Antifolding activity of hsp60 couples protein import into the mitochondrial matrix with export to the intermembrane space

Schizothorax prenanti Heat Shock Protein 27 Gene: Cloning, Expression, and Comparison with Other Heat Shock Protein Genes after Poly (I:C) Induction

We identified and cloned cDNA encoding the heat shock protein (Hsp) 27 gene from Schizothorax prenanti (SpHsp27), and compared its expression with that of SpHsp60, SpHsp70, and SpHsp90 in the liver, head kidney, hindgut, and spleen of S. prenanti that were injected with polyinosinic-polycytidylic acid [Poly (I:C)]. The SpHsp27 partial cDNA (sequence length, 653 bp; estimated molecular mass, 5.31 kDa; theoretical isoelectric point, 5.09) contained an open reading frame of 636 bp and a gene encoding 211 amino acids. The SpHsp27 amino acid sequence shared 61.0−92.89% identity with Hsp27 sequences from other vertebrates and SpHsp27 was expressed in seven S. prenanti tissues. Poly (I:C) significantly upregulated most SpHsps genes in the tissues at 12 or 24 h (p < 0.05) compared with control fish that were injected with phosphate-buffered saline. However, the intensity of responses of the four SpHsps was organ-specifically increased. The expression of SpHsp27 was increased 163-fold in the head kidney and 26.6-fold SpHsp27 in the liver at 24 h after Poly (I:C) injection. In contrast, SpHsp60 was increased 0.97−1.46-fold in four tissues and SpHsp90 was increased 1.21- and 1.16-fold in the liver and spleen at 12 h after Poly (I:C) injection. Our findings indicated that Poly (I:C) induced SpHsp27, SpHsp60, SpHsp70, and SpHsp90 expression and these organ-specific SpHsps are potentially involved in S. prenanti antiviral immunity or mediate pathological process.

Molecular Cloning of Heat Shock Protein 60 (SpHSP60) from Schizothorax prenanti and the Gene Expressions of Four SpHSPs during Lipopolysaccharide (LPS) Infection

Heat shock proteins (HSPs) play a key role in anti-stress and immune processes and are associated with autoimmune diseases. In order to explore the immunological role of HSPs from Schizothorax prenanti (S. prenanti), SpHSP60 was cloned for the first time in this study, and the gene expressions of SpHSP27, SpHSP60, SpHSP70 and SpHSP90 in the hepatopancreas, head kidney, hindgut and spleen were analyzed by quantitative real-time PCR (qPCR) after treatment with lipopolysaccharide (LPS). The open reading frame of the SpHSP60 gene (GenBank accession number ON245159) is 1728 bp. It encodes a protein of 575 amino acids. Its C-terminus is a highly conserved and repeated glycine sequence, which is an important cofactor in ATP binding. Compared with the control group, most of the SpHSPs were significantly upregulated in the tissues examined at 12 or 24 h after LPS challenge. The most abundant expression of SpHSP70 was found in the head kidney at 24 h after LPS injection, followed by SpHSP27 in the spleen at 24 h; both of these SpHSPs displayed strong expression under the LPS stresses, about 20–70 fold more than that of SpHSP60 and SpHSP90. The temporal expression patterns of the four SpHSP genes were different in the four tissues examined. Taken together, the results suggest that SpHSP27, SpHSP60, SpHSP70 and SpHSP90 participate in innate immunity stimulated by LPS, and the response intensity of the SpHSPs was organ-specific, indicating they could provide early warning information against bacterial infection. The findings in our study will contribute to better understanding the biological processes and important roles of SpHSPs involved in defending against pathogenic bacterial challenge.

Mapping protein interactions in the active TOM-TIM23 supercomplex

Nuclear-encoded mitochondrial proteins destined for the matrix have to be transported across two membranes. The TOM and TIM23 complexes facilitate the transport of precursor proteins with N-terminal targeting signals into the matrix. During transport, precursors are recognized by the TIM23 complex in the inner membrane for handover from the TOM complex. However, we have little knowledge on the organization of the TOM-TIM23 transition zone and on how precursor transfer between the translocases occurs. Here, we have designed a precursor protein that is stalled during matrix transport in a TOM-TIM23-spanning manner and enables purification of the translocation intermediate. Combining chemical cross-linking with mass spectrometric analyses and structural modeling allows us to map the molecular environment of the intermembrane space interface of TOM and TIM23 as well as the import motor interactions with amino acid resolution. Our analyses provide a framework for understanding presequence handover and translocation during matrix protein transport.

The TOM and TIM23 complexes facilitate the transport of nuclear-encoded proteins into the mitochondrial matrix. Here, the authors use a stalled client protein to purify the translocation supercomplex and gain insight into the TOM-TIM23 interface and the mechanism of protein handover from the TOM to the TIM23 complex.

The Role of Mitochondrial Dysfunction in Atrial Fibrillation: Translation to Druggable Target and Biomarker Discovery

Atrial fibrillation (AF) is the most prevalent and progressive cardiac arrhythmia worldwide and is associated with serious complications such as heart failure and ischemic stroke. Current treatment modalities attenuate AF symptoms and are only moderately effective in halting the arrhythmia. Therefore, there is an urgent need to dissect molecular mechanisms that drive AF. As AF is characterized by a rapid atrial activation rate, which requires a high energy metabolism, a role of mitochondrial dysfunction in AF pathophysiology is plausible. It is well known that mitochondria play a central role in cardiomyocyte function, as they produce energy to support the mechanical and electrical function of the heart. Details on the molecular mechanisms underlying mitochondrial dysfunction are increasingly being uncovered as a contributing factor in the loss of cardiomyocyte function and AF. Considering the high prevalence of AF, investigating the role of mitochondrial impairment in AF may guide the path towards new therapeutic and diagnostic targets. In this review, the latest evidence on the role of mitochondria dysfunction in AF is presented. We highlight the key modulators of mitochondrial dysfunction that drive AF and discuss whether they represent potential targets for therapeutic interventions and diagnostics in clinical AF.

Structural basis for the structural dynamics of human mitochondrial chaperonin mHsp60

Human mitochondrial chaperonin mHsp60 is essential for mitochondrial function by assisting folding of mitochondrial proteins. Unlike the double-ring bacterial GroEL, mHsp60 exists as a heptameric ring that is unstable and dissociates to subunits. The structural dynamics has been implicated for a unique mechanism of mHsp60. We purified active heptameric mHsp60, and determined a cryo-EM structure of mHsp60 heptamer at 3.4 Å. Of the three domains, the equatorial domains contribute most to the inter-subunit interactions, which include a four-stranded β sheet. Our structural comparison with GroEL shows that mHsp60 contains several unique sequences that directly decrease the sidechain interactions around the β sheet and indirectly shorten β strands by disengaging the backbones of the flanking residues from hydrogen bonding in the β strand conformation. The decreased inter-subunit interactions result in a small inter-subunit interface in mHsp60 compared to GroEL, providing a structural basis for the dynamics of mHsp60 subunit association. Importantly, the unique sequences are conserved among higher eukaryotic mitochondrial chaperonins, suggesting the importance of structural dynamics for eukaryotic chaperonins. Our structural comparison with the single-ring mHsp60-mHsp10 shows that upon mHsp10 binding the shortened inter-subunit β sheet is restored and the overall inter-subunit interface of mHsp60 increases drastically. Our structural basis for the mHsp10 induced stabilization of mHsp60 subunit interaction is consistent with the literature that mHsp10 stabilizes mHsp60 quaternary structure. Together, our studies provide structural bases for structural dynamics of the mHsp60 heptamer and for the stabilizing effect of mHsp10 on mHsp60 subunit association.

Transmembrane Coordination of Preprotein Recognition and Motor Coupling by the Mitochondrial Presequence Receptor Tim50

Mitochondrial preproteins contain amino-terminal presequences directing them to the presequence translocase of the mitochondrial inner membrane (TIM23 complex). Depending on additional downstream import signals, TIM23 either inserts preproteins into the inner membrane or translocates them into the matrix. Matrix import requires the coupling of the presequence translocase-associated motor (PAM) to TIM23. The molecular mechanisms coordinating preprotein recognition by TIM23 in the intermembrane space (IMS) with PAM activation in the matrix are unknown. Here we show that subsequent to presequence recognition in the IMS, the Tim50 matrix domain facilitates the recruitment of the coupling factor Pam17. Next, the IMS domain of Tim50 promotes PAM recruitment to TIM23. Finally, the Tim50 transmembrane segment stimulates the matrix-directed import-driving force exerted by PAM. We propose that recognition of preprotein segments in the IMS and transfer of signal information across the inner membrane by Tim50 determine import motor activation.

A signal peptide derived from Hsp60 induces protective cytotoxic T lymphocyte immunity against lymphoid malignancies independently of TAP and classical MHC-I

Hsp60sp, a signal peptide derived from the leader sequence of heat shock protein 60 kDa (Hsp60), is a Qa-1/HLA-E-binding peptide. We previously showed that Hsp60sp-specific CD8⁺ T cells are involved in the immunoregulation of autoimmune diseases by controlling the response of self-reactive lymphocytes. Here, we report that Hsp60sp-specific CD8⁺ T cells killed malignant lymphocytes in vitro independently of transporter associated with antigen processing (TAP) and classical MHC-I expression. Induction of this cytotoxic T lymphocyte (CTL) response in vivo, either by adoptive transfer of in vitro-amplified CTLs or peptide-loaded dendritic cell immunization, resulted in effective control of lymphoid tumors, including TAP- or classical MHC-I-deficient cells. Hsp60sp-specific immune activation combined with programmed cell death protein 1 (PD-1) blocking synergistically restrained mouse lymphoma development. Importantly, Hsp60sp-specific CD8⁺ T cells did not negatively affect normal tissues and cells. Our data suggest that Hsp60sp-based immunotherapy is an inviting strategy to control lymphoid malignancies.

Molecular Perspectives of Mitochondrial Adaptations and Their Role in Cardiac Proteostasis

Mitochondria are the key to properly functioning energy generation in the metabolically demanding cardiomyocytes and thus essential to healthy heart contractility on a beat-to-beat basis. Mitochondria being the central organelle for cellular metabolism and signaling in the heart, its dysfunction leads to cardiovascular disease. The healthy mitochondrial functioning critical to maintaining cardiomyocyte viability and contractility is accomplished by adaptive changes in the dynamics, biogenesis, and degradation of the mitochondria to ensure cellular proteostasis. Recent compelling evidence suggests that the classical protein quality control system in cardiomyocytes is also under constant mitochondrial control, either directly or indirectly. Impairment of cytosolic protein quality control may affect the position of the mitochondria in relation to other organelles, as well as mitochondrial morphology and function, and could also activate mitochondrial proteostasis. Despite a growing interest in the mitochondrial quality control system, very little information is available about the molecular function of mitochondria in cardiac proteostasis. In this review, we bring together current understanding of the adaptations and role of the mitochondria in cardiac proteostasis and describe the adaptive/maladaptive changes observed in the mitochondrial network required to maintain proteomic integrity. We also highlight the key mitochondrial signaling pathways activated in response to proteotoxic stress as a cellular mechanism to protect the heart from proteotoxicity. A deeper understanding of the molecular mechanisms of mitochondrial adaptations and their role in cardiac proteostasis will help to develop future therapeutics to protect the heart from cardiovascular diseases.

Ttm50 facilitates calpain activation by anchoring it to calcium stores and increasing its sensitivity to calcium

Calcium-dependent proteolytic calpains are implicated in a variety of physiological processes, as well as pathologies associated with calcium overload. However, the mechanism by which calpain is activated remains elusive since intracellular calcium levels under physiological conditions do not reach the high concentration range required to trigger calpain activation. From a candidate screening using the abundance of the calpain target glutamate receptor GluRIIA at the Drosophila neuromuscular junction as a readout, we uncovered that calpain activity was inhibited upon knockdown of Ttm50, a subunit of the Tim23 complex known to be involved in the import of proteins across the mitochondrial inner membrane. Unexpectedly, Ttm50 and calpain are co-localized at calcium stores Golgi and endoplasmic reticulum (ER), and Ttm50 interacts with calpain via its C-terminal domain. This interaction is required for calpain localization at Golgi/ER, and increases calcium sensitivity of calpain by roughly an order of magnitude. Our findings reveal the regulation of calpain activation by Ttm50, and shed new light on calpain-associated pathologies.

Progesterone at high doses reduces the growth of U87 and A172 glioblastoma cells: Proteomic changes regarding metabolism and immunity

While pregnancy may accelerate glioblastoma multiforme (GBM) growth, parity and progesterone (P4) containing treatments (ie, hormone replacement therapy) reduce the risk of GBM development. In parallel, low and high doses of P4 exert stimulating and inhibitory actions on GBM growth, respectively. The mechanisms behind the high‐dose P4‐suppression of GBM growth is unknown. In the present study, we assessed the changes in growth and proteomic profiles when high‐dose P4 (100 and 300 µM) was administered in human U87 and A172 GBM cell lines. The xCELLigence system was used to examine cell growth when different concentrations of P4 (20, 50, 100, and 300 µM) was administered. The protein profiles were determined by two‐dimensional gel electrophoresis in both cell lines when 100 and 300 µM P4 were administered. Finally, the pathways enriched by the differentially expressed proteins were assessed using bioinformatic tools. Increasing doses of P4 blocked the growth of both GBM cells. We identified 26 and 51 differentially expressed proteins (fc > 2) in A172 and U87 cell lines treated with P4, respectively. Only the pro‐tumorigenic mitochondrial ornithine aminotransferase and anti‐apoptotic mitochondrial 60 kDa heat shock protein were downregulated in A172 cell line and U87 cell line when treated with P4, respectively. Detoxification of reactive oxygen species, cellular response to stress, glucose metabolism, and immunity‐related proteins were altered in P4‐treated GBM cell lines. The paradox on the effect of low and high doses of P4 on GBM growth is gaining attention. The mechanism related to the high dose of P4 on GBM growth can be explained by the alterations in detoxification mechanisms, stress, and immune response and glucose metabolism. P4 suppresses GBM growth and as it is nontoxic in comparison to classical chemotherapeutics, it can be used as a new strategy in GBM treatment in the future.

Potential osmoprotective roles of branchial heat shock proteins towards Na+, K+-ATPase in milkfish (Chanos chanos) exposed to hypotonic stress

In euryhaline teleosts, osmoregulatory mechanisms vary with osmotic stresses, and heat shock proteins (HSPs) play a central role in maintaining cellular homeostasis. The present study aimed to investigate the expression and potential roles of HSP70 and HSP90 in the gills of seawater (SW)- and freshwater (FW)-acclimated milkfish (Chanos chanos). Four HSP genes, including Cchsc70 (heat shock cognate 70), Cchsp70, Cchsp90α, and Cchsp90β, were analyzed in milkfish gills. Among these genes, only the mRNA abundance of branchial Cchsp90α was significantly lower in the FW-acclimated than in the SW-acclimated milkfish. Immunoblotting showed no significant difference in the relative protein abundance of branchial HSP70 and HSP90 between the two groups. The time-course experiments (from SW to FW) showed that the protein abundance of HSP70 and HSP90 at the 3 h and 6 h post-transfer and then declined gradually. To further illustrate the potential osmoregulatory roles of HSP70 and HSP90, their interaction with Na⁺, K⁺-ATPase (NKA, the primary driving force for osmoregulation) was analyzed using co-immunoprecipitation. The results showed the interaction between HSP70, HSP90 and NKA after acclimation to SW or FW increased within 3 h; and then returned to normal levels within 7 days. To our knowledge, the present study was the first to demonstrate that the interaction between HSP70, HSP90 and NKA changes with hypotonic stress in euryhaline teleosts. Before the transfer, no interaction was detected. When transferred to FW from SW, the interaction of HSP70 and HSP90 with NKA were detected. The results suggested that HSP70 and HSP90 participated in the acute responses of osmoregulatory mechanisms to protect branchial NKA from hypotonic stress in milkfish.

RIPC provides neuroprotection against ischemic stroke by suppressing apoptosis via the mitochondrial pathway

Ischemic stroke is a common disease with high morbidity and mortality. Remote ischemic preconditioning (RIPC) can stimulate endogenous protection mechanisms by inducing ischemic tolerance to reduce subsequent damage caused by severe or fatal ischemia to non-ischemic organs. This study was designed to assess the therapeutic properties of RIPC in ischemic stroke and to elucidate their underlying mechanisms. Neurobehavioral function was evaluated with the modified neurological severity score (mNSS) test and gait analysis. PET/CT was used to detect the ischemic volume and level of glucose metabolism. The protein levels of cytochrome c oxidase-IV (COX-IV) and heat shock protein 60 (HSP60) were tested by Western blotting. TUNEL and immunofluorescence staining were used to analyze apoptosis and to observe the nuclear translocation and colocalization of apoptosis-inducing factor (AIF) and endonuclease G (EndoG) in apoptotic cells. Transmission electron microscopy (TEM) was used to detect mitochondrial-derived vesicle (MDV) production and to assess mitochondrial ultrastructure. The experimental results showed that RIPC exerted significant neuroprotective effects, as indicated by improvements in neurological dysfunction, reductions in ischemic volume, increases in glucose metabolism, inhibition of apoptosis, decreased nuclear translocation of AIF and EndoG from mitochondria and improved MDV formation. In conclusion, RIPC alleviates ischemia/reperfusion injury after ischemic stroke by inhibiting apoptosis via the endogenous mitochondrial pathway.

Msp1 cooperates with the proteasome for extraction of arrested mitochondrial import intermediates

The mitochondrial AAA ATPase Msp1 is well known for extraction of mislocalized tail-anchored ER proteins from the mitochondrial outer membrane. Here, we analyzed the extraction of precursors blocking the import pore in the outer membrane. We demonstrate strong genetic interactions of Msp1 and the proteasome with components of the TOM complex, the main translocase in the outer membrane. Msp1 and the proteasome both contribute to the removal of arrested precursor proteins that specifically accumulate in these mutants. The proteasome activity is essential for the removal as proteasome inhibitors block extraction. Furthermore, the proteasomal subunit Rpn10 copurified with Msp1. The human Msp1 homologue has been implicated in neurodegenerative diseases, and we show that the lack of the Caenorhabditis elegans Msp1 homologue triggers an import stress response in the worm, which indicates a conserved role in metazoa. In summary, our results suggest a role of Msp1 as an adaptor for the proteasome that drives the extraction of arrested and mislocalized proteins at the mitochondrial outer membrane.

Comprehensive Analysis of Protein Glycation Reveals Its Potential Impacts on Protein Degradation and Gene Expression in Human Cells

Glycation as a type of non-enzymatic protein modification is related to aging and chronic diseases, especially diabetes. Global analysis of protein glycation will aid in a better understanding of its formation mechanism and biological significance. In this work, we comprehensively investigated protein glycation in human cells (HEK293T, Jurkat, and MCF7 cells). The current results indicated that this non-enzymatic modification was not random, and protein at the extracellular regions and the nucleus were more frequently glycated. Systematic and site-specific analysis of glycated proteins allowed us to study the effect of the primary sequences and secondary structures of proteins on glycation. Furthermore, nearly every enzyme in the glycolytic pathway was found to be glycated and a possible mechanism was proposed. Many glycation sites were also previously reported as acetylation and ubiquitination sites, which strongly suggested that this non-enzymatic modification may disturb protein degradation and gene expression. The current results will facilitate further studies of protein glycation in biomedical and clinical research.

Heat-Shock Proteins in Neuroinflammation

The heat-shock response, one of the main pro-survival mechanisms of a living organism, has evolved as the biochemical response of cells to cope with heat stress. The most well-characterized aspect of the heat-shock response is the accumulation of a conserved set of proteins termed heat-shock proteins (HSPs). HSPs are key players in protein homeostasis acting as chaperones by aiding the folding and assembly of nascent proteins and protecting against protein aggregation. HSPs have been associated with neurological diseases in the context of their chaperone activity, as they were found to suppress the aggregation of misfolded toxic proteins. In recent times, HSPs have proven to have functions apart from the classical molecular chaperoning in that they play a role in a wider scale of neurological disorders by modulating neuronal survival, inflammation, and disease-specific signaling processes. HSPs are gaining importance based on their ability to fine-tune inflammation and act as immune modulators in various bodily fluids. However, their effect on neuroinflammation processes is not yet fully understood. In this review, we summarize the role of neuroinflammation in acute and chronic pathological conditions affecting the brain. Moreover, we seek to explore the existing literature on HSP-mediated inflammatory function within the central nervous system and compare the function of these proteins when they are localized intracellularly compared to being present in the extracellular milieu.

Molecular cloning and characteristics of DnaJa1and DnaJb1 in Coilia nasus: possible function involved in oogenesis during spawning migration

BACKGROUND

Coilia nasus oogenesis/spawning migration is a well-defined synchronous arrangement process. DnaJs are indispensable molecular chaperones for oogenesis process. However, how DnaJs involved the anadromous spawning migration mechanism is outstanding and plausible.

RESULTS

In this regard, two DnaJs (Cn-DnaJa1 and Cn-DnaJb1) are cloned from the Coilia nasus's ovary. Their structure both contains J domain, G/F domain and ZF domain. Their mRNA transcripts were found extensively expressed in all the sampled tissues and significantly highly in gonads, which probably mean that DnaJs involved in C. nasus's gonad development basal metabolic processes. In the process of spawning migration, Cn-DnaJa1 and Cn-DnaJb1 mRNA transcripts were also expressed with significant differences during oogenesis with highest levels in the development phase, and maintaining high levels during the multiplication, mature and spawning phase. Further study showed that the DnaJa1and DnaJb1protein have high distribution in the onset phase and mainly distributed in the oocyte cytoplasm especially during the migration development phase's.

CONCLUSIONS

This experiment study demonstrated that DnaJs participate in reproductive regulation during the spawning migration process in C. nasus and possibly play a vital role in the ovary development process. These findings also provided a base knowledge for further molecular mechanism study of spawning migration.

Antagonism between HTRA3 and TGFβ1 Contributes to Metastasis in Non-Small Cell Lung Cancer

High temperature requirement A3 (HTRA3, long and short isoforms) is a member of the HtrA family and has been implicated as a tumor suppressor in cancer progression in multiple cancer types, yet its molecular functions in non-small cell lung cancer (NSCLC) are not well understood. Here, we report that decreased levels of HTRA3 negatively correlate with elevated TGFβ1 in lung tumor tissue with metastasis. Furthermore, high expression of HTRA3 indicated better prognosis independent of TGFβ1 expression. In NSCLC cell lines, exogenous TGFβ1 significantly downregulated the level of HTRA3, especially the long isoform, during induction of epithelial-mesenchymal transition (EMT). Mechanistically, c-Jun, which is elevated by TGFβ1, directly bound the promoter of HTRA3-L and inhibited its transcription. As a negative feedback loop, overexpression of HTRA3-L attenuated TGFβ1-mediated invasion-metastasis cascades via activation of SMAD2/3 and sensitized cells to anti-PD-L1 treatment. Taken together, our findings suggest that in the early stages of cancer, overexpressed HTRA3 acts as a brake on the oncogenic effects of TGFβ1 and inhibits tumor metastasis. In later stages, the role of HTRA3 is weakened and TGFβ1 efficiently promotes EMT in the absence of the HTRA3 brake. SIGNIFICANCE: This study provides new mechanistic insight of the interaction between HTRA3 and TGFβ in lung cancer by illustrating that HTRA3 is a novel mediator acting as a suppressor of TGFβ1-related oncogenic effects.

Novel proteomic changes in brain mitochondria provide insights into mitochondrial dysfunction in mouse models of Huntington's disease

Huntington's disease (HD) is a progressive ultimately fatal disorder caused by a glutamine-encoding CAG expansion in the huntingtin (HTT) gene that results in degeneration mainly in striatal and cerebro-cortical brain regions. Mitochondrial dysfunction is one important facet of HD pathogenesis. Here we used R6/2 and YAC128 HD mouse models of human HD, that express different HTT transgenes and have different progression rates, to identify HD brain mitochondrial proteomic signatures. Cerebral cortical mitochondrial preparations from HD and wild-type litter mate mice were compared by two-dimensional SDS-PAGE electrophoresis and MALDI-TOF/TOF mass spectrometry. Proteomic analyses inferred 17 and 12 differentially expressed proteins, respectively in 12 week R6/2 and 15 month YAC128 HD mice, compared to controls. Peroxiredoxin 3, stress-70, DJ-1, isocitrate dehydrogenase [NAD] α subunit and ATP synthase subunit D were differentially expressed in both models. Using the PANTHER (Protein ANalysis THrough Evolutionary Relationships) classification system we show that the inferred proteins are involved in oxidative stress defense, oxidative phosphorylation, the citric acid cycle, pyruvate metabolism, apoptosis, protein folding and iron metabolism. Common mitochondrial proteomic changes are significant in mouse models of middle (YAC128) and advanced (R6/2) HD despite differences in the HTT transgenes, age, genetic background and disease stage. The findings identify a proteomic signature of HD mitochondria in mouse models that includes previously unrecognized proteins.

Comparative proteomic analysis of hepatic mechanisms of Megalobrama amblycephala infected by Aeromonas hydrophila

Hemorrhage syndrome is one of the most prevalent and epidemic diseases that is mainly caused by Aeromonas hydrophila invasion in Megalobrama amblycephala. Recent studies have uncovered a number of immune enzymes and transcripts that are differently expressed in this disease, but the molecular mechanism elicited still remain largely unknown. Here, we constructed an in vivo A. hydrophila infection to investigate the immune mechanism in M. amblycephala using comparative proteomic approach at the one day after infection. 30 altered protein spots were found to undergo differential expression against A. hydrophila infection in the hepatopancreas of M. amblycephala based on 2-DE and were all successfully identified using MALDI-TOF/TOF, representing 18 unique proteins. These proteins were functionally classified into metabolism, antioxidant, cofactors and vitamins, chaperone and signal transduction. Network interaction and Gene Ontology annotation indicated 13 unique proteins were closely related to immune response and directly regulated by each other. Compared with the control group, A. hydrophila infection significantly decreased the metabolism-related mRNA expressions of ENO3, APOA1, CAT and FASN, but increased the mRNA expressions of MDH, ALDOB and RSP12, which was consistent with the protein expression. Nevertheless, FAH was down-regulated at both levels but had no significant difference in mRNA level, ALDH8a1 was down-regulated at protein level but non-significantly up-regulated at the mRNA level. GSTm was up-regulated at protein level but down-regulated at the mRNA level. Consequently, these results revealed that A. hydrophila infection altered the related antioxidative proteins via complex regulatory mechanisms and reduced the immune ability of M. amblycephala at the one day after infection.

Habitual aerobic exercise and circulating proteomic patterns in healthy adults: relation to indicators of healthspan

Habitual aerobic exercise enhances physiological function and reduces risk of morbidity and mortality throughout life, but the underlying molecular mechanisms are largely unknown. The circulating proteome reflects the intricate network of physiological processes maintaining homeostasis and may provide insight into the molecular transducers of the health benefits of physical activity. In this exploratory study, we assessed the plasma proteome (SOMAscan proteomic assay; 1,129 proteins) of healthy sedentary or aerobic exercise-trained young women and young and older men ( n = 47). Using weighted correlation network analysis to identify clusters of highly co-expressed proteins, we characterized 10 distinct plasma proteomic modules (patterns). In healthy young (24 ± 1 yr) men and women, 4 modules were associated with aerobic exercise status and 1 with participant sex. In healthy young and older (64 ± 2 yr) men, 5 modules differed with age, but 2 of these were partially preserved at young adult levels in older men who exercised; among all men, 4 modules were associated with exercise status, including 3 of the 4 identified in young adults. Exercise-linked proteomic patterns were related to pathways involved in wound healing, regulation of apoptosis, glucose-insulin and cellular stress signaling, and inflammation/immune responses. Importantly, several of the exercise-related modules were associated with physiological and clinical indicators of healthspan, including diastolic blood pressure, insulin resistance, maximal aerobic capacity, and vascular endothelial function. Overall, these findings provide initial insight into circulating proteomic patterns modulated by habitual aerobic exercise in healthy young and older adults, the biological processes involved, and their relation to indicators of healthspan. NEW & NOTEWORTHY This is the first study to assess the relation between plasma proteomic patterns and aerobic exercise status in healthy adults. Weighted correlation network analysis identified 10 distinct proteomic modules, including 5 patterns specific for exercise status. Additionally, 5 modules differed with aging in men, two of which were preserved in older exercising men. Exercise-associated modules included proteins related to inflammation, stress pathways, and immune function and correlated with clinical and physiological indicators of healthspan.

Regulation of Antimicrobial Pathways by Endogenous Heat Shock Proteins in Gastrointestinal Disorders

Heat shock proteins (HSPs) are essential mediators of cellular homeostasis by maintaining protein functionality and stability, and activating appropriate immune cells. HSP activity is influenced by a variety of factors including diet, microbial stimuli, environment and host immunity. The overexpression and down-regulation of HSPs is associated with various disease phenotypes, including the inflammatory bowel diseases (IBD) such as Crohn’s disease (CD). While the precise etiology of CD remains unclear, many of the putative triggers also influence HSP activity. The development of different CD phenotypes therefore may be a result of the disease-modifying behavior of the environmentally-regulated HSPs. Understanding the role of bacterial and endogenous HSPs in host homeostasis and disease will help elucidate the complex interplay of factors. Furthermore, discerning the function of HSPs in CD may lead to therapeutic developments that better reflect and respond to the gut environment.

The transcriptomic and proteomic responses of Daphnia pulex to changes in temperature and food supply comprise environment-specific and clone-specific elements

Background

Regulatory adjustments to acute and chronic temperature changes are highly important for aquatic ectotherms because temperature affects their metabolic rate as well as the already low oxygen concentration in water, which can upset their energy balance. This also applies to severe changes in food supply. Thus, we studied on a molecular level (transcriptomics and/or proteomics) the immediate responses to heat stress and starvation and the acclimation to different temperatures in two clonal isolates of the model microcrustacean Daphnia pulex from more or less stressful environments, which showed a higher (clone M) or lower (clone G) tolerance to heat and starvation.

Results

The transcriptomic responses of clone G to acute heat stress (from 20 °C to 30 °C) and temperature acclimation (10 °C, 20 °C, and 24 °C) and the proteomic responses of both clones to acute heat, starvation, and heat-and-starvation stress comprised environment-specific and clone-specific elements. Acute stress (in particular heat stress) led to an early upregulation of stress genes and proteins (e.g., molecular chaperones) and a downregulation of metabolic genes and proteins (e.g., hydrolases). The transcriptomic responses to temperature acclimation differed clearly. They also varied depending on the temperature level. Acclimation to higher temperatures comprised an upregulation of metabolic genes and, in case of 24 °C acclimation, a downregulation of genes for translational processes and collagens. The proteomic responses of the clones M and G differed at any type of stress. Clone M showed markedly stronger and less stress-specific proteomic responses than clone G, which included the consistent expression of a specific heat shock protein (HSP60) and vitellogenin (VTG-SOD).

Conclusions

The expression changes under acute stress can be interpreted as a switch from standard products of gene expression to stress-specific products. The expression changes under temperature acclimation probably served for an increase in energy intake (via digestion) and, if necessary, a decrease in energy expenditures (e.g, for translational processes). The stronger and less stress-specific proteomic responses of clone M indicate a lower degree of cell damage and an active preservation of the energy balance, which allowed adequate proteomic responses under stress, including the initiation of resting egg production (VTG-SOD expression) as an emergency reaction.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4742-6) contains supplementary material, which is available to authorized users.

Toward Developing Chemical Modulators of Hsp60 as Potential Therapeutics

The 60 kDa heat shock protein (Hsp60) is classically known as a mitochondrial chaperonin protein working together with co-chaperonin 10 kDa heat shock protein (Hsp10). This chaperonin complex is essential for folding proteins newly imported into mitochondria. However, Hsp60, and/or Hsp10 have also been shown to reside in other subcellular compartments including extracellular space, cytosol, and nucleus. The proteins in these extra-mitochondrial compartments may possess a wide range of functions dependent or independent of its chaperoning activity. But the mechanistic details remain unknown. Mutations in Hsp60 gene have been shown to be associated with neurodegenerative disorders. Abnormality in expression level and/or subcellular localization have also been detected from different diseased tissues including inflammatory diseases and various cancers. Therefore, there is a strong interest in developing small molecule modulators of Hsp60. Most of the reported inhibitors were discovered through various chemoproteomics strategies. In this review, we will describe the recent progress in this area with reported inhibitors from both natural products and synthetic compounds. The former includes mizoribine, epolactaene, myrtucommulone, stephacidin B, and avrainvillamide while the latter includes o-carboranylphenoxyacetanilides and gold (III) porphyrins. The potencies of the known inhibitors range from low micromolar to millimolar concentrations. The potential applications of these inhibitors include anti-cancer, anti-inflammatory diseases, and anti-autoimmune diseases.

HSP60 is required for stemness and proper differentiation of mouse embryonic stem cells

Embryonic stem cells (ESCs) are metabolically distinct from their differentiated counterparts. ESC mitochondria are less complex and fewer in number than their differentiated progeny. However, few studies have examined the proteins responsible for differences in mitochondrial structure and function between ESCs and somatic cells. Therefore, in this study, we aimed to investigate the differences between mitochondrial proteins in these two cell types. We demonstrate that HSP60 is more abundant in mouse ESC mitochondria than in mouse embryonic fibroblasts. Depletion of HSP60 inhibited mouse ESC proliferation and self-renewal, characterized by decreased OCT4 expression. HSP60 depletion also enhanced apoptosis during mouse ESC differentiation into embryoid bodies. Our results suggest that HSP60 expression has an essential role in ESC self-renewal and survival of differentiated cells from ESCs.

Pharmacological modulation of mitochondrial calcium homeostasis

Mitochondria are pivotal organelles in calcium (Ca²⁺ ) handling and signalling, constituting intracellular checkpoints for numerous processes that are vital for cell life. Alterations in mitochondrial Ca²⁺ homeostasis have been linked to a variety of pathological conditions and are critical in the aetiology of several human diseases. Efforts have been taken to harness mitochondrial Ca²⁺ transport mechanisms for therapeutic intervention, but pharmacological compounds that direct and selectively modulate mitochondrial Ca²⁺ homeostasis are currently lacking. New avenues have, however, emerged with the breakthrough discoveries on the genetic identification of the main players involved in mitochondrial Ca²⁺ influx and efflux pathways and with recent hints towards a deep understanding of the function of these molecular systems. Here, we review the current advances in the understanding of the mechanisms and regulation of mitochondrial Ca²⁺ homeostasis and its contribution to physiology and human disease. We also introduce and comment on the recent progress towards a systems-level pharmacological targeting of mitochondrial Ca²⁺ homeostasis.

Physicochemical Properties of the Mammalian Molecular Chaperone HSP60

The E. coli GroEL/GroES chaperonin complex acts as a folding cage by producing a bullet-like asymmetric complex, and GroEL exists as double rings regardless of the presence of adenosine triphosphate (ATP). Its mammalian chaperonin homolog, heat shock protein, HSP60, and co-chaperonin, HSP10, play an essential role in protein folding by capturing unfolded proteins in the HSP60/HSP10 complex. However, the structural transition in ATPase-dependent reaction cycle has remained unclear. We found nucleotide-dependent association and dissociation of the HSP60/HSP10 complex using various analytical techniques under near physiological conditions. Our results showed that HSP60 exist as a significant number of double-ring complexes (football- and bullet-type complexes) and a small number of single-ring complexes in the presence of ATP and HSP10. HSP10 binds to HSP60 in the presence of ATP, which increased the HSP60 double-ring formation. After ATP is hydrolyzed to Adenosine diphosphate (ADP), HSP60 released the HSP10 and the dissociation of the double-ring to single-rings occurred. These results indicated that HSP60/HSP10 undergoes an ATP-dependent transition between the single- and double-rings in their system that is highly distinctive from the GroEL/GroES system particularly in the manner of complex formation and the roles of ATP binding and hydrolysis in the reaction cycle.

Effects of endocrine disrupting chemicals on estrogen receptor alpha and heat shock protein 60 gene expression in primary cultures of loggerhead sea turtle (Caretta caretta) erythrocytes

The loggerhead turtle (Caretta caretta) can be considered a good indicator species for studying the ecological impact of endocrine disrupting chemicals (EDCs) on wildlife. However, the effect of these environmental pollutants on nuclear steroid hormone signaling has not yet been addressed in sea turtles mainly due to the legal constraints of their endangered status. Here we describe the use of primary erythrocyte cell cultures as in vitro models for evaluating the effects of different EDCs on the expression of estrogen receptor α (ERα). In addition, we evaluated erythrocyte toxicity caused by EDCs using Alamar Blue assay and heat shock proteins 60 (HSP60) expression. Primary cultures of erythrocytes were exposed to increasing concentrations of 4-nonylphenol (4NP), Diisodecyl phthalate (DiDP), Tri-m-cresyl phosphate (TMCP) and Tributyltin (TBT) for 48h. Alamar Blue demonstrated that exposure of erythrocytes to each contaminant for up to 48h led to a significant impairment of cellular metabolic activity at 100μM, with the exception of TBT. Moreover, our data indicate that loggerhead erythrocytes constitutively express ERα and HSP60 at the transcript level and respond to EDCs by up-regulating their expression. In this regard, ERα was up-regulated in a dose-dependent manner after 48h exposure to both 4NP and TMCP. Interestingly, the dosage-dependent effects of DiDP on ERα expression were opposite in comparison to that obtained following exposure to the other tested compounds. This work provides the first indication regarding the potential of primary erythrocytes as study models for evaluating the effects of EDCs on sea turtles.

Developmental Expression of HSP60 and HSP10 in the Coilia nasus Testis during Upstream Spawning Migration

Heat shock protein 60 (HSP60) and heat shock protein 10 (HSP10) are important chaperones, which have been proven to have essential roles in mediating the correct folding of nuclear encoded proteins imported to mitochondria. Mitochondria are known as the power house of the cell, with which it produces energy and respires aerobically. In this regard, the obtained HSP60 and HSP10 have typical characteristics of the HSP60/10 family signature. Their mRNA transcripts detected were highest during the developmental phase (in April), while the lowest levels were found in the resting phase (after spawning in late July). Additionally, the strongest immunolabeling positive signals were found in the primary spermatocyte, with lower positive staining in secondary sperm cells, and a weak or absent level in the mature sperm. At the electron microscopic level, immunogold particles were localized in the mitochondrial matrix. Data indicated that HSP10 and HSP60 were inducible and functional in the Coilia nasus testis development and migration process, suggesting their essential roles in this process. The results also indicated that HSP60 may be one indicator of properly working mitochondrial import and refolding in the fish testis. This study also provides an expanded perspective on the role of heat shock protein families in spawning migration biology.

Differential protein acetylation assists import of excess SOD2 into mitochondria and mediates SOD2 aggregation associated with cardiac hypertrophy in the murine SOD2-tg heart

SOD2 is the primary antioxidant enzyme neutralizing ^•O₂^- in mitochondria. Cardiac-specific SOD2 overexpression (SOD2-tg) induces supernormal function and cardiac hypertrophy in the mouse heart. However, the reductive stress imposed by SOD2 overexpression results in protein aggregation of SOD2 pentamers and differential hyperacetylation of SOD2 in the mitochondria and cytosol. Here, we studied SOD2 acetylation in SOD2-tg and wild-type mouse hearts. LC-MS/MS analysis indicated the presence of four acetylated lysines in matrix SOD2 and nine acetylated lysines in cytosolic SOD2 from the SOD2-tg heart. However, only one specific acetylated lysine residue was detected in the mitochondria of the wild-type heart, which was consistent with Sirt3 downregulation in the SOD2-tg heart. LC-MS/MS further detected hyperacetylated SOD2 with a signaling peptide in the mitochondrial inner membrane and matrix of the SOD2-tg heart, indicating partial arrest of the SOD2 precursor in the membrane during translocation into the mitochondria. Upregulation of HSP 70 and cytosolic HSP 60 enabled the translocation of excess SOD2 into mitochondria. In vitro acetylation of matrix SOD2 with Ac₂O deaggregated pentameric SOD2, restored the profile of cytosolic SOD2 hyperacetylation, and decreased matrix SOD2 activity. As revealed by 3D structure, acetylation of K89, K134, and K154 of cytosolic SOD2 induces unfolding of the tertiary structure and breaking of the salt bridges that are important for the quaternary structure, suggesting that hyperacetylation and HSP 70 upregulation maintain the unfolded status of SOD2 in the cytosol and mediate the import of SOD2 across the membrane. Downregulation of Sirt3, HSP 60, and presequence protease in the mitochondria of the SOD2-tg heart promoted protein misfolding that led to pentameric aggregation.

Cylindrospermopsin effects on protein profile of HepG2 cells

Human hepatoma cells (HepG2) were exposed to purified cylindrospermopsin (CYN), a potent toxicant for eukaryotic cells produced by several cyanobacteria. Exposure to 10 μg l^-1 of CYN for 24 h resulted in alteration of expression of 48 proteins, from which 26 were identified through mass spectrometry. Exposure to 100 μg l^-1 of CYN for 24 h affected nuclear area and actin filaments intensity, which can be associated with cell proliferation and toxicity. The proteins are implicated in different biological processes: protein folding, xenobiotic efflux, antioxidant defense, energy metabolism and cell anabolism, cell signaling, tumorigenic potential, and cytoskeleton structure. Protein profile indicates that CYN exposure may lead to alteration of glucose metabolism that can be associated with the supply of useful energy to cells respond to chemical stress and proliferate. Increase of G protein-coupled receptors (GPCRs), heterogeneous nuclear ribonucleoproteins (hnRNP), and reactive oxygen species (ROS) levels observed in HepG2 cells can associate with cell proliferation and resistance. Increase of MRP3 and glutathione peroxidase can protect cells against some chemicals and ROS. CYN exposure also led to alteration of the expression of cytoskeleton proteins, which may be associated with cell proliferation and toxicity.

Tyrosine phosphorylation modulates mitochondrial chaperonin Hsp60 and delays rotavirus NSP4-mediated apoptotic signaling in host cells

Phosphoproteomics-based platforms have been widely used to identify post translational dynamics of cellular proteins in response to viral infection. The present study was undertaken to assess differential tyrosine phosphorylation during early hours of rotavirus (RV) SA11 infection. Heat shock proteins (Hsp60) were found to be enriched in the data set of RV-SA11 induced differentially tyrosine-phosphorylated proteins at 2 hr post infection (hpi). Hsp60 was further found to be phosphorylated by an activated form of Src kinase on 227th tyrosine residue, and tyrosine phosphorylation of mitochondrial chaperonin Hsp60 correlated with its proteasomal degradation at 2-2.5hpi. Interestingly, mitochondrial Hsp60 positively influenced translocation of the rotaviral nonstructural protein 4 to mitochondria during RV infections. Phosphorylation and subsequent transient degradation of mitochondrial Hsp60 during early hours of RV-SA11 infection resulted in inhibition of premature import of nonstructural protein 4 into mitochondria, thereby delaying early apoptosis. Overall, the study highlighted one of the many strategies rotavirus undertakes to prevent early apoptosis and subsequent reduced viral progeny yield.

A disulfide bond in the TIM23 complex is crucial for voltage gating and mitochondrial protein import

Here, Ramesh et al. show that import and oxidation of Tim17, a membrane-embedded subunit of the mitochondrial protein import machinery, are mediated by the mitochondrial disulfide relay, although its disulfide bond is formed differently than soluble intermembrane space proteins.

Tim17 is a central, membrane-embedded subunit of the mitochondrial protein import machinery. In this study, we show that Tim17 contains a pair of highly conserved cysteine residues that form a structural disulfide bond exposed to the intermembrane space (IMS). This disulfide bond is critical for efficient protein translocation through the TIM23 complex and for dynamic gating of its preprotein-conducting channel. The disulfide bond in Tim17 is formed during insertion of the protein into the inner membrane. Whereas the import of Tim17 depends on the binding to the IMS protein Mia40, the oxidoreductase activity of Mia40 is surprisingly dispensable for Tim17 oxidation. Our observations suggest that Tim17 can be directly oxidized by the sulfhydryl oxidase Erv1. Thus, import and oxidation of Tim17 are mediated by the mitochondrial disulfide relay, though the mechanism by which the disulfide bond in Tim17 is formed differs considerably from that of soluble IMS proteins.

De novo Transcriptome Analysis of Chinese Citrus Fly, Bactrocera minax (Diptera: Tephritidae), by High-Throughput Illumina Sequencing

The Chinese citrus fly, Bactrocera minax (Enderlein), is one of the most devastating pests of citrus in the temperate areas of Asia. So far, studies involving molecular biology and physiology of B. minax are still scarce, partly because of the lack of genomic information and inability to rear this insect in laboratory. In this study, de novo assembly of a transcriptome was performed using Illumina sequencing technology. A total of 20,928,907 clean reads were obtained and assembled into 33,324 unigenes, with an average length of 908.44 bp. Unigenes were annotated by alignment against NCBI non-redundant protein (Nr), Swiss-Prot, Clusters of Orthologous Groups (COG), Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes Pathway (KEGG) database. Genes potentially involved in stress tolerance, including 20 heat shock protein (Hsps) genes, 26 glutathione S-transferases (GSTs) genes, and 2 ferritin subunit genes, were identified. These genes may play roles in stress tolerance in B. minax diapause stage. It has previously been found that 20E application on B. minax pupae could avert diapause, but the underlying mechanisms remain unknown. Thus, genes encoding enzymes in 20E biosynthesis pathway, including Neverland, Spook, Phantom, Disembodied, Shadow, Shade, and Cyp18a1, and genes encoding 20E receptor proteins, ecdysone receptor (EcR) and ultraspiracle (USP), were identified. The expression patterns of 20E-related genes among developmental stages and between 20E-treated and untreated pupae demonstrated their roles in diapause program. In addition, 1,909 simple sequence repeats (SSRs) were detected, which will contribute to molecular marker development. The findings in this study greatly improve our genetic understanding of B. minax, and lay the foundation for future studies on this species.

Comparative proteomic analysis of the effects of high-concentrate diet on the hepatic metabolism and inflammatory response in lactating dairy goats

Background

To understand the impact of feeding a high-concentrate diet to mid-lactating goats for a long time on liver metabolism and inflammatory response, two dimensional polyacrylamide gel electrophoresis (2-DE) and real-time PCR method were employed to detect proteins differentially expressed in liver and their mRNAs expression in goats fed high concentrate diet (HC) or low concentrate diet (LC). Twelve lactating dairy goats were randomly assigned to either a HC diet group (65 % concentrate of dry matter; n = 6) or a LC diet group (35 % concentrate of dry matter; n = 6) for 10 wk.

Results

Twenty differentially expressed spots (≥2.0-fold changes) in the hepatic tissues were excised and successfully identified using MALDI TOF/TOF. Of these, 8 proteins were up-regulated, while the rest 12 proteins were down-regulated in HC goats compared to LC. Differential expressed proteins including alpha enolase 1 (ENO1), glutamate dehydrogenase 1 (GLUD1), glutathione S-transferase A1 (GSTA1), ATP synthase subunit 5β (ATP5β), superoxide dismutase [Cu-Zn] (SOD1), cytochrom c oxidase subunit Via (COX6A1) and heat shock protein 60 (HSP60) were further verified by real-time PCR and/or western blot at mRNA or protein expression level. Consistent with the 2-DE results, a significant decrease of β-actin protein expression and SOD enzyme activity was observed in liver of HC goats (P < 0.05), while ENO1 protein expression was significantly up-regulated in HC compared to LC goats (P < 0.05) . However, western blot analysis did not show a significant difference of hepatic HSP60 protein between HC and LC group, which did not match the decrease of HSP60 content detected by 2-DE analysis. Real-time PCR showed that glutathione S-transferase P1 (GSTP1) and SOD1 mRNA expression was significantly decreased in liver of HC goats, while cytochrom c oxidase (COX3) and ATPase 8 (ATP8) mRNAs expression were markedly increased compared to LC (P < 0.05). Gene Ontology (GO) analysis revealed that HC diet resulted in altered expression of proteins related to catalytic and mitochondrial metabolism in the liver, and may increase the stress response with up-regulating the expression of differentiation 14 (CD14) cluster and serum amyloid A (SAA) as well as C-reactive protein (CRP) in the liver.

Conclusions

These results suggest that feeding high concentrate diet to lactating goats for 10 wk leads to the activation of the inflammatory response, and decreases the anti-oxidant capacity, and subsequently impairs the mitochondrial function in the liver.

Electronic supplementary material

The online version of this article (doi:10.1186/s40104-016-0065-0) contains supplementary material, which is available to authorized users.

Protein Import by the Mitochondrial Presequence Translocase in the Absence of a Membrane Potential

The highly organized mitochondrial inner membrane harbors enzymes that produce the bulk of cellular ATP via oxidative phosphorylation. The majority of inner membrane protein precursors are synthesized in the cytosol. Precursors with a cleavable presequence are imported by the presequence translocase (TIM23 complex), while other precursors containing internal targeting signals are imported by the carrier translocase (TIM22 complex). Both TIM23 and TIM22 are activated by the transmembrane electrochemical potential. Many small inner membrane proteins, however, do not resemble canonical TIM23 or TIM22 substrates and their mechanism of import is unknown. We report that subunit e of the F1Fo-ATP synthase, a small single-spanning inner membrane protein that is critical for inner membrane organization, is imported by TIM23 in a process that does not require activation by the membrane potential. Absence of positively charged residues at the matrix-facing amino-terminus of subunit e facilitates membrane potential-independent import. Instead, engineered positive charges establish a dependence of the import reaction on the electrochemical potential. Our results have two major implications. First, they reveal an unprecedented pathway of protein import into the mitochondrial inner membrane, which is mediated by TIM23. Second, they directly demonstrate the role of the membrane potential in driving the electrophoretic transport of positively charged protein segments across the inner membrane.

The impact of mitochondrial aldehyde dehydrogenase (ALDH2) activation by Alda-1 on the behavioral and biochemical disturbances in animal model of depression

The etiology of depression remains still unclear. Recently, it has been proposed, that mitochondrial dysfunction may be associated with development of mood disorders, such as depression, bipolar disorder and anxiety disorders. Mitochondrial aldehyde dehydrogenase (ALDH2), an enzyme responsible for the detoxification of reactive aldehydes, is considered to exert protective function in mitochondria. We investigated the influence of Alda-1, a small-molecule activator of ALDH2, on depressive- and anxiety-like behaviors in an animal model of depression - the prenatally stressed rats - using behavioral, molecular and proteomic methods. Prolonged Alda-1 administration significantly increased the climbing time, tended to reduce the immobility time and increased the swimming time of the prenatally stressed rats in the forced swim test. Moreover, treatment of prenatally stressed rats with Alda-1 significantly increased number of entries into the open arms of the maze and the time spent therein, as assessed by elevated plus-maze test. Such actions were associated with reduction of plasma 4-HNE-protein content, decrease of TNF-α mRNA and increase of PGC-1α (regulator of mitochondrial biogenesis) mRNA level in the frontal cortex and hippocampus of the prenatally stressed rats as well as with normalization of peripheral immune parameters and significant changes in expression of 6 and 4 proteins related to mitochondrial functions in the frontal cortex and hippocampus, respectively. Collectively, ALDH2 activation by Alda-1 led to a significant attenuation of depressive- and anxiety-like behaviors in the prenatally stressed rats. The pattern of changes suggested mitoprotective effect of Alda-1, however the exact functional consequences of the revealed alterations require further investigation.

Multiple loci not only Rf3 involved in the restoration ability of pollen fertility, anther exsertion and pollen shedding to S type cytoplasmic male sterile in maize

Thirty loci for fertility restoration of pollen fertility, anther exsertion and pollen shedding to maize CMS-S were identified by GWAS. S type cytoplasmic male sterile (CMS-S) is the main type of CMS in maize; poor understanding of the genetic architecture of fertility restoration to CMS-S is one of the reasons to impede its utility in hybrid breeding. In this study, genome-wide identification of genetic loci for fertility restoration ability to CMS-S was firstly conducted with a set of testcrossing association mapping panel in three environments. A total of 19, 3 and 8 significant loci (P < 1.8 × 10(-6), α = 1) for pollen fertility, anther exsertion and pollen shedding were identified, respectively, and individual locus explained up to 28.26% of phenotypic variation. Of them, only Rf3, the main restorer-fertility gene of CMS-S, was identified for the three traits simultaneously. In addition, 83 candidate genes within the 100 kb extension regions of these loci were predicted. These results revealed that besides Rf3 multiple genetic loci and mechanisms are involved in the fertility restoration ability to CMS-S. Results in this study would provide important information for understanding the genetic architecture of fertility restoration to CMS-S in maize.

Functional structure and physiological functions of mammalian wild-type HSP60

The Chaperonins comprise a family of molecular chaperones having a double-ring structure and similar sequence homology. These proteins play an essential role in biological reactions that mediate the folding of newly synthesized polypeptides and partially denatured proteins. In the prokaryotic group I chaperonins, structural and reaction cycle analyses of GroEL and its co-chaperone GroES have been performed in detail. While in eukaryotes, there have been limited reports analyzing the group I chaperonin HSP60 and its co-chaperone HSP10. In the present study, we purified the wild type HSP60 from porcine liver and investigated the interaction between HSP60 and HSP10, including conformation and physiological relationships. Based on the results of transmission electron microscopy, native PAGE, and gel filtration column chromatography, the wild type HSP60 displayed a heptameric single-ring structure in the absence of ATP. In contrast, HSP60 formed mainly a "football-type" complex with HSP10 in the presence of ATP and mediated the refolding of denatured substrate protein. The functional conformation cycle of the purified mammalian HSP60 is distinct from the cycle of the prokaryotic GroEL/GroES chaperonin.

Hsp90, Hsp60 and sHsp families of heat shock protein genes in channel catfish and their expression after bacterial infections

Heat shock proteins (Hsps) are a suite of highly conserved proteins whose expressions are generally induced by elevated temperature. However, many Hsps play important roles in both innate and adaptive immunity. On the basis of our previous work on Hsp40 and Hsp70 gene families in channel catfish (Ictalurus punctatus), the objective of this study was to characterize Hsp90, Hsp60, Hsp10, and small Hsp genes, and to investigate their expression profiles after bacterial infections. A total of 20 Hsp genes were identified and annotated in the channel catfish genome, including five Hsp90 genes, one Hsp60 gene, one Hsp10 gene, and 13 sHsp genes. Six Hsp genes were differentially expressed after Edwardsiella ictaluri infection, and 12 were differentially expressed after Flavobacterium columnare infection. Although expression of these genes exhibited both temporal and spatial regulation, the induction of Hsp genes was observed soon after bacterial infection, while the suppression of Hsp genes was observed at later time-points, suggesting their distinct roles in immune responses and disease defenses. A pathogen-specific expression pattern of Hsp90 was observed. After F. columnare infection, all Hsp90 genes were found up-regulated except Hsp90ab1, which was not significantly regulated. However, after E. ictaluri infection, only one Hsp90 gene was found significantly down-regulated. Both pathogen-specific and tissue-specific pattern of expression were observed with small Hsps after E. ictaluri and F. columnare bacterial infections. These results suggested that most of Hsp genes may play important roles in immune response and/or disease defense in channel catfish.

Control of mitochondrial integrity in ageing and disease

Various molecular and cellular pathways are active in eukaryotes to control the quality and integrity of mitochondria. These pathways are involved in keeping a 'healthy' population of this essential organelle during the lifetime of the organism. Quality control (QC) systems counteract processes that lead to organellar dysfunction manifesting as degenerative diseases and ageing. We discuss disease- and ageing-related pathways involved in mitochondrial QC: mtDNA repair and reorganization, regeneration of oxidized amino acids, refolding and degradation of severely damaged proteins, degradation of whole mitochondria by mitophagy and finally programmed cell death. The control of the integrity of mtDNA and regulation of its expression is essential to remodel single proteins as well as mitochondrial complexes that determine mitochondrial functions. The redundancy of components, such as proteases, and the hierarchies of the QC raise questions about crosstalk between systems and their precise regulation. The understanding of the underlying mechanisms on the genomic, proteomic, organellar and cellular levels holds the key for the development of interventions for mitochondrial dysfunctions, degenerative processes, ageing and age-related diseases resulting from impairments of mitochondria.

In vitro analysis of the mitochondrial preprotein import machinery using recombinant precursor polypeptides

The import of proteins into mitochondria represents an essential process for the survival of eukaryotic cells. Most mitochondrial proteins are synthesized as cytosolic precursor proteins. A complex chain of reactions needs to be followed to achieve a successful transport of these precursors from the cytosol through the double membrane system to their final destination inside the mitochondria. In order to elucidate the details of the translocation process, in vitro import assays have been developed that are based on the incubation of isolated active mitochondria with natural or artificial precursor proteins containing the appropriate targeting information. Using this basic system, most of the protein components of the import machinery have been identified and functionally characterized. However, a detailed definition of the molecular mechanisms requires more specialized assay techniques. Here we describe modifications of the standard in vitro import assay technique that are based on the utilization of large amounts of recombinant preprotein constructs. The application of saturating amounts of substrate preproteins is a prerequisite for the determination of translocation kinetics and energy requirements of the import process. Accumulation of preproteins as membrane-spanning translocation intermediates further provides a basis for the functional and structural characterization of the active translocation machinery.

Mgr2 functions as lateral gatekeeper for preprotein sorting in the mitochondrial inner membrane

The majority of preproteins destined for mitochondria carry N-terminal presequences. The presequence translocase of the inner mitochondrial membrane (TIM23 complex) plays a central role in protein sorting. Preproteins are either translocated through the TIM23 complex into the matrix or are laterally released into the inner membrane. We report that the small hydrophobic protein Mgr2 controls the lateral release of preproteins. Mgr2 interacts with preproteins in transit through the TIM23 complex. Overexpression of Mgr2 delays preprotein release, whereas a lack of Mgr2 promotes preprotein sorting into the inner membrane. Preproteins with a defective inner membrane sorting signal are translocated into the matrix in wild-type mitochondria but are released into the inner membrane in Mgr2-deficient mitochondria. We conclude that Mgr2 functions as a lateral gatekeeper of the mitochondrial presequence translocase, providing quality control for the membrane sorting of preproteins.

Mitochondrial quality control in the myocardium: cooperation between protein degradation and mitophagy

Mitochondria are critical for cardiomyocyte survival and maintenance of normal cardiac function. However, changes in the extra- or intracellular environments during stress can cause excessive damage to mitochondria and lead to activation of cell death. In fact, there is evidence that mitochondrial dysfunction is an important contributor to both development of heart failure and the aging process. To counteract the adverse effects resulting from mitochondrial damage, cells have evolved mitochondrial quality control pathways that act at both the protein and organelle levels. Quality control of proteins in the outer mitochondrial membrane is monitored by the ubiquitin-protease system, whereas chaperones and proteases act in the various compartments of the mitochondria. When the damage is too excessive and the degradation machinery is overwhelmed, the entire mitochondrion is eliminated by an autophagosome. Together, these pathways ensure that myocytes maintain a functional network of mitochondria which provides ATP for contraction. Unfortunately, chronic stress and aging can negatively affect proteins that are involved in the mitochondrial quality control pathways which leads to accumulation of dysfunctional mitochondria and loss of myocytes. In this review, we provide an overview of the proteins and pathways that regulate mitochondrial quality control in the cell with an emphasis on pathways involved in maintaining protein and organelle homeostasis. We also delve into the effects of reduced mitochondrial quality control on aging and cardiovascular disease.

Visualizing active membrane protein complexes by electron cryotomography

Unravelling the structural organization of membrane protein machines in their active state and native lipid environment is a major challenge in modern cell biology research. Here we develop the STAMP (Specifically TArgeted Membrane nanoParticle) technique as a strategy to localize protein complexes in situ by electron cryotomography (cryo-ET). STAMP selects active membrane protein complexes and marks them with quantum dots. Taking advantage of new electron detector technology that is currently revolutionizing cryotomography in terms of achievable resolution, this approach enables us to visualize the three-dimensional distribution and organization of protein import sites in mitochondria. We show that import sites cluster together in the vicinity of crista membranes, and we reveal unique details of the mitochondrial protein import machinery in action. STAMP can be used as a tool for site-specific labelling of a multitude of membrane proteins by cryo-ET in the future.

Changes in the expression of four heat shock proteins during the aging process in Brachionus calyciflorus (rotifera)

Heat shock proteins (HSPs) are molecular chaperones and have an important role in the refolding and degradation of misfolded proteins, and these functions are related to aging. Rotifer is a useful model organism in aging research, owing to small body size (0.1-1 mm), short lifespan (6-14 days), and senescence phenotypes that can be measured relatively easily. Therefore, we used rotifer as a model to determine the role of four typical hsp genes on the aging process in order to provide a better understanding of rotifer aging. We cloned cDNA encoding hsp genes (hsp40, hsp60, hsp70, and hsp90) from the rotifer Brachionus calyciflorus Pallas, analyzed their molecular characteristics, determined its modulatory response under different temperatures and H2O2 concentrations and investigated the changes in expression of these genes during the aging process. We found that Bchsp70 mRNA expression significantly decreased with aging. In addition, we also studied the effects of dietary restriction (DR) and vitamin E on rotifer lifespan and reproduction and analyzed the changes in expression of these four Bchsp genes in rotifers treated with DR and vitamin E. The results showed that DR extended the lifespan of rotifers and reduced their fecundity, whereas vitamin E had no significant effect on rotifer lifespan or reproduction. Real-time PCR indicated that DR increased the expression of these four Bchsps. However, vitamin E only improved the expression of Bchsp60, and reduced the expression of Bchsp40, Bchsp70, and Bchsp90. DR pretreatment also increased rotifer survival rate under paraquat-induced oxidative stress. These results indicated that hsp genes had an important role in the anti-aging process.

Overexpression of CD38 decreases cellular NAD levels and alters the expression of proteins involved in energy metabolism and antioxidant defense

Nicotinamide adenine dinucleotide (NAD) is a coenzyme found in all living cells and mediates multiple cellular signaling pathways. In the present study, a 35% decrease of cellular NAD level is achieved by stable expression of the N-terminal truncated CD38, a NAD hydrolase. CD38-expressing (CD38(+)) cells have the lower growth rate and are more susceptive to oxidative stress than the wild type cells and empty vector-transfected (CD38(-)) cells. Quantitative proteomic analysis shows that 178 proteins are down-regulated in CD38(+) cells, which involve in diverse cellular processes including glycolysis, RNA processing and protein synthesis, antioxidant, and DNA repair. Down regulation of six selected proteins is confirmed by Western blotting. However, down-regulation of mRNA expressions of genes associated with glycolysis, antioxidant, and DNA repair is less significant than the corresponding change in protein expression, suggesting the low NAD level impairs the protein translational machinery in CD38(+) cells. Down-regulation of antioxidant protein and DNA-repair protein expression contributes to the susceptibility of CD38(+) cells to oxidative stress. Taken together, these results demonstrate that CD38(+) cells are a useful model to study effects of the cellular NAD levels on cellular processes and establish a new linker between cellular NAD levels and oxidative stress.

Azacytidine induces necrosis of multiple myeloma cells through oxidative stress

Azacytidine is an inhibitor of DNA methyltransferase and is known to be an anti-leukemic agent to induce cancer cell apoptosis. In the present study, multiple myeloma cells were treated with azacytidine at clinically relevant concentrations to induce necrosis through oxidative stress. Necrotic myeloma cells exhibit unique characteristics, including enrichment of the cell-bound albumin and overexpression of endoplasmic reticulum (ER)- and mitochondrial-specific chaperones, which were not observed in other necrotic cells, including HUH-7, A2780, A549, and Hoc1a. Proteomic analysis shows that HSP60 is the most abundant up-regulated mitochondrial specific chaperone, and azacytidine-induced overexpression of HSP60 is confirmed by western blot analysis. In contrast, expression levels of cytosolic chaperones such as HSP90 and HSP71 were down-regulated in azacytidine-treated myeloma cells, concomitant with an increase of these chaperones in the cell culture medium, suggesting that mitochondrial chaperones and cytosolic chaperones behave differently in necrotic myeloma cells; ER- and mitochondrial-chaperones being retained, and cytosolic chaperones being released into the cell culture medium through the ruptured cell membrane. Our data suggest that HSP60 is potentially a new target for multiple myeloma chemotherapy.

Oxidative stress induces monocyte necrosis with enrichment of cell-bound albumin and overexpression of endoplasmic reticulum and mitochondrial chaperones

In the present study, monocytes were treated with 5-azacytidine (azacytidine), gossypol or hydrogen peroxide to induce cell death through oxidative stress. A shift from apoptotic to necrotic cell death occurred when monocytes were treated with 100 µM azacytidine for more than 12 hours. Necrotic monocytes exhibited characteristics, including enrichment of cell-bound albumin and up-regulation of endoplasmic reticulum (ER)- and mitochondrial-specific chaperones to protect mitochondrial integrity, which were not observed in other necrotic cells, including HUH-7, A2780, A549 and HOC1a. Our results show that the cell-bound albumin originates in the culture medium rather than from monocyte-derived hepatocytes, and that HSP60 is a potential binding partner of the cell-bound albumin. Proteomic analysis shows that HSP60 and protein disulfide isomerase are the most abundant up-regulated mitochondrial and ER-chaperones, and that both HSP60 and calreticulin are ubiquitinated in necrotic monocytes. In contrast, expression levels of the cytosolic chaperones HSP90 and HSP71 were down-regulated in the azacytidine-treated monocytes, concomitant with an increase in the levels of these chaperones in the cell culture medium. Collectively, our results demonstrates that chaperones from different organelles behave differently in necrotic monocytes, ER- and mitochondrial chaperones being retained and cytosolic and nuclear chaperones being released into the cell culture medium through the ruptured cell membrane. HSP60 may serve as a new target for development of myeloid leukemia treatment.