The first ER-targeting flavone-based fluorescent probe for Cys: Applications in real-time tracking in an epilepsy model and food analysis.

Epilepsy is one of the most commonly-seen neurological disorders, and both endoplasmic reticulum stress (ERS) and oxidative stress (OS) have been demonstrated to be associated with epileptic seizures. As one of the three endogenous thiol-containing amino acids, cysteine (Cys) is recognized not only as an important biomarker of various biological processes but also widely used as a significant additive in the food industry. However, the exact role that Cys plays in ERS has not been well answered up to now. In this paper, we reported the first flavone-based fluorescent probe (namely BFC) with nice endoplasmic reticulum (ER)-targeting ability, which was capable of monitoring Cys in a fast response (3.0 min), large stokes shift (130 nm) and low detection limit (10.4 nM). The recognition mechanism of Cys could be attributed to the addition-cyclization reaction involving a Cys residue and an acrylate group, resulting in the release of the strong excited-state intramolecular proton transfer (ESIPT) emission molecule of benzoflavonol (BF). The low cytotoxicity and good biocompatibility of the probe BFC allowed for monitoring the fluctuation of endogenous Cys levels under both ERS and OS processes, as well as in zebrafish models of epilepsy. Quantitative determination of Cys with the probe BFC was also achieved in three different food samples. Additionally, a probe-immersed test strips integrated with a smartphone device was successfully constructed for on-site colorimetric detection of Cys. Undoubtedly, our work provided a valuable tool for tracking Cys levels in both an epilepsy model and real food samples.

Melastoma dodecandrum lour. Protects against cerebral ischemia-reperfusion injury by ameliorating oxidative stress and endoplasmic reticulum stress.

ETHNOPHARMACOLOGICAL RELEVANCE: Melastoma dodecandrum Lour. (MD), a traditional Chinese medicine used by the She ethnic group, has been used to treat cerebral ischemia-reperfusion (CIR) injury due to its efficacy in promoting blood circulation and removing blood stasiss; however, the therapeutic effects and mechanisms of MD in treating CIR injury remain unclear. AIM: To investigate the protective effects of MD on CIR injury, in addition to its impact on oxidative stress, endoplasmic reticulum (ER) stress, and cell apoptosis. MATERIALS AND METHODS: The research was conducted using both cell experiments and animal experiments. The CCK-8 method, immunofluorescence staining, and flow cytometry were used to analyze the effects of MD-containing serum on oxygen-glucose deprivation/reperfusion (OGD/R)-induced PC12 cell viability, reactive oxygen species (ROS) clearance, anti-inflammatory, neuroprotection and inhibition of apoptosis. Furthermore, 2,3,5-Triphenyl tetrazolium chloride staining, hematoxylin and eosin staining, Nissl staining, and immunohistochemistry were used to detect infarct size, pathological changes, Nissl corpuscula and neuronal protein expression in middle cerebral artery occlusion (MCAO) rats. Polymerase chain reaction and Western Blotting were conducted in cell and animal experiments to detect the expression levels of ER stress-related genes and proteins. RESULTS: The MD extract enhanced the viability of PC12 cells under OGD/R modeling, reduced ROS and IL-6 levels, increased MBP levels, and inhibited cell apoptosis. Furthermore, MD improved the infarct area in MCAO rats, increased the number of Nissl bodies, and regulated neuronal protein levels including Microtubule-Associated Protein 2 (MAP-2), Myelin Basic Protein (MBP), Glial Fibrillary Acidic Protein (GFAP), and Neurofilament 200 (NF200). Additionally, MD could regulate the expression levels of oxidative stress proteins malondialdehyde (MDA), nitric oxide (NO), superoxide dismutase (SOD), and catalase (CAT). Both cell and animal experiments demonstrated that MD could inhibit ER stress-related proteins (GRP78, ATF4, ATF6, CHOP) and reduce cell apoptosis. CONCLUSION: This study confirmed that the therapeutic mechanism of the MD extract on CIR injury was via the inhibition of oxidative stress and the ER stress pathway, in addition to the inhibition of apoptosis.

Cotton Bollworm (H. armigera) Effector PPI5 Targets FKBP17-2 to Inhibit ER Immunity and JA/SA Responses, Enhancing Insect Feeding.

The cotton bollworm causes severe mechanical damage to plants during feeding and leaves oral secretions (OSs) at the mechanical wounds. The role these OSs play in the invasion of plants is still largely unknown. Here, a novel H. armigera effector peptidyl prolyl trans-isomerase 5 (PPI5) was isolated and characterized. PPI5 induces the programmed cell death (PCD) due to the unfolded protein response (UPR) in tobacco leaf. We reveal that PPI5 is important for the growth and development of cotton bollworm on plants, as it renders plants more susceptible to feeding. The GhFKBP17-2, was identified as a host target for PPI5 with peptidyl-prolyl isomerase (PPIase) activity. CRISPR/Cas9 knock-out cotton mutant (CR-GhFKBP17-1/3), VIGS (TRV: GhFKBP17-2) and overexpression lines (OE-GhFKBP17-1/3) were created and the data indicate that GhFKBP17-2 positively regulates endoplasmic reticulum (ER) stress-mediated plant immunity in response to cotton bollworm infestation. We further confirm that PPI5 represses JA and SA levels by downregulating the expression of JA- and SA-associated genes, including JAZ3/9, MYC2/3, JAR4, PR4, LSD1, PAD4, ICS1 and PR1/5. Taken together, our results reveal that PPI5 reduces plant defense responses and makes plants more susceptible to cotton bollworm infection by targeting and suppressing GhFKBP17-2 -mediated plant immunity.

Emc1 is essential for vision and zebrafish photoreceptor outer segment morphogenesis.

Inherited retinal diseases (IRDs) are a rare group of eye disorders characterized by progressive dysfunction and degeneration of retinal cells. In this study, we characterized the raifteirí (raf) zebrafish, a novel model of inherited blindness, identified through an unbiased ENU mutagenesis screen. A mutation in the largest subunit of the endoplasmic reticulum membrane protein complex, emc1 was subsequently identified as the causative raf mutation. We sought to elucidate the cellular and molecular phenotypes in the emc1-/- knockout model and explore the association of emc1 with retinal degeneration. Visual behavior and retinal electrophysiology assays demonstrated that emc1-/- mutants had severe visual impairments. Retinal histology and morphometric analysis revealed extensive abnormalities, including thinning of the photoreceptor layer, in addition to large gaps surrounding the lens. Notably, photoreceptor outer segments were drastically smaller, outer segment protein expression was altered and hyaloid vasculature development was disrupted. Transcriptomic profiling identified cone and rod-specific phototransduction genes significantly downregulated by loss of emc1. These data shed light on why emc1 is a causative gene in inherited retinal disease and how outer segment morphogenesis is regulated.

NLRX1 attenuates endoplasmic reticulum stress via STING in cardiac hypertrophy.

Endoplasmic reticulum stress-induced cell apoptosis is a pivotal mechanism underlying the progression of cardiac hypertrophy. NLRX1, a member of the NOD-like receptor family, modulates various cellular processes, including STING, NF-κB, MAPK pathways, reactive oxygen species production, essential metabolic pathways, autophagy and cell death. Emerging evidence suggests that NLRX1 may offer protection against diverse cardiac diseases. However, the impacts and mechanisms of NLRX1 on endoplasmic reticulum stress in cardiac hypertrophy remains largely unexplored. In our study, we observed that the NLRX1 and phosphorylated STING (p-STING) were highly expressed in both hypertrophic mouse heart and cellular model of cardiac hypertrophy. Whereas over-expression of NLRX1 mitigated the expression levels of p-STING, as well as the endoplasmic reticulum stress markers, including transcription activating factor 4 (ATF4), C/EBP homologous protein (CHOP) and the ratios of phosphorylated PERK to PERK, phosphorylated IRE1 to IRE1 and phosphorylated eIF2α to eIF2α in an Angiotensin II (Ang II)-induced cellular model of cardiac hypertrophy. Importantly, the protective effects of NLRX1 were attenuated upon pretreatment with the STING agonist, DMXAA. Our findings provide the evidence that NLRX1 attenuates the PERK-eIF2α-ATF4-CHOP axis of endoplasmic reticulum stress response via inhibition of p-STING in Ang II-treated cardiomyocytes, thereby ameliorating the development of cardiac hypertrophy.

Curcumin attenuates ochratoxin A and hypoxia co-induced liver injury in grass carp (Ctenopharyngodon idella) by dual targeting endoplasmic reticulum stress and apoptosis via reducing ROS content.

BACKGROUND: Ochratoxin A (OTA) is a toxin widely found in aquafeed ingredients, and hypoxia is a common problem in fish farming. In practice, aquatic animals tend to be more sensitive to hypoxia while feeds are contaminated with OTA, but no studies exist in this area. This research investigated the multiple biotoxicities of OTA and hypoxia combined on the liver of grass carp and explored the mitigating effect of curcumin (CUR). METHODS: A total of 720 healthy juvenile grass carp (11.06 ± 0.05 g) were selected and assigned randomly to 4 experimental groups: control group (without OTA and CUR), 1.2 mg/kg OTA group, 400 mg/kg CUR group, and 1.2 mg/kg OTA + 400 mg/kg CUR group with three replicates each for 60 d. Subsequently, 32 fish were selected, divided into normoxia (18 fish) and hypoxia (18 fish) groups, and subjected to hypoxia stress for 96 h. RESULTS: CUR can attenuate histopathological damage caused by coming to OTA and hypoxia by reducing vacuolation and nuclear excursion. The alleviation of this damage was associated with the attenuation of apoptosis in the mitochondrial pathway by decreasing the expression of the pro-apoptotic proteins Caspase 3, 8, 9, Bax, and Apaf1 while increasing the expression of the anti-apoptotic protein Bcl-2, and attenuation of endoplasmic reticulum stress (ERS) by reducing Grp78 expression and chop levels. This may be attributed to the fact that the addition of CUR increased the levels of catalase (CAT) and glutathione reductase (GSH), increased antioxidant capacity, and ensured the proper functioning of respiratory chain complexes I and II, which in turn reduced the high production of reactive oxygen species (ROS), thus alleviating apoptosis and ERS. CONCLUSIONS: In conclusion, our data demonstrate the effectiveness of CUR in attenuating liver injury caused by the combination of OTA and hypoxia. This study confirms the feasibility and efficacy of adding natural products to mitigate toxic damage to aquatic animals.

KDELR2 is necessary for chronic obstructive pulmonary disease airway Mucin5AC hypersecretion via an IRE1α/XBP-1s-dependent mechanism.

Airway mucus hypersecretion, a crucial pathological feature of chronic obstructive pulmonary disease (COPD), contributes to the initiation, progression, and exacerbation of this disease. As a macromolecular mucin, the secretory behaviour of Mucin5AC (MUC5AC) is highly dependent on a series of modifying and folding processes that occur in the endoplasmic reticulum (ER). In this study, we focused on the ER quality control protein KDEL receptor (KDELR) and demonstrated that KDELR2 and MUC5AC were colocalized in the airway epithelium of COPD patients and COPD model rats. In addition, knockdown of KDELR2 markedly reduced the expression of MUC5AC both in vivo and in vitro and knockdown of ATF6 further decreased the levels of KDELR2. Furthermore, pretreatment with 4µ8C, an IRE1α inhibitor, led to a partial reduction in the expression of KDELR2 and MUC5AC both in vivo and in vitro, which indicated the involvement of IRE1α/XBP-1s in the upstream signalling cascade. Our study revealed that KDELR2 plays a crucial role in airway MUC5AC hypersecretion in COPD, which might be dependent on ATF6 and IRE1α/XBP-1s upstream signalling.

Fibroblast growth factor 21 attenuates pulmonary ischemia/reperfusion injury via inhibiting endoplasmic reticulum stress-induced ferroptosis though FGFR1/PPARδ signaling pathway.

BACKGROUND: Acute lung injury is a critical life-threatening complication of pulmonary and cardiac surgery with a high rate of morbidity and mortality. Fibroblast growth factor 21 (FGF21) has been reported to play an important role in protecting vital organs from damage. This study aims to investigate the potential protective role and mechanism of FGF21 in pulmonary ischemia/reperfusion (I/R)-induced acute lung injury. METHODS: A pulmonary epithelial cell line was treated with hypoxia/regeneration (H/R) in vitro and a mouse model of acute lung injury was induced with pulmonary I/R in vivo. Lung injury after pulmonary I/R was compared between FGF21-konckout (KO) mice and wild-type (WT) mice. Recombinant FGF21 was administrated in vivo and in vitro to determine its therapeutic effect. RESULTS: Circulating levels of FGF21 in mice with pulmonary I/R injury were significantly higher than in those without pulmonary I/R injury. Lung injury was aggravated in FGF21-KO mice compared with WT mice and the administration of FGF21 alleviated lung injury in mouse treated with I/R and pulmonary epithelial cell injury treated with H/R. FGF21 treatment decreased endoplasmic reticulum (ER) stress, Fe2+ and lipid reactive oxygen species (ROS) contents and GPX4 expression and increased PTGS2 levels. Mechanistically, FGF21 upregulated the expression of FGFR1 and PPARδ, ameliorated ER stress and ER stress induced-ferroptosis. Furthermore, FGF21 increased the expression level of PPARδ in pulmonary epithelial cell exposed to H/R, which was inhibited by FGFR1 inhibitor (PD173074). The protective effects of FGF21 were abolished by co-treatment with PPARδ inhibitor (GSK0660), indicating FGF21 attenuated ER stress-induced ferroptosis by dependent on FGFR1/PPARδ signaling pathway. CONCLUSION: Our study reveals that FGF21 protects against pulmonary I/R injury via inhibiting ER stress-induced ferroptosis though FGFR1/PPARδ signaling pathway. Boosting endogenous FGF21 or the administration of recombinant FGF21 could be promising therapeutic strategies for pulmonary IRI.

Dual regulation of IP3 receptors by IP3 and PIP2 controls the transition from local to global Ca2+ signals.

The spatial organization of inositol 1,4,5-trisphosphate (IP3)-evoked Ca2+ signals underlies their versatility. Low stimulus intensities evoke Ca2+ puffs, localized Ca2+ signals arising from a few IP3 receptors (IP3Rs) within a cluster tethered beneath the plasma membrane. More intense stimulation evokes global Ca2+ signals. Ca2+ signals propagate regeneratively as the Ca2+ released stimulates more IP3Rs. How is this potentially explosive mechanism constrained to allow local Ca2+ signaling? We developed methods that allow IP3 produced after G-protein coupled receptor (GPCR) activation to be intercepted and replaced by flash photolysis of a caged analog of IP3. We find that phosphatidylinositol 4,5-bisphosphate (PIP2) primes IP3Rs to respond by partially occupying their IP3-binding sites. As GPCRs stimulate IP3 formation, they also deplete PIP2, relieving the priming stimulus. Loss of PIP2 resets IP3R sensitivity and delays the transition from local to global Ca2+ signals. Dual regulation of IP3Rs by PIP2 and IP3 through GPCRs controls the transition from local to global Ca2+ signals.

Cellular communication network factor 2 regulates smooth muscle cell transdifferentiation and lipid accumulation in atherosclerosis.

AIMS: Accruing evidence illustrates an emerging paradigm of dynamic vascular smooth muscle cell (SMC) transdifferentiation during atherosclerosis progression. However, the molecular regulators that govern SMC phenotype diversification remain poorly defined. This study aims to elucidate the functional role and underlying mechanisms of cellular communication network factor 2 (CCN2), a matricellular protein, in regulating SMC plasticity in the context of atherosclerosis. METHODS AND RESULTS: In both human and murine atherosclerosis, an up-regulation of CCN2 is observed in transdifferentiated SMCs. Using an inducible murine SMC CCN2 deletion model, we demonstrate that SMC-specific CCN2 knockout mice are hypersusceptible to atherosclerosis development as evidenced by a profound increase in lipid-rich plaques along the entire aorta. Single-cell RNA sequencing studies reveal that SMC deficiency of CCN2 positively regulates machinery involved in endoplasmic reticulum stress, endocytosis, and lipid accumulation in transdifferentiated macrophage-like SMCs during the progression of atherosclerosis, findings recapitulated in CCN2-deficient human aortic SMCs. CONCLUSION: Our studies illuminate an unanticipated protective role of SMC-CCN2 against atherosclerosis. Disruption of vascular wall homeostasis resulting from vascular SMC CCN2 deficiency predisposes mice to atherosclerosis development and progression.

Activating transcription factor 4 plays a major role in shaping the transcriptional response to isoginkgetin in HCT116 cells.

Activating transcription factor 4 (ATF4) plays a central role in the integrated stress response (ISR) and one overlapping branch of the unfolded protein response (UPR). We recently reported that the splicing inhibitor isoginkgetin (IGG) induced ATF4 protein along with several known ATF4-regulated transcripts in a response that resembled the ISR and UPR. However, the contribution of ATF4-dependent and -independent transcriptional responses to IGG exposure was not known. Here we used RNA-sequencing in HCT116 colon cancer cells and an isogenic subline lacking ATF4 to investigate the contribution of ATF4 to IGG-induced changes in gene expression. Approximately 85% of the IGG-responsive DEGs in HCT116 cells were also differentially expressed in response to the ER stressor thapsigargin (Tg) and these were enriched for genes associated with the UPR and ISR. Most of these were positively regulated by IGG with impaired responses in the ATF4-deficient cells. Nonetheless, there were DEGs that responded similarly in both cell lines. The ATF4-independent IGG-induced DEGs included several metal responsive transcripts encoding metallothionines and a zinc transporter. Taken together, the predominant IGG response was ATF4-dependent in these cells and resembled the UPR and ISR while a second less prominent response involved the ATF4-independent regulation of metal responsive mRNAs.

Reticulophagy and viral infection.

All viruses are obligate intracellular parasites that use host machinery to synthesize viral proteins. In infected eukaryotes, viral secreted and transmembrane proteins are synthesized at the endoplasmic reticulum (ER). Many viruses refashion ER membranes into bespoke factories where viral products accumulate while evading host pattern recognition receptors. ER processes are tightly regulated to maintain cellular homeostasis, so viruses must either conform to ER regulatory mechanisms or subvert them to ensure efficient viral replication. Reticulophagy is a catabolic process that directs lysosomal degradation of ER components. There is accumulating evidence that reticulophagy serves as a form of antiviral defense; we call this defense "xERophagy" to acknowledge its relationship to xenophagy, the catabolic degradation of microorganisms by macroautophagy/autophagy. In turn, viruses can subvert reticulophagy to suppress host antiviral responses and support efficient viral replication. Here, we review the evidence for functional interplay between viruses and the host reticulophagy machinery.

Endoplasmic reticulum stress: The underlying mechanism of chronic pain.

Chronic pain (CP) affects over 30 % of the global population, imposing significant financial burdens on individuals and society. However, existing treatments for CP offer limited efficacy and troublesome side effects, primarily owing to a lack of knowledge of its precise underlying mechanism. Pathological stimuli disrupt the intricate process of protein folding and endoplasmic reticulum (ER) homeostasis. This disruption leads to the accumulation of misfolded or unfolded proteins in the ER, generating a condition termed ER stress. Emerging data have indicated that ER stress, occurring in the peripheral and central nervous systems, contributes to the development and maintenance of CP. This review aimed to comprehensively explore the intersection of ER stress and CP within the lower and upper nervous systems and highlight the cell-specific contributions of the unfolded protein response in different CP types. We provide a comprehensive synthesis of evidence from animal models, examining neuronal and non-neuronal mechanisms and discuss the damaging ER stress-linked inflammation, autophagy, oxidative stress, and apoptosis, which collectively drive disease progression and contribute to a neurotoxic environment. However, the mechanisms through which ER stress influences the most advanced centre-of-pain projections in the brain remain unclear. Further investigation in this area is crucial to elucidate the relationship between ER stress and CP and facilitate the development of novel therapeutic drugs for this intractable dilemma.

Circulating Extracellular Vesicles from Heart Failure Patients Inhibit Human Cardiomyocyte Activities.

Extracellular vesicles (EVs) have been implicated in cardiac remodeling during heart failure (HF). However, the role of circulating EVs (CEVs) in the process of HF is poorly understood. To elucidate the molecular mechanism associated with CEVs in the context of HF, the proteome of 4D label-free EVs from plasma samples was identified. Among the identified proteins, 6 exhibited upregulation while 9 demonstrated downregulation in CEVs derived from HF patients (HCEVs) compared to healthy controls (NCEVs). Our results showed that up-regulated proteins mainly participate in the primary metabolic, glycerolipid metabolic processes, oxidation-reduction process, and inflammatory amplification. In contrast, the down-regulated proteins influenced cell development, differentiation, and proliferation. Compared to NCEVs, HCEVs significantly induced inflammation and triacylglycerol (TAG) accumulation in human cardiomyocytes (HCMs) in vitro. They also compromised their regenerative capacities, triggered endoplasmic reticulum (ER) stress and increased autophagy in HCMs. Further, HCEVs induced differentiation of human cardiac fibroblasts (HCFs), amplifying pro-inflammatory, and pro-fibrotic factors, and enhancing extracellular matrix deposition. Notably, HCEVs are also associated with an increase in the HF biomarker MMP9 within HCFs and demonstrate a negative correlation with autophagic flux. In conclusion, HCEVs appear pivotal in advancing HF via pathological cardiac remodeling.

Interplay of α-Synuclein Oligomers and Endoplasmic Reticulum Stress in Parkinson'S Disease: Insights into Cellular Dysfunctions.

Oligomeric forms of α-synuclein (α-syn) are critical in the formation of α-synuclein fibrils, exhibiting neurotoxic properties that are pivotal in the pathogenesis of Parkinson's disease (PD). A salient feature of this pathology is the disruption of the protein folding capacity of the endoplasmic reticulum (ER), leading to a perturbation in the ER's protein quality control mechanisms. The accumulation of unfolded or misfolded proteins instigates ER stress. However, the onset of ER stress and the consequent activation of the Unfolded Protein Response (UPR) and Endoplasmic Reticulum-Associated Degradation (ERAD) pathways do not merely culminate in apoptosis when they fail to restore cellular homeostasis. More critically, this condition initiates a cascade of reactions involving ER-related structures and organelles, resulting in multifaceted cellular damage and, potentially, a feedback loop that precipitates neuroinflammation. In this review, we elucidate the interplay between UPR and ERAD, as well as the intricate crosstalk among the ER and other organelles such as mitochondria, lysosomes, and the Golgi apparatus, underscoring their roles in the neurodegenerative process.

Protein kinase C (PKC) inhibitor Calphostin C activates PKC in a light-dependent manner at high concentrations via the production of singlet oxygen.

Calphostin C (Cal-C) is a protein kinase C (PKC) inhibitor that binds to its C1 domain. The aim of the present study was to elucidate the action of Cal-C in addition to PKC inhibition. First, we confirmed that Cal-C at low concentrations (<200 nM) inhibit phorbol ester-induced PKC translocation and G-protein-coupled receptor (GPCR)-mediated PKC activation. Cal-C at higher concentrations (>2 µM) increased intracellular calcium ion concentrations ([Ca2+]i) in a concentration-dependent manner. The origin of this increase is the mobilization of the endoplasmic reticulum (ER), which does not involve GPCR or ryanodine receptors. Cal-C at high concentrations also cause structural changes in the ER, such as the formation of vacuoles and aggregates, and calcium leakage from the ER. At 2 µM, Cal-C translocated a calcium-sensitive PKCα. Studies using a C-kinase activity reporter and a myristoylated alanine-rich protein kinase C substrate fused with green fluorescent protein (GFP) have also revealed that Cal-C at high concentrations activate PKC in living cells. Additionally, the PKC-activating effects of Cal-C were light-dependent. Finally, studies using Si-DMA, an indicator of singlet oxygen, showed that Cal-C at high concentrations generated singlet oxygen, causing structural changes in the ER and leakage of calcium into the cytosol, which triggered PKC activation. This study confirms the novel action of Cal-C, solely considered a PKC inhibitor. Cal-C acted as a PKC inhibitor at low concentrations and a PKC activator at high concentrations by generating singlet oxygen in a light-dependent manner, suggesting that Cal-C can be used in photodynamic therapy.

Myosin VI Is Associated With the Endoplasmic Reticulum in Regions of Sertoli Cells Containing Tubulobulbar Complexes.

Myosin VI has been reported by others to localize in association with various regions of apical tubulobulbar complexes (TBCs) at sites of attachment between Sertoli cells and late spermatids in the mouse. Tubulobulbar complexes internalize "intact" intercellular junctions during sperm release and during spermatocyte translocation through the blood-testis barrier. Here, we use super-resolution (STED-stimulated emission depletion) and electron microscopy of immunolabeled sections of rat testis to clearly define the localization of anti-myosin VI reactivity both at apical and basal sites in the epithelium. In data stacks collected by STED imaging, staining at TBCs was predominantly associated with bulb regions of the complexes. At apical sites, when data stacks were analyzed with an Imaris software, staining appeared around and extended between adjacent bulbs. At basal sites, in addition to labeling at TBC bulbs, reactive sites appeared concentrated in regions close to but not directly associated with intercellular junctions. At the ultrastructural level, labeling was predominantly associated with cisternae of the endoplasmic reticulum associated with the bulbs of TBCs and near to basal junction complexes. We conclude that myosin VI may be associated with specific subdomains of the endoplasmic reticulum related to TBC bulbs and associated basal junction complexes between Sertoli cells.

The endoplasmic reticulum as an active liquid network.

The peripheral endoplasmic reticulum (ER) forms a dense, interconnected, and constantly evolving network of membrane-bound tubules in eukaryotic cells. While individual structural elements and the morphogens that stabilize them have been described, a quantitative understanding of the dynamic large-scale network topology remains elusive. We develop a physical model of the ER as an active liquid network, governed by a balance of tension-driven shrinking and new tubule growth. This minimalist model gives rise to steady-state network structures with density and rearrangement timescales predicted from the junction mobility and tubule spawning rate. Several parameter-independent geometric features of the liquid network model are shown to be representative of ER architecture in live mammalian cells. The liquid network model connects the timescales of distinct dynamic features such as ring closure and new tubule growth in the ER. Furthermore, it demonstrates how the steady-state network morphology on a cellular scale arises from the balance of microscopic dynamic rearrangements.

Unravelling the interplay between ER stress, UPR and the cGAS-STING pathway: Implications for osteoarthritis pathogenesis and treatment strategy.

Osteoarthritis (OA) is a debilitating chronic degenerative disease affecting the whole joint organ leading to pain and disability. Cellular stress and injuries trigger inflammation and the onset of pathophysiological changes ensue after irreparable damage and inability to resolve inflammation, impeding the completion of the healing process. Extracellular matrix (ECM) degradation leads to dysregulated joint tissue metabolism. The reparative effort induces the proliferation of hypertrophic chondrocytes and matrix protein synthesis. Aberrant protein synthesis leads to endoplasmic reticulum (ER) stress and chondrocyte apoptosis with consequent cartilage matrix loss. These events in a vicious cycle perpetuate inflammation, hindering the restoration of normal tissue homeostasis. Recent evidence suggests that inflammatory responses and chondrocyte apoptosis could be caused by the activation of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signalling axis in response to DNA damage. It has been reported that there is a crosstalk between ER stress and cGAS-STING signalling in cellular senescence and other diseases. Based on recent evidence, this review discusses the role of ER stress, Unfolded Protein Response (UPR) and cGAS-STING pathway in mediating inflammatory responses in OA.

Excessive or sustained endoplasmic reticulum stress: one of the culprits of adipocyte dysfunction in obesity.

As the prevalence of obesity continues to rise globally, the research on adipocytes has attracted more and more attention. In the presence of nutrient overload, adipocytes are exposed to pressures such as hypoxia, inflammation, mechanical stress, metabolite, and oxidative stress that can lead to organelle dysfunction. Endoplasmic reticulum (ER) is a vital organelle for sensing cellular pressure, and its homeostasis is essential for maintaining adipocyte function. Under conditions of excess nutrition, ER stress (ERS) will be triggered by the gathering of abnormally folded proteins in the ER lumen, resulting in the activation of a signaling response known as the unfolded protein responses (UPRs), which is a response system to relieve ERS and restore ER homeostasis. However, if the UPRs fail to rescue ER homeostasis, ERS will activate pathways to damage cells. Studies have shown a role for disturbed activation of adipocyte ERS in the pathophysiology of obesity and its complications. Prolonged or excessive ERS in adipocytes can aggravate lipolysis, insulin resistance, and apoptosis and affect the bioactive molecule production. In addition, ERS also impacts the expression of some important genes. In view of the fact that ERS influences adipocyte function through various mechanisms, targeting ERS may be a viable strategy to treat obesity. This article summarizes the effects of ERS on adipocytes during obesity.