BL-918, a small-molecule activator of ULK1, induces cytoprotective autophagy for amyotrophic lateral sclerosis therapy

The ER protein CANX (calnexin)-mediated autophagy protects against alzheimer disease

Although the relationship between macroautophagy/autophagy and Alzheimer disease (AD) is widely studied, the underlying mechanisms are poorly understood, especially the regulatory role of the initiation signaling of autophagy on AD. Here, we find that the ER transmembrane protein CANX (calnexin) is a novel interaction partner of the autophagy-inducing kinase ULK1 and is required for ULK1 recruitment to the ER under basal or starved conditions. Loss of CANX results in the inactivity of ULK1 kinase and inhibits autophagy flux. In the brains of people with AD and APP-PSEN1 mice, the interaction of CANX and ULK1 declines. In mice, the lack of CANX in hippocampal neurons causes the accumulation of autophagy receptors and neuron damage, which affects the cognitive function of C57BL/6 mice. Conversely, overexpression of CANX in hippocampal neurons enhances autophagy flux and partially contributes to improving cognitive function of APP-PSEN1 mice, but not the CANX variant lacking the interaction domain with ULK1. These findings reveal a novel role of CANX in autophagy activity and cognitive function by cooperating with ULK1.Abbreviation: AD: Alzheimer disease; APEX: ascorbate peroxidase; APP: amyloid beta precursor protein; APP-PSEN1 mice: amyloid beta precursor protein-presenilin 1 transgenic mice; ATG: autophagy related; Aβ: amyloid-β; BiFC: bimolecular fluorescence complementation; CANX: calnexin; EBSS: Earle's balanced salt solution; EM: electron microscopy; IP: immunopurification; KO: knockout; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MWM: Morris water maze; PLA: proximity ligation assay; PtdIns3K: class III phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol-3-phosphate; SQSTM1/p62, sequestosome 1.

Activating autophagy to eliminate toxic protein aggregates with small molecules in neurodegenerative diseases

Neurodegenerative diseases (NDs), such as Alzheimer disease, Parkinson disease, Huntington disease, amyotrophic lateral sclerosis, and frontotemporal dementia, are well known to pose formidable challenges for their treatment due to their intricate pathogenesis and substantial variability among patients, including differences in environmental exposures and genetic predispositions. One of the defining characteristics of NDs is widely reported to be the buildup of misfolded proteins. For example, Alzheimer disease is marked by amyloid beta and hyperphosphorylated Tau aggregates, whereas Parkinson disease exhibits α-synuclein aggregates. Amyotrophic lateral sclerosis and frontotemporal dementia exhibit TAR DNA-binding protein 43, superoxide dismutase 1, and fused-in sarcoma protein aggregates, and Huntington disease involves mutant huntingtin and polyglutamine aggregates. These misfolded proteins are the key biomarkers of NDs and also serve as potential therapeutic targets, as they can be addressed through autophagy, a process that removes excess cellular inclusions to maintain homeostasis. Various forms of autophagy, including macroautophagy, chaperone-mediated autophagy, and microautophagy, hold a promise in eliminating toxic proteins implicated in NDs. In this review, we focus on elucidating the regulatory connections between autophagy and toxic proteins in NDs, summarizing the cause of the aggregates, exploring their impact on autophagy mechanisms, and discussing how autophagy can regulate toxic protein aggregation. Moreover, we underscore the activation of autophagy as a potential therapeutic strategy across different NDs and small molecules capable of activating autophagy pathways, such as rapamycin targeting the mTOR pathway to clear α-synuclein and Sertraline targeting the AMPK/mTOR/RPS6KB1 pathway to clear Tau, to further illustrate their potential in NDs' therapeutic intervention. Together, these findings would provide new insights into current research trends and propose small-molecule drugs targeting autophagy as promising potential strategies for the future ND therapies. SIGNIFICANCE STATEMENT: This review provides an in-depth overview of the potential of activating autophagy to eliminate toxic protein aggregates in the treatment of neurodegenerative diseases. It also elucidates the fascinating interrelationships between toxic proteins and the process of autophagy of "chasing and escaping" phenomenon. Moreover, the review further discusses the progress utilizing small molecules to activate autophagy to improve the efficacy of therapies for neurodegenerative diseases by removing toxic protein aggregates.

BL-918 alleviates oxidative stress in rats after subarachnoid hemorrhage by promoting mitophagy through the ULK1/PINK1/Parkin pathway

BACKGROUND AND PURPOSE

Oxidative stress plays a critical role in early brain injury (EBI) following subarachnoid hemorrhage (SAH). The small molecule ULK1 agonist, BL-918, demonstrated neuroprotective effects in other central nervous system diseases; however, its role in SAH has not yet been explored. This study aimed to evaluate whether BL-918 could provide neuroprotective effects in rats following SAH.

METHODS

An SAH model was established in Sprague-Dawley rats using endovascular perforation. BL-918 was administered intraperitoneally after SAH, while the ULK1 inhibitor SBI was given intraperitoneally prior to SAH modeling. PINK1 siRNA was administered into the lateral ventricle before SAH induction. The neuroprotective effects and mechanisms of BL-918 were assessed through SAH grading, brain water content measurement, blood-brain barrier permeability, neurobehavioral tests, Western blot, immunofluorescence, TUNEL staining, DHE staining, and transmission electron microscopy (TEM).

RESULTS

After SAH, the expression levels of p-ULK1, PINK1, Parkin, and LC3Ⅱ increased, peaking at 24 h post-SAH. BL-918 treatment improved neurological function in rats, reduced brain water content and blood-brain barrier permeability, and exhibited anti-oxidative stress and anti-apoptotic effects. Western blot analysis revealed that BL-918 increased the expression of p-ULK1, PINK1, Parkin, LC3Ⅱ, Bcl-xl, and Bcl-2 while inhibiting the expression of Bax and Cleaved Caspase-3. Oxidative stress-related indicators showed that BL-918 alleviated oxidative stress. Immunofluorescence and TEM results demonstrated that BL-918 promoted mitophagy and preserved mitochondrial morphology. Furthermore, the positive effects of BL-918 were reversed by SBI and PINK1 siRNA, respectively.

CONCLUSION

BL-918 improved both short-term and long-term neurological impairments in rats after SAH and reduced oxidative stress by promoting mitophagy, at least partially through the ULK1/PINK1/Parkin signaling pathway.

Autophagy modulation in cancer therapy: Challenges coexist with opportunities

Autophagy, a crucial intracellular degradation process facilitated by lysosomes, plays a pivotal role in maintaining cellular homeostasis. The elucidation of autophagy key genes and signaling pathways has significantly advanced our understanding of this process and has led to the exploration of autophagy as a promising therapeutic approach. This review comprehensively assesses the latest developments in small molecule modulators targeting autophagy. Moreover, the review delves into the most recent strategies for drug discovery, specifically focusing on selective agents that exploit autophagosomes and lysosomes for targeted protein degradation. Additionally, this article highlights the prevailing challenges and outlines potential future advancements in the field. By amalgamating the cutting-edge knowledge in the field, we aim to offer valuable insights and references for the anti-cancer drug development of autophagy-targeted therapies, thus contributing to the advancement of novel therapeutic interventions.

ULK1 as a therapeutic target in kidney diseases: Current perspective

INTRODUCTION

Globally, ~850 million people are affected by different kidney diseases. The pathogenesis of kidney diseases is intricate, where autophagy is crucial for maintaining kidney homeostasis. Iteliminates damaged organelles, thus reducing renal lesions and allowing tissue regeneration. Therefore, targeting various autophagy proteins, e.g. Unc-51-like autophagy-activating kinase 1 (ULK1), is emerging as potential therapeutic strategy against kidney disease.

AREAS COVERED

This review provides insights into the role of ULK1 as a therapeutic target in kidney diseases. Additionally, we have discussed the recent evidence based on pre-clinical studies for possible novel therapies modulating ULK1-mediated autophagy in kidney diseases.

EXPERT OPINION

ULK1 is one of the critical regulators of autophagy. Moreover, ULK1 works differently for different types of kidney disease. Considering its significant role in kidney disease pathogenesis, it could be a potential target to tackle kidney diseases. However, the dynamic molecular understanding of ULK1 in the context of various kidney diseases is still in its infancy and should be investigated further.

To homeostasis and beyond! Recent advances in the medicinal chemistry of heterobifunctional derivatives

The field of induced proximity therapeutics has expanded dramatically over the past 3 years, and heterobifunctional derivatives continue to form a significant component of the activities in this field. Here, we review recent advances in the field from the perspective of the medicinal chemist, with a particular focus upon informative case studies, alongside a review of emerging topics such as Direct-To-Biology (D2B) methodology and utilities for heterobifunctional compounds beyond E3 ligase mediated degradation. We also include a critical evaluation of the latest thinking around the optimisation of physicochemical and pharmacokinetic attributes of these beyond Role of Five molecules, to deliver appropriate therapeutic exposure in vivo.

BL-918 activates PINK1/Parkin signaling pathway to ameliorate the progression of Parkinson's disease

The pathogenesis of Parkinson's disease (PD) has been associated with mitochondrial dysfunction. Given that the PINK1/Parkin pathway governs mitochondrial quality control by inducing mitophagy to remove damaged mitochondria, therapeutic approaches to activate PINK1/Parkin-mediated mitophagy have the potential in the treatment of PD. Here, we have identified a new small molecule, BL-918, as an inducer of mitophagy via activating the PINK1/Parkin pathway. BL-918 triggers PINK1 accumulation and Parkin mitochondrial translocation to initiate PINK1/Parkin-mediated mitophagy. We found that mitochondrial membrane potential and mitochondrial permeability transition pore were involved in BL-918-induced PINK1/Parkin pathway activation. Moreover, we showed that BL-918 mitigated PD progression in MPTP-induced PD mice in a PINK1-dependent manner. Our results unravel a new activator of the PINK1/Parkin signaling pathway and provide a potential strategy for the treatment of PD and other diseases with dysfunctional mitochondria.

Targeting autophagy drug discovery: Targets, indications and development trends

Autophagy plays a vital role in sustaining cellular homeostasis and its alterations have been implicated in the etiology of many diseases. Drugs development targeting autophagy began decades ago and hundreds of agents were developed, some of which are licensed for the clinical usage. However, no existing intervention specifically aimed at modulating autophagy is available. The obstacles that prevent drug developments come from the complexity of the actual impact of autophagy regulators in disease scenarios. With the development and application of new technologies, several promising categories of compounds for autophagy-based therapy have emerged in recent years. In this paper, the autophagy-targeted drugs based on their targets at various hierarchical sites of the autophagic signaling network, e.g., the upstream and downstream of the autophagosome and the autophagic components with enzyme activities are reviewed and analyzed respectively, with special attention paid to those at preclinical or clinical trials. The drugs tailored to specific autophagy alone and combination with drugs/adjuvant therapies widely used in clinical for various diseases treatments are also emphasized. The emerging drug design and development targeting selective autophagy receptors (SARs) and their related proteins, which would be expected to arrest or reverse the progression of disease in various cancers, inflammation, neurodegeneration, and metabolic disorders, are critically reviewed. And the challenges and perspective in clinically developing autophagy-targeted drugs and possible combinations with other medicine are considered in the review.

Natural products targeting macroautophagy signaling in hepatocellular carcinoma therapy: Recent evidence and perspectives

Hepatocellular carcinoma (HCC), presently the second leading cause of global cancer-related mortality, continues to pose significant challenges in the realm of medical oncology, impacting both clinical drug selection and mechanistic research. Recent investigations have unveiled autophagy-related signaling as a promising avenue for HCC treatment. A growing body of research has highlighted the pivotal role of autophagy-modulating natural products in inhibiting HCC progression. In this context, we provide a concise overview of the fundamental autophagy mechanism and delineate the involvement of autophagic signaling pathways in HCC development. Additionally, we review pertinent studies demonstrating how natural products regulate autophagy to mitigate HCC. Our findings indicate that natural products exhibit cytotoxic effects through the induction of excessive autophagy, simultaneously impeding HCC cell proliferation by autophagy inhibition, thereby depriving HCC cells of essential energy. These effects have been associated with various signaling pathways, including PI3K/AKT, MAPK, AMPK, Wnt/β-catenin, Beclin-1, and ferroautophagy. These results underscore the considerable therapeutic potential of natural products in HCC treatment. However, it is important to note that the present study did not establish definitive thresholds for autophagy induction or inhibition by natural products. Further research in this domain is imperative to gain comprehensive insights into the dual role of autophagy, equipping us with a better understanding of this double-edged sword in HCC management.

Targeting autophagy with small-molecule activators for potential therapeutic purposes

Autophagy is well-known to be a lysosome-mediated catabolic process for maintaining cellular and organismal homeostasis, which has been established with many links to a variety of human diseases. Compared with the therapeutic strategy for inhibiting autophagy, activating autophagy seems to be another promising therapeutic strategy in several contexts. Hitherto, mounting efforts have been made to discover potent and selective small-molecule activators of autophagy to potentially treat human diseases. Thus, in this perspective, we focus on summarizing the complicated relationships between defective autophagy and human diseases, and further discuss the updated progress of a series of small-molecule activators targeting autophagy in human diseases. Taken together, these inspiring findings would provide a clue on discovering more small-molecule activators of autophagy as targeted candidate drugs for potential therapeutic purposes.

In Vitro Models of Amyotrophic Lateral Sclerosis

Amyotrophic Lateral Sclerosis (ALS) is one of the commonest neurodegenerative diseases of adult-onset, which is characterized by the progressive death of motor neurons in the cerebral cortex, brain stem and spinal cord. The dysfunction and death of motor neurons lead to the progressive muscle weakness, atrophy, fasciculations, spasticity and ultimately the whole paralysis of body. Despite the identification of several genetic mutations associated with the pathogenesis of ALS, including mutations in chromosome 9 open reading frame 72 leading to the abnormal expansion of GGGGCC repeat sequence, TAR DNA-binding protein 43, fused in sarcoma/translocated in liposarcoma, copper/zinc superoxide dismutase 1 (SOD1) and TANK-binding kinase 1, the exact mechanisms underlying the specific degeneration of motor neurons that causes ALS remain incompletely understood. At present, since the transgenic model expressed SOD1 mutants was established, multiple in vitro models of ALS have been developed for studying the pathology, pathophysiology and pathogenesis of ALS as well as searching the effective neurotherapeutics. This review reviewed the details of present established in vitro models used in studying the pathology, pathophysiology and pathogenesis of ALS. Meanwhile, we also discussed the advantages, disadvantages, cost and availability of each models.

Autophagy: A Cellular Guardian against Hepatic Lipotoxicity

Lipotoxicity is a phenomenon of lipid-induced cellular injury in nonadipose tissue. Excess of free saturated fatty acids (SFAs) contributes to hepatic injury in nonalcoholic fatty liver disease (NAFLD), which has been growing at an unprecedented rate in recent years. SFAs and their derivatives such as ceramides and membrane phospholipids have been shown to induce intrahepatic oxidative damage and ER stress. Autophagy represents a cellular housekeeping mechanism to counter the perturbation in organelle function and activation of stress signals within the cell. Several aspects of autophagy, including lipid droplet assembly, lipophagy, mitophagy, redox signaling and ER-phagy, play a critical role in mounting a strong defense against lipotoxic lipid species within the hepatic cells. This review provides a succinct overview of our current understanding of autophagy-lipotoxicity interaction and its pharmacological and nonpharmacological modulation in treating NAFLD.