Initially thought to be an opioid receptor subtype, Sigma-1 receptors (S1R) are now known to be unique proteins that have chaperone-like properties. As such, they play critical roles in cellular signaling, homeostasis, and cell survival. These roles offer significant insight for understanding homeostasis of normal physiologic processes, and the pathophysiologic consequences of disruption of normal function. Because of the broad nature of chaperone action, S1R agonists and antagonists represent potential drug discovery goals for the pharmacotherapeutic treatment of a variety of disorders that result from dysfunctional proteins. The present study summarizes the S1R as a pharmacologic chaperone crucial for protein folding and cellular homeostasis. Through literature review and thermodynamic analysis, it explores how S1R stabilizes target proteins, influencing neuroprotection and potential drug therapies. The binding of chaperones to target proteins is thermodynamically favorable, offering insights into treating diseases linked to protein misfolding.
The polymer translocation through a nanopore from a donor space(or named cis side) to a receiver space(trans side) in the chaperone-induced crowded environment has attracted increasing attention in recent years due to its significance in biological systems and technological applications. In this work, we mainly focus on the effects of chaperone concentration and chaperone-polymer interaction on the polymer translocation. By assuming the polymer translocation to be a quasi-equilibrium process, the free energy F of the polymer can be estimated by Rosenbluth-Rosenbluth method and then the translocation time τ can be calculated by Fokker-Plank equation based on the obtained free energy landscape. Our calculation results show that the translocation time can be controlled by independently tuning the chaperone concentration and chaperone-polymer interaction at the cis side or the trans side. There exists a critical chaperone-polymer attraction ε~*=-0.2 at which the volume exclusion and interaction effects of the chaperone can balance each other. Additionally, we also find that at large chaperone-polymer attraction, the translocation time is mainly governed by the diffusion coefficient of the polymer.
Objective:To investigate the role and the molecular mechanisms of apoptotic signaling in ferroptosis to regulate tumor radiosensitivity.Methods:Reactive oxygen species(ROS)and lipid peroxide levels were detected in Mouse embryonic fibroblasts(MEFs)with Bcl-xL or Mcl-1 deficiency induced by erastin.Colony formation,ROS,lipid peroxidation and the transcription/translation levels of PTGS2 were measured in Bcl-xL knockdown tumor cells induced by 5 Gyγ-rays or co-treated with ferrostatin-1(Ferr-1).The protein levels of LPCAT3,ACSL4 and PEBP1 in Bcl-xL knockout MEF cells were evaluated in Bcl-xL knockout MEF cells post-radiation.Moreover,the interaction of heat shock protein 90(HSP90)with Bcl-xL,GPX4,or LAMP2A was detected by protein mass spectrometry and immunoprecipitation assays.Results:Manipulating Bcl-xL levels facilitated radiation-induced ferroptosis by augmenting the enzymatic oxidation of polyunsaturated fatty acids(PUFAs)and enhancing chaperone-mediated autophagy(CMA)of glutathione peroxidase 4(GPX4)(MEF cell line:t=4.540,P<0.01;A549 cell line:t=56.16,P<0.0001;t=4.885,P<0.01;HCT116 cell line:t=14.75,P<0.01;t=7.363,P<0.05).Downregulating Bcl-xL expression promoted the activity of acyl-CoA synthetase long-chain family member 4(ACSL4),thus increasing the enzymatic oxidation of PUFAs(t=4.258,P<0.01).Moreover,depletion of Bcl-xL expedited the CMA process targeting GPX4 by facilitating the association of GPX4 with heat shock protein 90(HSP90)and LAMP2A following radiation exposure.Subsequent degradation of GPX4 led to the accumulation of lipid peroxides,ultimately triggering ferroptosis.Conclusions:Our study provides initial insights into the regulatory role of Bcl-xL in ferroptosis and underscores the potential of targeting Bcl-xL as a promising therapeutic strategy for cancer by modulating both apoptotic and ferroptotic pathways.
Dear Editor,The passage of DNA replication forks during eukaryotic cell division disrupts the nucleosomes they encounter,and de novo assembly of nucleosomes onto replicated DNA must take place to restore chromatin structure.There are two sources of histones for the replicationcoupled nucleosome assembly.
The presence of protein aggregates in numerous human diseases underscores the significance of detecting these aggregates to comprehend disease mechanisms and develop novel therapeutic approaches for combating these disorders.Despite the development of various biosensors and fluorescent probes that selectively target amyloid fibers or amorphous aggregates,there is still a lack of tools capable of simultaneously detecting both types of aggregates.Herein,we demonstrate the quantitative discernment of amorphous aggregates by QM-FN-SO3,an aggregationinduced emission(AIE)probe initially designed for detecting amyloid fibers.This probe easily penetrates the membranes of the widely-used prokaryotic model organism Escherichia coli,enabling the visualization of both amorphous aggregates and amyloid fibers through near-infrared fluorescence.Notably,the probe exhibits sensitivity in distinguishing the varying aggregation propensities of proteins,regardless of whether they form amorphous aggregates or amyloid fibers in vivo.These properties contribute to the successful application of the QM-FN-SO3 probe in the subsequent investigation of the antiaggregation activities of two outer membrane protein(OMP)chaperones,both in vitro and in their physiological environment.Overall,our work introduces a near-infrared fluorescent chemical probe that can quantitatively detect amyloid fibers and amorphous aggregates with high sensitivity in vitro and in vivo.Furthermore,it demonstrates the applicability of the probe in chaperone biology and its potential as a high-throughput screening tool for protein aggregation inhibitors and folding factors.
Wei HeYuanyuan YangYuhui QianZhuoyi ChenYongxin ZhengWenping ZhaoChenxu YanZhiqian GuoShu Quan
Protein misfolding and aggregation are crucial pathogenic factors for cataracts,which are the leading cause of visual impairment worldwide.α-crystallin,as a small molecular chaperone,is involved in preventing protein misfolding and maintaining lens transparency.The chaperone activity of α-crystallin depends on its oligomeric state.Our previous work identified a natural compound,celastrol,which could regulate the oligomeric state of αB-crystallin.In this work,based on the UNcle and SEC analysis,we found that celastrol induced𝛼αB-crystallin to form large oligomers.Large oligomer formation enhanced the chaperone activity of αB-crystallin and prevented aggregation of the cataract-causing mutant αA3-G91del.The interactions between𝛼αB-crystallin and celastrol were detected by the FRET(Fluorescence Resonance Energy Transfer)technique,and verified by molecular docking.At least 9 binding patterns were recognized,and some binding sites covered the groove structure of αB-crystallin.Interestingly,αB-R120G,a cataract-causing mutation located at the groove structure,and celastrol can decrease the aggregates of αB-R120G.Overall,our results suggested celastrol not only promoted the formation of large αB-crystallin oligomers,which enhanced its chaperone activity,but also bound to the groove structure of its α-crystallin domain to maintain its structural stability.Celastrol might serve as a chemical and pharmacological chaperone for cataract treatment.