Suppressor of cytokine signaling 2 is induced in Huntington's disease and involved in autophagy

Neurexin1 level in Huntington's Disease and decreased Neurexin1 in disease progression

Huntington's disease (HD) is a neurodegenerative disorder characterized by the presence of abnormally expanded polyglutamine tracts in huntingtin protein (HTT). Mutant HTT disrupts synaptic transmission and plasticity, particularly in the striatum and cortex, leading to early dysfunctions, such as altered neurotransmitter release, impaired synaptic vesicle recycling, and disrupted postsynaptic receptor function. Synaptic loss precedes neuronal degeneration and contributes to disease progression. Neurexin1 (NRXN1), a synaptic cell adhesion molecule primarily located in the presynaptic membrane, plays a crucial role in maintaining synaptic integrity. The present study investigated the role of NRXN1 in HD. This study researched whether the changed level has been related to expanded polyQ stretch and disease progression. Here, we report a reduction in NRXN1 levels in post-symptomatic HD mice and in neuronal cells expressing abnormally expanded polyQ tracts. Mutant HTT was found to decrease NRXN1 levels while increasing LAMP2A levels, which promotes lysosomal degradation of NRXN1. In HD cells expressing Q111, downregulated LAMP2A restored NRXN1 levels and maintained cell proliferation compared with cells expressing Q7. These findings suggest that NRXN1 is regulated by LAMP2A-mediated way and that decreased NRXN1 levels are associated with symptomatic progression and neuronal cell loss in HD.

Decreased SREBP2 of the striatal cell relates to disrupted protein degradation in Huntington's disease

This study delineated the intricate relation between cholesterol metabolism, protein degradation mechanisms, and the pathogenesis of Huntington's disease (HD). Through investigations using both animal models and cellular systems, we have observed significant alterations in cholesterol levels, particularly in the striatum, which is the primary lesion site in HD. Our findings indicate the dysregulation of cholesterol metabolism-related factors, such as LDLR and SREBP2, in HD, which may contribute to disease progression. Additionally, we uncovered disruptions in protein degradation pathways, including decreased neddylated proteins and dysregulated autophagy, which further exacerbated HD pathology. Moreover, our study highlighted the potential therapeutic implications of targeting these pathways. By restoring cholesterol levels and modulating protein degradation mechanisms, particularly through interventions, such as MLN4924, we observed potential improvements in cellular function, as indicated by the increased BDNF levels. These insights underscore the importance of simultaneously addressing cholesterol metabolism and protein degradation to alleviate HD pathology. Collectively, this study provides a basic understanding of the interplay between the decrease of SREBP2 and the dysfunctional protein degradation system derived from disrupted cholesterol metabolism in HD and HD cells.

Characterization and functional analysis of SOCS9 from orange-spotted grouper (Epinephelus coioides) during virus infection

The suppressor of cytokine signaling (SOCS) proteins family have twelve members including eight known mammalian SOCS members (CISH, SOCS1-7) and four new discovery members (SOCS3b, SOCS5b, SOCS8 and SOCS9) that is regarded as a classic feedback inhibitor of cytokine signaling. Although the function of the mammalian SOCS proteins have been well studied, little is known about the roles of SOCS in fish during viral infection. In this study, the molecular characteristics of SOCS9 from orange-spotted grouper (Epinephelus coioides, EcSOCS9) is investigated. The EcSOCS9 protein encoded 543 amino acids with typical SH2 (389-475aa) and SOCS_box (491-527aa), sharing high identities with reported fish SOCS9. EcSOCS9 was expressed in all detected tissues and highly expressed in kidney. After red-spotted grouper nervous necrosis virus (RGNNV) infection, the expression of EcSOCS9 was significantly induced in vitro. Furthermore, EcSOCS9 overexpression enhanced RGNNV replication, promoted virus-induced mitophagy that evidenced by the increased level of LC3-Ⅱ, BCL2, PGAM5 and decreased level of BNIP3 and FUNDC1. Besides, EcSOCS9 overexpression suppressed the expression levels of ATP6, CYB, ND4, ATP level and induced ROS level. The expression levels of interferon (IFN) related factors (IRF1, IRF3, IRF7, P53), inflammatory factors (IL1-β, IL8, TLR2, TNF-α) and IFN-3, ISRE, NF-κB, AP1 activities were also reduced by overexpressing EcSOCS9. These date suggests that EcSOCS9 impacts RGNNV infection through modulating mitophagy, regulating the expression levels of IFN- related and inflammatory factors, which will expand our understanding of fish immune responses during viral infection.

Translocator Protein (TSPO) Alleviates Neuropathic Pain by Activating Spinal Autophagy and Nuclear SIRT1/PGC-1α Signaling in a Rat L5 SNL Model

Purpose

Recent studies showed promotion of astrocyte autophagy in the spinal cord would provide analgesic effects. Silent information regulator T1 (SIRT1) and α subunit of peroxisome proliferator-activated receptor-γ coactivator-1 (PGC-1α) are two master regulators of endogenous antioxidant defense and mitochondrial biogenesis. They play vital roles in both autophagy and neuropathic pain (NP). Our previous study showed that TSPO agonist Ro5-4864 elicited potent analgesic effects against NP, but the mechanisms remain unclear. This study aims to investigate the effects of TSPO agonist Ro5-4864 on autophagy and nuclear SIRT1/PGC-1α signaling in spinal dorsal horn.

Methods

A rat model of L5 spinal nerve ligation (SNL) was adopted. Rats were randomly assigned to the Sham group, the SNL group, the Ro (TSPO agonist Ro5-4864) group and the Ro+3-MA group. The behavior assessments were conducted at baseline, on Day 1, 3, 7 and 14 after SNL. The autophagy-related proteins (ATG7, Beclin1, LC3, and P62) in spinal dorsal horn were assayed and the nuclear SIRT1/PGC-1α and downstream factors were analyzed.

Results

Ro5-4864 alleviated the mechanical allodynia induced by SNL (P < 0.01 vs the SNL group), which could be totally abrogated by autophagy inhibitor 3-MA (P < 0.01 vs the Ro group). SNL induced elevated ATG7 (P < 0.01), Beclin1 (P < 0.01) and LC3-II/LC3-I (P < 0.01) contents and P62 accumulation (P < 0.01) on Day 7 and Day 14, which suggested an autophagy flux impairment. Ro5-4864 augmented ATG7 (P < 0.01), Beclin1 (P < 0.01) and LC3-II/LC3-I (P < 0.05) with decreased P62 (P < 0.01), which indicated a more fluent autophagic process. These effects were also totally abrogated by 3-MA (P < 0.01). Furthermore, Ro5-4864 activated the spinal nuclear SIRT1/PGC-1α signaling pathway.

Conclusion

TSPO improved both autophagy impairment and mitochondrial biogenesis, which may provide a new strategy for the treatment of NP.

Suppressor of Cytokine Signaling 2 Regulates Retinal Pigment Epithelium Metabolism by Enhancing Autophagy

Retinal pigment epithelium (RPE) serves critical functions in maintaining retinal homeostasis. An important function of RPE is to degrade the photoreceptor outer segment fragments daily to maintain photoreceptor function and longevity throughout life. An impairment of RPE functions such as metabolic regulation leads to the development of age-related macular degeneration (AMD) and inherited retinal degenerative diseases. As substrate recognition subunit of a ubiquitin ligase complex, suppressor of cytokine signaling 2 (SOCS2) specifically binds to the substrates for ubiquitination and negatively regulates growth hormone signaling. Herein, we explore the role of SOCS2 in the metabolic regulation of autophagy in the RPE cells. SOCS2 knockout mice exhibited the irregular morphological deposits between the RPE and Bruch’s membrane. Both in vivo and in vitro experiments showed that RPE cells lacking SOCS2 displayed impaired autophagy, which could be recovered by re-expressing SOCS2. SOCS2 recognizes the ubiquitylated proteins and participates in the formation of autolysosome by binding with autophagy receptors and lysosome-associated membrane protein2 (LAMP-2), thereby regulating the phosphorylation of glycogen synthase kinase 3β (GSK3β) and mammalian target of rapamycin (mTOR) during the autophagy process. Our results imply that SOCS2 participates in ubiquitin-autophagy-lysosomal pathway and enhances autophagy by regulating GSK3β and mTOR. This study provides a potential therapeutic target for AMD.

Circular RNA hsa_circ_0005567 overexpression promotes M2 type macrophage polarization through miR-492/SOCS2 axis to inhibit osteoarthritis progression

Synovial macrophage polarization is essential for osteoarthritis (OA) development. Our study aims to investigate the underlying function and the molecular mechanisms of hsa_circ_0005567 in macrophage polarization. Circular RNA (CircRNA), microRNA (miRNA), and mRNA expression levels were detected by quantitative reverse transcription polymerase chain reaction (RT-qPCR). RNA pull down, luciferase reporter were employed to test the interaction between miR-492 and hsa_circ_0005567/suppressors of cytokine signaling 2 (SOCS2). Ectopic overexpression was used to evaluate the function of hsa_circ_0005567. The supernatant of THP-1 cells was used to incubate chondrocytes. Cell Counting Kit-8 (CCK-8) and flow cytometry were conducted to determine cell viability, proportion of M1 or M2 macrophages and apoptotic rate. The results showed that the hsa_circ_0005567 expression level was downregulated in the synovial tissues of osteoarthritis patients. Overexpression of hsa_circ_0005567 inhibited M1 macrophage polarization, and promoted M2 macrophage polarization. Hsa_circ_0005567 was proved to be a molecular sponge for miR-492, and SOCS2 was verified as the target of miR-492. MiR-492 mimic could reverse the effect of hsa_circ_0005567 overexpression on macrophage polarization. Besides, the supernatant from LPS-treated THP-1 macrophage significantly decreased chondrocytes cell viability and increased cell apoptosis ratio, which was reversed by hsa_circ_0005567 overexpression. In conclusion, hsa_circ_0005567 overexpression promoted M2 macrophage polarization through miR-492/SOCS2 axis to reduced chondrocyte apoptosis, which could inhibit osteoarthritis progression.