A small heat shock protein (sHSP) from Sinonovacula constricta against heavy metals stresses

Heat shock proteins and metal ions - Reaction or interaction?

Heat shock proteins (HSPs) are part of the cell's molecular chaperone system responsible for the proper folding (or refolding) of proteins. They are expressed in cells of a wide variety of organisms, from bacteria and fungi to humans. While some HSPs require metal ions for proper functioning, others are expressed as a response of the organism to either essential or toxic metal ions. Their presence can influence the occurrence of cellular processes, even those as significant as programmed cell death. The development of research methods and structural modeling has enabled increasingly accurate recognition of new HSP functions, including their role in maintaining metal ion homeostasis. Current investigations on the expression of HSPs in response to heavy metal ions include not only the direct effect of these ions on the cell but also analysis of reactive oxygen species (ROS) and the increased production of HSPs with increasing ROS concentration. This minireview contains information about the direct and indirect interactions of heat shock proteins with metal ions, both those of biological importance and heavy metals.

Effects of wildfire ashes on aquatic invertebrates: First molecular approach on Chironomus riparius larvae

The wildfire magnification in recent years has raised increasing concern about their adverse impacts on the environment. Wildfires are recognized as an important source of diffuse pollution for the nearby aquatic systems being potentially toxic to aquatic life. Albeit previous studies with wildfire runoff/ashes observed effects in aquatic organisms, to date, different severity origins of ashes and their impact at the sub-organismal level on aquatic biota have not been assessed. In this work, the molecular response of Chironomus riparius exposed to wildfire with low (LS) and high (HS) severity ashes from burnt Pine plantations was evaluated by employing an array of 42 genes related to crucial metabolic pathways by Real time-PCR. IV instar larvae were exposed for 72 h to aqueous extract of ashes (12.5 %, 25 %, 50 %, 75 % and 100 %) prepared from LS and HS ashes. Mn, Zn, and Pb were the metals found at highest concentration in both ash extracts, for HS notable Cd, Mn and Cr presence. From the 42 genes studied only 4 were not altered (22 genes modulated their response by LS and 38 genes in the case of HS) showing the opposite response at 100% with downregulated by LS and upregulated by HS. The 12.5 %, 25 %, 100 % HS and 25 % LS were the main modulators, confirmed by the integrative biomarkers response (IBR). Remarkable genotoxicity was generated by ashes even activating the apoptosis response, and endocrine disruption observed could modify the development. Moreover, detoxification and stress response were strongly activated, limiting the organism's future response to external aggressions. The employment of this novelty approach with molecular tools act as early alarm signal preventing greater damages. Overall, wildfire ashes showed to be a significant environmental disruptor to C. riparius even at lower concentration and the short exposure time employed, emphasizing the strong impact of wildfires on aquatic systems.

A 28.6-kD small heat shock protein (MnHSP28.6) protects Macrobrachium nipponense against heavy metal toxicity and oxidative stress by virtue of its anti-aggregation activity

Small heat shock proteins (sHSPs) are ATP-independent chaperones and involved into various physiological and stress processes. In the present study, a 28.6-kD sHSP coding gene, MnHSP28.6, was cloned and characterized from the oriental river prawn Macrobrachium nipponense. Tissue distribution analysis via qPCR and western blot revealed that MnHSP28.6 predominantly expressed in muscle. The temporal transcription of MnHSP28.6 in muscle after bacterial challenge, heavy metal exposure and doxorubicin (DOX) injection was investigated by qPCR. The results showed that the expression of MnHSP28.6 were strongly enhanced by both Cd²⁺ and Cu²⁺ exposure, as well as DOX injection, but not by bacterial infection. Aggregation assays showed that recombinant MnHSP28.6 could effectively prevent temperature-induced aggregation of citrate synthase, and reduction-induced aggregation of insulin in vitro. MnHSP28.6 also could protect muscle extracts from heat-induced protein denaturation and superoxide dismutase (SOD) inactivation. Expressing MnHSP28.6 in E. coli conferred host cell impressive protection against H₂O₂ compared to control. These results suggest a protective role of MnHSP28.6 in maintaining protein homeostasis, preventing aggregation, promoting resistance to heavy metal and keeping redox balance.

Acid stress induces cross-protection for cadmium tolerance of multi-stress-tolerant Pichia kudriavzevii by regulating cadmium transport and antioxidant defense system

The toxicity of cadmium (Cd) is the major limitation to its removal using microorganisms. The Cd tolerance of Pichia kudriavzevii was obviously enhanced by acid stress based on multi-stress cross-protection. RNA-Seq showed that most differentially expressed genes (DEGs) in the Pentose phosphate pathway, Citrate cycle (TCA cycle), Glycolysis/Gluconeogenesis, Peroxisome and Glutathione metabolism were up-regulated by acid stress. The up-regulated expression of genes related to ATP synthesis (GOR1, ALD5, ADH4, ADH6, MDH2, IDH1, IDH2, and ATP19) and Cd transport (GSTY2, GTO2, GLO2, and YOR1), and the improvement of intracellular GSH level and GST activity, reduced the Cd toxicity towards P. kudriavzevii. Cd efflux by YOR1 played a key role in the decline of intracellular Cd level. Acid stress obviously improved the gene expression levels and activities of antioxidant enzymes (SOD, POD, and CAT), which inhibited the Cd-induced ROS outburst and oxidative damage of proteins and membrane lipids. In addition, the enhanced expression of HSP12 protected P. kudriavzevii from the damage of Cd stress. These results provide some important clues to reconstruct robust strains using for Cd removal in aquatic environments.

Novel Ca2+-independent C-type lectin involved in immune defense of the razor clam Sinonovacula constricta

C-type lectins (CTLs) are important pattern recognition molecules that participate in bacterial binding and agglutination by specific recognition of carbohydrates from pathogens. In this study, a full-length cDNA of CTL was cloned from Sinonovacula constricta (designated ScCTL-2). ScCTL-2 has a length of 981 bp, a 5'-untranslated region (UTR) of 47 bp, a short 3'-UTR of 37 bp, and an open reading frame (ORF) of 894 bp, which encodes a polypeptide of 298 amino acid residues. The deduced amino acid of ScCTL-2 possesses a conserved carbohydrate-recognition domain (CRD) similar to that of C³¹-E¹⁷¹. Spatial distribution analysis demonstrated that ScCTL-2 was constitutively expressed in all tested tissues, with dominant expression in foot and siphon and weak expression in hepatopancreas. The mRNA expression level of ScCTL-2 in gills and hepatopancreas was significantly upregulated at 6 and 12 h after challenge with the pathogen Vibrio parahaemolyticus. The recombinant ScCTL-2 showed specific binding and agglutinate capacities to all examined Gram-negative bacterial species, namely, Escherichia coli, Vibro anguillarum, and V. parahaemolyticus in a Ca²⁺-independent manner. However, these binding activities were not detected in Gram-positive Micrococcus luteus. Our results indicated that ScCTL-2 could be a novel pattern recognition receptor that can specifically recognize Gram-negative microorganisms in the innate immunity of S. constricta.

Cadmium detoxification induced by salt stress improves cadmium tolerance of multi-stress-tolerant Pichia kudriavzevii

Heavy metal tolerance of microorganisms is the basis of heavy metal removal by growing cells. In this study, a cross-protection effect generated by salt stress significantly enhanced the cadmium tolerance of multi-stress-tolerant Pichia kudriavzevii. Comparative transcriptome analysis using RNA-Seq linked with physiological and biochemical observation was used to elucidate the underlying mechanisms of the improved cadmium tolerance. The expression of cadmium transport related genes (GSTY2, GLR1, GLO2, YCF1 and YOR1), GSH content and GST activity were elevated by salt stress, suggesting enhanced cadmium conjugation and detoxification in yeast cells. The inhibited cadmium uptake by ZRT1 and enhanced cadmium efflux by YOR1 contributed to the decrease in the intracellular cadmium concentration. The improved expression of antioxidant enzyme genes (SOD1, SOD2, SOD6, CAT1 and PRXIID), along with the enhanced activities of antioxidant enzymes (SOD, CAT and POD) resulted in a decrease in cadmium-induced ROS production, protein carbonylation, lipid peroxidation and cell death. The abundant expression of heat shock protein genes (HSP12, HSP10 and SSC1) and genes related to trehalose synthesis (TPS1 and TSL1) induced by salt stress protected yeast cells against complex stress conditions, contributing to the improved cadmium tolerance. These findings will be useful to develop cadmium-tolerant yeasts for cadmium removal by growing cells.

Two I84 family protease inhibitors from Chinese razor clams Sinonovacula constricta expressed in response to environmental challenges

Protease inhibitors play critical roles in numerous biological processes including host defense in all multicellular organisms. Eighty three evolutionary families of protease inhibitors are currently accommodated in the MEROPS database and the I84 family currently consists of 3 novel serine protease inhibitors from the eastern oyster Crassostrea virginica. In this study, we identified 2 new I84 family members from the Chinese razor clam Sinonovacula constricta, scSI-1 and scSI-2, using cDNA cloning and sequencing. The scSI-1 cDNA consisted of 494 bp with a 282 bp ORF encoding a 93-amino acid polypeptide that was predicted to have a 19-amino acid signal peptide and a 74-residue mature protein with a calculated molecular mass of 8248.5 Da. The scSI-2 cDNA was 490 bp long with a 273 bp ORF encoding a 90-amino acid polypeptide that was predicted to have an 18-amino acid signal peptide and a 72-residue nature protein with a calculated molecular mass of 7528.4 Da. ScSI-1 and scSI-2 shared high sequence similarity with the 3 known members of I84 family and both expressed primarily in the clam digestive glands. Protease inhibitory activity in the clam plasma also exhibited the signature kinetic characteristics of the I84 members from the oyster. In addition, levels of scSI-1 and scSI-2 gene expression in digestive glands and the protease inhibitory activity in plasma elevated significantly in clams challenged by bacterial injections and Vibrio harveyi was more effective than Staphylococcus epidermidis in inducing the gene expression and plasma protease inhibitory activity. Moreover, drastic changes of salinity and temperature also caused significant changes in the gene expression and plasma activity. These results indicated that scSI-1 and scSI-2 represented 2 new members of the I84 family and they likely play a role in clam host defense against infections and in reactions against physiochemical stressors.

Heterologous expression of AgsA enhances Escherichia coli tolerance to the combined effect of elevated temperature and Zinc toxicity

Small heat shock proteins (sHSPs) are ubiquitous stress proteins that are able to protect the cells against cellular insults from temperature, heavy metal etc. However, the molecular chaperone roles of sHSPs in enhancing growth and adaptation under combined temperature and metal stresses in Escherichia coli cells have been poorly understood. Here, we analyze the function of recombinant AgsA, a small heat shock protein from Salmonella enterica serovar Typhimurium under combined temperature and zinc stress in E. coli. Our results show that the heterologous expression of AgsA significantly increases the tolerance of E. coli cells to the combined effect of temperature stress and zinc toxicity by maintaining the stability of soluble proteins. Furthermore, there was remarkable and significant difference in the half effect concentration (EC50) of zinc at all temperatures treatments in both test cells. The EC50s of zinc at 37 °C, 42 °C and 50 °C were 15.24 mg/L, 29.30 mg/L, and 5.98 mg/L respectively in the AgsA-transformed E. coli cells, and 3.03 mg/L, 2.38 mg/L, and 0.373 mg/L, respectively in the control cells lacking AgsA. Together, our data indicate a good concentration-response relationship between all three temperatures treatment and zinc toxicity in E. coli, and establish for the first time the combined effects of temperature and zinc toxicity on E. coli cells. Also, the AgsA protein response to combined thermal and metal stress could serve as a molecular biomarker for the assessment of interactive stress damage to the cells.

The anti-stresses capability of GRP78 in Penaeus monodon: Evidence from in vitro and in vivo studies

Glucose-regulated protein 78 (GRP78) is an important member of the heat shock protein 70 (HSP70) family, which plays important roles in the response to stimulation from various external environmental stimuli. In this study, the full-length cDNA of GRP78 (PmGRP78) was cloned from Penaeus monodon. The qRT-PCR analysis showed that PmGRP78 was ubiquitously expressed in all the tested shrimp tissues, and the expression pattern of PmGRP78 in the gill and hepatopancreas tissues after a pH challenge, osmotic stress, and heavy metal exposure was also detected. A chaperone activity assay was performed to study the function of PmGRP78, and the results showed that the recombinant PmGRP78 possesses biological activity and could protect alcohol dehydrogenase (ADH) from denaturing in vitro. To further explore the role played by PmGRP78 in vivo, RNA interference (RNAi) technology was adopted to silence the expression of PmGRP78 in P. monodon, and a cumulative mortality rate assay was carried out. In conclusion, we inferred that PmGRP78 may play important roles in the defence against environmental stresses in P. monodon.

RNA-seq analysis revealed ROS-mediated related genes involved in cadmium detoxification in the razor clam Sinonovacula constricta

The razor clam Sinonovacula constricta is a eukaryotic benthic intertidal bivalve species that is tolerant to different heavy metals, such as cadmium ion (Cd(2+)). However, the mechanism by which S. constricta responds to Cd(2+)-induced stress remains unclear. In this study, eight transcriptome libraries were constructed and sequenced using razor clams exposed to Cd(2+) for 12 and 48 h. A total of 18,330 unigenes with an average length of 500 bp were annotated. Among these 18,330 unigenes, 582 and 649 displayed differential expression profiles at 12 and 48 h in the gill, respectively. The corresponding differential unigenes in the hepatopancreas were 1056 and 382. Gene Ontology annotation revealed that these unigenes were highly pronounced in metabolic process, cellular process, binding, and catalytic activity. Notably, ROS production-related genes, such as heat shock proteins 32, metallothionein, and glutathione, were synchronously enriched in all experimental samples with induced expression profiles, which was also validated by qPCR. Our results highlighted the relation between immune regulation and Cd(2+)-induced stress in razor clam and provided new insights into the molecular mechanisms of heavy toxicology.

A novel small heat shock protein of Haliotis discus hannai: characterization, structure modeling, and expression profiles under environmental stresses

Small heat shock proteins (sHsps) are a class of chaperones with low molecular weight, feathered by a C-terminal α-crystallin domain (ACD). They participate in reestablishing the stability of partially denatured proteins and therefore contribute to cellular homeostasis. In this work, we identified a sHsp homolog (designated as sHsp19) from Haliotis discus hannai, an economically important farmed mollusk in East Asia. sHsp19 possesses a sHsp hallmark domain, which exhibits the typical fold of ACD as revealed by a three-dimensional model constructed through an iterative threading assembly refinement method. The amino acid sequence sHsp19 shares low identities with any other known sHsps, with percentages below 35 %. Besides, sHsp19 shows relatively distant phylogenetic relationships with sHsps of various mollusks, including two other identified sHsps of abalone subspecies. qRT-PCR analysis indicated that the expression of sHsp19 occurred in multiple tissues. Upon exposure to thermal, oxidative, and multiple toxic metal stresses, the level of sHsp19 mRNA was rapidly elevated in a persistent fashion, with the maximum increase up to 170.58-, 405.84-, and 361.96-fold, respectively. These results indicate sHsp is a novel sHsp that possesses the distinguishing structural feature of sHsps but has remote homologies with known sHsps. It is likely to be important in stress adaptation of abalone and may be applied as a bioindicator for monitoring pollution or detrimental changes of environment in abalone culture.

Characterization of small HSPs from Anemonia viridis reveals insights into molecular evolution of alpha crystallin genes among cnidarians

Gene family encoding small Heat-Shock Proteins (sHSPs containing α-crystallin domain) are found both in prokaryotic and eukaryotic organisms; however, there is limited knowledge of their evolution. In this study, two small HSP genes termed AvHSP28.6 and AvHSP27, both organized in one intron and two exons, were characterised in the Mediterranean snakelocks anemone Anemonia viridis. The release of the genome sequence of Hydra magnipapillata and Nematostella vectensis enabled a comprehensive study of the molecular evolution of α-crystallin gene family among cnidarians. Most of the H. magnipapillata sHSP genes share the same gene organization described for AvHSP28.6 and AvHSP27, differing from the sHSP genes of N. vectensis which mainly show an intronless architecture. The different genomic organization of sHSPs, the phylogenetic analyses based on protein sequences, and the relationships among Cnidarians, suggest that the A.viridis sHSPs represent the common ancestor from which H. magnipapillata genes directly evolved through segmental genome duplication. Additionally retroposition events may be considered responsible for the divergence of sHSP genes of N. vectensis from A. viridis. Analyses of transcriptional expression profile showed that AvHSP28.6 was constitutively expressed among different tissues from both ectodermal and endodermal layers of the adult sea anemones, under normal physiological conditions and also under different stress condition. Specifically, we profiled the transcriptional activation of AvHSP28.6 after challenges with different abiotic/biotic stresses showing induction by extreme temperatures, heavy metals exposure and immune stimulation. Conversely, no AvHSP27 transcript was detected in such dissected tissues, in adult whole body cDNA library or under stress conditions. Hence, the involvement of AvHSP28.6 gene in the sea anemone defensome is strongly suggested.