Autophagy-lysosome Pathway Research Articles

Age-related cataract: GSTP1 ubiquitination and degradation by Parkin inhibits its anti-apoptosis in lens epithelial cells

PurposeOxidative stress-induced apoptosis of lens epithelial cells (LECs) contributes to the pathogenesis of age-related cataract (ARC). The purpose of this research is to underlie the potential mechanism of E3 ligase Parkin and its oxidative stress-associated substrate in cataractogenesis. MethodsThe central anterior capsules were obtained from patients with ARC, Emory mice, and corresponding controls. SRA01/04 cells were exposed to H2O2 combined with cycloheximide (a translational inhibitor), MG-132 (a proteasome inhibitor), chloroquine (an autophagy inhibitor), Mdivi-1 (a mitochondrial division inhibitor), respectively. Co-immunoprecipitation was employed to detect protein-protein interactions and ubiquitin-tagged protein products. Levels of proteins and mRNA were evaluated by western blotting and quantitative RT-PCR assays. ResultsGlutathione-S-transferase P1 (GSTP1) was identified as a novel Parkin substrate. Compared with corresponding controls, GSTP1 was significantly decreased in the anterior lens capsules obtained from human cataracts and Emory mice. Similarly, GSTP1 was declined in H2O2-stimulated SRA01/04 cells. Ectopic expression of GSTP1 mitigated H2O2-induced apoptosis, whereas silencing GSTP1 aggregated apoptosis. In addition, H2O2 stimulation and Parkin overexpression could promote the degradation of GSTP1 through the ubiquitin-proteasome system, autophagy-lysosome pathway, and mitophagy. After co-transfection with Parkin, the non-ubiquitinatable GSTP1 mutant maintained its anti-apoptotic function, while wildtype GSTP1 failed. Mechanistically, GSTP1 might promote mitochondrial fusion through upregulating Mitofusins 1/2 (MFN1/2). ConclusionOxidative stress induces LECs apoptosis via Parkin-regulated degradation of GSTP1, which may provide potential targets for ARC therapy.

The Protective Effect of (-)-Tetrahydroalstonine against OGD/R-Induced Neuronal Injury via Autophagy Regulation

Here, (-)-Tetrahydroalstonine (THA) was isolated from Alstonia scholaris and investigated for its neuroprotective effect towards oxygen-glucose deprivation/re-oxygenation (OGD/R)-induced neuronal damage. In this study, primary cortical neurons were pre-treated with THA and then subjected to OGD/R induction. The cell viability was tested by the MTT assay, and the states of the autophagy-lysosomal pathway and Akt/mTOR pathway were monitored by Western blot analysis. The findings suggested that THA administration increased the cell viability of OGD/R-induced cortical neurons. Autophagic activity and lysosomal dysfunction were found at the early stage of OGD/R, which were significantly ameliorated by THA treatment. Meanwhile, the protective effect of THA was significantly reversed by the lysosome inhibitor. Additionally, THA significantly activated the Akt/mTOR pathway, which was suppressed after OGD/R induction. In summary, THA exhibited promising protective effects against OGD/R-induced neuronal injury by autophagy regulation through the Akt/mTOR pathway.

A novel selective estrogen receptor degrader induces cell cycle arrest in breast cancer via ERα degradation and the autophagy-lysosome pathway

Breast cancer (BC), a well-known estrogen-dependent cancer, is the most common cancer among women and the leading cause of cancer deaths. One of the most important therapeutic approaches for BC is endocrine therapy targeting estrogen receptor alpha (ERα) and thus blocking the estrogen receptor signaling pathway. Drugs, such as tamoxifen or fulvestrant, are developed based on this theory and have benefited numerous patients with BC for many years. However, many patients with advanced BC, such as tamoxifen-resistant BC, cannot benefit from these developed drugs anymore. Therefore, new drugs targeting ERα are urgently needed by patients with BC. Recently, elacestrant, a novel selective estrogen receptor degrader (SERD), was approved by the United States Food and Drug Administration (FDA), highlighting the importance of ERα degradation in endocrine therapy. Proteolysis targeting chimera (PROTAC) has been considered a powerful technique for targeting protein degradation (TPD). In this regard, we developed and studied a novel ERα degrader, which is a PROTAC-like SERD named 17e. We found that compound 17e can inhibit the growth of BC both in vitro and in vivo and induce the cell cycle arrest of BC. Importantly, 17e displayed no apparent toxicity toward healthy kidney and liver cells. Moreover, we observed that the presence of 17e led to a dramatic increase in the autophagy-lysosome pathway in an ERα-independent manner. Finally, we revealed that a decrease in MYC, a frequent deregulation oncogene in human cancers, was mediated by both ERα degradation and autophagy activation in the presence of 17e. Collectively, we discovered that compound 17e induced ERα degradation and exerts significant anti-cancer effects on BC mainly through promoting the autophagy-lysosome pathway and decreasing MYC level.

The Cys/N-degron pathway in the ubiquitin-proteasome system and autophagy.

The N-degron pathway is a degradative system in which the N-terminal residues of proteins modulate the half-lives of proteins and other cellular materials. The majority of amino acids in the genetic code have the potential to induce cis or trans degradation in diverse processes, which requires selective recognition between N-degrons and cognate N-recognins. Of particular interest is the Cys/N-degron branch, in which the N-terminal cysteine (Nt-Cys) induces proteolysis via either the ubiquitin (Ub)-proteasome system (UPS) or the autophagy-lysosome pathway (ALP), depending on physiological conditions. Recent studies provided new insights into the central role of Nt-Cys in sensing the fluctuating levels of oxygen and reactive oxygen species (ROS). Here, we discuss the components, regulations, and functions of the Cys/N-degron pathway.

Post-translational proteomics platform identifies neurite outgrowth impairments in Parkinson’s disease GBA-N370S dopamine neurons

Variants at the GBA locus, encoding glucocerebrosidase, are the strongest common genetic risk factor for Parkinson's disease (PD). To understand GBA-related disease mechanisms, we use a multi-part-enrichment proteomics and post-translational modification (PTM) workflow, identifying large numbers of dysregulated proteins and PTMs in heterozygous GBA-N370S PD patient induced pluripotent stem cell (iPSC) dopamine neurons. Alterations in glycosylation status show disturbances in the autophagy-lysosomal pathway, which concur with upstream perturbations in mammalian target of rapamycin (mTOR) activation in GBA-PD neurons. Several native and modified proteins encoded by PD-associated genes are dysregulated in GBA-PD neurons. Integrated pathway analysis reveals impaired neuritogenesis in GBA-PD neurons and identify tau as a key pathway mediator. Functional assays confirm neurite outgrowth deficits and identify impaired mitochondrial movement in GBA-PD neurons. Furthermore, pharmacological rescue of glucocerebrosidase activity in GBA-PD neurons improves the neurite outgrowth deficit. Overall, this study demonstrates the potential of PTMomics to elucidate neurodegeneration-associated pathways and potential drug targets in complex disease models.

Lysosomal dysfunction in Schwann cells is involved in bortezomib-induced peripheral neurotoxicity.

Bortezomib (BTZ) is a proteasome inhibitor serves as a first-line drug for multiple myeloma treatment. BTZ-induced peripheral neuropathy (BIPN) is the most common adverse effect of BTZ with an incidence as high as 40-60%. However, the pathological mechanisms underlying BIPN remain largely unclear. BTZ leads to dramatic Schwann cell demyelination in sciatic nerves. Previous studies implied that myelin debris was predominantly degraded via autophagy-lysosome pathway in Schwann cells. However, the association of autophagy with BIPN has not been made. Mice were treated with BTZ (2mg/kg, i.v.) on Day1 and Day4 each week for continuous 4weeks. BTZ-treated mice showed enhanced mechanical hyperalgesia, decreased tail nerve conduction and sciatic nerve demyelination. Unexpectedly, BTZ led to the accumulation of autophagic vesicles, LC3-II and p62 in the sciatic nerve. Moreover, BTZ blocked autophagic flux in RSC96 Schwann cells as determined by mcherry-GFP-LC3 assay, suggesting BTZ may impair lysosomal function rather than inducing autophagy in Schwann cells. BTZ significantly reduced the lysosomal activity in Schwann cells as determined by reduced LysoTracker Red and DQ-Red-BSA staining and increased the level of immature Cathepsin B (CTSB). Remarkably, lysosomal activators PP242 and Torin1, significantly reversed the blockage of autophagic flux by BTZ. We further verified that Torin1 rescued the demyelination, nerve conduction and reduced the mechanical hyperalgesia in BIPN mice. Additionally, Torin1 did not compromise the efficacy of BTZ in suppressing multiple myeloma RPMI8226 cell. Taken together, we identified that lysosomal dysfunction in Schwann cells caused by BTZ is involved in the BIPN pathology. Improved lysosomal function in Schwann cells can be a promising strategy for BIPN treatment.

Serine hydroxymethyltransferase 2 knockdown induces apoptosis in ccRCC by causing lysosomal membrane permeabilization via metabolic reprogramming

Serine hydroxymethyltransferase 2 (SHMT2) plays an important role in converting serine to glycine and supplying carbon to one-carbon metabolism to sustain cancer cell proliferation. However, the expression, function, and underlying mechanisms of SHMT2 in clear cell renal cell carcinoma (ccRCC) remain largely unknown. In this study, we demonstrated that SHMT2 was upregulated in ccRCC tissues compared with controls and associated with patient survival. SHMT2 knockdown inhibited proliferation, migration, and invasion in ccRCC cells. Overexpression of SHMT2 promoted tumor progression. Mechanistically, SHMT2 depletion disrupted one-carbon metabolism, increased reactive oxygen species (ROS) levels, and decreased ATP levels via metabolic reprogramming, which destroyed cell homeostasis. The SHMT2 knockdown-induced stress activated autophagy. A mass of autophagosomes fused with lysosomes, resulting in lysosomal membrane permeabilization (LMP) and leakage of lysosomal contents into the cytoplasm, which eventually led to apoptosis. Our work reveals that SHMT2 functions as an oncogenic gene to promote ccRCC progression. SHMT2 depletion induces apoptosis by causing LMP through excessive activation of the autophagy-lysosome pathway via metabolic reprogramming.

Trigonochinene E promotes lysosomal biogenesis and enhances autophagy via TFEB/TFE3 in human degenerative NP cells against oxidative stress

BackgroundMacroautophagy (henceforth autophagy) is the major form of autophagy, which delivers intracellular cargo to lysosomes for degradation. Considerable research has revealed that the impairment of lysosomal biogenesis and autophagic flux exacerbates the development of autophagy-related diseases. Therefore, reparative medicines restoring lysosomal biogenesis and autophagic flux in cells may have therapeutic potential against the increasing prevalence of these diseases. PurposeThe aim of the present study was thus to explore the effect of trigonochinene E (TE), an aromatic tetranorditerpene isolated from Trigonostemon flavidus, on lysosomal biogenesis and autophagy and to elucidate the potential underlying mechanism. MethodsFour human cell lines, HepG2, nucleus pulposus (NP), HeLa and HEK293 cells were applied in this study. The cytotoxicity of TE was evaluated by MTT assay. Lysosomal biogenesis and autophagic flux induced by 40 μM TE were analyzed using gene transfer techniques, western blotting, real-time PCR and confocal microscopy. Immunofluorescence, immunoblotting and pharmacological inhibitors/activators were applied to determine the changes in the protein expression levels in mTOR, PKC, PERK, and IRE1α signaling pathways. ResultsOur results showed that TE promotes lysosomal biogenesis and autophagic flux by activating the transcription factors of lysosomes, transcription factor EB (TFEB) and transcription factor E3 (TFE3). Mechanistically, TE induces TFEB and TFE3 nuclear translocation through an mTOR/PKC/ROS-independent and endoplasmic reticulum (ER) stress-mediated pathway. The PERK and IRE1α branches of ER stress are crucial for TE-induced autophagy and lysosomal biogenesis. Whereas TE activated PERK, which mediated calcineurin dephosphorylation of TFEB/TFE3, IRE1α was activated and led to inactivation of STAT3, which further enhanced autophagy and lysosomal biogenesis. Functionally, knockdown of TFEB or TFE3 impairs TE-induced lysosomal biogenesis and autophagic flux. Furthermore, TE-induced autophagy protects NP cells from oxidative stress to ameliorate intervertebral disc degeneration (IVDD). ConclusionsHere, our study showed that TE can induce TFEB/TFE3-dependent lysosomal biogenesis and autophagy via the PERK-calcineurin axis and IRE1α-STAT3 axis. Unlike other agents regulating lysosomal biogenesis and autophagy, TE showed limited cytotoxicity, thereby providing a new direction for therapeutic opportunities to use TE to treat diseases with impaired autophagy-lysosomal pathways, including IVDD.

Effect of ubiquitin-proteasome system and autophagy-lysosome pathway on intracellular replication of Brucella.suis

The ubiquitin-proteasome system (UPS) and autophagy-lysosome pathway (ALP) are two major protein degradation pathways in eukaryotic cells. In the present study, we investigated the role of two systems and their interaction after Brucella.suis (B.suis) infected RAW264.7 murine macrophage. We demonstrated that B.suis activated ALP by upregulating LC3-Ⅱlevels as well as incomplete inhibition of P62 expression in RAW264.7 cells. On the other hand, we used pharmacological agents to confirm that ALP contributed the intracellular proliferation of B.suis. At present, the studies on the relationship between UPS and Brucella remain less understanding. In the study, we demonstrated that UPS machinery was also activated by promoting expression of 20 s proteasome after B.suis infected RAW264.7 cells, and that, the UPS could also promote intracellular proliferation of B.suis. Many recent studies propose the close link and dynamic interconversion between UPS and ALP. Currently, the experiments demonstrated that after RAW264.7 cells infected B.suis, ALP was activated following UPS inhibition, while the UPS was not effectively activated after ALP inhibition. Last, we compared the ability to promote intracellular proliferation of B.suis between UPS and ALP. The results displayed that the ability of UPS to promote intracellular proliferation of B.suis was stronger than that of ALP, and simultaneous inhibition of UPS and ALP led to seriously affection on intracellular proliferation of B.suis. All above, our research provides a better understanding on the interaction between Brucella and both systems.

Zebrafish maoc1 Attenuates Spring Viremia of Carp Virus Propagation by Promoting Autophagy-Lysosome-Dependent Degradation of Viral Phosphoprotein.

Spring viremia of carp virus (SVCV) is the causative agent of spring viremia of carp (SVC), an important infectious disease that causes high mortality in aquaculture cyprinids. How the host defends against SVCV infection and the underlying mechanisms are still elusive. In this study, we identify that a novel gene named maoc1 is induced by SVCV infection. maoc1-deficient zebrafish are more susceptible to SVCV infection, with higher virus replication and antiviral gene induction. Further assays indicate that maoc1 interacts with the P protein of SVCV to trigger P protein degradation through the autophagy-lysosomal pathway, leading to the restriction of SVCV propagation. These findings reveal a unique zebrafish defense machinery in response to SVCV infection. IMPORTANCE SVCV P protein plays an essential role in the virus replication and viral immune evasion process. Here, we identify maoc1 as a novel SVCV-inducible gene and demonstrate its antiviral capacity through attenuating SVCV replication, by directly binding to P protein and mediating its degradation via the autophagy-lysosomal pathway. Therefore, this study not only reveals an essential role of maoc1 in fighting against SVCV infection but also demonstrates an unusual host defense mechanism in response to invading viruses.

Efficacy of IAPP suppression in mouse and human islets by GLP-1 analogue conjugated antisense oligonucleotide.

Insulin resistance is the major risk factor for Type 2 diabetes (T2D). In vulnerable individuals, insulin resistance induces a progressive loss of insulin secretion with islet pathology revealing a partial deficit of beta cells and islet amyloid derived from islet amyloid polypeptide (IAPP). IAPP is co-expressed and secreted with insulin by beta cells, expression of both proteins being upregulated in response to insulin resistance. If IAPP expression exceeds the threshold for clearance of misfolded proteins, beta cell failure occurs exacerbated by the action of IAPP toxicity to compromise the autophagy lysosomal pathway. We postulated that suppression of IAPP expression by an IAPP antisense oligonucleotide delivered to beta cells by the GLP-1 agonist exenatide (eGLP1-IAPP-ASO) is a potential disease modifying therapy for T2D. While eGLP1-IAPP-ASO suppressed mouse IAPP and transgenic human IAPP expression in mouse islets, it had no discernable effects on IAPP expression in human islets under the conditions studied. Suppression of transgenic human IAPP expression in mouse islets attenuated disruption of the autophagy lysosomal pathway in beta cells, supporting the potential of this strategy.

TNEA therapy promotes the autophagic degradation of NLRP3 inflammasome in a transgenic mouse model of Alzheimer’s disease via TFEB/TFE3 activation

BackgroundThe impairment in the autophagy-lysosomal pathway (ALP) and the activation of NLR family pyrin domain containing 3 (NLRP3) inflammasome represent two molecular events leading to neurodegeneration and neuroinflammation in Alzheimer’s disease (AD), a devastating neurodegenerative disorder without a cure. Previously we demonstrated the cognitive-enhancing effect of a combined electroacupuncture (EA) therapy termed TNEA in a transgenic mouse model of AD, involving activation of transcription factor EB (TFEB), a master regulator of ALP. However, whether and how TNEA inhibits NLRP3 inflammasome via TFEB-mediated ALP in AD remains to be investigated.Methods5xFAD mice overexpressing amyloid-β (Aβ) were treated with TNEA or EA on its composing acupoints (GB13 and GV24). The changes in the signaling pathways regulating NLRP3 inflammasome, the association of NLRP3 inflammasome with ALP, and the roles of TFEB/TFE3 in mice brains were determined by immunoblots, immunohistochemistry and AAV-mediated knockdown assays.ResultsTNEA inhibits the activation of NLRP3 inflammasome and the release of active interleukin 1β (IL1B) in the hippocampi of 5xFAD mice. Mechanistically, TNEA promoted the autophagic degradation of inflammasome components via activating both TFEB and TFE3 by modulating kinases including AMPK and AKT. The composing acupoints in TNEA showed synergistic effects on regulating these molecular events and memory improvement.ConclusionOur findings suggest that TNEA attenuates AD-associated memory impairment via promoting TFEB/TFE3-mediated autophagic clearance of Aβ and NLRP3 inflammasome, and partially reveal the molecular basis of combined acupoints therapy originated from ancient wisdom.

Effect of the Ketone Body, D-β-Hydroxybutyrate, on Sirtuin2-Mediated Regulation of Mitochondrial Quality Control and the Autophagy-Lysosomal Pathway.

Mitochondrial activity and quality control are essential for neuronal homeostasis as neurons rely on glucose oxidative metabolism. The ketone body, D-β-hydroxybutyrate (D-BHB), is metabolized to acetyl-CoA in brain mitochondria and used as an energy fuel alternative to glucose. We have previously reported that D-BHB sustains ATP production and stimulates the autophagic flux under glucose deprivation in neurons; however, the effects of D-BHB on mitochondrial turnover under physiological conditions are still unknown. Sirtuins (SIRTs) are NAD+-activated protein deacetylases involved in the regulation of mitochondrial biogenesis and mitophagy through the activation of transcription factors FOXO1, FOXO3a, TFEB and PGC1α coactivator. Here, we aimed to investigate the effect of D-BHB on mitochondrial turnover in cultured neurons and the mechanisms involved. Results show that D-BHB increased mitochondrial membrane potential and regulated the NAD+/NADH ratio. D-BHB enhanced FOXO1, FOXO3a and PGC1α nuclear levels in an SIRT2-dependent manner and stimulated autophagy, mitophagy and mitochondrial biogenesis. These effects increased neuronal resistance to energy stress. D-BHB also stimulated the autophagic-lysosomal pathway through AMPK activation and TFEB-mediated lysosomal biogenesis. Upregulation of SIRT2, FOXOs, PGC1α and TFEB was confirmed in the brain of ketogenic diet (KD)-treated mice. Altogether, the results identify SIRT2, for the first time, as a target of D-BHB in neurons, which is involved in the regulation of autophagy/mitophagy and mitochondrial quality control.

Recruiting the autophagy-lysosome pathway to engineered condensate-forming proteins.

Biomolecular condensates (BCs) are membraneless, subcellular compartments segregated from the cytoplasm by liquid-liquid phase separation, a thermodynamic process driven by the chemical properties of the constituent biomolecules. BCs are involved in a range of cellular processes such as signalling and transcriptional regulation, as well as the autophagy-lysosome pathway, one of the cell's main degradation mechanisms. Selective autophagy can recognise BCs containing cargo proteins through direct interactions with LC3, a protein present on the inner membrane of phagophores. Consensus tetratricopeptide repeat proteins (CTPRs) are highly stable proteins composed of repeated helix-turn-helix subunits that are useful in protein engineering as a result of their modular architecture and amenability to rational design. In this project, the CTPR scaffold that has been engineered to bind LC3 through grafted LIR motifs is fused to low complexity domains (LCDs) to induce BC formation. Here we investigate the effects of different LIR motifs within the engineered BCs to understand how LC3 interactions can change the physico-chemical properties of the condensates. Using these BCs we hope to gain a better understanding of how and why the autophagy-lysosome pathway utilises BCs for client degradation, with the potential for adapting the engineered proteins as targeted protein degradation therapeutics.

Proteostasis in Parkinson's disease: Recent development and possible implication in diagnosis and therapeutics.

The protein dyshomeostasis is identified as the hallmark of many age-related neurodegenerative disorders including Parkinson's disease (PD). The diseased brain shows the deposition of Lewy bodies composed of α-synuclein protein aggregates. Functional proteostasis is characterized by the well-coordinated signaling network constituting unfolded protein response (UPR), the ubiquitin-proteasome system (UPS), and the autophagy-lysosome pathway (ALP). These networks ensure proper synthesis, folding, confirmation, and degradation of protein i.e., α-synuclein protein in PD. The proper functioning the of intricately woven proteostasis network is quite resilient to sustain under the influence of stressors. The synuclein protein turnover is hugely influenced by the autosomal dominant, recessive, and X-linked mutational changes of a gene involved in UPR, UPS, and ALP. The methylation, acetylation-related epigenetic modifications of DNA and histone proteins along with microRNA-mediated transcriptional changes also lead to extensive proteostasis dysregulation. The result of defective proteostasis is the deposition of many proteins which start appearing in the biofluids and can be identified as potential biomarkers for early diagnosis of PD. The therapeutic intervention targeted at different strata of proteostasis machinery holds great possibilities for delaying the age-related accumulation of pathological hallmarks.

T-cell selection in the thymus: New routes toward the identification of the self-peptide ligandome presented by thymic epithelial cells.

Within the thymus, thymic epithelial cells (TECs) provide a dedicated niche for the selection of functional T cells expressing a highly variable and self-tolerant T-cell receptor (TCR) repertoire. In this minireview, we start by summarizing recent studies that have improved our understanding on the composition of cortical TEC and medullary TEC microenvironments. Next, we focus on the molecular processes that control the function of TECs in T-cell selection. In particular, we discuss the role of cortical TECs in positive selection and the pathways employed by these cells to generate and present selecting self-peptides:MHC II complexes. Several studies have underscored the role of the β5t-containing thymoproteasome in the production of unique MHC I-bound peptides critical for CD8 T-cell selection. Contrarily, the identity of the molecular determinants that regulate the generation of MHC II-bound self-peptides capable of positive selecting CD4 T cells is far more uncertain. We highlight recent advances that interconnect the autophagy-lysosomal pathway, the presentation of specific sets of self-peptide:MHC II complexes, and the diversification of CD4 TCR repertoire. Lastly, we discuss how these findings may open up new avenues for deciphering the identity of the MHC I and MHC II ligandome in the thymus.

Calpain-2 Facilitates Autophagic/Lysosomal Defects and Apoptosis in ARPE-19 Cells and Rats Induced by Exosomes from RPE Cells under NaIO3 Stimulation.

Although accumulated evidence supports the notion that calpain contributes to eye disease, the mechanisms by which calpain promotes RPE injury are not defined. The present study is aimed at investigating whether the effect of NaIO3-exos (exosomes derived from RPE cells under NaIO3 stimulation) on the dysfunction of the autophagy-lysosomal pathway (ALP) and apoptosis is based on its regulation of calpain activation in ARPE-19 cells and rats. The results showed that calpain-2 activation, ALP dysfunction, and apoptosis were induced by NaIO3-exos in ARPE-19 cells. NaIO3-exo significantly increased autophagic substrates by activating lysosomal dysfunction. ALP dysfunction and apoptosis in vitro could be eliminated by knocking down calpain-2 (si-C2) or the inhibitor calpain-2-IN-1. Further studies indicated that NaIO3-exo enhanced calpain-2 expression, ALP dysfunction, apoptosis, and retinal damage in rats. In summary, these results demonstrate for the first time that calpain-2 is one of the key players in the NaIO3-exo-mediated ALP dysfunction, apoptosis, and retinal damage and identify calpain-2 as a promising target for therapies aimed at age-related macular degeneration (AMD).

Slingshot homolog-1 amplifies mitochondrial abnormalities by distinctly impairing health and clearance of mitochondria.

Accumulating toxic protein assemblies, including Aβ and tau, and dysfunctional mitochondria are associated with synaptic and neuronal loss in Alzheimer's disease (AD). Such accumulations are thought to be owing to clearance defects in the autophagy-lysosome pathway. Mitochondrial dysfunction is evident in AD brains and animal models at multiple levels, such as mitochondrial genomic mutations, disrupted bioenergetics, deregulated mitochondrial dynamics and impaired clearance of damaged mitochondria (mitophagy). Slingshot homolog-1 (SSH1) is a phosphatase activated by oxidative stress, high intracellular levels of Ca2+ and Aβ42 oligomers (Aβ42O), known for its function to dephosphorylate/activate cofilin through the N-terminal region. SSH1-mediated cofilin dephosphorylation results in Ab42O-induced severing of F-actin and translocation of cofilin to mitochondria, which promotes mitochondria-mediated apoptosis, synaptic loss and synaptic deficits. On the other hand, SSH1-mediated dephosphorylation/deactivation of the autophagy-cargo receptor p62 (SQSTM1), through its C-terminal region, inhibits p62 autophagy flux. However, the interplay between these two different activities of SSH1 in Aβ42O-induced mitochondrial toxicity remains unclear. In this study, we assessed the role of endogenous SSH1 and different regions of SSH1 in regulating mitochondrial health, mitochondrial respiration, clearance of damaged mitochondria and synaptic integrity in vitro and in vivo. Our results indicate that SSH1 suppresses mitochondrial health and respiration through the cofilin-binding N-terminal region, whereas SSH1 impairs mitophagy through a newly identified ~ 100 residue p62-binding domain in the C-terminal region. These results indicate that both N-terminal and C-terminal regions negatively impact mitochondria by distinct and independent modalities to amplify mitochondrial abnormalities, making SSH1 an excellent target to mitigate AD pathogenesis.

Myrcene Salvages Rotenone-Induced Loss of Dopaminergic Neurons by Inhibiting Oxidative Stress, Inflammation, Apoptosis, and Autophagy.

Parkinson's disease (PD) is characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta, resulting in motor deficits. The exact etiology of PD is currently unknown; however, the pathological hallmarks of PD include excessive production of reactive oxygen species, enhanced neuroinflammation, and overproduction of α-synuclein. Under normal physiological conditions, aggregated α-synuclein is degraded via the autophagy lysosomal pathway. However, impairment of the autophagy lysosomal pathway results in α-synuclein accumulation, thereby facilitating the pathogenesis of PD. Current medications only manage the symptoms, but are unable to delay, prevent, or cure the disease. Collectively, oxidative stress, inflammation, apoptosis, and autophagy play crucial roles in PD; therefore, there is an enormous interest in exploring novel bioactive agents of natural origin for their protective roles in PD. The present study evaluated the role of myrcene, a monoterpene, in preventing the loss of dopaminergic neurons in a rotenone (ROT)-induced rodent model of PD, and elucidated the underlying mechanisms. Myrcene was administered at a dose of 50 mg/kg, 30 min prior to the intraperitoneal injections of ROT (2.5 mg/kg). Administration of ROT caused a considerable loss of dopaminergic neurons, subsequent to a significant reduction in the antioxidant defense systems, increased lipid peroxidation, and activation of microglia and astrocytes, along with the production of pro-inflammatory cytokines (IL-6, TNF-α, IL-1β) and matrix metalloproteinase-9. Rotenone also resulted in impairment of the autophagy lysosomal pathway, as evidenced by increased expression of LC3, p62, and beclin-1 with decreased expression in the phosphorylation of mTOR protein. Collectively, these factors result in the loss of dopaminergic neurons. However, myrcene treatment has been observed to restore antioxidant defenses and attenuate the increase in concentrations of lipid peroxidation products, pro-inflammatory cytokines, diminished microglia, and astrocyte activation. Myrcene treatment also enhanced the phosphorylation of mTOR, reinstated neuronal homeostasis, restored autophagy-lysosomal degradation, and prevented the increased expression of α-synuclein following the rescue of dopaminergic neurons. Taken together, our study clearly revealed the mitigating effect of myrcene on dopaminergic neuronal loss, attributed to its potent antioxidant, anti-inflammatory, and anti-apoptotic properties, and favorable modulation of autophagic flux. This study suggests that myrcene may be a potential candidate for therapeutic benefits in PD.

New unexpected role for Wolfram Syndrome protein WFS1: a novel therapeutic target for Alzheimer's disease?

New unexpected role for Wolfram Syndrome protein WFS1: a novel therapeutic target for Alzheimer's disease?