Plasmodium yoelii: cloning and characterization of the gene encoding for the mitochondrial heat shock protein 60

Genome-wide identification and structural analysis of heat shock protein gene families in the marine rotifer Brachionus spp.: Potential application in molecular ecotoxicology

Heat shock proteins (Hsp) are class of conserved and ubiquitous stress proteins present in all living organisms from primitive to higher level. Various studies have demonstrated multiple cellular functions of Hsp in living organisms as an important biomarker in response to abiotic and biotic stressors including temperature, salinity, pH, hypoxia, environmental pollutants, and pathogens. However, full understanding on the mechanism and pathway involved in the induction of Hsp still remains challenging, especially in aquatic invertebrates. In this study, the entire Hsp family and subfamily members in the marine rotifers Brachionus spp., one of the cosmopolitan ecotoxicological model organisms, have been genome-widely identified. In Brachionus spp. Hsp family was comprised of Hsp10, small hsp (sHsp), Hsp40, Hsp60, Hsp70/105, and Hsp90, with highest number of genes found within Hsp40 DnaJ homolog subfamily C members. Also, the differences in the orientation of the conserved motifs within Hsp family may have induced differences in transcriptional gene modulation in response to thermal stress in Brachionus koreanus. Overall, Hsp family-specific domains were highly conserved in all three Brachionus spp., relative to Homo sapiens and across other animal taxa and these findings will be helpful for future ecotoxicological studies focusing on Hsps.

Interaction of heat shock protein 60 (HSP60) with microRNA in Chinese mitten crab during Spiroplasma eriocheiris infection

Heat shock protein 60 from the Chinese mitten crab Eriocheir sinensis (EsHSP60) was previously identified in relation to Spiroplasma eriocheiris infection by isobaric tags for relative and absolute quantitation labelling followed by liquid chromatography-tandem mass spectrometry. In the present study, to validate the immune function of this protein, the cDNA of the EsHSP60 gene was cloned. Various crab tissues were assessed using real-time PCR, which showed that EsHSP60 transcription occurred in all tissues examined. The expression profiles of EsHSP60 in haemolymph at transcription and protein levels when infected with S. eriocheiris were investigated by real-time PCR and Western blot analysis, respectively. A significant increase of EsHSP60 transcription and protein expression appeared post-injection in response to S. eriocheiris infection when compared to the control group. The double-luciferase reporter gene assay showed that the microRNA PC-533-3p interacted with the 3'-untranslated region of EsHSP60 and inhibited the translation of EsHSP60. The expression profiles of PC-533-3p during S. eriocheiris infection were also investigated by real-time PCR. However, the change tendency of PC-533-3p was opposite to that of the EsHSP60 after S. eriocheiris challenge. These data indicate that the EsHSP60 proteins may play an important role in mediating the immune responses of E. sinensis to an S. eriocheiris challenge.

Characterization and function analysis of Hsp60 and Hsp10 under different acute stresses in black tiger shrimp, Penaeus monodon

Heat shock proteins (Hsps) are a class of highly conserved proteins produced in virtually all living organisms from bacteria to humans. Hsp60 and Hsp10, the most important mitochondrial chaperones, participate in environmental stress responses. In this study, the full-length complementary DNAs (cDNAs) of Hsp60 (PmHsp60) and Hsp10 (PmHsp10) were cloned from Penaeus monodon. Sequence analysis showed that PmHsp60 and PmHsp10 encoded polypeptides of 578 and 102 amino acids, respectively. The expression profiles of PmHsp60 and PmHsp10 were detected in the gills and hepatopancreas of the shrimps under pH challenge, osmotic stress, and heavy metal exposure, and results suggested that PmHsp60 and PmHsp10 were involved in the responses to these stimuli. ATPase and chaperone activity assay indicated that PmHsp60 could slow down protein denaturation and that Hsp60/Hsp10 may be combined to produce a chaperone complex with effective chaperone and ATPase activities. Overall, this study provides useful information to help further understand the functional mechanisms of the environmental stress responses of Hsp60 and Hsp10 in shrimp.

Characterization of Precursor PfHsp60 in Plasmodium falciparum Cytosol during Its Asexual Development in Human Erythrocytes

Mitochondrial heat shock protein 60 (Hsp60) is a nuclear encoded gene product that gets post-translationally translocated into the mitochondria. Using multiple approaches such as immunofluorescence experiments, isoelectric point analysis with two-dimensional gel electrophoresis, and mass spectrometric identification of the signal peptide, we show that Hsp60 from Plasmodium falciparum (PfHsp60) accumulates in the parasite cytoplasm during the ring, trophozoite, and schizont stages of parasite development before being imported into the parasite mitochondria. Using co-immunoprecipitation experiments with antibodies specific to cytoplasmic PfHsp90, PfHsp70-1, and PfHsp60, we show association of precursor PfHsp60 with cytoplasmic chaperone machinery. Metabolic labeling involving pulse and chase indicates translocation of the precursor pool into the parasite mitochondrion during chase. Analysis of results obtained with Geldanamycin treatment confirmed precursor PfHsp60 to be one of the clients for PfHsp90. Cytosolic chaperones bind precursor PfHsp60 prior to its import into the mitochondrion of the parasite. Our data suggests an inefficient co-ordination in the synthesis and translocation of mitochondrial PfHsp60 during asexual growth of malaria parasite in human erythrocytes.

Characterization and expression of SpHsp60 in hemocytes after challenge to bacterial, osmotic and thermal stress from the mud crab Scylla paramamosain

Hsp60 play a crucial role in the process of pathogenic and protective immune responses and is implicated in autoimmune disease. In order to understand the environmental response and immune response of this gene, we cloned a Hsp60 (SpHsp60) gene from the mud crab Scylla paramamosain, localized SpHsp60 in hemocytes by in situ hybridization, and detected the expression of SpHsp60 after stresses in relation to three housekeeping genes (β-actin, 18S rRNA and GAPDH). The full-length of the SpHsp60 cDNA was found to be 2424 bp. The predicted ORF encoded a protein of 576 amino acids with a predicted molecular mass of 61.19 kDa and a theoretical isoelectric point (pI) of 5.46. It shared high scoring identity 95% with the swimming crab Portunus trituberculatus. In situ hybridization assay showed that a higher expression occurred in the granular and semigranular cells when compared to the hyaline hemocytes. It suggested that SpHsp60 was mainly contributed from the granular and semigranular cells in hemolymph. The expression level of SpHsp60 in hemocytes showed a clear time-dependent pattern during the 96 h after stimulated by Vibrio alginolyticus. During this experiment the gene was induced and the highest expression level was observed at 3 h. The significantly up-regulated expression and rapid response of SpHsp60 indicated that the crabs were sensitive to bacterial challenge. After osmotic stress, the expression of SpHsp60 in hemocytes showed that this gene was induced by the high salinity (30‰) and the crabs had its adaptive responses to high salinity, when compared to the normal salinity (15‰). SpHsp60 mRNA expression in hemocytes was analyzed after thermal stress at 6 h, the highest and the lowest expression levels of SpHsp60 were observed at 36 and 32 °C, respectively. This study demonstrated that SpHsp60 was easily induced at the higher temperatures. Based on our research, SpHsp60 participate in innate immune and environmental response of S. paramamosain. It could be used as a biomarker to test the stress caused by the local aquaculture environment.

Molecular cloning of heat shock protein 60 (PtHSP60) from Portunus trituberculatus and its expression response to salinity stress

Heat shock protein 60 (HSP60) is a highly conserved and multi-functional molecular chaperone that plays an essential role in both cellular metabolism and stress response. Portunus trituberculatus is an important marine fishery and aquaculture species, and water salinity condition influenced its artificial propagations significantly. In order to investigate the function of P. trituberculatus HSP60 against osmotic stress, P. trituberculatus HSP60 gene was firstly cloned. The full-length cDNA of PtHSP60 contains 1,743 nucleotides encoding 577 amino acids with a calculated molecular weight of 61.25 kDa. Multiple alignments indicated that the deduced amino acid sequences of PtHSP60 shared a high level of identity with invertebrate and vertebrate HSP60 sequence including shrimp, fruit fly, zebrafish, and human. The expression profiles of PtHSP60 at mRNA and protein levels under salinity treatment were investigated by semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot analysis, respectively. It was found that the mRNA transcripts of PtHSP60 gene varied among different tissues under normal salinity conditions, and the antennal gland showed the highest expression level among the tissues tested. As for low salinity challenge, the mRNA expression of PtHSP60 gene was higher in the gill and appendicular muscle compared with other tissues, and gill and hypodermis represented the higher gene expressions during the hyperosmotic stress, which indicated that those tissues were salinity-sensitive tissues. In addition, salinity challenges significantly altered the expression of PtHSP60 at mRNA and protein level in a salinity- and time-dependent manner in P. trituberculatus gill tissue. The results indicate that PtHSP60 played important roles in mediating the salinity stress in P. trituberculatus.

Expression of HSP60 and HSP70 in white shrimp, Litopenaeus vannamei in response to bacterial challenge

In the present study, cDNA encoding a heat shock protein 60 (LvHSP60) gene in Litopenaeus vannamei was cloned using a combination of homology and rapid amplification of cDNA end (RACE) methods. The full length of the LvHSP60 cDNA was found to be 2379bp, with a 1737bp open reading frame. The translated amino acid sequence consisted of 579 residues with a calculated molecular mass of 60.8kD and an isoelectronic point (pI) of 5.97. Comparison of the deduced amino acid sequence showed that it has high identity (85-89%) with HSP60/chaperonins from insects and mammals. Quantitative real-time PCR and Western blot analysis were carried out to investigate the expression patterns and distribution profiles of LvHSP60 before and after stimulation with the Gram-positive bacterium Staphylococcus aureus and the Gram-negative bacterium Vibrio alginolyticus. LvHSP60 mRNA was found to be both constitutive and inducible, and was highly expressed in haemocytes and almost all tissues examined, including muscle, stomach, heart, hepatopancreas and gill tissue, but it was less strongly expressed in the intestine. The expression analysis revealed that LvHSP60 was significantly up-regulated in the gills, hepatopancreas and haemocytes after bacterial challenge. Transcription of LvHSP70 was also induced in haemocytes and the hepatopancreas after different bacteria injection. Subsequent flow cytometry analysis showed that the concentration of Ca(2+) ions increased significantly within bacteria-challenged haemocytes by 1.5h after injection. The results indicate that LvHSP60 and LvHSP70 may play important roles in mediating the immune responses of L. vannamei to bacterial challenge, and that the Ca(2+) signalling transduction pathway may be involved in the initiation of the shrimp's immune responses in early stages of infection.

Plasmodial heat shock proteins: targets for chemotherapy

Heat shock proteins act as molecular chaperones, facilitating protein folding in cells of living organisms. Their role is particularly important in parasites because environmental changes associated with their life cycles place a strain on protein homoeostasis. Not surprisingly, some heat shock proteins are essential for the survival of the most virulent malaria parasite, Plasmodium falciparum. This justifies the need for a greater understanding of the specific roles and regulation of malarial heat shock proteins. Furthermore, heat shock proteins play a major role during invasion of the host by the parasite and mediate in malaria pathogenesis. The identification and development of inhibitor compounds of heat shock proteins has recently attracted attention. This is important, given the fact that traditional antimalarial drugs are increasingly failing, as a consequence of parasite increasing drug resistance. Heat shock protein 90 (Hsp90), Hsp70/Hsp40 partnerships and small heat shock proteins are major malaria drug targets. This review examines the structural and functional features of these proteins that render them ideal drug targets and the challenges of targeting these proteins towards malaria drug design. The major antimalarial compounds that have been used to inhibit heat shock proteins include the antibiotic, geldanamycin, deoxyspergualin and pyrimidinones. The proposed mechanisms of action of these molecules and the pathways they inhibit are discussed.

Increased light intensity induces heat shock protein Hsp60 in coral species

The effect of increased light intensity and heat stress on heat shock protein Hsp60 was examined in two coral species using a branched coral and a laminar coral, selected for their different resistance to environmental perturbation. Transient Hsp60 induction was observed in the laminar coral following either light or thermal stress. Sustained induction was observed when these stresses were combined. The branched coral exhibited comparatively weak transient Hsp60 induction after heat stress and no detectable induction following light stress, consistent with its susceptibility to bleaching in native environments compared to the laminar coral. Our observations also demonstrate that increased light intensity and heat stress exhibited a greater negative impact on the photosynthetic capacity of environmentally sensitive branched coral than the more resistant laminar coral. This supports a correlation between stress induction of Hsp60 and (a) ability to counter perturbation of photosynthetic capacity by light and heat stress and (b) resistance to environmentally induced coral bleaching.

The mitochondrial 60-kDa heat shock protein in marine invertebrates: biochemical purification and molecular characterization

Sessile marine invertebrates undergo constant direct exposure to the surrounding environmental conditions, including local and global environmental fluctuations that may lead to fatal protein damage. Induction of heat shock proteins (Hsps) constitutes an important defense mechanism that protects these organisms from deleterious stress conditions. In a previous study, we reported the immunological detection of a 60-kDa Hsp (Hsp60) in the sea anemone Anemonia viridis (formerly called Anemonia sulcata) and studied its expression under a variety of stress conditions. In the present study, we show that the sponge Tetilla sp. from tidal habitats with a highly variable temperature regime is characterized by an increased level of Hsp60. Moreover, we show the expression of Hsp60 in various species among Porifera and Cnidaria, suggesting a general importance of this protein among marine invertebrates. We further cloned the hsp60 gene from A viridis, using a combination of conventional protein isolation methods and screening of a complementary deoxyribonucleic acid library by polymerase chain reaction. The cloned sequence (1764 bp) encodes for a protein of 62.8 kDa (588 amino acids). The 62.8-kDa protein, which contains an amino terminal extension that may serve as a mitochondrial targeting signal, shares a significant identity with mitochondrial Hsp60s from several animals but less identity with Hsp60s from either bacteria or plants.

Characterization of a mitochondrion-like organelle in Cryptosporidium parvum

Cryptosporidium parvum is a protozoan parasite that causes widespread diarrhoeal disease in humans and other animals and is responsible for large waterborne outbreaks of cryptosporidiosis. Unlike many organisms belonging to the phylum Apicomplexa, such as Plasmodium spp. and Toxoplasma gondii, there is no clinically proven drug treatment against this parasite. Aspects of the basic biology of C. parvum remain poorly understood, including a detailed knowledge of key metabolic pathways, its genome organization and organellar complement. Previous studies have proposed that C. parvum lacks a relic plastid organelle, or 'apicoplast', but that it may possess a mitochondrion. Here we characterize a mitochondrion-like organelle in C. parvum by (i) ultrastructural and morphological description (ii) localization of heterologous mitochondrial chaperonin antibody probes (iii) phylogenetic analysis of genes encoding mitochondrial transport proteins (iv) identification and analysis of mitochondrion-associated gene sequences. Our descriptive morphological analysis was performed by energy-filtering transmission electron microscopy (EFTEM) of C. hominis and C. parvum. The 'mitochondrion-like' organelle was characterized by labelling the structure with a heterologous mitochondrial chaperonin probe (hsp60) both in immunoelectron microscopy (IMEM) and immunofluorescence (IMF). Phylogenetic analysis of the mitochondrial import system and housekeeping components (hsp60 and hsp70-dnaK) suggested that the C. parvum mitochondrion-like organelle is likely to have descended from a common ancestral apicomplexan mitochondrion. We also identified a partial cDNA sequence coding for an alternative oxidase (AOX) gene, a component of the electron transport chain which can act as an alternative to the terminal mitochondrial respiratory complexes III and IV, which has not yet been reported in any other member of this phylum. Degenerate primers developed to identify selected mitochondrial genes failed to identify either cytochrome oxidase subunit I, or cytochrome b. Taken together, our data aim to provide new insights into the characterization of this Cryptosporidium organelle and a logical framework for future functional investigation.

Cryptosporidium parvum Cpn60 targets a relict organelle

Chaperonin 60 (Cpn60) is a well-established marker protein for eukaryotic mitochondria and plastids. In order to determine whether the small double-membrane-bounded organelle posterior to the nucleus in the apicomplexan Cryptosporidium parvum is a mitochondrion, the Cpn60 gene of C. parvum sporozoites ( CpCpn60) was analyzed and antibodies were generated for localization of the peptide. Sequence and phylogenetic analyses indicated that CpCpn60 is a mitochondrial isotype and that antibodies against it localize to the rough endoplasmic reticulum-enveloped remnant organelle of C. parvum sporozoites. These data show this organelle is of mitochondrial origin.

Immunogenicity and protective efficacy of a Plasmodium yoelii Hsp60 DNA vaccine in BALB/c mice

The gene encoding the 60-kDa heat shock protein of Plasmodium yoelii (PyHsp60) was cloned into the VR1012 and VR1020 mammalian expression vectors. Groups of 10 BALB/c mice were immunized intramuscularly at 0, 3, and 9 weeks with 100 microg of PyHsp60 DNA vaccine alone or in combination with 30 microg of pmurGMCSF. Sera from immunized mice but not from vector control groups recognized P. yoelii sporozoites, liver stages, and infected erythrocytes in an indirect fluorescent antibody test. Two weeks after the last immunization, mice were challenged with 50 P. yoelii sporozoites. In one experiment the vaccine pPyHsp60-VR1012 used in combination with pmurGMCSF gave 40% protection (Fisher's exact test; P = 0.03, vaccinated versus control groups). In a second experiment this vaccine did not protect any of the immunized mice but induced a delay in the onset of parasitemia. In neither experiment was there any evidence of a protective effect against the asexual erythrocytic stage of the life cycle. In a third experiment mice were primed with PyHsp60 DNA, were boosted 2 weeks later with 2 x 10(3) irradiated P. yoelii sporozoites, and were challenged several weeks later. The presence of PyHsp60 in the immunization regimen did not lead to reduced blood-stage infection or development of parasites in hepatocytes. PyHsp60 DNA vaccines were immunogenic in BALB/c mice but did not consistently, completely protect against sporozoite challenge. The observation that in some of the PyHsp60 DNA vaccine-immunized mice there was protection against infection or a delay in the onset of parasitemia after sporozoite challenge deserves further evaluation.

Stress and molecular chaperones in disease

Stress, a common phenomenon in today's society, is suspected of playing a role in the development of disease. Stressors of various types, psychological, physical, and biological, abound. They occur in the working and social environments, in air, soil, water, food, and medicines. Stressors impact on cells directly or indirectly, cause protein denaturation, and elicit a stress response. This is mediated by stress (heat-shock) genes and proteins, among which are those named molecular chaperones because they assist other proteins to achieve and maintain a functional shape (the native configuration), and to recover it when partially lost due to stress. Denatured proteins tend to aggregate and precipitate. The same occurs with abnormal proteins due to mutations, or to failure of post-transcriptional or post-translational mechanisms. These abnormal proteins need the help of molecular chaperones as much as denatured molecules do, especially during stress. A cell with normal antistress mechanisms, including a complete and functional set of chaperones, may be able to withstand stress if its intensity is not beyond that which will cause irreversible protein damage. There is a certain threshold that normal cells have above which they cannot cope with stress. A cell with an abnormal protein that has an intrinsic tendency to misfold and aggregate is more vulnerable to stress than normal counterparts. Furthermore, these abnormal proteins may precipitate even in the absence of stress and cause diseases named proteinopathies. It is possible that stress contributes to the pathogenesis of proteinopathies by promoting protein aggregation, even in cells that possess a normal chaperoning system. Examples of proteinopathies are age-related degenerative disorders with protein deposits in various tissues, most importantly in the brain where the deposits are associated with neuronal degeneration. It is conceivable that stress enhances the progression of these diseases by facilitating protein unfolding and misfolding, which lead to aggregation and deposition. A number of reports in the last few years have described research aimed at elucidating the role of heatshock proteins, molecular chaperones in particular, in the pathogenesis of neurodegenerative disorders. The findings begin to shed light on the molecular mechanism of protein aggregation and deposition, and of the ensuing cell death. The results also begin to elucidate the role of molecular chaperones in pathogenesis. This is a fascinating area of research with great clinical implications. Although there are already several experimental models for the study of proteinopathies, others should be developed using organisms that are better known now than only a few years ago and that offer unique advantages. Use of these systems and of information available in databases from genome sequencing efforts should boost research in this field. It should be possible in the not-too-distant future to develop therapeutic and preventive means for proteinopathies based on the use of heat-shock protein and molecular chaperone genes and proteins.