Decoding the molecular mechanism of selective autophagy of glycogen mediated by autophagy receptor STBD1.

Autophagy of glycogen (glycophagy) is crucial for the maintenance of cellular glucose homeostasis and physiology in mammals. STBD1 can serve as an autophagy receptor to mediate glycophagy by specifically recognizing glycogen and relevant key autophagic factors, but with poorly understood mechanisms. Here, we systematically characterize the interactions of STBD1 with glycogen and related saccharides, and determine the crystal structure of the STBD1 CBM20 domain with maltotetraose, uncovering a unique binding mode involving two different oligosaccharide-binding sites adopted by STBD1 CBM20 for recognizing glycogen. In addition, we demonstrate that the LC3-interacting region (LIR) motif of STBD1 can selectively bind to six mammalian ATG8 family members. We elucidate the detailed molecular mechanism underlying the selective interactions of STBD1 with ATG8 family proteins by solving the STBD1 LIR/GABARAPL1 complex structure. Importantly, our cell-based assays reveal that both the STBD1 LIR/GABARAPL1 interaction and the intact two oligosaccharide binding sites of STBD1 CBM20 are essential for the effective association of STBD1, GABARAPL1, and glycogen in cells. Finally, through mass spectrometry, biochemical, and structural modeling analyses, we unveil that STBD1 can directly bind to the Claw domain of RB1CC1 through its LIR, thereby recruiting the key autophagy initiation factor RB1CC1. In all, our findings provide mechanistic insights into the recognitions of glycogen, ATG8 family proteins, and RB1CC1 by STBD1 and shed light on the potential working mechanism of STBD1-mediated glycophagy.

Defect in degradation of glycogenin-exposed residual glycogen in lysosomes is the fundamental pathomechanism of Pompe disease.

Pompe disease is a lysosomal storage disorder that preferentially affects muscles, and it is caused by GAA mutation coding acid alpha-glucosidase in lysosome and glycophagy deficiency. While the initial pathology of Pompe disease is glycogen accumulation in lysosomes, the special role of the lysosomal pathway in glycogen degradation is not fully understood. Hence, we investigated the characteristics of accumulated glycogen and the mechanism underlying glycophagy disturbance in Pompe disease. Skeletal muscle specimens were obtained from the affected sites of patients and mouse models with Pompe disease. Histological analysis, immunoblot analysis, immunofluorescence assay, and lysosome isolation were utilized to analyze the characteristics of accumulated glycogen. Cell culture, lentiviral infection, and the CRISPR/Cas9 approach were utilized to investigate the regulation of glycophagy accumulation. We demonstrated residual glycogen, which was distinguishable from mature glycogen by exposed glycogenin and more α-amylase resistance, accumulated in the skeletal muscle of Pompe disease. Lysosome isolation revealed glycogen-free glycogenin in wild type mouse lysosomes and variously sized glycogenin in Gaa-/- mouse lysosomes. Our study identified that a defect in the degradation of glycogenin-exposed residual glycogen in lysosomes was the fundamental pathological mechanism of Pompe disease. Meanwhile, glycogenin-exposed residual glycogen was absent in other glycogen storage diseases caused by cytoplasmic glycogenolysis deficiencies. In vitro, the generation of residual glycogen resulted from cytoplasmic glycogenolysis. Notably, the inhibition of glycogen phosphorylase led to a reduction in glycogenin-exposed residual glycogen and glycophagy accumulations in cellular models of Pompe disease. Therefore, the lysosomal hydrolysis pathway played a crucial role in the degradation of residual glycogen into glycogenin, which took place in tandem with cytoplasmic glycogenolysis. These findings may offer a novel substrate reduction therapeutic strategy for Pompe disease. © 2024 The Pathological Society of Great Britain and Ireland.

Myocardial glycophagy flux dysregulation and glycogen accumulation characterize diabetic cardiomyopathy.

Diabetic heart disease morbidity and mortality is escalating. No specific therapeutics exist and mechanistic understanding of diabetic cardiomyopathy etiology is lacking. While lipid accumulation is a recognized cardiomyocyte phenotype of diabetes, less is known about glycolytic fuel handling and storage. Based on in vitro studies, we postulated the operation of an autophagy pathway in the myocardium specific for glycogen homeostasis - glycophagy. Here we visualize occurrence of cardiac glycophagy and show that the diabetic myocardium is characterized by marked glycogen elevation and altered cardiomyocyte glycogen localization. We establish that cardiac glycophagy flux is disturbed in diabetes. Glycophagy may represent a potential therapeutic target for alleviating the myocardial impacts of metabolic disruption in diabetic heart disease.

D-pinitol alleviates diabetic cardiomyopathy by inhibiting the optineurin-mediated endoplasmic reticulum stress and glycophagy signaling pathway.

Diabetic cardiomyopathy (DCM) is an important complication resulting in heart failure and death of diabetic patients. However, there is no effective drug for treatments. This study investigated the effect of D-pinitol (DP) on cardiac injury using diabetic mice and glycosylation injury of cardiomyocytes and its molecular mechanisms. We established the streptozotocin-induced SAMR1 and SAMP8 mice and DP (150 mg/kg/day) intragastrically and advanced glycation end-products (AGEs)-induced H9C2 cells. H9C2 cells were transfected with optineurin (OPTN) siRNA and overexpression plasmids. The metabolic disorder indices, cardiac dysfunction, histopathology, immunofluorescence, western blot, and immunoprecipitation were investigated. Our results showed that DP reduced the blood glucose and AGEs, and increased the expression of heart OPTN in diabetic mice and H9C2 cells, thereby inhibiting the endoplasmic reticulum stress (GRP78, CHOP) and glycophagy (STBD1, GABARAPL1), and alleviating the myocardial apoptosis and fibrosis of DCM. The expression of filamin A as an interaction protein of OPTN downregulated by AGEs decreased OPTN abundance. Moreover, OPTN siRNA increased the expression of GRP78, CHOP, STBD1, and GABARAPL1 and inhibited the expression of GAA via GSK3ß phosphorylation and FoxO1. DP may be helpful to treat the onset of DCM. Targeting OPTN with DP could be translated into clinical application in the fighting against DCM.

Glycogen-autophagy: Molecular machinery and cellular mechanisms of glycophagy.

Autophagy is an essential cellular process involving degradation of superfluous or defective macromolecules and organelles as a form of homeostatic recycling. Initially proposed to be a "bulk" degradation pathway, a more nuanced appreciation of selective autophagy pathways has developed in the literature in recent years. As a glycogen-selective autophagy process, "glycophagy" is emerging as a key metabolic route of transport and delivery of glycolytic fuel substrate. Study of glycophagy is at an early stage. Enhanced understanding of this major noncanonical pathway of glycogen flux will provide important opportunities for new insights into cellular energy metabolism. In addition, glycogen metabolic mishandling is centrally involved in the pathophysiology of several metabolic diseases in a wide range of tissues, including the liver, skeletal muscle, cardiac muscle, and brain. Thus, advances in this exciting new field are of broad multidisciplinary interest relevant to many cell types and metabolic states. Here, we review the current evidence of glycophagy involvement in homeostatic cellular metabolic processes and of molecular mediators participating in glycophagy flux. We integrate information from a variety of settings including cell lines, primary cell culture systems, ex vivo tissue preparations, genetic disease models, and clinical glycogen disease states.

Glycogen-binding protein STBD1: Molecule and role in pathophysiology.

Starch-binding domain-containing protein 1 (STBD1) is a glycogen-binding protein discovered in skeletal muscle gene differential expression that is pivotal to cellular energy metabolism. Recent studies have indicated that STBD1 is involved in many physiological processes, such as glycophagy, glycogen accumulation, and lipid droplet formation. Moreover, dysregulation of STBD1 causes multiple diseases, including cardiovascular disease, metabolic disease, and even cancer. Deletions and/or mutations in STBD1 promote tumorigenesis. Therefore, STBD1 has garnered considerable interest in the pathology community. In this review, we first summarized the current understanding of STBD1, including its structure, subcellular localization, tissue distribution, and biological functions. Next, we examined the roles and molecular mechanisms of STBD1 in related diseases. Based on available research, we discussed the novel function and future of STBD1, including its potential application as a therapeutic target in glycogen-related diseases. Given the significance of STBD1 in energy metabolism, an in-depth understanding of the protein is crucial for understanding physiological processes and developing therapeutic strategies for related diseases.

Asiatic acid alleviates ischemic myocardial injury in mice by modulating mitophagy- and glycophagy-based energy metabolism.

Myocardial infarction (MI) causes disturbances in myocardial energy metabolism, ultimately leading to a poor prognosis. Cytosolic glycogen autophagy (glycophagy) and mitochondrial autophagy (mitophagy) are upregulated in MI to optimize energy metabolism but to a limited extent. Asiatic acid (AA), a pentacyclic triterpene derived from the traditional Chinese herb Centella asiatica, displays anti-inflammatory, antioxidant, and antiapoptotic activities. AA has been found to alleviate focal cerebral and liver ischemic injury by reversing mitochondrial dysfunction. In this study, we investigated whether AA exerted cardioprotective effects against MI by activating glycophagy and mitophagy to improve the energy balance. In vitro cardioprotective effects were examined in neonatal mouse cardiomyocytes subjected to oxygen-glucose deprivation for 12 h. Treatment with AA (2-50 µM) significantly increased cell viability and improved the energy metabolism evidenced by increased ATP level and phosphocreatine/ATP ratio. In vivo cardioprotective effects were studied in a mouse model of MI. Administration of AA (5-125 mg·kg-1·d-1, ig) significantly reduced infarct size and ischemic myocardial injury, and improved cardiac function. AA treatment also promoted mitophagy and relieved mitochondrial edema evidenced by increased number of mitophagosomes in ischemic myocardium in vivo and increased mitochondria-light chain 3 (LC3)-II colocalization in ODG-treated cardiomyocytes in vitro. Mitophagy activation was accompanied by activation of the AMPK signaling pathway. Knockdown of AMPK abolished AA-activated mitophagy. Furthermore, we showed that glycophagy was upregulated in OGD cardiomyocytes evidenced by increased starch binding domain protein 1 (STBD1)-GABA type A receptor-associated protein-like 1(GABARAPL1) interaction and extracellular acidification rate, whereas AA treatment further promoted glycophagy accompanied by PI3K/Akt activation. PI3K inhibitor LY294002 or Akt inhibitor GSK690693 blocked the effects of AA on glycophagy and glycolysis. Finally, simultaneous inhibition of glycophagy and mitophagy abolished the cardioprotective effects and energy regulation of AA. These results demonstrate that AA protects ischemic cardiomyocytes by modulating glycophagy- and mitophagy-based energy metabolism through the PI3K/Akt and AMPK pathways.

Uncovering the Role of Glycogen in Brown Adipose Tissue.

The presence of glycogen in the brown adipose tissue (BAT) has been described 60 years ago. However, the role of this energetic storage in brown adipocytes has been long time underestimated. We have recently shown that during brown adipocyte differentiation in the embryo, glycogen accumulates and is degraded by glycophagy, a dynamic essential for lipid droplets biogenesis. Recent studies have shown that the storage and degradation of triglycerides in BAT are not essential for the activation of BAT in response to cold exposure in adults, and that glycogen can compensate for their absence. In this review, we report the recent advances related to the importance of glycogen in brown adipocytes.

Characterization of the endolysosomal system in human chordoma cell lines: is there a role of lysosomes in chemoresistance of this rare bone tumor?

Chordoma is a rare tumor of the bone derived from remnants of the notochord with pronounced chemoresistance. A common feature of the notochord and chordoma cells is distinct vacuolization. Recently, the notochord vacuole was described as a lysosome-related organelle. Since lysosomes are considered as mediators of drug resistance in cancer, we were interested whether they may also play a role in chemoresistance of chordoma. We characterized the lysosomal compartment in chordoma cell lines by cytochemistry, electron microscopy (ELMI) and mutational analysis of genes essential for the physiology of lysosomes. Furthermore, we tested for the first time the cytotoxicity of chloroquine, which targets lysosomes, on chordoma. Cytochemical stainings clearly demonstrated a huge mass of lysosomes in chordoma cell lines with perinuclear accumulation. Also vacuoles in chordoma cells were positive for the lysosomal marker LAMP1 but showed no acidic pH. Genetic analysis detected no apparent mutation associated with known lysosomal pathologies suggesting that vacuolization and the huge lysosomal mass of chordoma cell lines is rather a relict of the notochord than a result of transformation. ELMI investigation of chordoma cells confirmed the presence of large vacuoles, lysosomes and autophagosomes with heterogeneous ultrastructure embedded in glycogen. Interestingly, chordoma cells seem to mobilize cellular glycogen stores via autophagy. Our first preclinical data suggested no therapeutically benefit of chloroquine for chordoma. Even though, chordoma cells are crammed with lysosomes which are according to their discoverer de Duve "cellular suicide bags". Destabilizing these "suicide bags" might be a promising strategy for the treatment of chordoma.

Myocardial glycogen dynamics: new perspectives on disease mechanisms.

Cardiac glycogen regulation involves a complex interplay between multiple signalling pathways, allosteric activation of enzymes, and sequestration for autophagic degradation. Signalling pathways appear to converge on glycogen regulatory enzymes via insulin (glycogen synthase kinase 3ß, protein phosphatase 1, allosteric action of glucose-6-phosphate), ß-adrenergic (phosphorylase kinase protein phosphatase 1 inhibitor), and 5' adenosine monophosphate-activated protein kinase (allosteric action of glucose-6-phosphate, direct glycogen binding, insulin receptor). While cytosolic glycogen synthesis and breakdown are relatively well understood, recent findings relating to phagic glycogen degradation highlight a new area of investigation in the heart. It has been recently demonstrated that a specific glycophagy pathway is operational in the myocardium. Proteins involved in recruiting glycogen to the forming phagosome have been identified. Starch-binding domain-containing protein 1 is involved in binding glycogen and mediating membrane anchorage via interaction with a homologue of the phagosomal protein light-chain 3. Specifically, it has been shown that starch-binding domain-containing protein 1 and light-chain 3 have discrete phagosomal immunolocalization patterns in cardiomyocytes, indicating that autophagic trafficking of glycogen and protein cargo in cardiomyocytes can occur via distinct pathways. There is strong evidence from glycogen storage diseases that phagic/lysosomal glycogen breakdown is important for maintaining normal cardiac glycogen levels and does not simply constitute a redundant 'alternative' breakdown route for glycogen. Advancing understanding of glycogen handling in the heart is an important priority with relevance not only to genetic glycogen storage diseases but also to cardiac metabolic stress disorders such as diabetes and ischaemia.

Autophagy of Glycogen Is Non-Selective in Komagataella phaffii.

Glycogen is an important reserve polysaccharide from bacteria to human. It is organized in glycogen granules that also contain several proteins involved in their metabolism. Glycogen granules can be mobilized in mammalian lysosomes and yeast vacuoles. They are delivered to these organelles by macroautophagy (hereafter autophagy). However, whether this is a selective or a non-selective process remains a matter of debate. It was proposed to be selective and called "glycophagy" (for selective autophagy of glycogen) in the mouse liver. However, the evidence of this selectivity is lacking in other glycogen-rich organs, such as the heart and skeletal muscle, which both are heavily impacted by the aberrant lysosomal accumulation of glycogen in Pompe disease. We recently developed the Komagataella phaffii yeast as a simple model to study the relationship of glycogen and autophagy. Using this model, we showed that cytosolic glycogen granules are delivered to the vacuole by non-selective autophagy, at least during nitrogen starvation. We speculate that this type of autophagy might be responsible for the lysosomal glycogen turnover in non-hepatic mammalian tissues.

Dysfunction of astrocytic glycophagy exacerbates reperfusion injury in ischemic stroke.

Glycophagy has evolved from an alternative glycogen degradation pathway into a multifaceted pivot to regulate cellular metabolic hemostasis in peripheral tissues. However, the pattern of glycophagy in the brain and its potential therapeutic impact on ischemic stroke remain unknown. Here, we observed that the dysfunction of astrocytic glycophagy was caused by the downregulation of the GABA type A receptor-associated protein like 1 (GABARAPL1) during reperfusion in ischemic stroke patients and mice. PI3K-Akt pathway activation is involved in driving GABARAPL1 downregulation during cerebral reperfusion. Moreover, glycophagy dysfunction-induced glucosamine deficiency suppresses the nuclear translocation of specificity protein 1 and TATA binding protein, the transcription factors for GABARAPL1, by decreasing their O-GlcNAcylation levels, and accordingly feedback inhibits GABARAPL1 in astrocytes during reperfusion. Restoring astrocytic glycophagy by overexpressing GABARAPL1 decreases DNA damage and oxidative injury in astrocytes and improves the survival of surrounding neurons during reperfusion. In addition, a hypocaloric diet in the acute phase after cerebral reperfusion can enhance astrocytic glycophagic flux and accelerate neurological recovery. In summary, glycophagy in the brain links autophagy, metabolism, and epigenetics together, and glycophagy dysfunction exacerbates reperfusion injury after ischemic stroke.

Hepatic ChREBP orchestrates intrahepatic carbohydrate metabolism to limit hepatic glucose 6-phosphate and glycogen accumulation in a mouse model for acute Glycogen Storage Disease type Ib.

OBJECTIVE: Carbohydrate Response Element Binding Protein (ChREBP) is a glucose 6-phosphate (G6P)-sensitive transcription factor that acts as a metabolic switch to maintain intracellular glucose and phosphate homeostasis. Hepatic ChREBP is well-known for its regulatory role in glycolysis, the pentose phosphate pathway, and de novo lipogenesis. The physiological role of ChREBP in hepatic glycogen metabolism and blood glucose regulation has not been assessed in detail, and ChREBP's contribution to carbohydrate flux adaptations in hepatic Glycogen Storage Disease type 1 (GSD I) requires further investigation. METHODS: The current study aimed to investigate the role of ChREBP as a regulator of glycogen metabolism in response to hepatic G6P accumulation, using a model for acute hepatic GSD type Ib. The immediate biochemical and regulatory responses to hepatic G6P accumulation were evaluated upon G6P transporter inhibition by the chlorogenic acid S4048 in mice that were either treated with a short hairpin RNA (shRNA) directed against ChREBP (shChREBP) or a scrambled shRNA (shSCR). Complementary stable isotope experiments were performed to quantify hepatic carbohydrate fluxes in vivo. RESULTS: ShChREBP treatment normalized the S4048-mediated induction of hepatic ChREBP target genes to levels observed in vehicle- and shSCR-treated controls. In parallel, hepatic shChREBP treatment in S4048-infused mice resulted in a more pronounced accumulation of hepatic glycogen and further reduction of blood glucose levels compared to shSCR treatment. Hepatic ChREBP knockdown modestly increased glucokinase (GCK) flux in S4048-treated mice while it enhanced UDP-glucose turnover as well as glycogen synthase and phosphorylase fluxes. Hepatic GCK mRNA and protein levels were induced by shChREBP treatment in both vehicle- and S4048-treated mice, while glycogen synthase 2 (GYS2) and glycogen phosphorylase (PYGL) mRNA and protein levels were reduced. Finally, knockdown of hepatic ChREBP expression reduced starch domain binding protein 1 (STBD1) mRNA and protein levels while it inhibited acid alpha-glucosidase (GAA) activity, suggesting reduced capacity for lysosomal glycogen breakdown. CONCLUSIONS: Our data show that ChREBP activation controls hepatic glycogen and blood glucose levels in acute hepatic GSD Ib through concomitant regulation of glucose phosphorylation, glycogenesis, and glycogenolysis. ChREBP-mediated control of GCK enzyme levels aligns with corresponding adaptations in GCK flux. In contrast, ChREBP activation in response to acute hepatic GSD Ib exerts opposite effects on GYS2/PYGL enzyme levels and their corresponding fluxes, indicating that GYS2/PYGL expression levels are not limiting to their respective fluxes under these conditions.

Glycogen Granules Are Degraded by Non-Selective Autophagy in Nitrogen-Starved Komagataella phaffii.

Autophagy was initially recognized as a bulk degradation process that randomly sequesters and degrades cytoplasmic material in lysosomes (vacuoles in yeast). In recent years, various types of selective autophagy have been discovered. Glycophagy, the selective autophagy of glycogen granules, is one of them. While autophagy of glycogen is an important contributor to Pompe disease, which is characterized by the lysosomal accumulation of glycogen, its selectivity is still a matter of debate. Here, we developed the Komagataella phaffii yeast as a simple model of glycogen autophagy under nitrogen starvation conditions to address the question of its selectivity. For this, we turned the self-glucosylating initiator of glycogen synthesis, Glg1, which is covalently bound to glycogen, into the Glg1-GFP autophagic reporter. Our results revealed that vacuolar delivery of Glg1-GFP and its processing to free GFP were strictly dependent on autophagic machinery and vacuolar proteolysis. Notably, this process was independent of Atg11, the scaffold protein common for many selective autophagy pathways. Importantly, the non-mutated Glg1-GFP (which synthesizes and marks glycogen) and mutated Glg1Y212F-GFP (which does not synthesize glycogen and is degraded by non-selective autophagy as cytosolic Pgk1-GFP) were equally well delivered to the vacuole and had similar levels of released GFP. Therefore, we concluded that glycogen autophagy is a non-selective process in K. phaffii yeast under nitrogen starvation conditions.

Glycophagy mediated glucose-induced changes of hepatic glycogen metabolism via OGT1-AKT1-FOXO1Ser238 pathway.

Glycophagy is the autophagy degradation of glycogen. However, the regulatory mechanisms for glycophagy and glucose metabolism remain unexplored. Herein, we demonstrated that high-carbohydrate diet (HCD) and high glucose (HG) incubation induced glycogen accumulation, protein kinase B (AKT)1 expression and AKT1-dependent phosphorylation of forkhead transcription factor O1 (FOXO1) at Ser238 in the liver tissues and hepatocytes. The glucose-induced FOXO1 phosphorylation at Ser238 prevents FOXO1 entry into the nucleus and the recruitment to the GABA(A) receptor-associated protein like 1 (gabarapl1) promoter, reduces the gabarapl1 promoter activity, and inhibits glycophagy and glucose production. The glucose-dependent O-GlcNAcylation of AKT1 by O-GlcNAc transferase (OGT1) enhances the stability of AKT1 protein and promotes its binding with FOXO1. Moreover, the glycosylation of AKT1 is crucial for promoting FOXO1 nuclear translocation and inhibiting glycophagy. Our studies elucidate a novel mechanism for glycophagy inhibition by high carbohydrate and glucose via OGT1-AKT1-FOXO1Ser238 pathway in the liver tissues and hepatocytes, which provides critical insights into potential intervention strategies for glycogen storage disorders in vertebrates, as well as human beings.

ROS generation attenuates the anti-cancer effect of CPX on cervical cancer cells by inducing autophagy and inhibiting glycophagy.

Cervical cancer is one of the most common gynecological malignancies with poor prognosis due to constant chemoresistance and repeated relapse. Ciclopirox olamine (CPX), a synthetic antifungal agent, has recently been identified to be a promising anti-cancer candidate. However, the detailed mechanisms related to its anti-cancer effects remain unclear and need to be further elucidated. In this study, we found that CPX could induce proliferation inhibition in cervical cancer cells by targeting PARK7. Further results demonstrated that CPX could induce cytoprotective autophagy by downregulating the expression of PARK7 to activate PRKAA1 or by PARK7-independent accumulation of ROS to inhibit mTOR signaling. Meanwhile, CPX treatment increased the glycogen clustering and glycophagy in cervical cancer cells. The presence of N-acetyl-l-cysteine (NAC), a ROS scavenger, led to further clustering of glycogen in cells by reducing autophagy and enhancing glycophagy, which promoted CPX-induced inhibition of cervical cancer cell proliferation. Together, our study provides new insights into the molecular mechanisms of CPX in the anti-cancer therapy and opens new avenues for the glycophagy in cancer therapeutics.

Follicle-Stimulating Hormone Alleviates Ovarian Aging by Modulating Mitophagy- and Glycophagy-Based Energy Metabolism in Hens.

As a predominant hormone in the reproductive axis, follicle-stimulating hormone (FSH) is known as the primary surviving factor for follicular growth. In this study, the alleviating effect of FSH on aging chicken granulosa cells (GCs) was investigated. Results showed that FSH activated mitophagy and relieved mitochondrial edema in D-gal-induced senescent GCs, which was evidenced by an increased number of mitophagosomes as well as increased mitochondria-light chain 3 (LC3) colocalization. Mitophagy activation was accompanied by the activation of the AMP-activated protein kinase (AMPK) signaling pathway. Furthermore, upregulated glycophagy was demonstrated by an increased interaction of starch-binding domain protein 1 (STBD1) with GABA type A receptor-associated protein-like 1 (GABARAPL1) in D-gal-induced senescent GCs. FSH treatment further promoted glycophagy, accompanied by PI3K/AKT activation. PI3K inhibitor LY294002 and AKT inhibitor GSK690693 attenuated the effect of FSH on glycophagy and glycolysis. The inhibition of FSH-mediated autophagy attenuated the protective effect of FSH on naturally aging GC proliferation and glycolysis. The simultaneous blockage of PI3K/AKT and AMPK signaling also abolished the positive effect of FSH on naturally senescent ovarian energy regulation. These data reveal that FSH prevents chicken ovarian aging by modulating glycophagy- and mitophagy-based energy metabolism through the PI3K/AKT and AMPK pathways.

Sacubitril/valsartan combination enhanced cardiac glycophagy and prevented the progression of murine diabetic cardiomyopathy.

BACKGROUND: Diabetic cardiomyopathy (DCM) is linked to disturbance in cardiac glucose handling and increased cardiac glycogen storage. This study tested the potential role of sacubitril/valsartan on the progression of DCM in high fat diet (HFD)/streptozotocin (STZ)-induced type 2 diabetic rats compared to valsartan alone, including their effects on the cardiac glycophagy process. MATERIALS AND METHODS: Rats were fed on HFD for 6 weeks followed by single low-dose STZ (35 mg/kg). After confirming hyperglycemia, diabetic rats were continued on HFD and divided into three subgroups: Untreated-diabetic, Valsartan-treated diabetic and Sacubitril/valsartan-treated diabetic groups; in addition to a control group. Changes in ECG, blood glucose, serum insulin, lipid profile, and Homeostasis model of assessment of insulin resistance (HOMA-IR) were assessed and the degree of cardiac fibrosis was examined. Cardiac glycogen content and glycophagy process were evaluated. RESULTS: Sacubitril/valsartan administration to diabetic rats resulted in improvement of metabolic changes more than valsartan alone. Also, sacubitril/valsartan effectively prevented diabetes-associated cardiac hypertrophy, QTc prolongation, and fibrosis. Finally, cardiac glycogen concentrations in diabetic rats were decreased by sacubitril/valsartan combination, coupled with significant induction of glycophagy process in the diabetic rats' heart. CONCLUSION: Sacubitril/valsartan therapy provides a more favorable metabolic and cardioprotective response compared to valsartan alone in a rat model of DCM. These findings may be due to a direct cardioprotective impact of sacubitril/valsartan and secondary beneficial effects of improved hyperglycemia and dyslipidemia. In addition, these beneficial cardiac effects could be attributed to the induction of the glycophagy process and alleviating cardiac glycogen overload.

iCAL: a new pipeline to investigate autophagy selectivity and cancer.

Macroautophagy/autophagy can selectively degrade misfolded proteins, damaged organelles and other cargoes. It is conceivable that alteration of the degradation processes could disrupt normal cellular signaling and contribute to human diseases such as cancer. To explore the link between aberrant autophagy selectivity and human cancer, we have developed a pipeline called "inference of cancer-associated LC3-interacting region-containing proteins" (iCAL), which integrates a sequence-based predictor, a model-based computational method, publicly available cancer mutations, and multiple experimental approaches. Using iCAL, we have identified 222 LIR motif-associated mutations (LAMs) in 148 LIR-containing proteins (LIRCPs), and validated that LAMs in ATG4B, STBD1, EHMT2 and BRAF impair their interactions with LC3 and/or autophagy activities. Moreover, we uncovered that STBD1, a previously poorly-characterized protein, inhibits tumor growth via metabolism reprogramming in cancer cells. A patient-derived mutation in STBD1 (W203C) disrupts the interaction with LC3 and promotes tumor growth. Taken together, iCAL provides an exciting new avenue to discover novel autophagy pathways that contribute to carcinogenesis.

Myocardial Energy Stress, Autophagy Induction, and Cardiomyocyte Functional Responses.

Significance: Energy stress in the myocardium occurs in a variety of acute and chronic pathophysiological contexts, including ischemia, nutrient deprivation, and diabetic disease settings of substrate disturbance. Although the heart is highly adaptive and flexible in relation to fuel utilization and routes of adenosine-5'-triphosphate (ATP) generation, maladaptations in energy stress situations confer functional deficit. An understanding of the mechanisms that link energy stress to impaired myocardial performance is crucial. Recent Advances: Emerging evidence suggests that, in parallel with regulated enzymatic pathways that control intracellular substrate supply, other processes of "bulk" autophagic macromolecular breakdown may be important in energy stress conditions. Recent findings indicate that cargo-specific autophagic activity may be important in different stress states. In particular, induction of glycophagy, a glycogen-specific autophagy, has been described in acute and chronic energy stress situations. The impact of elevated cardiomyocyte glucose flux relating to glycophagy dysregulation on contractile function is unknown. Critical Issues: Ischemia- and diabetes-related cardiac adverse events comprise the majority of cardiovascular disease morbidity and mortality. Current therapies involve management of systemic comorbidities. Cardiac-specific adjunct treatments targeted to manage myocardial energy stress responses are lacking. Future Directions: New knowledge is required to understand the mechanisms involved in selective recruitment of autophagic responses in the cardiomyocyte energy stress response. In particular, exploration of the links between cell substrate flux, calcium ion (Ca2+) flux, and phagosomal cargo flux is required. Strategies to target specific fuel "bulk" management defects in cardiac energy stress states may be of therapeutic value.