Explore the vast range of titles available.

Most secreted and membrane proteins are targeted to and translocated across the endoplasmic reticulum (ER) membrane through the Sec61 protein-conducting channel. Evolutionarily conserved Sec62 and Sec63 associate with the Sec61 channel, forming the Sec complex and mediating translocation of a subset of proteins. For the last three decades, it has been thought that ER protein targeting and translocation occur via two distinct pathways: signal recognition particle (SRP)-dependent co-translational or SRP-independent, Sec62/Sec63 dependent post-translational translocation pathway. However, recent studies have suggested that ER protein targeting and translocation through the Sec translocon are more intricate than previously thought. This review summarizes the current understanding of the molecular functions of Sec62/Sec63 in ER protein translocation.

Background We have previously reported that histamine-induced pruritus was attenuated in toll-like receptor 4 (TLR4) knockout mice due to decreased transient receptor potential V1 (TRPV1) sensitivity. Our results implied that TLR4 potentiated TRPV1 activation in sensory neurons; however, the molecular mechanism has yet to be elucidated. In this study, we investigated the molecular mechanisms of TLR4-mediated TRPV1 potentiation using TLR4-deficient sensory neurons and a heterologous expression system. Methods Primary sensory neurons were obtained from wild-type or TLR4 knockout mice, and HEK293T cells expressing TRPV1 and TLR4 were prepared by transient transfection. TRPV1 activity was analyzed by calcium imaging, fluorophotometry, and patch-clamp recording. Subcellular protein distribution was tested by immunocytochemistry and cell surface biotinylation assay. Protein interaction was assessed by western blot and immunoprecipitation assay. Results Direct association between TRPV1 and TLR4 was detected in HEK293T cells upon heterologous TRPV1 and TLR4 expression. In an immunoprecipitation assay using TLR4-deletion mutants and soluble toll/interleukin-1 receptor (TIR) protein, the cytoplasmic TIR domain of TLR4 was required for TLR4-TRPV1 association and TRPV1 potentiation. In TLR4-deficient sensory neurons, the activation-induced desensitization of TRPV1 increased, accompanied by enhanced TRPV1 clearance from the cell membrane upon activation compared to wild-type neurons. In addition, heterologous TLR4 expression inhibited activation-induced TRPV1 endocytosis and lysosomal degradation in HEK293T cells. Conclusion Our data show that direct association between TRPV1 and TLR4 through the TIR domain enhances TRPV1 activity by blocking activation-induced TRPV1 desensitization.

Triple-negative breast cancer (TNBC) is an aggressive subtype characterized by a lack of targetable receptors, leading to limited treatment options and a critical need for novel therapeutic strategies. This study aimed to evaluate the potential of azelastine, a clinically approved H1-antihistamine, for drug repositioning against TNBC and to elucidate its underlying HRH1-independent mechanism of action. Cell viability assays (CCK-8) were performed on TNBC cell lines (MDA-MB-231 and BT-549) following treatment with azelastine and its major metabolite, desmethyl azelastine. After observing ambiguous clinical associations between HRH1 expression and patient prognosis, HRH1 dependency was assessed through histamine stimulation and HRH1 knockdown (siRNA). Subsequently, the role of ADP-ribosylation factor 1 (ARF1), found to be overexpressed in TNBC and linked to poor prognosis, was investigated using ARF1 knockdown (siRNA), co-treatment with the Golgi-specific brefeldin A-resistance guanine nucleotide exchange factor 1 (GBF1) inhibitor golgicide A (GCA), and co-treatment with the Drp1 inhibitor M-divi 1. Azelastine and desmethyl azelastine potently reduced MDA-MB-231 cell viability in a dose- and time-dependent manner, achieving cell survivals of 61.3 ± 6.1% (30 µM) and 34.9 ± 3.7% (50 µM) for azelastine, and 52.4 ± 12.5% (30 µM) for desmethyl azelastine, respectively, after 72 h, with an IC of 35.93 µM determined for azelastine in MDA-MB-231 cells. Additionally, azelastine significantly reduced the viability of BT-549 cells. Bioinformatic analysis of clinical datasets revealed HRH1 downregulation in tumors and, functionally, neither histamine stimulation nor HRH1 knockdown mediated azelastine cytotoxicity in cell culture. Importantly, ARF1 expression was significantly upregulated in TNBC and associated with poor prognosis. Co-treatment with GCA, preventing ARF1 activation, restored viability to near-control levels, supporting dependence on the GBF1-ARF1 activation axis of azelastine, whereas the Dynamic-related protein 1 (Drp1) inhibitor M-divi 1 not only partially rescued CCK-8-based cell viability but also normalized azelastine-induced loss of MitoTracker™ Red CMXRos signal and partially preserved (4',6-diamidino-2-phenylindole) DAPI-based cell density, indicating Drp1-dependent mitochondrial dysfunction. Furthermore, azelastine selectively reduced p-ERK phosphorylation in the cell signaling pathway. Azelastine exerts potent anticancer effects in TNBC cells via an HRH1-independent, ARF1-dependent mechanism that attenuates the Extracellular signal-regulated kinase (ERK)-Drp1 axis, and induces Drp1-dependent mitochondrial dysfunction, independent of its canonical HRH1 receptor function. This ARF1-dependent mechanism provides strong scientific rationale for the drug repositioning of azelastine as an effective therapeutic agent for ARF1-driven TNBC.

Chronic hyperglycemia is linked to neuronal dysfunction and mood disorders, but the underlying molecular mechanisms remain unclear. In the present study, we examined the role of sarco/endoplasmic reticulum Ca²⁺-ATPase 2 (SERCA2) in depression-like behaviors induced by hyperglycemia, using in vivo and in vitro models. Streptozotocin (STZ)-induced hyperglycemic mice exhibited elevated glucose levels and depression-like behaviors, along with increased hippocampal endoplasmic reticulum (ER) stress markers such as C/EBP homologous protein (CHOP), neuronal loss, and reduced SERCA2 expression. Human SH-SY5Y neuroblastoma cells exposed to high-glucose (40 mM) similarly showed decreased SERCA2, elevated ER stress markers, and impaired ER calcium homeostasis. Pharmacological activation of SERCA2 by CDN1163 suppressed ER stress and reversed depression-like behaviors in STZ mice; it also restored ER calcium levels in SH-SY5Y cells. Intrahippocampal infusion of SERCA2 inhibitor thapsigargin induced ER stress and depression-like behaviors without changing SERCA2 expression, indicating that SERCA2 dysfunction alone can trigger pathology. Treatment with the ER stress inhibitor tauroursodeoxycholic acid (TUDCA) alleviated both molecular and behavioral alterations in hyperglycemic mice, supporting ER stress as a downstream effect of calcium dysregulation. These findings implicate hippocampal SERCA2 dysfunction as a central mechanism linking hyperglycemia to depression-like behaviors, highlighting SERCA2 as a potential therapeutic target.

Hippocalcin (HPCA), a neuron-enriched calcium-binding protein, plays a critical role in brain function, but its role in neural precursor cells remains unclear. N-methyl-D-aspartate (NMDA) receptors are calcium-permeable glutamate receptors essential for neurodevelopment and synaptic plasticity, and their function has been implicated in neurological conditions. In this study, we investigated the role of HPCA in regulating NMDA receptor expression and function in mouse hippocampal neural precursor cells (mHNPCs). HPCA knockdown significantly reduced the expression of NMDA receptor-related genes, including Grin2C, Shank1, Serpine2, and selectively attenuated NMDA-induced calcium signaling. Transcriptomic analysis identified ELAV-like RNA-binding protein 3 (Elavl3), a neuron-enriched factor associated with neuronal activity, as a downstream candidate affected by HPCA knockdown. Consistently, Elavl3 suppression phenocopied HPCA deficiency, resulting in impaired NMDA receptor activity and reduced neuronal differentiation. Furthermore, hippocampal HPCA knockdown in vivo led to alterations in locomotor activity, contextual memory, and affective behaviors. Taken together, these findings demonstrate that HPCA supports NMDA receptor function and neuronal development, in part through Elavl3-associated pathways, and highlight HPCA as an important regulator of hippocampal function.

Chemotherapy-induced peripheral neuropathy (CIPN) is a major drawback in the use of chemotherapeutic agents for patients with cancer. Although studies have investigated a broad number of molecules that might be related to CIPN, the differences in the chemokine pathways between various chemotherapeutic agents, such as vincristine and oxaliplatin, which are some of the most widely used treatments, have not been fully elucidated. We confirmed that the administration (intraperitoneal injections for seven days) of vincristine (0.1 mg/kg) and oxaliplatin (3 mg/kg) induced pain by using the von Frey behavioral test. Subsequent applications with vincristine and oxaliplatin led to mechanical allodynia that lasted more than one week from the fifth day. After the induction of mechanical allodynia, the mRNA expression of CXCR2, CXCL1, CXCL3, and CXCL5 was examined in the dorsal root ganglia (DRG) and spinal cord of the CIPN models. As a result, the mRNA expression of CXCR2 robustly increased in the lumbar spinal cord in the oxaliplatin-treated mice. Next, to evaluate the involvement of CXCR2 in CIPN, reparixin, a CXCR1/2 inhibitor, was administered intrathecally or intraperitoneally with vincristine or oxaliplatin and was further verified by treatment with ruxolitinib, which inhibits Janus kinase 2 downstream of the CXCR1/2 pathway. Reparixin and ruxolitinib blocked oxaliplatin-induced allodynia but not vincristine-induced allodynia, which suggests that CXCR2-related pathways are associated with the development of oxaliplatin-induced neuropathy. Together with the above results, this suggests that the prevention of oxaliplatin-induced neuropathy by CXCR2 inhibition can lead to successful chemotherapy, and it is important to provide appropriate countermeasures against CIPN development for each specific chemotherapeutic agent.

Transient receptor potential melastatin type 2 (TRPM2) is a nonselective cation channel involved in synaptic plasticity. We investigated its role in contextual fear conditioning and extinction of conditioned fear using Trpm2- deficient ( Trpm2 −/− ) mice. Trpm2 −/− mice exhibited reduced acquisition of contextual fear memory during conditioning but had an intact freezing response to conditioning context 24 h after conditioning. They also showed a reduced freezing response to extinction training, indicating facilitated extinction. Consistent with this, infusion of flufenamic acid (FFA), a TRPM2 antagonist, into the dentate gyrus (DG) of the hippocampus in fear-conditioned mice facilitated extinction of contextual fear. The enhanced extinction in Trpm2 −/− and FFA-treated mice was associated with down-regulation of immediate-early genes (IEGs) including Npas4, c-Fos, Arc and Egr1 in the hippocampus after extinction training. Our results indicate that TRPM2 plays a positive role in retention of contextual fear memory by modulating neuronal activity in the hippocampus, and suggest that TRPM2 activity could potentially be targeted to strengthen extinction-based exposure therapies for post-traumatic stress disorder (PTSD).

Major depressive disorder (MDD) is a devastating disease that arises in a background of environmental risk factors, such as chronic stress, that produce reactive oxygen species (ROS) in the brain. The chronic stress-induced ROS production involves Ca2+ signals; however, the mechanism is poorly understood. Transient receptor potential melastatin type 2 (TRPM2) is a Ca2+-permeable cation channel that is highly expressed in the brain. Here we show that in animal models of chronic unpredictable stress (CUS), deletion of TRPM2 (Trpm2 −/−) produces antidepressant-like behaviors in mice. This phenotype correlates with reduced ROS, ROS-induced calpain activation, and enhanced phosphorylation of two Cdk5 targets including synapsin 1 and histone deacetylase 5 that are linked to synaptic function and gene expression, respectively. Moreover, TRPM2 mRNA expression is increased in hippocampal tissue samples from patients with MDD. Our findings suggest that TRPM2 is a key agent in stress-induced depression and a possible target for treating depression.

In an aging society with an increasing threat to higher brain cognitive functions due to dementia, it becomes imperative to identify new molecular remedies for supporting adult neurogenesis. Interleukin-6 (IL-6) is a promising cytokine that can support neurogenesis under conditions of neurodegeneration, and neuron replacement is eventually possible due to its agonistic acting soluble receptor sIL-6R. Here, we report that activation of the IL-6–signal transducer and activator of transcription 3 (STAT3) axis is neurogenic and has potential therapeutic applications for the treatment of neurodegenerative diseases such as Parkinson’s disease (PD).