Characterization of four heat-shock protein genes from Nile tilapia (Oreochromis niloticus) and demonstration of the inducible transcriptional activity of Hsp70 promoter

A Review on the Involvement of Heat Shock Proteins (Extrinsic Chaperones) in Response to Stress Conditions in Aquatic Organisms

Heat shock proteins (HSPs) encompass both extrinsic chaperones and stress proteins. These proteins, with molecular weights ranging from 14 to 120 kDa, are conserved across all living organisms and are expressed in response to stress. The upregulation of specific genes triggers the synthesis of HSPs, facilitated by the interaction between heat shock factors and gene promoter regions. Notably, HSPs function as chaperones or helper molecules in various cellular processes involving lipids and proteins, and their upregulation is not limited to heat-induced stress but also occurs in response to anoxia, acidosis, hypoxia, toxins, ischemia, protein breakdown, and microbial infection. HSPs play a vital role in regulating protein synthesis in cells. They assist in the folding and assembly of other cellular proteins, primarily through HSP families such as HSP70 and HSP90. Additionally, the process of the folding, translocation, and aggregation of proteins is governed by the dynamic partitioning facilitated by HSPs throughout the cell. Beyond their involvement in protein metabolism, HSPs also exert a significant influence on apoptosis, the immune system, and various characteristics of inflammation. The immunity of aquatic organisms, including shrimp, fish, and shellfish, relies heavily on the development of inflammation, as well as non-specific and specific immune responses to viral and bacterial infections. Recent advancements in aquatic research have demonstrated that the HSP levels in populations of fish, shrimp, and shellfish can be increased through non-traumatic means such as water or oral administration of HSP stimulants, exogenous HSPs, and heat induction. These methods have proven useful in reducing physical stress and trauma, while also facilitating sustainable husbandry practices such as vaccination and transportation, thereby offering health benefits. Hence, the present review discusses the importance of HSPs in different tissues in aquatic organisms (fish, shrimp), and their expression levels during pathogen invasion; this gives new insights into the significance of HSPs in invertebrates.

Molecular cloning, expression HSP70 and its response to bacterial challenge and heat stress in Microptenus salmoides

The gene encoding HSP70 was isolated from Microptenus salmoides by homologous cloning and rapid amplification of cDNA ends (RACE). The HSP70 transcripts were 2116 bp long and contained 1953 open reading frames encoding proteins of 650 amino acids with a molecular mass of 71.2 kDa and theoretical isoelectric point of 5.22. The qRT-PCR analysis showed that the HSP70 gene was differentially expressed in various tissues under normal conditions, and the highest HSP70 level was observed in the spleen and the lowest levels in the muscle and heart. The clear time-dependent expression level of HSP70 was observed after bacterial challenge and heat stress. A significant increase in HSP70 expression level was detected and reached a maximum at 3 h and 6 h in liver, spleens and gill tissues after Aeromonas hydrophila infection and heat stress, respectively (P < 0.05). As time progressed, the expression of HSP70 transcript was downregulated and mostly dropped back to the original level at 48 h. The concentration of cortisol, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) increased as the time of stress progressed, with the highest level found on 3 h and later declined rapidly and reached to the control levels at the 48 h. Those results suggested that HSP70 was involved in the immune response to bacterial challenge and heat stress. The cloning and expression analysis of the HSP70 provide theoretical basis to further study the mechanism of anti-adverseness in Microptenus salmoides.

Cloning and identification of grass carp transcription factor HSF1 and its characterization involving the production of fish HSP70

In mammals, heat shock transcription factor 1 (HSF1) is well documented as the critical transcript factor to regulate heat shock protein 70 (HSP70) expression under different stresses, such as heat shock or bacterial infection. In fish, Hsf1 responses to physiological and environmental stresses and regulates Hsp70 expression under thermal exposure. However, the functional role of Hsf1 in Hsp70 production is still elusive under bacterial infection. In the present study, a coding sequence of grass carp hsf1 (gchsf1) gene was cloned and identified. Using Ctenopharyngodon idellus kidney (CIK) cells as the model, we found that lipopolysaccharide (LPS) exerted stimulatory effects on the expression of grass carp hsp70 (gchsp70) and hsf1, implying possible relationship of Hsp70 and Hsf1 under immune stimulation in fish. To validate the hypothesis, overexpression of gcHsf1 was performed in CIK cells, and the effects of overexpressing gcHsf1 on the expression of gcHsp70 in the absence or presence of LPS were examined. Results showed that LPS significantly upregulated the transcription and protein synthesis of gcHsp70, and these stimulatory effects were further amplified when overexpression of gcHsf1 was performed. Furthermore, luciferase reporter assays in CIK cells revealed that both overexpression of Hsf1 and LPS upregulated gchsp70 transcription, and their combined treatment further enhanced the gchsp70 promoter activity. Moreover, the regions responsive to these treatments were mapped to the promoter of gchsp70. Besides transcriptional level and cellular protein contents, gcHsp70 secretion was measured by competitive ELISA, uncovering that gcHsf1 enhanced the release of gcHsp70 induced by LPS in the same cells. These data not only demonstrated the enhancement of Hsf1 in Hsp70 production but also initially revealed the involvement of Hsf1-Hsp70 axis in mediating inflammatory response in fish.

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.

Deleterious impacts of heat stress on steroidogenesis markers, immunity status and ovarian tissue of Nile tilapia (Oreochromis niloticus)

The water temperature of aquacultures is a primary factor of fish welfare, reproductive patterns, and immunity. To elucidate the molecular and biological processes of the temperature modulation of reproduction and immunity, female Nile tilapia (190 ± 10g) were allocated into five groups following acclimatization (150 females, three replicates, each n = 10). Each group was subjected to various temperatures (28 °C, 30 °C, 32 °C, 34 °C, and 37 °C), the group at 28 °C representing the control. Their serum levels of estradiol, cortisol, and vitellogenin were measured as well as serum triiodothyronine (T3) hormone, thyroxine (T4) hormone, and non-specific immunity (phagocytic and lysozyme activity). In addition, steroidogenic acute regulatory protein (STAR), vitellogenin gene receptor, and heat shock protein 70 (HSP70) gene expression were evaluated. The serum levels of estradiol, cortisol, and vitellogenin markedly declined (P < 0.05) in fish group at higher temperatures. In addition to T3, T4 was significantly affected (P < 0.05) in the control group. The expressions of the STAR gene (steroidogenesis) and vitellogenin receptors were also considerably down-regulated. The histopathological photomicrograph of fish subjected to high water temperature revealed injuries in ovary tissues, demonstrating its harmful effects. The experimental results verified the possible role of water temperature as a main stressor on Nile tilapia' physiology through modulation of steroidogenesis-related gene expression and immunity.

HOXC13 and HSP27 Expression in Skin and the Periodic Growth of Secondary Fiber Follicles from Longdong Cashmere Goats Raised in Different Production Systems

This experiment was conducted to identify periodic changes in secondary follicles (SFs) over one year of extensive (grazed) and intensive (housed and fed supplement) farming of Longdong cashmere goats. One-year old goats (n = 24, 12 extensively fed and 12 intensively fed) were studied. The diameter, depth, density, activity, and ultra-structural features of SFs were assessed using light microscopy and transmission electron microscopy. HOXC13 and HSP27 expression were studied using immunohistochemistry and immunofluorescence method. The anagen stage in the extensively grazed goats was from April to September, but was longer (April to October) in the housed, supplementary fed group. The depth and activity of the SF in anagen and catagen differed (P < 0.05) between the groups. HSP27 and HOXC13 protein were present in both the epidermis and dermis, with HSP27 immunoreactivity highest in the hair shaft (HS), outer root sheath (ORS) and inner root sheath (IRS). HOXC13 expression was prominent in both the eprdermis and ORS. HSP27 and HOXC13 expression were prominent during anagen, and less so during catagen and telogen. In anagen, HSP27 expression in the HS, IRS, and ORS of the extensively fed group was higher than in the intensively fed group (p < 0.05). In contrast, HOXC13 expression in HS, IRS and ORS of the extensively fed group was lower than in the intensively fed group (P < 0.05). This suggests the growth of cashmere is influenced by nutrition and that housed goats could be used in cashmere production. Anat Rec, 301:742-752, 2018. © 2017 Wiley Periodicals, Inc.

LncRNA and mRNA profiling during activation of tilapia macrophages by HSP70 and Streptococcus agalactiae antigen

Objectives

To investigate the lncRNA profiling during tilapia peritoneal macrophages (TPMs) activation and discuss the relationship between lncRNA and mRNA.

Materials and Methods

RNA sequencing was used to investigate the lncRNA and mRNA profiles of TPMs activation following stimulation with Streptococcus agalactiae (Sa) antigen, heat shock protein 70 (HSP70) and HSP70+Sa. The expressions of lncRNA and mRNA were confirmed by qPCR. 356 lncRNA, 10173 mRNA and 1782 transcripts of uncertain coding potential (TUCP) were differentially expressed by pairwise comparison. These lncRNAs were shorter in length, fewer in exon number and higher in expression levels as compared with mRNAs. 683 lncRNAs and 4320 mRNAs were co-located, while 316 lncRNAs and 9997 mRNAs were in co-expression networks. Seven mRNAs (ANKRD34A, FMODA, GJA3, CNTN5, BMP10, BAI2 and HS3ST6) were involved in both networks of LNC_00035 and LNC_000466. Differentially expressed genes were involved in signaling pathways, such as "phosphorylation", "cytokine-cytokine receptor interaction", "endocytosis" and "MHC protein complex". LNC_000792, LNC_000215, LNC_000035 and LNC_000310, with cis and/or trans relationships with mRNAs, were also involved in ceRNA network.

Conclusions

These results might represent the first identified expression profile of lncRNAs and mRNAs in tilapia macrophages activated by HSP70 and Sa.

The role of three heat shock protein genes in the immune response to Aeromonas hydrophila challenge in marbled eel, Anguilla marmorata

Heat shock proteins (HSPs) are highly conserved molecular chaperones that play critical roles in both innate and adaptive immunity. However, little information about HSPs from marbled eel Anguilla marmorata is known. In this study, the full-length Amhsp90 (2527 bp), Amhsp70 (2443 bp) and Amhsc70 (2247 bp) were first cloned from A. marmorata, using rapid amplification of cDNA ends, containing open reading frames of 2181, 1932 and 1950 bp in length, and encoding proteins with 726, 643 and 649 amino acids, respectively. The deduced amino acid sequences of three Amhsps shared a high homology similarity with other migratory fish. Real-time fluorescent quantitative polymerase chain reaction was used to evaluate tissue-specific distribution and mRNA expression levels of three Amhsps subjected to infection with Aeromonas hydrophila. The mRNA expression of three Amhsps in eight tested tissues, namely liver, heart, muscle, gill, spleen, kidney, brain and intestine, of juvenile A. marmorata was evaluated to reveal the major expression distribution in liver, intestine, muscle and heart. After pathogen challenge treatments, mRNA transcriptions of three Amhsps revealed a significant regulation at various time points in the same tissue. All these findings suggest that Amhsps may be involved in the immune response in A. marmorata.

The N-terminal zinc finger domain of Tgf2 transposase contributes to DNA binding and to transposition activity

Active Hobo/Activator/Tam3 (hAT) transposable elements are rarely found in vertebrates. Previously, goldfish Tgf2 was found to be an autonomously active vertebrate transposon that is efficient at gene-transfer in teleost fish. However, little is known about Tgf2 functional domains required for transposition. To explore this, we first predicted in silico a zinc finger domain in the N-terminus of full length Tgf2 transposase (L-Tgf2TPase). Two truncated recombinant Tgf2 transposases with deletions in the N-terminal zinc finger domain, S1- and S2-Tgf2TPase, were expressed in bacteria from goldfish cDNAs. Both truncated Tgf2TPases lost their DNA-binding ability in vitro, specifically at the ends of Tgf2 transposon than native L-Tgf2TPase. Consequently, S1- and S2-Tgf2TPases mediated gene transfer in the zebrafish genome in vivo at a significantly (p < 0.01) lower efficiency (21%–25%), in comparison with L-Tgf2TPase (56% efficiency). Compared to L-Tgf2TPase, truncated Tgf2TPases catalyzed imprecise excisions with partial deletion of TE ends and/or plasmid backbone insertion/deletion. The gene integration into the zebrafish genome mediated by truncated Tgf2TPases was imperfect, creating incomplete 8-bp target site duplications at the insertion sites. These results indicate that the zinc finger domain in Tgf2 transposase is involved in binding to Tgf2 terminal sequences, and loss of those domains has effects on TE transposition.

Zebrafish and Streptococcal Infections

Streptococcal bacteria are a versatile group of gram-positive bacteria capable of infecting several host organisms, including humans and fish. Streptococcal species are common colonizers of the human respiratory and gastrointestinal tract, but they also cause some of the most common life-threatening, invasive infections in humans and aquaculture. With its unique characteristics and efficient tools for genetic and imaging applications, the zebrafish (Danio rerio) has emerged as a powerful vertebrate model for infectious diseases. Several zebrafish models introduced so far have shown that zebrafish are suitable models for both zoonotic and human-specific infections. Recently, several zebrafish models mimicking human streptococcal infections have also been developed. These models show great potential in providing novel information about the pathogenic mechanisms and host responses associated with human streptococcal infections. Here, we review the zebrafish infection models for the most relevant streptococcal species: the human-specific Streptococcus pneumoniae and Streptococcus pyogenes, and the zoonotic Streptococcus iniae and Streptococcus agalactiae. The recent success and the future potential of these models for the study of host-pathogen interactions in streptococcal infections are also discussed.

Prokaryotic expression and purification of soluble goldfish Tgf2 transposase with transposition activity

Goldfish Tgf2 transposon of Hobo/Activator/Tam3 (hAT) family can mediate gene insertion in a variety of aquacultural fish species by transposition; however, the protein structure of Tgf2 transposase (TPase) is still poorly understood. To express the goldfish Tgf2 TPase in Escherichia coli, the 2061-bp coding region was cloned into pET-28a(+) expression vector containing an N-terminal (His)6-tag. The pET-28a(+)-Tgf2 TPase expression cassette was transformed into Rosetta 1 (DE3) E. coli lines. A high yield of soluble proteins with molecular weight of ~80 kDa was obtained by optimized cultures including low-temperature (22 °C) incubation and early log phase (OD600 = 0.3-0.4) induction. Mass spectrometry analysis following trypsin digestion of the recombinant proteins confirmed a Tgf2 TPase component in the eluate of Ni(2+)-affinity chromatography. When co-injected into 1-2 cell embryos with a donor plasmid harboring a Tgf2 cis-element, the prokaryotic expressed Tgf2 TPase can mediate high rates (45 %) of transposition in blunt snout bream (Megalobrama amblycephala). Transposition was proved by the presence of 8-bp random direct repeats at the target sites, which is the signature of hAT family transposons. Production of the Tgf2 Tpase protein in a soluble and active form not only allows further investigation of its structure, but provides an alternative tool for fish transgenesis and insertional mutagenesis.

The polymorphism in the promoter of HSP70 gene is associated with heat tolerance of two congener endemic bay scallops (Argopecten irradians irradians and A. i. concentricus)

Background

The heat shock protein 70 (HSP70) is one kind of molecular chaperones, which plays a key role in protein metabolism under normal and stress conditions.

Methodology

In the present study, the mRNA expressions of HSP70 under normal physiological condition and after acute heat stress were investigated in gills of two bay scallop populations (Argopecten irradians irradians and A. i. concentricus). The heat resistant scallops A. i. concentricus showed significantly lower basal level and higher induction of HSP70 compared with that of the heat sensitive scallops A. i. irradians. The promoter sequence of HSP70 gene from bay scallop (AiHSP70) was cloned and the polymorphisms within this region were investigated to analyze their association with heat tolerance. Totally 11 single nucleotide polymorphisms (SNPs) were identified, and four of them (−967, −480, −408 and −83) were associated with heat tolerance after HWE analysis and association analysis. Based on the result of linkage disequilibrium analysis, the in vitro transcriptional activities of AiHSP70 promoters with different genotype were further determined, and the results showed that promoter from A. i. concentricus exhibited higher transcriptional activity than that from A. i. irradians (P<0.05).

Conclusions

The results provided insights into the molecular mechanisms underlying the thermal adaptation of different congener endemic bay scallops, which suggested that the increased heat tolerance of A. i. concentricus (compared with A. i. irradians) was associated with the higher expression of AiHSP70. Meanwhile, the −967 GG, −480 AA, −408 TT and −83 AG genotypes could be potential markers for scallop selection breeding with higher heat tolerance.

Expression of HSPA12B in acute cardiac allograft rejection in rats

HSP70 may play a more important role in regulating antigen-specific immune response than other HSPs; however, HSPA12B production in transplanted heart remains obscure, which was identified as the newest member of the HSP70 family. In the current study, we performed a heart transplantation model in adult rats and investigated the dynamic changes of HSPA12B expression in the cardiac grafts. The cardiac grafts of allogeneic (Wistar-Lewis rat) and syngeneic (Lewis-Lewis rat) rat models were subjected to histopathological and immunohistochemical analyses for HSPA12B expression on days 0-7 after operation. We also examined the expression profiles of active caspase-3, whose changes were correlated with the expression profiles of HSPA12B. Our results demonstrated that HSPA12B protein exhibited biphasic patterns in transplanted heart. The first expression phase correlated with ischemical reperfusion injury over 2 days post-transplant. The second peak of HSPA12B expression was found only in allografts on day 5, concurrent with the expression of caspase-3. Immunohistochemical assay showed that compared with rare expression in isografts, there were significant protein expressions of HSPA12B and caspase-3 in heart allografts from day 5 to 7 post-transplant. Furthermore, double immunofluorescence staining for active caspase-3 and HSPA12B in isografts and allografts at day 5 post-transplant were analyzed and colocalization of HSPA12B/active caspase-3 was detected in allografts. In conclusion, this is the first description of HSPA12B expression in acute cardiac allograft rejection. Our results suggested that HSPA12B might play crucial roles in heart pathophysiology after transplantation.

Gene delivery to Nile tilapia spermatogonial stem cells using carboxi-functionalized multiwall carbon nanotubes

Carboxi-functionalized multiwall carbon nanotubes (fMWCNTs), when complexed with DNA, can promote gene delivery to Nile tilapia spermatogonial stem cells with higher transfection efficiency than cationic lipids or electroporation, causing also less cell death.