Structural insights into the recognition of phosphorylated FUNDC1 by LC3B in mitophagy

The interplay between mitochondrial dynamics and autophagy: From a key homeostatic mechanism to a driver of pathology

The complex relationship between mitochondrial dynamics and autophagy illustrates how two cellular housekeeping processes are intimately linked, illuminating fundamental principles of cellular homeostasis and shedding light on disparate pathological conditions including several neurodegenerative disorders. Here we review the basic tenets of mitochondrial dynamics i.e., the concerted balance between fusion and fission of the organelle, and its interplay with macroautophagy and selective mitochondrial autophagy, also dubbed mitophagy, in the maintenance of mitochondrial quality control and ultimately in cell viability. We illustrate how conditions of altered mitochondrial dynamics reverberate on autophagy and vice versa. Finally, we illustrate how altered interplay between these two key cellular processes participates in the pathogenesis of human disorders affecting multiple organs and systems.

Liver Cell Mitophagy in Metabolic Dysfunction-Associated Steatotic Liver Disease and Liver Fibrosis

Metabolic dysfunction-associated steatotic liver disease (MASLD) affects approximately one-third of the global population. MASLD and its advanced-stage liver fibrosis and cirrhosis are the leading causes of liver failure and liver-related death worldwide. Mitochondria are crucial organelles in liver cells for energy generation and the oxidative metabolism of fatty acids and carbohydrates. Recently, mitochondrial dysfunction in liver cells has been shown to play a vital role in the pathogenesis of MASLD and liver fibrosis. Mitophagy, a selective form of autophagy, removes and recycles impaired mitochondria. Although significant advances have been made in understanding mitophagy in liver diseases, adequate summaries concerning the contribution of liver cell mitophagy to MASLD and liver fibrosis are lacking. This review will clarify the mechanism of liver cell mitophagy in the development of MASLD and liver fibrosis, including in hepatocytes, macrophages, hepatic stellate cells, and liver sinusoidal endothelial cells. In addition, therapeutic strategies or compounds related to hepatic mitophagy are also summarized. In conclusion, mitophagy-related therapeutic strategies or compounds might be translational for the clinical treatment of MASLD and liver fibrosis.

Mitochondrial quality control in human health and disease

Mitochondria, the most crucial energy-generating organelles in eukaryotic cells, play a pivotal role in regulating energy metabolism. However, their significance extends beyond this, as they are also indispensable in vital life processes such as cell proliferation, differentiation, immune responses, and redox balance. In response to various physiological signals or external stimuli, a sophisticated mitochondrial quality control (MQC) mechanism has evolved, encompassing key processes like mitochondrial biogenesis, mitochondrial dynamics, and mitophagy, which have garnered increasing attention from researchers to unveil their specific molecular mechanisms. In this review, we present a comprehensive summary of the primary mechanisms and functions of key regulators involved in major components of MQC. Furthermore, the critical physiological functions regulated by MQC and its diverse roles in the progression of various systemic diseases have been described in detail. We also discuss agonists or antagonists targeting MQC, aiming to explore potential therapeutic and research prospects by enhancing MQC to stabilize mitochondrial function.

The hepatoprotective effect of 4-phenyltetrahydroquinolines on carbon tetrachloride induced hepatotoxicity in rats through autophagy inhibition

BACKGROUND

The liver serves as a metabolic hub within the human body, playing a crucial role in various essential functions, such as detoxification, nutrient metabolism, and hormone regulation. Therefore, protecting the liver against endogenous and exogenous insults has become a primary focus in medical research. Consequently, the potential hepatoprotective properties of multiple 4-phenyltetrahydroquinolines inspired us to thoroughly study the influence of four specially designed and synthesized derivatives on carbon tetrachloride (CCl4)-induced liver injury in rats.

METHODS AND RESULTS

Seventy-seven Wistar albino male rats weighing 140 ± 18 g were divided into eleven groups to investigate both the toxicity profile and the hepatoprotective potential of 4-phenyltetrahydroquinolines. An in-vivo hepatotoxicity model was conducted using CCl4 (1 ml/kg body weight, a 1:1 v/v mixture with corn oil, i.p.) every 72 h for 14 days. The concurrent treatment of rats with our newly synthesized compounds (each at a dose of 25 mg/kg body weight, suspended in 0.5% CMC, p.o.) every 24 h effectively lowered transaminases, preserved liver tissue integrity, and mitigated oxidative stress and inflammation. Moreover, the histopathological examination of liver tissues revealed a significant reduction in liver fibrosis, which was further supported by the immunohistochemical analysis of α-SMA. Additionally, the expression of the apoptotic genes BAX and BCL2 was monitored using real-time PCR, which showed a significant decrease in liver apoptosis. Further investigations unveiled the ability of the compounds to significantly decrease the expression of autophagy-related proteins, Beclin-1 and LC3B, consequently inhibiting autophagy. Finally, our computer-assisted simulation dockingonfirmed the obtained experimental activities.

CONCLUSION

Our findings suggest that derivatives of 4-phenyltetrahydroquinoline demonstrate hepatoprotective properties in CCl4-induced liver damage and fibrosis in rats. The potential mechanism of action may be due to the inhibition of autophagy in liver cells.

The structure and function of FUN14 domain-containing protein 1 and its contribution to cardioprotection by mediating mitophagy

Cardiovascular disease (CVD) is a serious public health risk, and prevention and treatment efforts are urgently needed. Effective preventive and therapeutic programs for cardiovascular disease are still lacking, as the causes of CVD are varied and may be the result of a multifactorial combination. Mitophagy is a form of cell-selective autophagy, and there is increasing evidence that mitophagy is involved in cardioprotective processes. Recently, many studies have shown that FUN14 domain-containing protein 1 (FUNDC1) levels and phosphorylation status are highly associated with many diseases, including heart disease. Here, we review the structure and functions of FUNDC1 and the path-ways of its mediated mitophagy, and show that mitophagy can be effectively activated by dephosphorylation of Ser13 and Tyr18 sites, phosphorylation of Ser17 site and ubiquitination of Lys119 site in FUNDC1. By effectively activating or inhibiting excessive mitophagy, the quality of mitochondria can be effectively controlled. The main reason is that, on the one hand, improper clearance of mitochondria and accumulation of damaged mitochondria are avoided, and on the other hand, excessive mitophagy causing apoptosis is avoided, both serving to protect the heart. In addition, we explore the possible mechanisms by which FUNDC1-mediated mitophagy is involved in exercise preconditioning (EP) for cardioprotection. Finally, we also point out unresolved issues in FUNDC1 and its mediated mitophagy and give directions where further research may be needed.

Chinese botanical drugs targeting mitophagy to alleviate diabetic kidney disease, a comprehensive review

Diabetic kidney disease (DKD) is one of the chronic microvascular complications caused by diabetes, which is characterized by persistent albuminuria and/or progressive decline of estimated glomerular filtration rate (eGFR), and has been the major cause of dialysis around the world. At present, although the treatments for DKD including lifestyle modification, glycemic control and even using of Sodium-glucose cotransporter 2 (SGLT2) inhibitors can relieve kidney damage caused to a certain extent, there is still a lack of effective treatment schemes that can prevent DKD progressing to ESRD. It is urgent to find new complementary and effective therapeutic agents. Growing animal researches have shown that mitophagy makes a great difference to the pathogenesis of DKD, therefore, exploration of new drugs that target the restoration of mitophagy maybe a potential perspective treatment for DKD. The use of Chinese botanical drugs (CBD) has been identified to be an effective treatment option for DKD. There is growing concern on the molecular mechanism of CBD for treatment of DKD by regulating mitophagy. In this review, we highlight the current findings regarding the function of mitophagy in the pathological damages and progression of DKD and summarize the contributions of CBD that ameliorate renal injuries in DKD by interfering with mitophagy, which will help us further explain the mechanism of CBD in treatment for DKD and explore potential therapeutic strategies for DKD.

Deciphering mitochondrial dysfunction: Pathophysiological mechanisms in vascular cognitive impairment

Vascular cognitive impairment (VCI) encompasses a range of cognitive deficits arising from vascular pathology. The pathophysiological mechanisms underlying VCI remain incompletely understood; however, chronic cerebral hypoperfusion (CCH) is widely acknowledged as a principal pathological contributor. Mitochondria, crucial for cellular energy production and intracellular signaling, can lead to numerous neurological impairments when dysfunctional. Recent evidence indicates that mitochondrial dysfunction-marked by oxidative stress, disturbed calcium homeostasis, compromised mitophagy, and anomalies in mitochondrial dynamics-plays a pivotal role in VCI pathogenesis. This review offers a detailed examination of the latest insights into mitochondrial dysfunction within the VCI context, focusing on both the origins and consequences of compromised mitochondrial health. It aims to lay a robust scientific groundwork for guiding the development and refinement of mitochondrial-targeted interventions for VCI.

Molecular mechanisms of TACE refractoriness: Directions for improvement of the TACE procedure

Transcatheter arterial chemoembolisation (TACE) is the standard of care for intermediate-stage hepatocellular carcinoma and selected patients with advanced hepatocellular carcinoma. However, TACE does not achieve a satisfactory objective response rate, and the concept of TACE refractoriness has been proposed to identify patients who do not fully benefit from TACE. Moreover, repeated TACE is necessary to obtain an optimal and sustained anti-tumour response, which may damage the patient's liver function. Therefore, studies have recently been performed to improve the effectiveness of TACE. In this review, we summarise the detailed molecular mechanisms associated with TACE responsiveness and relapse after this treatment to provide more effective targets for adjuvant therapy while helping to improve TACE regimens.

Alterations in the molecular control of mitochondrial turnover in COPD lung and airway epithelial cells

Abnormal mitochondria have been observed in bronchial- and alveolar epithelial cells of patients with chronic obstructive pulmonary disease (COPD). However, it is unknown if alterations in the molecular pathways regulating mitochondrial turnover (mitochondrial biogenesis vs mitophagy) are involved. Therefore, in this study, the abundance of key molecules controlling mitochondrial turnover were assessed in peripheral lung tissue from non-COPD patients (n = 6) and COPD patients (n = 11; GOLDII n = 4/11; GOLDIV n = 7/11) and in both undifferentiated and differentiated human primary bronchial epithelial cells (PBEC) from non-COPD patients and COPD patients (n = 4-7 patients/group). We observed significantly decreased transcript levels of key molecules controlling mitochondrial biogenesis (PPARGC1B, PPRC1, PPARD) in peripheral lung tissue from severe COPD patients. Interestingly, mRNA levels of the transcription factor TFAM (mitochondrial biogenesis) and BNIP3L (mitophagy) were increased in these patients. In general, these alterations were not recapitulated in undifferentiated and differentiated PBECs with the exception of decreased PPARGC1B expression in both PBEC models. Although these findings provide valuable insight in these pathways in bronchial epithelial cells and peripheral lung tissue of COPD patients, whether or not these alterations contribute to COPD pathogenesis, underlie changes in mitochondrial function or may represent compensatory mechanisms remains to be established.

Selective autophagy in cancer: mechanisms, therapeutic implications, and future perspectives

Eukaryotic cells engage in autophagy, an internal process of self-degradation through lysosomes. Autophagy can be classified as selective or non-selective depending on the way it chooses to degrade substrates. During the process of selective autophagy, damaged and/or redundant organelles like mitochondria, peroxisomes, ribosomes, endoplasmic reticulum (ER), lysosomes, nuclei, proteasomes, and lipid droplets are selectively recycled. Specific cargo is delivered to autophagosomes by specific receptors, isolated and engulfed. Selective autophagy dysfunction is closely linked with cancers, neurodegenerative diseases, metabolic disorders, heart failure, etc. Through reviewing latest research, this review summarized molecular markers and important signaling pathways for selective autophagy, and its significant role in cancers. Moreover, we conducted a comprehensive analysis of small-molecule compounds targeting selective autophagy for their potential application in anti-tumor therapy, elucidating the underlying mechanisms involved. This review aims to supply important scientific references and development directions for the biological mechanisms and drug discovery of anti-tumor targeting selective autophagy in the future.

Mitophagy in renal interstitial fibrosis

As a high energy consumption organ, kidney relies on a large number of mitochondria to ensure normal physiological activities. Under specific stimulation, mitophagy and mitochondrial dynamics (fission, fusion) cooperatively regulate mitochondrial quality and participate in many life activities such as energy metabolism, inflammatory response, oxidative stress, cell senescence and death. Mitophagy plays a key role in the progression of acute kidney injury and chronic kidney disease. The early induction of oxidative stress in renal parenchyma, the activation of pro-inflammatory cytokines and TGF-β signal pathway are closely related to renal interstitial fibrosis. Macrophage reprogramming is also considered to be an important participant in the progression of kidney fibrosis. This review summarizes the molecular mechanism of mitochondrial autophagy and its relationship with the pathway of promoting fibrosis, and discusses the possibility of restoring mitophagy balance as a pharmacological target for the treatment of renal interstitial fibrosis, so as to provide new ideas for more efficient anti-fibrosis and delay the progress of chronic kidney disease.

FUNDC1/PFKP-mediated mitophagy induced by KD025 ameliorates cartilage degeneration in osteoarthritis

Osteoarthritis (OA) is the most common joint disease, but no disease-modifying drugs have been approved for OA treatment. Mitophagy participates in mitochondrial homeostasis regulation by selectively clearing dysfunctional mitochondria, which might contribute to cartilage degeneration in OA. Here, we provide evidence of impaired mitophagy in OA chondrocytes, which exacerbates chondrocyte degeneration. Among the several classic mitophagy-regulating pathways and receptors, we found that FUNDC1 plays a key role in preserving chondrocyte homeostasis by inducing mitophagy. FUNDC1 knockdown in vitro and knockout in vivo decreased mitophagy and exacerbated mitochondrial dysfunction, exacerbating chondrocyte degeneration and OA progression. FUNDC1 overexpression via intra-articular injection of adeno-associated virus alleviated cartilage degeneration in OA. Mechanistically, our study demonstrated that PFKP interacts with and dephosphorylates FUNDC1 to induce mitophagy in chondrocytes. Further analysis identified KD025 as a candidate drug for restoring chondrocyte mitophagy by increasing the FUNDC1-PFKP interaction and thus alleviating cartilage degeneration in mice with DMM-induced OA. Our study highlights the role of the FUNDC1-PFKP interaction in chondrocyte homeostasis via mitophagy induction and identifies KD025 as a promising agent for treating OA by increasing chondrocyte mitophagy.

Co-chaperone BAG3 enters autophagic pathway via its interaction with microtubule associated protein 1 light chain 3 beta

The co-chaperone BAG3 is a hub for a variety of cellular pathways via its multiple domains and its interaction with chaperones of the HSP70 family or small HSPs. During aging and under cellular stress conditions in particular, BAG3, together with molecular chaperones, ensures the sequestration of aggregated or aggregation-prone ubiquitinated proteins to the autophagic-lysosomal system via ubiquitin receptors. Accumulating evidence for BAG3-mediated selective autophagy independent of cargo ubiquitination led to analyses predicting a direct interaction of BAG3 with LC3 proteins. Phylogenetically, BAG3 comprises several highly conserved potential LIRs, LC3-interacting regions, which might allow for the direct targeting of BAG3 including its cargo to autophagosomes and drive their autophagic degradation. Based on pull-down experiments, peptide arrays and proximity ligation assays, our results provide evidence of an interaction of BAG3 with LC3B. In addition, we could demonstrate that disabling all predicted LIRs abolished the inducibility of a colocalization of BAG3 with LC3B-positive structures and resulted in a substantial decrease of BAG3 levels within purified native autophagic vesicles compared with wild-type BAG3. These results suggest an autophagic targeting of BAG3 via interaction with LC3B. Therefore, we conclude that, in addition to being a key co-chaperone to HSP70, BAG3 may also act as a cargo receptor for client proteins, which would significantly extend the role of BAG3 in selective macroautophagy and protein quality control.

Unraveling the Intricacies of Autophagy and Mitophagy: Implications in Cancer Biology

Autophagy is an essential lysosome-mediated degradation pathway that maintains cellular homeostasis and viability in response to various intra- and extracellular stresses. Mitophagy is a type of autophagy that is involved in the intricate removal of dysfunctional mitochondria during conditions of metabolic stress. In this review, we describe the multifaceted roles of autophagy and mitophagy in normal physiology and the field of cancer biology. Autophagy and mitophagy exhibit dual context-dependent roles in cancer development, acting as tumor suppressors and promoters. We also discuss the important role of autophagy and mitophagy within the cancer microenvironment and how autophagy and mitophagy influence tumor host-cell interactions to overcome metabolic deficiencies and sustain the activity of cancer-associated fibroblasts (CAFs) in a stromal environment. Finally, we explore the dynamic interplay between autophagy and the immune response in tumors, indicating their potential as immunomodulatory targets in cancer therapy. As the field of autophagy and mitophagy continues to evolve, this comprehensive review provides insights into their important roles in cancer and cancer microenvironment.

Lysosome and related protein degradation technologies

Recently, targeted protein degradation technologies based on lysosomal pathways have been developed. Lysosome-based targeted protein degradation technology has a broad range of substrates and the potential to degrade intracellular and extracellular proteins, protein aggregates, damaged organelles and non-protein molecules. Thus, they hold great promise for drug R&D. This study has focused on the biogenesis of lysosomes, their basic functions, lysosome-associated diseases and targeted protein degradation technologies through the lysosomal pathway. In addition, we thoroughly examine the potential applications and limitations of this technology and engage in insightful discussions on potential avenues for future research. Our primary objective is to foster preclinical research on this technology and facilitate its successful clinical implementation.

Transcription Factor Forkhead Box P (Foxp) 1 Reduces Brain Damage During Cerebral Ischemia-Reperfusion Injury in Mice Through FUN14 Domain-containing Protein 1

Mitophagy plays a significant role in modulating the activation of pyrin domain-containing protein 3 (NLRP3) inflammasome, which is a major contributor to the inflammatory response that exacerbates cerebral ischemia-reperfusion (I/R) injury. Despite this, the transcriptional regulation mechanism that governs mitophagy remains unclear. This study sought to explore the potential mechanism of Forkhead Box P1 (Foxp1) and its impact on cerebral I/R injury. We investigated the potential neuroprotective role of Foxp1 in cerebral I/R injury by the middle cerebral artery occlusion (MCAO) mouse model. Additionally, we assessed whether FUN14 domain-containing protein 1 (FUNDC1) could rescue the protective effect of Foxp1. Our results showed that overexpression of Foxp1 prevented brain damage during cerebral I/R injury and promoted NLRP3 inflammasome activation, whereas knockdown of Foxp1 had the opposite effect. Notably, Foxp1 overexpression directly promotes FUNDC1 expression, enhanced mitophagy activation, and inhibited the inflammatory response mediated by the NLRP3 inflammasome. Furthermore, we confirmed through chromatin immunoprecipitation (ChIP) and luciferase reporter assays that FUNDC1 is a direct target gene of Foxp1 downstream. Furthermore, the knockdown of FUNDC1 reversed the increased activation of mitophagy and suppressed NLRP3 inflammasome activation induced by Foxp1 overexpression. Collectively, our findings suggest that Foxp1 inhibits NLRP3 inflammasome activation through FUNDC1 to reduce cerebral I/R injury.

Targeting mitophagy for depression amelioration: a novel therapeutic strategy

Major depressive disorder is a global psychiatric condition characterized by persistent low mood and anhedonia, which seriously jeopardizes the physical and mental well-being of affected individuals. While various hypotheses have been proposed to explicate the etiology of depression, the precise pathogenesis and effective treatment of this disorder remain elusive. Mitochondria, as the primary organelles responsible for cellular energy production, possess the ability to meet the essential energy demands of the brain. Research indicated that the accumulation of damaged mitochondria is associated with the onset of depression. Mitophagy, a type of cellular autophagy, specifically targets and removes excess or damaged mitochondria. Emerging evidence demonstrated that mitophagy dysfunction was involved in the progression of depression, and several pharmacological interventions that stimulating mitophagy exerted excellent antidepressant actions. We provided an overview of updated advancements on the regulatory mechanism of mitophagy and the mitophagy abnormality in depressed patients and animals, as well as in cell models of depression. Meanwhile, various therapeutic strategies to restore mitophagy for depression alleviation were also discussed in this review.

The mitophagy pathway and its implications in human diseases

Mitochondria are dynamic organelles with multiple functions. They participate in necrotic cell death and programmed apoptotic, and are crucial for cell metabolism and survival. Mitophagy serves as a cytoprotective mechanism to remove superfluous or dysfunctional mitochondria and maintain mitochondrial fine-tuning numbers to balance intracellular homeostasis. Growing evidences show that mitophagy, as an acute tissue stress response, plays an important role in maintaining the health of the mitochondrial network. Since the timely removal of abnormal mitochondria is essential for cell survival, cells have evolved a variety of mitophagy pathways to ensure that mitophagy can be activated in time under various environments. A better understanding of the mechanism of mitophagy in various diseases is crucial for the treatment of diseases and therapeutic target design. In this review, we summarize the molecular mechanisms of mitophagy-mediated mitochondrial elimination, how mitophagy maintains mitochondrial homeostasis at the system levels and organ, and what alterations in mitophagy are related to the development of diseases, including neurological, cardiovascular, pulmonary, hepatic, renal disease, etc., in recent advances. Finally, we summarize the potential clinical applications and outline the conditions for mitophagy regulators to enter clinical trials. Research advances in signaling transduction of mitophagy will have an important role in developing new therapeutic strategies for precision medicine.

Mitochondria in hypoxic pulmonary hypertension, roles and the potential targets

Mitochondria are the centrol hub for cellular energy metabolisms. They regulate fuel metabolism by oxygen levels, participate in physiological signaling pathways, and act as oxygen sensors. Once oxygen deprived, the fuel utilizations can be switched from mitochondrial oxidative phosphorylation to glycolysis for ATP production. Notably, mitochondria can also adapt to hypoxia by making various functional and phenotypes changes to meet the demanding of oxygen levels. Hypoxic pulmonary hypertension is a life-threatening disease, but its exact pathgenesis mechanism is still unclear and there is no effective treatment available until now. Ample of evidence indicated that mitochondria play key factor in the development of hypoxic pulmonary hypertension. By hypoxia-inducible factors, multiple cells sense and transmit hypoxia signals, which then control the expression of various metabolic genes. This activation of hypoxia-inducible factors considered associations with crosstalk between hypoxia and altered mitochondrial metabolism, which plays an important role in the development of hypoxic pulmonary hypertension. Here, we review the molecular mechanisms of how hypoxia affects mitochondrial function, including mitochondrial biosynthesis, reactive oxygen homeostasis, and mitochondrial dynamics, to explore the potential of improving mitochondrial function as a strategy for treating hypoxic pulmonary hypertension.

Chemical mitophagy modulators: Drug development strategies and novel regulatory mechanisms

Maintaining mitochondrial homeostasis is a potential therapeutic strategy for various diseases, including neurodegenerative diseases, cardiovascular diseases, metabolic disorders, and cancer. Selective degradation of mitochondria by autophagy (mitophagy) is a fundamental mitochondrial quality control mechanism conserved from yeast to humans. Indeed, small-molecule modulators of mitophagy are valuable pharmaceutical tools that can be used to dissect complex biological processes and turn them into potential drugs. In the past few years, pharmacological regulation of mitophagy has shown promising therapeutic efficacy in various disease models. However, with the increasing number of chemical mitophagy modulator studies, frequent methodological flaws can be observed, leading some studies to draw unreliable or misleading conclusions. This review attempts (a) to summarize the molecular mechanisms of mitophagy; (b) to propose a Mitophagy Modulator Characterization System (MMCS); (c) to perform a comprehensive analysis of methods used to characterize mitophagy modulators, covering publications over the past 20 years; (d) to provide novel targets for pharmacological intervention of mitophagy. We believe this review will provide a panorama of current research on chemical mitophagy modulators and promote the development of safe and robust mitophagy modulators with therapeutic potential by introducing high methodological standards.

To eat or not to eat mitochondria? How do host cells cope with mitophagy upon bacterial infection?

Mitochondria fulfil a plethora of cellular functions ranging from energy production to regulation of inflammation and cell death control. The fundamental role of mitochondria makes them a target of choice for invading pathogens, with either an intracellular or extracellular lifestyle. Indeed, the modulation of mitochondrial functions by several bacterial pathogens has been shown to be beneficial for bacterial survival inside their host. However, so far, relatively little is known about the importance of mitochondrial recycling and degradation pathways through mitophagy in the outcome (success or failure) of bacterial infection. On the one hand, mitophagy could be considered as a defensive response triggered by the host upon infection to maintain mitochondrial homeostasis. However, on the other hand, the pathogen itself may initiate the host mitophagy to escape from mitochondrial-mediated inflammation or antibacterial oxidative stress. In this review, we will discuss the diversity of various mechanisms of mitophagy in a general context, as well as what is currently known about the different bacterial pathogens that have developed strategies to manipulate the host mitophagy.

Mitophagy in atherosclerosis: from mechanism to therapy

Mitophagy is a type of autophagy that can selectively eliminate damaged and depolarized mitochondria to maintain mitochondrial activity and cellular homeostasis. Several pathways have been found to participate in different steps of mitophagy. Mitophagy plays a significant role in the homeostasis and physiological function of vascular endothelial cells, vascular smooth muscle cells, and macrophages, and is involved in the development of atherosclerosis (AS). At present, many medications and natural chemicals have been shown to alter mitophagy and slow the progression of AS. This review serves as an introduction to the field of mitophagy for researchers interested in targeting this pathway as part of a potential AS management strategy.

Mitophagy as a mitochondrial quality control mechanism in myocardial ischemic stress: from bench to bedside

Myocardial ischemia reduces the supply of oxygen and nutrients to cardiomyocytes, leading to an energetic crisis or cell death. Mitochondrial dysfunction is a decisive contributor to the reception, transmission, and modification of cardiac ischemic signals. Cells with damaged mitochondria exhibit impaired mitochondrial metabolism and increased vulnerability to death stimuli due to disrupted mitochondrial respiration, reactive oxygen species overproduction, mitochondrial calcium overload, and mitochondrial genomic damage. Various intracellular and extracellular stress signaling pathways converge on mitochondria, so dysfunctional mitochondria tend to convert from energetic hubs to apoptotic centers. To interrupt the stress signal transduction resulting from lethal mitochondrial damage, cells can activate mitophagy (mitochondria-specific autophagy), which selectively eliminates dysfunctional mitochondria to preserve mitochondrial quality control. Different pharmacological and non-pharmacological strategies have been designed to augment the protective properties of mitophagy and have been validated in basic animal experiments and pre-clinical human trials. In this review, we describe the process of mitophagy in cardiomyocytes under ischemic stress, along with its regulatory mechanisms and downstream effects. Then, we discuss promising therapeutic approaches to preserve mitochondrial homeostasis and protect the myocardium against ischemic damage by inducing mitophagy.

Emerging role of mitophagy in heart failure: from molecular mechanism to targeted therapy

Heart failure is defined as a drop in heart's pump function, accounting for reduced blood output and venous stasis, and constitutes the end stage of various cardiovascular diseases. Although mild mitochondrial dysfunction may hinder cardiomyocyte metabolism and impair myocardial function, severe mitochondrial injury is accompanied by cardiomyocyte apoptosis, leading to irreversible damage of the heart. Selective autophagy of mitochondria, or mitophagy, serves to rapidly remove dysfunctional mitochondria and restore the health of the mitochondrial population within cells by allowing reutilization of degradative substrates such as amino acids, fatty acids, and nucleotides. Although mitophagy represents a protective program that prevents the accumulation of poorly structured or damaged mitochondria, excessive mitophagy leads to mitochondrial population decline, impaired oxidative phosphorylation, and decreased ATP production. In this review, we first discuss the molecular underpinnings of mitophagy and the roles of different mitophagy adaptors. Then, the multiple and complex influence of mitophagy on heart failure is summarized. Finally, novel pharmacological strategies targeting mitophagy to relieve heart failure are briefly summarized.

The role of autophagy in cardiovascular disease: Cross-interference of signaling pathways and underlying therapeutic targets

Autophagy is a conserved lysosomal pathway for the degradation of cytoplasmic proteins and organelles, which realizes the metabolic needs of cells and the renewal of organelles. Autophagy-related genes (ATGs) are the main molecular mechanisms controlling autophagy, and their functions can coordinate the whole autophagic process. Autophagy can also play a role in cardiovascular disease through several key signaling pathways, including PI3K/Akt/mTOR, IGF/EGF, AMPK/mTOR, MAPKs, p53, Nrf2/p62, Wnt/β-catenin and NF-κB pathways. In this paper, we reviewed the signaling pathway of cross-interference between autophagy and cardiovascular diseases, and analyzed the development status of novel cardiovascular disease treatment by targeting the core molecular mechanism of autophagy as well as the critical signaling pathway. Induction or inhibition of autophagy through molecular mechanisms and signaling pathways can provide therapeutic benefits for patients. Meanwhile, we hope to provide a unique insight into cardiovascular treatment strategies by understanding the molecular mechanism and signaling pathway of crosstalk between autophagy and cardiovascular diseases.

Mitochondrial mechanisms in Alzheimer's disease: Quest for therapeutics

Mitochondrial function is essential for maintaining neuronal integrity, because neurons have a high energy demand. Neurodegenerative diseases, such as Alzheimer's disease (AD), are exacerbated by mitochondrial dysfunction. Mitochondrial autophagy (mitophagy) attenuates neurodegenerative diseases by eradicating dysfunctional mitochondria. In neurodegenerative disorders, there is disruption of the mitophagy process. High levels of iron also interfere with the mitophagy process and the mtDNA released after mitophagy is proinflammatory and triggers the cGAS-STING pathway that aids AD pathology. In this review, we critically discuss the factors that affect mitochondrial impairment and different mitophagy processes in AD. Furthermore, we discuss the molecules used in mouse studies as well as clinical trials that could result in potential therapeutics in the future.

Autophagy/Mitophagy Regulated by Ubiquitination: A Promising Pathway in Cancer Therapeutics

Autophagy is essential for organismal development, maintenance of energy homeostasis, and quality control of organelles and proteins. As a selective form of autophagy, mitophagy is necessary for effectively eliminating dysfunctional mitochondria. Both autophagy and mitophagy are linked with tumor progression and inhibition. The regulation of mitophagy and autophagy depend upon tumor type and stage. In tumors, mitophagy has dual roles: it removes damaged mitochondria to maintain healthy mitochondria and energy production, which are necessary for tumor growth. In contrast, mitophagy has been shown to inhibit tumor growth by mitigating excessive ROS production, thus preventing mutation and chromosomal instability. Ubiquitination and deubiquitination are important modifications that regulate autophagy. Multiple E3 ubiquitin ligases and DUBs modulate the activity of the autophagy and mitophagy machinery, thereby influencing cancer progression. In this review, we summarize the mechanistic association between cancer development and autophagy/mitophagy activities regulated by the ubiquitin modification of autophagic proteins. In addition, we discuss the function of multiple proteins involved in autophagy/mitophagy in tumors that may represent potential therapeutic targets.

Autophagy and autophagy-related molecules in neurodegenerative diseases

Autophagy is one of the degradation pathways to remove proteins or damaged organelles in cells that plays an important role in neuroprotection. Different stages of autophagy are regulated by autophagy-related genes, and many molecules such as transcription factor EB (TFEB) are involved. The complete autophagy process plays an important role in maintaining the dynamic balance of autophagy and is crucial to the homeostasis of intracellular substance and energy metabolism. Autophagy balance is disrupted in neurodegenerative diseases, accounting for a variety of degeneration disorders. These impairments can be alleviated or treated by the regulation of autophagy through molecules such as TFEB.

RosettaDDGPrediction for high-throughput mutational scans: From stability to binding

Reliable prediction of free energy changes upon amino acid substitutions (ΔΔGs) is crucial to investigate their impact on protein stability and protein-protein interaction. Advances in experimental mutational scans allow high-throughput studies thanks to multiplex techniques. On the other hand, genomics initiatives provide a large amount of data on disease-related variants that can benefit from analyses with structure-based methods. Therefore, the computational field should keep the same pace and provide new tools for fast and accurate high-throughput ΔΔG calculations. In this context, the Rosetta modeling suite implements effective approaches to predict folding/unfolding ΔΔGs in a protein monomer upon amino acid substitutions and calculate the changes in binding free energy in protein complexes. However, their application can be challenging to users without extensive experience with Rosetta. Furthermore, Rosetta protocols for ΔΔG prediction are designed considering one variant at a time, making the setup of high-throughput screenings cumbersome. For these reasons, we devised RosettaDDGPrediction, a customizable Python wrapper designed to run free energy calculations on a set of amino acid substitutions using Rosetta protocols with little intervention from the user. Moreover, RosettaDDGPrediction assists with checking completed runs and aggregates raw data for multiple variants, as well as generates publication-ready graphics. We showed the potential of the tool in four case studies, including variants of uncertain significance in childhood cancer, proteins with known experimental unfolding ΔΔGs values, interactions between target proteins and disordered motifs, and phosphomimetics. RosettaDDGPrediction is available, free of charge and under GNU General Public License v3.0, at https://github.com/ELELAB/RosettaDDGPrediction.

Pharmacological Progress of Mitophagy Regulation

With the advancement in novel drug discovery, biologically active compounds are considered pharmacological tools to understand complex biological mechanisms and the identification of potent therapeutic agents. Mitochondria boast a central role in different integral biological processes and mitochondrial dysfunction is associated with multiple pathologies. It is, therefore, prudent to target mitochondrial quality control mechanisms by using pharmacological approaches. However, there is a scarcity of biologically active molecules, which can interact with mitochondria directly. Currently, the chemical compounds used to induce mitophagy include oligomycin and antimycin A for impaired respiration and acute dissipation of mitochondrial membrane potential by using CCCP/FCCP, the mitochondrial uncouplers. These chemical probes alter the homeostasis of the mitochondria and limit our understanding of the energy regulatory mechanisms. Efforts are underway to find molecules that can bring about selective removal of defective mitochondria without compromising normal mitochondrial respiration. In this report, we have tried to summarize and status of the recently reported modulators of mitophagy.

Mitochondrial quality control in the brain: The physiological and pathological roles

The human brain has high energetic expenses and consumes over 20% of total oxygen metabolism. Abnormal brain energy homeostasis leads to various brain diseases. Among multiple factors that contribute to these diseases, mitochondrial dysfunction is one of the most common causes. Maintenance of mitochondrial integrity and functionality is of pivotal importance to brain energy generation. Mitochondrial quality control (MQC), employing the coordination of multiple mechanisms, is evolved to overcome many mitochondrial defects. Thus, not surprisingly, aberrant mitochondrial quality control results in a wide range of brain disorders. Targeting MQC to preserve and restore mitochondrial function has emerged as a promising therapeutic strategy for the prevention and treatment of brain diseases. Here, we set out to summarize the current understanding of mitochondrial quality control in brain homeostasis. We also evaluate potential pharmaceutically and clinically relevant targets in MQC-associated brain disorders.

Vaspin Attenuates Atrial Abnormalities by Promoting ULK1/FUNDC1-Mediated Mitophagy

The worldwide incidence and prevalence of atrial fibrillation (AF) are increasing, making it a life-threatening condition due to the higher numbers of people suffering from obesity. Vaspin, an adipokine derived from epicardial adipose tissue, has been reported to reduce inflammation, inhibit apoptosis, and induce autophagy; however, its role in the pathogenesis of AF is not known. In this study, we investigated the role of vaspin in patients with AF and explored the molecular mechanisms using atrial myocytes in vitro. Our data showed that vaspin levels were significantly reduced in the plasma of patients with AF. Lower plasma levels of vaspin were also associated with a higher risk of AF in patients with obesity. Vaspin treatment in vitro alleviated cardiomyocyte injury, atrial fibrosis, atrial myocyte apoptosis, and mitochondrial injury in atrial myocytes following Ang-II stress. Moreover, our results demonstrated that vaspin protected against Ang-II-induced atrial myocyte dysfunction by inducing mitophagy. We also observed that vaspin treatment enhanced the phosphorylation of Fun14 domain-containing protein 1 (FUNDC1) at Ser17 by unc-51 like autophagy activating kinase 1 (ULK1), resulting in the induction of mitophagy. These positive effects of vaspin were reversed by ULK1 silencing in Ang-II-stimulated HL-1 cells. Our study is the first to propose that vaspin plays a vital role in AF pathogenesis via ULK1/FUNDC1-regulated mitophagy and could be a novel therapeutic target for AF.

Mitophagy: A Potential Target for Pressure Overload-Induced Cardiac Remodelling

The pathological mechanisms underlying cardiac remodelling and cardiac dysfunction caused by pressure overload are poorly understood. Mitochondrial damage and functional dysfunction, including mitochondrial bioenergetic disorder, oxidative stress, and mtDNA damage, contribute to heart injury caused by pressure overload. Mitophagy, an important regulator of mitochondrial homeostasis and function, is triggered by mitochondrial damage and participates in the pathological process of cardiovascular diseases. Recent studies indicate that mitophagy plays a critical role in the pressure overload model, but evidence on the causal relationship between mitophagy abnormality and pressure overload-induced heart injury is inconclusive. This review summarises the mechanism, role, and regulation of mitophagy in the pressure overload model. It also pays special attention to active compounds that may regulate mitophagy in pressure overload, which provide clues for possible clinical applications.

Mitochondrial-Endoplasmic Reticulum Communication-Mediated Oxidative Stress and Autophagy

Oxidative stress is an imbalance between free radicals and the antioxidant system causing overgeneration of free radicals (oxygen-containing molecules) ultimately leading to oxidative damage in terms of lipid peroxidation, protein denaturation, and DNA mutation. Oxidative stress can activate autophagy to alleviate oxidative damage and maintain normal physiological activities of cells by degrading damaged organelles or local cytoplasm. When oxidative stress is not eliminated by autophagy, it activates the apoptosis cascade. This review provides a brief summary of mitochondrial-endoplasmic reticulum communication-mediated oxidative stress and autophagy. Mitochondria and endoplasmic reticulum being important organelles in cells are directly or indirectly connected to each other through mitochondria-associated endoplasmic reticulum membranes and jointly regulate oxidative stress and autophagy. The reactive oxygen species (ROS) produced by the mitochondrial respiratory chain are the main inducers of oxidative stress. Damaged mitochondria can be effectively cleared by the process of mitophagy mediated by PINK1/parkin pathway, Nix/BNIP3 pathways, and FUNDC1 pathway, avoiding excessive ROS production. However, the mechanism of mitochondrial-endoplasmic reticulum communication in the regulation of oxidative stress and autophagy is rarely known. For this reason, this review explores the mutual connection of mitochondria and endoplasmic reticulum in mediating oxidative stress and autophagy through ROS and Ca²⁺ and aims to provide part of the theoretical basis for alleviating oxidative stress through autophagy mediated by mitochondrial-endoplasmic reticulum communication.

Mitophagy: Critical Role in Atherosclerosis Progression

Autophagy maintains intracellular homeostasis in the cardiovascular system, including in cardiomyocytes, endothelial cells (ECs), and arterial smooth muscle cells. Mitophagy, a selective autophagy that specifically removes damaged and dysfunctional mitochondria, is particularly important for cardiovascular homeostasis. Dysfunctional mitophagy contributes to cardiovascular disease, particularly atherosclerosis (AS). This review focuses on the advances of regulator mechanisms of mitophagy and its potential roles in AS. The findings are beneficial to understanding the pathological processes of atherosclerotic lesions and provide new ideas for the prevention and clinical treatment of AS.

FUNDC1-mediated mitophagy and HIF1α activation drives pulmonary hypertension during hypoxia

Hypoxic pulmonary hypertension (PH) is a progressive disease characterized by hyper-proliferation of pulmonary vascular cells including pulmonary artery smooth muscle cells (PASMCs) and can lead to right heart failure and early death. Selective degradation of mitochondria by mitophagy during hypoxia regulates mitochondrial functions in many cells, however, it is not clear if mitophagy is involved in the pathogenesis of hypoxic PH. By employing the hypoxic mitophagy receptor Fundc1 knockout (KO) and transgenic (TG) mouse models, combined hypoxic PH models, the current study found that mitophagy is actively involved in hypoxic PH through regulating PASMC proliferation. In the pulmonary artery medium from hypoxic PH mice, mitophagy was upregulated, accompanied with the increased active form of FUNDC1 protein and the enhanced binding affinity of FUNDC1 with LC3B. In PASMCs, overexpression of FUNDC1 increased mitophagy and cell proliferation while knockdown of FUNDC1 inhibited hypoxia-induced mitophagy and PASMC proliferation. Stimulation of mitophagy by FUNDC1 in PASMCs elevated ROS production and inhibited ubiquitination of hypoxia inducible factor 1α (HIF1α), and inhibition of mitophagy by FUNDC1 knockdown or knockout abolished hypoxia-induced ROS-HIF1α upregulation. Moreover, Fundc1 TG mice developed severe hemodynamics changes and pulmonary vascular remodeling, and Fundc1 KO mice were much resistant to hypoxic PH. In addition, intraperitoneal injection of a specific FUNDC1 peptide inhibitor to block mitophagy ameliorated hypoxic PH. Our results reveal that during hypoxic PH, FUNDC1-mediated mitophagy is upregulated which activates ROS-HIF1α pathway and promotes PASMC proliferation, ultimately leads to pulmonary vascular remodeling and PH.

The Role of PTEN-L in Modulating PINK1-Parkin-Mediated Mitophagy

An inherent challenge that mitochondria face is the continuous exposure to diverse stresses which increase their likelihood of dysregulation. In response, human cells have evolved sophisticated quality control mechanisms to identify and eliminate abnormal dysfunctional mitochondria. One pivotal mitochondrial quality control pathway is PINK1/Parkin-dependent mitophagy which mediates the selective removal of the dysfunctional mitochondria from the cell by autophagy. PTEN-induced putative kinase 1 (PINK1) is a mitochondrial Ser/Thr kinase that was originally identified as a gene responsible for autosomal recessive early-onset Parkinson's disease (PD). Notably, upon failure of mitochondrial import, Parkin, another autosomal-recessive PD gene, is recruited to mitochondria and mediates the autophagic clearance of deregulated mitochondria. Importantly, recruitment of Parkin to damaged mitochondria hinges on the accumulation of PINK1 on the outer mitochondrial membrane (OMM). Normally, PINK1 is imported from the cytosol through the translocase of the outer membrane (TOM) complex, a large multimeric channel responsible for the import of most mitochondrial proteins. After import, PINK1 is rapidly degraded. Thus, at steady-state, PINK1 levels are kept low. However, upon mitochondrial import failure, PINK1 accumulates and forms a high-molecular weight > 700 kDa complex with TOM on the OMM. Thus, PINK1 functions as sensor, tagging dysfunctional mitochondria for Parkin-mediated mitophagy. Although much has been learned about the function of PINK1 in mitophagy, the biochemical and structural basis of negative regulation of PINK1 operation and functions is far from clear. Recent work unveiled new players as PTEN-l as negative regulator of PINK1 function. Herein, we review key aspects of mitophagy and PINK1/Parkin-mediated mitophagy with highlighting the role of negative regulation of PINK1 function and presenting some of the key future directions in PD cell biology.

FUN14 Domain Containing 1 (FUNDC1): A Promising Mitophagy Receptor Regulating Mitochondrial Homeostasis in Cardiovascular Diseases

Mitochondria, the intracellular organelles for cellular aerobic respiration and energy production, play an important role in the regulation of cell metabolism and cell fate. Mitophagy, a selective form of autophagy, maintains dynamic homeostasis of cells through targeting long-lived or defective mitochondria for timely clearance and recycling. Dysfunction in mitophagy is involved in the molecular mechanism responsible for the onset and development of human diseases. FUN14 domain containing 1 (FUNDC1) is a mitochondrial receptor located in the outer mitochondria membrane (OMM) to govern mitophagy process. Emerging evidence has demonstrated that levels and phosphorylation states of FUNDC1 are closely related to the occurrence, progression and prognosis of cardiovascular diseases, indicating a novel role for this mitophagy receptor in the regulation of mitochondrial homeostasis in cardiovascular system. Here we review mitophagy mediated by FUNDC1 in mitochondria and its role in various forms of cardiovascular diseases.

Regulation of Transactivation at C-TAD Domain of HIF-1α by Factor-Inhibiting HIF-1α (FIH-1): A Potential Target for Therapeutic Intervention in Cancer

Hypoxia-inducible factor-1alpha (HIF-1α) is a major transcription factor that adapts to low oxygen homeostasis and regulates the expression of several hypoxic genes, which aid in cancer survival and development. It has recently piqued the interest of translational researchers in the disciplines of cancer sciences. Hypoxia triggers an ample adaptive mechanism mediated via the HIF-1α transcriptional domain. Anaerobic glycolysis, angiogenesis, metastasis, and mitophagy are adaptive mechanisms that support tumor survival by promoting oxygen supply and regulating oxygen demand in hypoxic tumor cells. Throughout this pathway, the factor-inhibiting HIF-1α is a negative regulator of HIF-1α leading to its hydroxylation at the C-TAD domain of HIF-1α under normoxia. Thus, hydroxylated HIF-1α is unable to proceed with the transcriptional events due to interference in binding of C-TAD and CBP/p300. From this review, we can hypothesize that remodeling of FIH-1 activity is a unique mechanism that decreases the transcriptional activity of HIF-1α and, as a result, all of its hypoxic consequences. Hence, this review manuscript details the depth of knowledge of FIH-1 on hypoxia-associated cellular and molecular events, a potential strategy for targeting hypoxia-induced malignancies.

Hypoxia Acclimation Protects against Heart Failure Postacute Myocardial Infarction via Fundc1-Mediated Mitophagy

Mitochondrial dysfunction is the main cause of heart failure (HF) postacute myocardial infarction (AMI). Hypoxia acclimation (HA) reduces efficiently the area of AMI caused by ischemia and/or reperfusion and delays HF. Here, we examined whether HA improves mitochondrial structure and function through the hypoxic autophagy receptor FUNDC1 to prevent HF post-AMI. Male adult mice were acclimated in a low-pressure hypoxic animal chamber (11% oxygen (O2)) for 8 h/day for 28 days, and then, an induced HF post-AMI model via left anterior descending (LAD) artery ligation was structured to explore the efficacy and mechanism of HA. Our results showed that HA exposure can improve cardiac structure and function in mice with HF post-AMI and protected myocardial mitochondrial morphology and function. Further studies showed that HA increased the expression of Fundc1 protein and its associated mitophagy protein LC3 in myocardial tissue after infarction. We then established a cellular model of oxygen glucose deprivation (OGD) in vitro, and knockdown of FUNDC1 attenuated the protective effect of HA exposed on cardiomyocyte mitochondria and increased cardiomyocyte apoptosis. In conclusion, the protective effect of HA on HF post-AMI is achieved by regulating Fundc1-mediated mitophagy in myocardial tissue. FUNDC1-mediated mitophagy could be a promising strategy to treat cardiovascular diseases, including HF.

Dysregulated mitochondrial metabolism upon cigarette smoke exposure in various human bronchial epithelial cell models

Exposure to cigarette smoke (CS) is the primary risk factor for developing chronic obstructive pulmonary disease. The impact of CS exposure on the molecular mechanisms involved in mitochondrial quality control in airway epithelial cells is incompletely understood. Undifferentiated or differentiated primary bronchial epithelial cells were acutely/chronically exposed to whole CS (WCS) or CS extract (CSE) in submerged or air-liquid interface conditions. Abundance of key regulators controlling mitochondrial biogenesis, mitophagy and mitochondrial dynamics was assessed. Acute exposure to WCS or CSE increased the abundance of components of autophagy and receptor-mediated mitophagy in all models. Although mitochondrial content and dynamics appeared to be unaltered in response to CS, changes in both the molecular control of mitochondrial biogenesis and a shift toward an increased glycolytic metabolism were observed in particular in differentiated cultures. These alterations persisted, at least in part, after chronic exposure to WCS during differentiation and upon subsequent discontinuation of WCS exposure. In conclusion, smoke exposure alters the regulation of mitochondrial metabolism in airway epithelial cells, but observed alterations may differ between various culture models used. This article has an associated First Person interview with the joint first authors of the paper.

FUNDC1: A Promising Mitophagy Regulator at the Mitochondria-Associated Membrane for Cardiovascular Diseases

Mitochondrial autophagy (or mitophagy) regulates the mitochondrial network and function to contribute to multiple cellular processes. The protective effect of homeostatic mitophagy in cardiovascular diseases (CVDs) has attracted increasing attention. FUN14 domain containing 1 (FUNDC1), an identified mitophagy receptor, plays an essential role in CVDs. Different expression levels of FUNDC1 and its phosphorylated state at different sites alleviate or exacerbate hypoxia and ischemia/reperfusion injury, cardiac hypertrophy, or metabolic damage through promotion or inhibition of mitophagy. In addition, FUNDC1 can be enriched at contact sites between mitochondria and the endoplasmic reticulum (ER), determining the formation of mitochondria-associated membranes (MAMs) that regulate cellular calcium (Ca²⁺) homeostasis and mitochondrial dynamics to prevent heart dysfunction. Moreover, FUNDC1 has also been involved in inflammatory cardiac diseases such as septic cardiomyopathy. In this review, we collect and summarize the evidence on the roles of FUNDC1 exclusively in various CVDs, describing its interactions with different cellular organelles, its involvement in multiple cellular processes, and its associated signaling pathways. FUNDC1 may become a promising therapeutic target for the prevention and management of various CVDs.

The role of FUNDC1 in mitophagy, mitochondrial dynamics and human diseases

Mitochondria are the principal sites of energy metabolism and provide most of the energy needed for normal cellular function. They are dynamic organelles that constantly undergo fission, fusion and mitophagy to maintain their homeostasis and function. However, dysregulated mitochondrial dynamics and mitophagy leads to reduced ATP generation and mutation of their DNA, which ultimately leads to cell death. Increasing evidence has shown that the FUN14 domain-containing protein 1 (FUNDC1), a novel mitophagy receptor, participates in the process of mitochondrial dynamics and mitophagy and plays a critical role in various human diseases. Herein, we review the role of FUNDC1 in mitophagy and mitochondrial dynamics, thus providing a better understanding of the relationship between the two processes. Moreover, we summarize the treatments targeting FUNDC1, and suggest that FUNDC1 may represent a promising therapeutic target for the treatment of several human diseases such as cardiovascular diseases, metabolic syndrome, cancer and chronic obstructive pulmonary disease (COPD).

Mitophagy in Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the most common cause of end-stage kidney disease worldwide and is the main microvascular complication of diabetes. The increasing prevalence of diabetes has increased the need for effective treatment of DKD and identification of new therapeutic targets for better clinical management. Mitophagy is a highly conserved process that selectively removes damaged or unnecessary mitochondria via the autophagic machinery. Given the important role of mitophagy in the increased risk of DKD, especially with the recent surge in COVID-19-associated diabetic complications, in this review, we provide compelling evidence for maintaining homeostasis in the glomeruli and tubules and its underlying mechanisms, and offer new insights into potential therapeutic approaches for treatment of DKD.

Emerging roles of ATG7 in human health and disease

The cardinal stages of macroautophagy are driven by core autophagy-related (ATG) proteins, whose ablation largely abolishes intracellular turnover. Disrupting ATG genes is paradigmatic of studying autophagy deficiency, yet emerging data suggest that ATG proteins have extensive biological importance beyond autophagic elimination. An important example is ATG7, an essential autophagy effector enzyme that in concert with other ATG proteins, also regulates immunity, cell death and protein secretion, and independently regulates the cell cycle and apoptosis. Recently, a direct association between ATG7 dysfunction and disease was established in patients with biallelic ATG7 variants and childhood-onset neuropathology. Moreover, a prodigious body of evidence supports a role for ATG7 in protecting against complex disease states in model organisms, although how dysfunctional ATG7 contributes to manifestation of these diseases, including cancer, neurodegeneration and infection, in humans remains unclear. Here, we systematically review the biological functions of ATG7, discussing the impact of its impairment on signalling pathways and human pathology. Future studies illuminating the molecular relationship between ATG7 dysfunction and disease will expedite therapies for disorders involving ATG7 deficiency and/or impaired autophagy.

The crystal structure of the FAM134B-GABARAP complex provides mechanistic insights into the selective binding of FAM134 to the GABARAP subfamily

The mammalian Atg8 family (Atg8s proteins) consists of two subfamilies: GABARAP and LC3. All members can bind to the LC3‐interacting region (LIR) or Atg8‐interacting motif and participate in multiple steps of autophagy. The endoplasmic reticulum (ER) autophagy receptor FAM134B contains an LIR motif that can bind to Atg8s, but whether it can differentially bind to the two subfamilies and, if so, the structural basis for this preference remains unknown. Here, we found that FAM134B bound to the GABARAP subfamily more strongly than to the LC3 subfamily. We then solved the crystal structure of the FAM134B–GABARAP complex and demonstrated that FAM134B used both its LIR core and the C‐terminal helix to bind to GABARAP. We further showed that these properties might be conserved in FAM134A or FAM134C. The structure also allowed us to identify the structural determinants for the binding selectivity. Our work may be valuable for studying the differential functions of GABARAP and LC3 subfamilies in ER phagy in future.

Advances in Cardiotoxicity Induced by Altered Mitochondrial Dynamics and Mitophagy

Mitochondria are the most abundant organelles in cardiac cells, and are essential to maintain the normal cardiac function, which requires mitochondrial dynamics and mitophagy to ensure the stability of mitochondrial quantity and quality. When mitochondria are affected by continuous injury factors, the balance between mitochondrial dynamics and mitophagy is broken. Aging and damaged mitochondria cannot be completely removed in cardiac cells, resulting in energy supply disorder and accumulation of toxic substances in cardiac cells, resulting in cardiac damage and cardiotoxicity. This paper summarizes the specific underlying mechanisms by which various adverse factors interfere with mitochondrial dynamics and mitophagy to produce cardiotoxicity and emphasizes the crucial role of oxidative stress in mitophagy. This review aims to provide fresh ideas for the prevention and treatment of cardiotoxicity induced by altered mitochondrial dynamics and mitophagy.

The impact of Traditional Chinese Medicine on mitophagy in disease models

Mitophagy plays an important role in maintaining mitochondrial quality and cell homeostasis through the degradation of damaged, aged, and dysfunctional mitochondria and misfolded proteins. Many human diseases, particularly neurodegenerative diseases, are related to disorders of mitochondrial phagocytosis. Exploring the regulatory mechanisms of mitophagy is of great significance for revealing the molecular mechanisms underlying the related diseases. Herein, we summarize the major mechanisms of mitophagy, the relationship of mitophagy with human diseases, and the role of traditional Chinese medicine (TCM) in mitophagy. These discussions enhance our knowledge of mitophagy and its potential therapeutic targets using TCM.

Mitochondria and Inflammatory Bowel Diseases: Toward a Stratified Therapeutic Intervention

Mitochondria serve numerous critical cellular functions, rapidly responding to extracellular stimuli and cellular demands while dynamically communicating with other organelles. Mitochondrial function in the gastrointestinal epithelium plays a critical role in maintaining intestinal health. Emerging studies implicate the involvement of mitochondrial dysfunction in inflammatory bowel disease (IBD). This review presents mitochondrial metabolism, function, and quality control that converge in intestinal epithelial stemness, differentiation programs, barrier integrity, and innate immunity to influence intestinal inflammation. Intestinal and disease characteristics that set the stage for mitochondrial dysfunction being a key factor in IBD, and in turn, pathogenic mitochondrial mechanisms influencing and potentiating the development of IBD, are discussed. These findings establish the basis for potential mitochondrial-targeted interventions for IBD therapy. Expected final online publication date for the Annual Review of Physiology, Volume 84 is February 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

The mitophagy receptor FUN14 domain-containing 1 (FUNDC1): A promising biomarker and potential therapeutic target of human diseases

Mitochondrial autophagy (mitophagy) is the selective clearance of damaged or incomplete mitochondria by autophagy, which is critical for the functional integrity of the entire mitochondrial network and cell survival. Because dysfunction of mitophagy is closely related to many diseases, it is important to study the specific molecular mechanism and pathophysiological significance of mitophagy. FUN14 domain-containing 1 (FUNDC1) is a newly identified mitochondrial outer membrane protein that induces receptor-mediated mitophagy by its interaction with LC3 during hypoxia. The expression, phosphorylation, regulation and significance of FUNDC1 are reviewed in the context of a large number of pathophysiological conditions. Emerging evidence has demonstrated that levels and phosphorylation states of FUNDC1 are closely related to occurrence, progression and prognosis of various diseases including heart diseases and cancers, indicating that FUNDC1 may serve as a promising biomarker and potential therapeutic target.