Molecular chaperones in stroke-induced immunosuppression

Stroke-induced immunosuppression is a process that leads to peripheral suppression of the immune system after a stroke and belongs to the central nervous system injury-induced immunosuppressive syndrome.Stroke-induced immunosuppression leads to increased susceptibility to post-stroke infections,such as urinary tract infections and stroke-associated pneumonia,worsening prognosis.Molecular chaperones are a large class of proteins that are able to maintain proteostasis by directing the folding of nascent polypeptide chains,refolding misfolded proteins,and targeting misfolded proteins for degradation.Various molecular chaperones have been shown to play roles in stroke-induced immunosuppression by modulating the activity of other molecular chaperones,cochaperones,and their associated pathways.This review summarizes the role of molecular chaperones in stroke-induced immunosuppression and discusses new approaches to restore host immune defense after stroke.

A novel protein refolding method integrating ion exchange chromatography with artificial molecular chaperone

Artificial molecular chaperone （AMC） and ion exchange chromatography （IEC） were integrated, thus a new refolding method, artificial molecular chaperone-ion exchange chromatography （AMC-IEC） was developed. Compared with AMC and IEC, the activity recovery of lysozyme obtained by AMC-IEC was much higher in the investigated range of initial protein concentrations, and the results show that AMC-IEC is very efficient for protein refolding at high concentrations. When the initial concentration of lysozyme is 180 mg/mL, its activity recovery obtained by AMC-IEC is still as high as 76.6%, while the activity recoveries obtained by AMC and IEC are 45.6% and 42.4%, respectively.

Molecular chaperones and hypoxic-ischemic encephalopathy

Hypoxic-ischemic encephalopathy（HIE） is a disease that occurs when the brain is subjected to hypoxia,resulting in neuronal death and neurological deficits,with a poor prognosis.The mechanisms underlying hypoxic-ischemic brain injury include excitatory amino acid release,cellular proteolysis,reactive oxygen species generation,nitric oxide synthesis,and inflammation.The molecular and cellular changes in HIE include protein misfolding,aggregation,and destruction of organelles.The apoptotic pathways activated by ischemia and hypoxia include the mitochondrial pathway,the extrinsic Fas receptor pathway,and the endoplasmic reticulum stress-induced pathway.Numerous treatments for hypoxic-ischemic brain injury caused by HIE have been developed over the last half century.Hypothermia,xenon gas treatment,the use of melatonin and erythropoietin,and hypoxic-ischemic preconditioning have proven effective in HIE patients.Molecular chaperones are proteins ubiquitously present in both prokaryotes and eukaryotes.A large number of molecular chaperones are induced after brain ischemia and hypoxia,among which the heat shock proteins are the most important.Heat shock proteins not only maintain protein homeostasis; they also exert anti-apoptotic effects.Heat shock proteins maintain protein homeostasis by helping to transport proteins to their target destinations,assisting in the proper folding of newly synthesized polypeptides,regulating the degradation of misfolded proteins,inhibiting the aggregation of proteins,and by controlling the refolding of misfolded proteins.In addition,heat shock proteins exert anti-apoptotic effects by interacting with various signaling pathways to block the activation of downstream effectors in numerous apoptotic pathways,including the intrinsic pathway,the endoplasmic reticulum-stress mediated pathway and the extrinsic Fas receptor pathway.Molecular chaperones play a key role in neuroprotection in HIE.In this review,we provide an overview of the mechanisms of HIE and discuss the various treatment strategies.Given their critical role in the disease,molecular chaperones are promising therapeutic targets for HIE.

Molecular chaperones and neurodegenerative diseases

Neurodegenerative diseases are characterized by the accumulation of intracellular or extracellular protein aggregates that result from conformational changes in proteins. These diseases may result from an imbalance between the produetion of misfolded proteins and normal chaperone capacity. Molecular chaperones provide a first line of defenee against misfolded, aggragation-prone proteins and are, therefore, promising therapeutic targets for neurodegenerative diseases.

Single-step Purification of Molecular Chaperone GroEL by Expanded Bed Chromatography

Expanded bed adsorption (EBA) is an integrative downstream processing technique for the purification of biological substances directly from unclarified feedstock. In this study, molecular chaperone GroEL, an important protein folding helper both in vivo and in vitro, was purified by the single-step EBA technique from the unclarified homogenate of recombinant E. coli cells. Compared with packed bed adsorption, the EBA technique provided a single-step approach to yield an electrophoretic purity of GroEL. After the homogenate loading and column washing in the expanded bed mode, the GroEL protein was recovered by stepwise salt-gradient elution in packed-bed or expanded-bed modes, respectively. The expanded-bed elution mode was found as efficient as the packed-bed mode in the purification of GroEL from cell disruptate.

Oxidative modification of the molecular chaperone family in a PC12 cell model of Parkinson's disease induced by Z-Ile-Glu(OtBu)-Ala-Leucinal

Previous studies have demonstrated that ubiquitin-proteasome system function is significantly decreased in the substantia nigra of Parkinson＇s disease patients. In the present study, proteasome inhibitor Z-Ile-Glu（OtBu）-Ala-Leucinal （PSI） was used to inhibit the function of the ubiquitin-proteasome system in PC12 cells to simulate Parkinson＇s disease. Oxidatively modified proteins were identified to determine pathogenesis of Parkinson＇s disease. Results demonstrated that 24 hours of 10 IJmol/L PSI-treatment in PC12 cells simulated pathological characteristics of Parkinson＇s disease： neuronal degeneration and eosinophilic inclusion formation in neurons. In PSI-treated PC12 cells, three oxidative proteins and a molecular chaperone family member were detected： chaperonin containing t-complex polypeptide 1 subunit 3, glucose-regulated protein 58, and heat shock protein 70. This is the first study to demonstrate oxidative modification of a molecule family in a cell model of Parkinson＇s disease induced with PSI.

Differential Expression of Molecular Chaperones in PC12 Cells Treated with PSI

Parkinson＇s disease（PD） is a common neurodegenerative disorder whose primary pathology features are the degeneration of dopaminergic neurons in the substantia nigra pars compacta（SNc） and the presence of eosinophilic inclusions called Lewy body in the cytoplasm of the remained neurons. Growing evidence suggests that dysfunction of the ubiquitin-proteasome system（UPS） is involved in the etiopathogenesis of PD. In order to investigate the pathogenetic mechanism of ubiquitin-proteasome dysfunction in PD, 2D-differential gel electrophoresis（2D-DIGE） and MALDI-TOF Pro MS were used to determine the proteins, which were differentially expressed, in PC12 cells that had undergone a synthetic proteasomal inhibitor PSI（10 μmol/L） treatment for 24 h. Forty-six protein spots were differentially expressed in response to PSI administration, of which 34 were increased and 12 decreased. Six of these were identified as molecular charperones： endoplasmin precursor（GRP94）, heat shock protein 105（HSP105）, HSC-70-psl, glucose ruglated protein 75（GRP75）, glucose ruglated protein 58（GRP58） and heat shock 27000 protein l（HSP27）. The results suggest that the molecular chaperones play an important role in the PD model induced by proteasomal inhibitor.

Effect of chaperone–client interaction strength on Hsp70-mediated protein folding

Protein folding in crowding cellular environment often relies on the assistance of various chaperones. Hsp70 is one of the most ubiquitous chaperones in cells. Previous studies showed that the chaperone–client interactions at the open state tend to remodel the protein folding energy landscape and direct the protein folding as a foldase. In this work, we further investigate how the chaperone–client interaction strength modulates the foldase function of Hsp70 by using molecular simulations. The results showed that the time of substrate folding(including the whole folding step and substrate release step) has a non-monotonic dependence on the interaction strength. With the increasing of the chaperone–client interaction strength, the folding time decreases first, and then increases. More detailed analysis showed that when the chaperone–client interaction is too strong, even small number of chaperones–client contacts can maintain the substrate bound with the chaperone. The sampling of the transient chaperones–client complex with sparse inter-molecule contacts makes the client protein have chance to access the misfolded state even it is bound with chaperone. The current results suggest that the interaction strength is an important factor controlling the Hsp70 chaperoning function.

AAA+ ClpB chaperone as a potential virulence factor of pathogenic microorganisms: Other aspect of its chaperone function

We describe and discuss the most recent findings on the activity and function of the oligomeric AAA+ chaperone ClpB from the Hsp100 protein family in pathogenic microorganisms. Pathogens are exposed to significant stress during infection of the host cells, frequently resulting in protein aggregation. The fact that ClpB is usually up-regulated in pathogens together with its immune reactivity suggests that ClpB acting as a protein disaggregase may be important for pathogen invasion and virulence. However, the specific function of ClpB in pathogenicity is still unclear. Since it is known that ClpB does not exist in mammals, it may serve as a potential target for the development of an effective therapy against several major bacterial diseases that do not respond to conventional antibiotics.

Fluorogenic sensing of amorphous aggregates,amyloid fibers,and chaperone activity via a near-infrared aggregation-induced emission-active probe

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.

The role of the molecular chaperone heat shock protein A2 （HSPA2） in regulating human sperm-egg recognition

One of the most common lesions present in the spermatozoa of human infertility patients is an idiopathic failure of sperm-egg recognition. Although this unique cellular interaction can now be readily by-passed by assisted reproductive strategies such as intracytoplasmic sperm injection （ICSI）, recent large-scale epidemiological studies have encouraged the cautious use of this technology and highlighted the need for further research into the mechanisms responsible for defective sperm-egg recognition. Previous work in this field has established that the sperm domains responsible for oocyte interaction are formed during spermatogenesis prior to being dynamically modified during epididymal maturation and capacitation in female reproductive tract. While the factors responsible for the regulation of these sequential maturational events are undoubtedly complex, emerging research has identified the molecular chaperone, heat shock protein A2 （HSPA2）, as a key regulator of these events in human spermatozoa. HSPA2 is a testis-enriched member of the 70 kDa heat shock protein family that promotes the folding, transport, and assembly of protein complexes and has been positively correlated with in vitro fertilization （IVF） success. Furthermore, reduced expression of HSPA2 from the human sperm proteome leads to an impaired capacity for cumulus matrix dispersal, sperm-egg recognition and fertilization following both IVF and ICSI. In this review, we consider the evidence supporting the role of HSPA2 in sperm function and explore the potential mechanisms by which it is depleted in the spermatozoa of infertile patients. Such information offers novel insights into the molecular mechanisms governing sperm function.

Application of heat shock protein expression for detecting natural adaptation and exposure to stress in natural populations

Heat-shock proteins （HSPs） play an undisputed role for maintaining cellular functioning under environmental challenges and protein denaturing conditions. Compelling evidence points to an evolutionary important role of HSPs and a strict evolutionary control of these proteins as a balance between benefits and costs. While there is a great potential for using HSP expression for detecting natural adaptation and exposure to stress in natural populations, some obstacles and key issues await investigation. From an ecological perspective these key issues needs to be resolved in order to fully appreciate the complex responses and adaptations to stress and to increase our understanding of HSPs and other molecular chaperones for stress adaptation and potential use as biomarkers. Here, the current knowledge and understanding of HSPs is reviewed and a number of key issues including the interpretation of elevated HSP levels, the complications of extrapolating between laboratory and field conditions, the effects of choice of traits and methodology and the larger intra-and extracellular networks of interactions that HSPs participate in are discussed [Current Zoology 56 （6）： 703-713, 2010].

Promising drug targets and associated therapeutic interventions in Parkinson's disease

Parkinson's disease(PD) is one of the most debilitating brain diseases. Despite the availability of symptomatic treatments, response towards the health of PD patients remains scarce. To fulfil the medical needs of the PD patients, an efficacious and etiological treatment is required. In this review, we have compiled the information covering limitations of current therapeutic options in PD, novel drug targets for PD, and finally, the role of some critical beneficial natural products to control the progression of PD.

The Life of a Protein Molecule——Protein Quality Control

The research progress in molecular chaperones, unfolded protein response （UPR） and ER-associated degradation （ERAD） involved in the protein quality control was summarized in this paper, and then the existing problems and the future devel- opment prospect were also discussed. It was pointed out that the life process of protein experienced four stages including synthesizing, folding, assembling and degradation, while each stage required strict quality control. In endoplasmic reticulum （ER）, a variety of proteins had been synthesized, folded and modified to form func- tional proteins with certain conformation. When the folding was blocked in ER, the unfolded proteins would aggregate and induce the UPR, which up-regulated the level of modification enzymes folded by a series of molecular chaperones and proteins to help them accomplish folding and assembling. If these proteins were still folded incorrectly, they would enter into ERAD for being degraded.

Modulation of protein fate decision by small molecules:targeting molecular chaperone machinery

Modulation of protein fate decision and protein homeostasis plays a significant role in altering the protein level,which acts as an orientation to develop drugs with new mechanisms.The molecular chaperones exert significant biological functions on modulation of protein fate decision and protein homeostasis under constantly changing environmental conditions through extensive protein-protein interactions(PPIs)with their client proteins.With the help of molecular chaperone machinery the processes of protein folding,trafficking,quality control and degradation of client proteins could be arranged properly.The core members of molecular chaperones,including heat shock proteins(HSPs)family and their co-chaperones,are emerging as potential drug targets since they are involved in numerous disease conditions.Development of small molecule modulators targeting not only chaperones themselves but also the PPIs among chaperones,co-chaperones and clients is attracting more and more attention.These modulators are widely used as chemical tools to study chaperone networks as well as potential drug candidates for a broader set of diseases.Here,we reviewed the key checkpoints of molecular chaperone machinery HSPs as well as their co-chaperones to discuss the small molecules targeting on them for modulation of protein fate decision.

The role of DJ-1 in the pathogenesis of Parkinson’s disease

Parkinson’s disease (PD) is a slowly progressive neurodegenerative disorder characterized clinically by bradykinesia, rigidity, tremor, gait dysfunction, and postural instability. Several genes have been identified for monogenic disorders that variably resemble Parkinson’s disease. Here, we focus on PARK7, a gene relates to an autosomal recessive form of early-onset Parkinsonism and encodes a protein named DJ-1. Though the exact role of DJ-1 needs to be elucidated, it is generally thought to be functioned as a molecular chaperone and an oxidative sensor (or antioxidative factor). We will review the protective role of DJ-1 to prevent dopaminergic neurons in the substantia nigra pars compacta (SNpc) from degeneration and how its dysfunction would lead to neurodegeneration.

Hsp90 at the crossroads of genetics and epigenetics

Hsp90 is a specialized molecular chaperone that is capable of buffering the expression of abnormal phenotypes. Inhibition of Hsp90 activity results in the expression of these phenotypes that are otherwise masked. Selection of offspring from the crossing of affected progenies results in inheritance and enrichment of these phenotypes, which can become independent of their original stimuli. The current combined evidence favours a model involving the interplay between genetics and epigenetics. The recent proteomics efforts to characterize the Hsp90 interaction networks provide further clues into the molecular mechanisms behind this complex phenomenon. This review summarizes the most recent experimental observations and briefly discusses the genetic and epigenetic views used in explaining the different observations.

Genetic analysis implicates a molecular chaperone complex in regulating epigenetic silencing of methylated genomic regions

DNA cytosine methylation confers stable epigenetic silencing in plants and many animals.However,the mechanisms underlying DNA methylation-mediated genomic silencing are not fully understood.We conducted a forward genetic screen for cellular factors required for the silencing of a heavily methylated p35S:NPTII transgene in the Arabidopsis thaliana rdm1-1 mutant background,which led to the identification of a Hsp20 family protein,RDS1(rdm1-1 suppressor 1).Loss-of-function mutations in RDS1 released the silencing of the p35S::NPTII transgene in rdm1-1 mutant plants,without changing the DNA methylation state of the transgene.Protein interaction analyses suggest that RDS1 exists in a protein complex consisting of the methyl-DNA binding domain proteins MBD5 and MBD6,two other Hsp20 family proteins,RDS2 and IDM3,a Hsp40/DNAJ family protein,and a Hsp70 family protein.Like rds1 mutations,mutations in RDS2,MBD5,or MBD6 release the silencing of the transgene in the rdm1 mutant background.Our results suggest that Hsp20,Hsp40,and Hsp70 proteins may form a complex that is recruited to some genomic regions with DNA methylation by methyl-DNA binding proteins to regulate the state of silencing of these regions.

Metabolism of minor isoforms of prion proteins Cytosolic prion protein and transmembrane prion protein

Transmissible spongiform encephalopathy or prion disease is triggered by the conversion from cellular prion protein to pathogenic prion protein. Growing evidence has concentrated on prion protein configuration changes and their correlation with prion disease transmissibility and patho- genicity. In vivo and in vitro studies have shown that several cytosolic forms of prion protein with specific topological structure can destroy intracellular stability and contribute to prion protein pathogenicity. In this study, the latest molecular chaperone system associated with endoplasmic re- ticulum-associated protein degradation, the endoplasmic reticulum resident protein quality-control system and the ubiquitination proteasome system, is outlined. The molecular chaperone system directly correlates with the prion protein degradation pathway. Understanding the molecular mechanisms will help provide a fascinating avenue for further investigations on prion disease treatment and prion protein-induced neurodegenerative diseases.

A Review of Heat Shock Proteins Research on Bemisia tabaci

Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) is the most destructive invasive pests in agricultural production and has a high tolerance to heat. Heat shock proteins play an essential role in life activities such as growth and development, reproduction and diapause of B. tabaci. At the same time, they are also crucial in resisting adverse environments and in adaptive evolution. The expression of heat shock protein in B. tabaci is not only related to temperature, but also to the tolerance of the environment. After receiving external stimuli, the expression level can be increased or decreased to maintain the stability of cells in vivo. This paper reviews the classification, biological characteristics, biological functions, and research status of HSPs in recent years. This mini-review will provide helpful information related to the use of heat shock proteins to study the occurrence and damage of B. tabaci. This has important theoretical and practical significance for revealing Hsps in explaining the population expansion mechanism of B. tabaci invasion and predicting population dynamics.