of the field‐oriented control strategy, performance comparisons of the standard STSM‐SC, the ESO‐based standard STSM‐SC, the modified STSM‐SC, and the proposed CSC are carried out on a suitably developed experimental setup. The experimental results are presented to validate the superiority of the proposed CSC.

A Trajectory Tracking and Local Path Planning Control Strategy for Unmanned Underwater Vehicles

The control strategy of an underdriven unmanned underwater vehicle (UUV) equipped with front sonar and actuator faults in a continuous task environment is investigated. Considering trajectory tracking and local path planning in complex-obstacle environments, we propose a task transition strategy under the event-triggered mechanism and design the corresponding state space and action space for the trajectory tracking task under the deep reinforcement learning framework. Meanwhile, a feed-forward compensation mechanism is designed to counteract the effects of external disturbances and actuator faults in combination with a reduced-order extended state observer. For the path planning task under the rapidly exploring random tree (RRT) framework, a reward component and angular factors are introduced to optimize the growth and exploration points of the extended tree under the consideration of the shortest distance, optimal energy consumption, and steering angle constraints. The effectiveness of the proposed method was verified through continuous task simulations of trajectory tracking and local path planning.

Microbiota-Specific T Cells Contribute to Graft-Versus-Host Disease after Allogeneic Stem Cell Transplantation

Background: Allogeneic T-cell expansion is the primary determinant of graft-versus-host disease (GVHD), and current dogma dictates that this is driven by histocompatibility antigen disparities between donor and recipient. This paradigm represents a fixed genetic system within which donor T cells interact with recipient-derived peptide-MHC complexes. However, the current model does not account for potential cognate interactions between donor T cells and microbe-derived antigen presented by the recipient. Prior studies in healthy patients have demonstrated the existence of circulating αβT cells targeting common bacterial species in the gastrointestinal (GI) tract. Whether microbe-specific T cells derived from the donor graft impact GVHD outcomes has not been studied. We tested the hypothesis that the recipient GI microbiota serve as a source of cognate antigen, contributing to clonotypic donor T-cell expansion and induction of GVHD. Methods: Functional studies utilized allogeneic stem cell transplant models in murine systems including both matched (Marilyn Tg to B6 male) and mismatched (B6 to B6D2F1) transplants as well as inducible MHCII knockout mice. Microbiota-specific transgenic T cells (MSTCs) targeting commensal flagellin (CBir1) and vendor-specific microbiome (segmented filamentous bacteria - SFB) in the context of I-A(b) were incorporated as part of the donor graft. Mechanistic studies utilized flow cytometry, cytokine stimulation and profiling, single-cell RNA sequencing, gene set enrichment analysis, NFAT-GFP T-hybridoma reporters, live-cell imaging (xCelligence RTCA eSight), and tissue analysis with RNA in-situ hybridization (ISH). Results: MSTCs lethally augmented GVHD when given as part of the donor graft in respectively colonized recipients. Taconic B6 male recipients (SFB-bearing) developed lethal GVHD when both donor Marilyn (Allo) Tg T cells and SFB T cells were introduced, but not when either transgenic T cell was introduced alone ( Figure A, p<0.0001). In contrast, Jackson B6 recipients (SFB-absent) receiving both Allo and SFB T cells did not develop lethal GVHD ( Figure A, p<0.0001), confirming functional relevance of microbe-specificity among the donor T cell pool. Lethal GVHD was also seen with addition of CBir1 T cells to the donor graft but not with addition of bulk T cells (log-rank p<0.0001). Similar results were seen in a mismatched transplant system. To determine how MSTCs promoted lethality in the context of an allogeneic (allo) response, we performed scRNA sequencing of T cells harvested in the recipient spleen at day 6 post-transplant (prior to mortality onset). Post-transplant MSTCs harbored a naïve phenotype (Sell high/CD44 low/CD69 low) when given as the primary source of donor T cells but shifted to an early activated phenotype (Sell int/CD44 low/CD69 high/TCF7 low) when Allo T cells were concurrently introduced (ANOVA q<0.01). MSTC activation was confirmed with augmented expression of IFNγ upon PMA/ionomycin stimulation observed in allo vs. syngeneic response (Wilcoxon rank-sum, p< 0.01). Introduction of Allo T cells increased the abundance of MSTCs in the mesenteric lymph nodes (day 5, 6, Wilcoxon, p<0.01). Ablation of MHCII on the GI epithelial surface using Villin-CreERT2 I-Ab flox recipients abrogated microbe-specific T cell activation in co-culture with recipient GI intraepithelial cells harvested at day 6 post-transplant vs. non-ablated control (8, 12, 24-hr NFAT-GFP intensity, p<0.001). RNA ISH probes targeting the CDR3 region of anti-microbial CBir1 T cells demonstrated an increase in MSTC infiltration at day 6 in the recipient GI lamina propria during an allo response ( Figure B) compared to a syngeneic response (# of MSTCs/terminal ileum cross section at day 6, Wilcoxon p<0.01). Conclusions: We confirm that clonotypic T cell expansion following allogeneic transplantation is not only driven by donor-recipient genetics, as reflected by major and minor histocompatibility matching, but also by differences in microbiota composition that can serve as a source of antigenic stimulation, providing a feed-forward mechanism to propagate GVHD. Furthermore, in the context of an alloreactive T cell response that damages gut integrity, microbial antigens can be presented by GI epithelia, allowing the gut to be concurrently targeted by microbiota specific T cells whose function is additionally enhanced by the alloreactive response.

Netrin-1 feedforward mechanism promotes pancreatic cancer liver metastasis via hepatic stellate cell activation, retinoid, and ELF3 signaling

The biology of metastatic pancreatic ductal adenocarcinoma (PDAC) is distinct from that of the primary tumor due to changes in cell plasticity governed by a distinct transcriptome. Therapeutic strategies that target this distinct biology are needed. We detect an upregulation of the neuronal axon guidance molecule Netrin-1 in PDAC liver metastases that signals through its dependence receptor (DR), uncoordinated-5b (Unc5b), to facilitate metastasis invitro and invivo. The mechanism of Netrin-1 induction involves a feedforward loop whereby Netrin-1 on the surface of PDAC-secreted extracellular vesicles prepares the metastatic niche by inducing hepatic stellate cell activation and retinoic acid secretion that in turn upregulates Netrin-1 in disseminated tumor cells via RAR/RXR and Elf3 signaling. While this mechanism promotes PDAC liver metastasis, it also identifies a therapeutic vulnerability, as it can be targeted using anti-Netrin-1 therapy to inhibit metastasis using the Unc5b DR cell death mechanism.

Robust model-based predictive iterative learning control for systems with non-repetitive disturbances

Iterative Learning Control (ILC) is commonly used for batch processes. However, it may face difficulties when dealing with non-repetitive disturbances and inconsistent initial states. In situations with non-repetitive disturbances, the output may disobey constraints and negatively impact tracking performance when using existing predictive ILC algorithms. This paper introduces a new model-predictive ILC incorporating feed-forward and feedback mechanisms. This new approach evaluates and attenuates the impact of non-repetitive disturbances on the output. As a result, constraints are guaranteed, and tracking performance is preserved and improved, even in the presence of non-repetitive disturbances. Furthermore, if the desired trajectory is unattainable, the proposed ILC can robustly track an optimal trajectory while still guaranteeing constraints. The convergence is proven rigorously. Finally, two examples are provided to demonstrate the effectiveness of this new approach.

Feedforward‐ or feedback‐based group regulation guidance in collaborative groups

AbstractBackgroundCollaboration is a crucial concept in learning and has the potential to foster learning. However, the fact that collaborative groups act with a common understanding in a common task brings many difficulties. Therefore, there is a need for group regulation and guidance to support effective group regulation in collaborative learning. On the other hand, the focus should be on the effect of group regulation guidance intervention on the improvement of both individual and group performance, modes of motivational regulation strategies, and the progression of group metacognition.ObjectivesIn this study, group regulation guidance approaches were developed to support the collaborative learning of Computer Science university students. The developed group regulation guidance approach consists of feedback and a feedforward mechanism. The purpose of this study was to examine the effectiveness of these approaches on academic performance, group regulation performance perception, self‐, co‐, and socially shared regulation of intrinsic motivation, and group metacognition levels.MethodsThe study was patterned with a quasi‐experimental design. 65 students participated in the study, and various scales were used to collect data. Data were analysed using paired sample t‐tests, analysis of covariance, and multivariate analysis of covariance.Results and ConclusionAccording to the research results, academic achievement showed an increase in the experimental groups after the intervention compared with the pre‐intervention. The group in which the feedforward‐supported regulation guidance approach was used showed better learning success. In the group using the feedback‐supported regulation guidance approach, better group regulation, motivational regulation strategies, and group metacognition scores were obtained. Modes of motivational regulation strategies and group metacognition scores differed according to the experimental groups.ImplicationsWhile the results provide important clues for teachers and instructional designers, the developed approaches can be used as a framework for different fields.

Feed-forward Activation of Habenula Cholinergic Neurons by Local Acetylcholine.

While the functional and behavioral role of the medial habenula (MHb) is still emerging, recent data indicate an involvement of this nuclei in regulating mood, aversion, and addiction. Unique to the MHb is a large cluster of cholinergic neurons that project to the interpeduncular nucleus and densely express acetylcholine receptors (AChRs) suggesting that the activity of these cholinergic neurons may be regulated by ACh itself. Whether endogenous ACh from within the habenula regulates cholinergic neuron activity has not been demonstrated. Supporting a role for ACh in modulating MHb activity, acetylcholinesterase inhibitors increased the firing rate of MHb cholinergic neurons in mouse habenula slices, an effect blocked by AChR antagonists and mediated by ACh which was detected via expressing fluorescent ACh sensors in MHb in vivo. To test if cholinergic afferents innervate MHb cholinergic neurons, we used anterograde and retrograde viral tracing to identify cholinergic inputs. Surprisingly, tracing experiments failed to detect cholinergic inputs into the MHb, including from the septum, suggesting that MHb cholinergic neurons may release ACh within the MHb to drive cholinergic activity. To test this hypothesis, we expressed channelrhodopsin in a portion of MHb cholinergic neurons while recording from non-opsin-expressing neurons. Light pulses progressively increased activity of MHb cholinergic neurons indicating feed-forward activation driven by MHb ACh release. These data indicate MHb cholinergic neurons may utilize a unique feed-forward mechanism to synchronize and increase activity by releasing local ACh.

Expectation Cues and False Percepts Generate Stimulus-Specific Activity in Distinct Layers of the Early Visual Cortex.

Perception has been proposed to result from the integration of feedforward sensory signals with internally generated feedback signals. Feedback signals are believed to play an important role in driving false percepts, that is, seeing things that are not actually there. Feedforward and feedback influences on perception can be studied using layer-specific fMRI, which we used here to interrogate neural activity underlying high-confidence false percepts while healthy human participants (N = 25, male and female) performed a perceptual orientation discrimination task. Auditory cues implicitly signaled the most likely upcoming orientation (referred to here as expectations). These expectations induced orientation-specific templates in the deep and superficial layers of V2, without affecting perception. In contrast, the orientation of falsely perceived stimuli with high confidence was reflected in the middle input layers of V2, suggesting a feedforward signal contributing to false percepts. The prevalence of high-confidence false percepts was related to everyday hallucination severity in a separate online sample (N = 100), suggesting a possible link with abnormal perceptual experiences. These results reveal a potential feedforward mechanism underlying false percepts, reflected by spontaneous stimulus-like activity in the input layers of the visual cortex, independent of top-down signals reflecting cued orientations.SIGNIFICANCE STATEMENT False percepts have been suggested to arise through excessive feedback signals. However, feedforward contributions to false percepts have remained largely understudied. Laminar fMRI has been shown to be useful in distinguishing feedforward from feedback activity as it allows the imaging of different cortical layers. In the present study we demonstrate that although cued orientations are encoded in the feedback layers of the visual cortex, the content of the false percepts are encoded in the feedforward layers and did not rely on these cued orientations. This shows that false percepts can in principle emerge from random feedforward signals in the visual cortex, with possible implications for disorders hallmarked by hallucinations like schizophrenia and Parkinson's disease.

Multistep ahead prediction of temperature and humidity in solar greenhouse based on FAM-LSTM model

Solar greenhouses offer favorable climatic environments for the production of off-season crops in northern China. Greenhouse temperature and humidity are critical environmental factors influencing crop growth; therefore, it is crucial to predict the temperature and humidity. In this research, we constructed a feed-forward attention mechanism- long-short term memory (FAM-LSTM) model for the multistep prediction of temperature and humidity in a solar greenhouse. The FAM-LSTM model considered both internal and external environmental factors influencing crop growth, where the factors include temperature, humidity, light, soil temperature, and soil moisture. Then, we performed corresponding experiments employing this model in predicting both temperature and humidity at prediction horizons of 12, 24, 36, and 48 h. The FAM-LSTM model stands out due to its high accuracy compared with different models. The temperature prediction error of the model at four prediction horizons is primarily within [−0.5, 0.9], [−2.1, 1.7], [−0.9, 2.7], and [−1.8, 2.9] ℃, respectively. The humidity prediction errors of the model at four prediction horizons are mainly within [−1.9, 1.8], [−4.4, 3.6], [−6.9, 2.4], and [−5.8, 4.4] %, respectively. This study offers an effective temperature and humidity prediction approach for precise environmental regulation and damage warnings in solar greenhouses.

An elite approach to re-design Aquila optimizer for efficient AFR system control.

Controlling the air-fuel ratio system (AFR) in lean combustion spark-ignition engines is crucial for mitigating emissions and addressing climate change. In this regard, this study proposes an enhanced version of the Aquila optimizer (ImpAO) with a modified elite opposition-based learning technique to optimize the feedforward (FF) mechanism and proportional-integral (PI) controller parameters for AFR control. Simulation results demonstrate ImpAO's outstanding performance compared to state-of-the-art algorithms. It achieves a minimum cost function value of 0.6759, exhibiting robustness and stability with an average ± standard deviation range of 0.6823±0.0047. The Wilcoxon signed-rank test confirms highly significant differences (p<0.001) between ImpAO and other algorithms. ImpAO also outperforms competitors in terms of elapsed time, with an average of 43.6072 s per run. Transient response analysis reveals that ImpAO achieves a lower rise time of 1.1845 s, settling time of 3.0188 s, overshoot of 0.1679%, and peak time of 4.0371 s compared to alternative algorithms. The algorithm consistently achieves lower error-based cost function values, indicating more accurate control. ImpAO demonstrates superior capabilities in tracking the desired input signal compared to other algorithms. Comparative assessment with recent metaheuristic algorithms further confirms ImpAO's superior performance in terms of transient response metrics and error-based cost functions. In summary, the simulation results provide strong evidence of the exceptional performance and effectiveness of the proposed ImpAO algorithm. It establishes ImpAO as a reliable and superior solution for optimizing the FF mechanism-supported PI controller for the AFR system, surpassing state-of-the-art algorithms and recent metaheuristic optimizers.

Investigating the thermal and chemical kinetic effects of the internal residual on the cyclic dynamics at the dilute limits of a spark-ignition engine

The cyclic variability in the misfire and partial burn regimes of a dilute spark-ignition engine are primarily due to the feed-forward mechanism present in the residual gases. This study experimentally investigates the influence of the specific heat capacity/thermal effect and chemical kinetic effect of the internal residual on the heat release dynamics in the misfire and partial burn regimes of a dilute spark-ignition engine. Each effect is investigated by displacing excess air with bottled N2 and CO. Both short-term and long-term heat release dynamics are analyzed using association rules. Results show both an increased amount of dilution and higher specific heat capacity can result in similar dynamics. It was also found the misfire regime appears to be more sensitive to the chemical kinetic effect than the partial burn regime. Comparison of spark-to-CA05 and spark-to-CA50 between dilution methods was also conducted, where it was found the chemical kinetic effect did tend to reduce both spark-to-CA05 and spark-to-CA50. Overall, results from this study suggest different control strategies may be necessary to effectively mitigate the combustion instabilities when operating in each regime.

Glutaredoxin attenuates glutathione levels via deglutathionylation of Otub1 and subsequent destabilization of system xC.

Glutathione (GSH) is a critical component of the cellular redox system that combats oxidative stress. The glutamate-cystine antiporter, system xC-, is a key player in GSH synthesis that allows for the uptake of cystine, the rate-limiting building block of GSH. It is unclear whether GSH or GSH-dependent protein oxidation [protein S-glutathionylation (PSSG)] regulates the activity of system xC-. We demonstrate that an environment of enhanced PSSG promotes GSH increases via a system xC--dependent mechanism. Absence of the deglutathionylase, glutaredoxin (GLRX), augmented SLC7A11 protein and led to significant increases of GSH content. S-glutathionylation of C23 or C204 of the deubiquitinase OTUB1 promoted interaction with the E2-conjugating enzyme UBCH5A, leading to diminished ubiquitination and proteasomal degradation of SLC7A11 and augmentation of GSH, effects that were reversed by GLRX. These findings demonstrate an intricate link between GLRX and GSH via S-glutathionylation of OTUB1 and system xC- and illuminate a previously unknown feed-forward regulatory mechanism whereby enhanced GSH protein oxidation augments cellular GSH.

Autonomic cardiovascular control during exercise.

The cardiovascular response to exercise is largely determined by neurocirculatory control mechanisms that help to raise blood pressure and modulate vascular resistance which, in concert with regional vasodilatory mechanisms, promote blood flow to active muscle and organs. These neurocirculatory control mechanisms include a feedforward mechanism, known as central command, and three feedback mechanisms, namely, 1) the baroreflex, 2) the exercise pressor reflex, and 3) the arterial chemoreflex. The hemodynamic consequences of these control mechanisms result from their influence on the autonomic nervous system and subsequent alterations in cardiac output and vascular resistance. Although stimulation of the baroreflex inhibits sympathetic outflow and facilitates parasympathetic activity, central command, the exercise pressor reflex, and the arterial chemoreflex facilitate sympathetic activation and inhibit parasympathetic drive. Despite considerable understanding of the cardiovascular consequences of each of these mechanisms in isolation, the circulatory impact of their interaction, which occurs when various control systems are simultaneously activated (e.g., during exercise at altitude), has only recently been recognized. Although aging and cardiovascular disease (e.g., heart failure, hypertension) have both been recognized to alter the hemodynamic consequences of these regulatory systems, this review is limited to provide a brief overview on the action and interaction of neurocirculatory control mechanisms in health.

Overexpression of PSR1 in Chlamydomonas reinhardtii induces luxury phosphorus uptake.

Remediation using micro-algae offers an attractive solution to environmental phosphate (PO4 3-) pollution. However, for maximum efficiency, pre-conditioning of algae to induce 'luxury phosphorus (P) uptake' is needed. To replicate this process, we targeted the global regulator PSR1 (Myb transcription factor: Phosphate Starvation Response 1) for over-expression in algae. Manipulating a single gene (PSR1) drove uptake of both PO4 3- and a Mg2+ counter-ion leading to increased PolyP granule size, raising P levels 4-fold to 8% dry cell weight, and accelerated removal of PO4 3- from the medium. Examination of the gene expression profile showed that the P-starvation response was mimicked under P-replete conditions, switching on luxury uptake. Hyper-accumulation of P depended on a feed-forward mechanism, where a small set of 'Class I' P-transporter genes were activated despite abundant external PO4 3- levels. The transporters drove a reduction in external PO4 3- levels, permitting more genes to be expressed (Class II), leading to more P-uptake. Our data pointed toward a PSR1-independent mechanism for detection of external PO4 3- which suppressed Class II genes. This model provided a plausible mechanism for P-overplus where prior P-starvation elevates PSR1 and on P-resupply causes luxury P-uptake. This is because the Class I genes, which include P-transporter genes, are not suppressed by the excess PO4 3-. Taken together, these discoveries facilitate a bio-circular approach of recycling nutrients from wastewater back to agriculture.

Dynamic Recruitment of the Feedforward and Recurrent Mechanism for Black-White Asymmetry in the Primary Visual Cortex.

Black and white information is asymmetrically distributed in natural scenes, evokes asymmetric neuronal responses, and causes asymmetric perceptions. Recognizing the universality and essentiality of black-white asymmetry in visual information processing, the neural substrates for black-white asymmetry remain unclear. To disentangle the role of the feedforward and recurrent mechanisms in the generation of cortical black-white asymmetry, we recorded the V1 laminar responses and LGN responses of anesthetized cats of both sexes. In a cortical column, we found that black-white asymmetry starts at the input layer and becomes more pronounced in the output layer. We also found distinct dynamics of black-white asymmetry between the output layer and the input layer. Specifically, black responses dominate in all layers after stimulus onset. After stimulus offset, black and white responses are balanced in the input layer, but black responses still dominate in the output layer. Compared with that in the input layer, the rebound response in the output layer is significantly suppressed. The relative suppression strength evoked by white stimuli is notably stronger and depends on the location within the ON-OFF cortical map. A model with delayed and polarity-selective cortical suppression explains black-white asymmetry in the output layer, within which prominent recurrent connections are identified by Granger causality analysis. In addition to black-white asymmetry in response strength, the interlaminar differences in spatial receptive field varied dynamically. Our findings suggest that the feedforward and recurrent mechanisms are dynamically recruited for the generation of black-white asymmetry in V1.SIGNIFICANCE STATEMENT Black-white asymmetry is universal and essential in visual information processing, yet the neural substrates for cortical black-white asymmetry remain unknown. Leveraging V1 laminar recordings, we provided the first laminar pattern of black-white asymmetry in cat V1 and found distinct dynamics of black-white asymmetry between the output layer and the input layer. Comparing black-white asymmetry across three visual hierarchies, the LGN, V1 input layer, and V1 output layer, we demonstrated that the feedforward and recurrent mechanisms are dynamically recruited for the generation of cortical black-white asymmetry. Our findings not only enhance our understanding of laminar processing within a cortical column but also elucidate how feedforward connections and recurrent connections interact to shape neuronal response properties.

Robust control of water quality in horizontal sub-surface flow wetlands using decentralized quantitative feedback theory based controller

This paper addresses the regulation of water quality influencers such as Organic Nitrogen, Ammonia Nitrogen, Nitrate Nitrogen, Dissolved Organic Carbon and Dissolved Oxygen for a sub-surface flow horizontal wetland in a controlled environment. The plant uncertainty is quantified by using measurement data. The robust control of the process is achieved using a decentralized quantitative feedback theory based control strategy. The control structure also employs a feed-forward mechanism to minimize loop interactions and feedback control to ensure stability, tracking and disturbance rejection. The numerical simulations and hardware-in-loop implementation show that the performance specifications are robustly met.

Self-attention in vision transformers performs perceptual grouping, not attention

Recently, a considerable number of studies in computer vision involve deep neural architectures called vision transformers. Visual processing in these models incorporates computational models that are claimed to implement attention mechanisms. Despite an increasing body of work that attempts to understand the role of attention mechanisms in vision transformers, their effect is largely unknown. Here, we asked if the attention mechanisms in vision transformers exhibit similar effects as those known in human visual attention. To answer this question, we revisited the attention formulation in these models and found that despite the name, computationally, these models perform a special class of relaxation labeling with similarity grouping effects. Additionally, whereas modern experimental findings reveal that human visual attention involves both feed-forward and feedback mechanisms, the purely feed-forward architecture of vision transformers suggests that attention in these models cannot have the same effects as those known in humans. To quantify these observations, we evaluated grouping performance in a family of vision transformers. Our results suggest that self-attention modules group figures in the stimuli based on similarity of visual features such as color. Also, in a singleton detection experiment as an instance of salient object detection, we studied if these models exhibit similar effects as those of feed-forward visual salience mechanisms thought to be utilized in human visual attention. We found that generally, the transformer-based attention modules assign more salience either to distractors or the ground, the opposite of both human and computational salience. Together, our study suggests that the mechanisms in vision transformers perform perceptual organization based on feature similarity and not attention.

1489-P: iPLA2gamma as a Mediator of Lipid-Induced Metabolic Inflammation and Insulin Resistance

We have reported that bromenol lactone (BEL) improves metabolic profile. Here, we studied effect of BEL and its target iPLA2 in inflammasome which is a crucial in insulin resistance and metabolic inflammation. BEL inhibited inflammasome by LPS+palmitic acid (PA). BEL also ameliorated mitochondrial ROS and mitochondrial potential loss by LPS+PA, explaining reduced inflammasome. BEL administration in vivo also reduced metabolic inflammation and inflammasome. iPLA2gamma-KO but not iPLA2beta-KO macrophages showed reduced inflammasome by LPS+PA. Mitochondrial ROS and mitochondrial potential loss by LPS+PA were markedly reduced by iPLA2gamma KO. Cardiolipin content in macrophages was reduced by LPS+PA, which was recovered by BEL or myxothiazol, an inhibitor of mitochondrial complex bc1. Cardiolipin loss by LPS+PA was also ameliorated by iPLA2gamma KO. Cardiolipin liposome or expression of CRLS1, a gene for rate-limiting step of cardiolipin biosynthesis, reduced inflammasome by LPS+PA, while CRLS1 siRNA aggravated, suggesting that reduced cardiolipin content is critical in inflammasome by LPS+PA. iPLA2gamma-KO mice were protected from diet-induced insulin resistance, associated with reduced inflammasome and metabolic inflammation. These results suggest that initial reduction of cardiolipin content by PA-induced ROS probably due to removal of oxidized cardiolipin by iPLA2gamma might induce further mitochondrial ROS accumulation likely due to compromised mitochondrial complex activity, which would eventually lead to massive mitochondrial ROS production, marked loss of mitochondrial cardiolipin, profound mitochondrial dysfunction, and finally metabolic inflammation with lipid-induced insulin resistance, through a feed-forward mechanism. Replenishment of cardiolipin could a novel modality for treatment of diet-induced insulin resistance through recovery of mitochondrial function and amelioration of lipid-mediated inflammasome or metabolic inflammation. Disclosure M.Lee: None. H.Kang: None. Funding National Research Foundation of Korea (2019R1A2C3002924)

PARK15/FBXO7 is dispensable for PINK1/Parkin mitophagy in iNeurons and HeLa cell systems.

The protein kinase PINK1 and ubiquitin ligase Parkin promote removal of damaged mitochondria via a feed-forward mechanism involving ubiquitin (Ub) phosphorylation (pUb), Parkin activation, and ubiquitylation of mitochondrial outer membrane proteins to support the recruitment of mitophagy receptors. The ubiquitin ligase substrate receptor FBXO7/PARK15 is mutated in an early-onset parkinsonian-pyramidal syndrome. Previous studies have proposed a role for FBXO7 in promoting Parkin-dependent mitophagy. Here, we systematically examine the involvement of FBXO7 in depolarization and mt UPR-dependent mitophagy in the well-established HeLa and induced-neurons cell systems. We find that FBXO7-/- cells have no demonstrable defect in: (i) kinetics of pUb accumulation, (ii) pUb puncta on mitochondria by super-resolution imaging, (iii) recruitment of Parkin and autophagy machinery to damaged mitochondria, (iv) mitophagic flux, and (v) mitochondrial clearance as quantified by global proteomics. Moreover, global proteomics of neurogenesis in the absence of FBXO7 reveals no obvious alterations in mitochondria or other organelles. These results argue against a general role for FBXO7 in Parkin-dependent mitophagy and point to the need for additional studies to define how FBXO7 mutations promote parkinsonian-pyramidal syndrome.

Yap controls notochord formation and neural tube patterning by integrating mechanotransduction with FoxA2 and Shh expression.

Correct notochord and neural tube (NT) formation is crucial to the development of the central nervous system and midline structures. Integrated biochemical and biophysical signaling controls embryonic growth and patterning; however, the underlying mechanisms remain poorly understood. Here, we took the opportunities of marked morphological changes during notochord and NT formation and identified both necessary and sufficient roles of Yap, a key mechanosensor and mechanotransducer, in biochemical signaling activation during formation of notochord and floor plate, the ventral signaling centers that pattern the dorsal-ventral axis of NT and the surrounding tissues. We showed that Yap activation by a gradient of mechanical stress and tissue stiffness in the notochord and ventral NT induces FoxA2 and Shh expression. Hedgehog signaling activation rescued NT patterning defects caused by Yap deficiency, but not notochord formation. Therefore, mechanotransduction via Yap activation acts in feedforward mechanisms to induce FoxA2 expression for notochord formation and activate Shh expression for floor plate induction by synergistically interacting with FoxA2.