Heat Shock Protein A2 (HSPA2): Regulatory Roles in Germ Cell Development and Sperm Function

Protective effects of benfotiamine on cyfluthrin-induced testicular damage and sperm characteristics during the prepubertal period

Cyfluthrin, a widely used synthetic pyrethroid insecticide, poses potential risks to both human health and the environment due to its extensive application in residential, agricultural, and outdoor settings. Conversely, benfotiamine, a fat-soluble derivative of vitamin B1, offers versatile therapeutic potential. This experimental study aimed to investigate the impact of cyfluthrin exposure during the prepubertal period on sperm characteristics and testicular tissue integrity in male rats, as well as to assess the protective effects of benfotiamine. A total of 32 4-week-old Wistar albino male rats were divided into four groups. Group I received daily oral gavage of 1 ml/kg/day of olive oil (control). Group II was administered cyfluthrin (54 mg/kg/day) dissolved in 1 ml of olive oil. Group III received both cyfluthrin (54 mg/kg/day) and benfotiamine (100 mg/kg/day) in olive oil. Group IV was given benfotiamine (100 mg/kg/day) in olive oil. After 5 weeks of treatment, the rats underwent evaluations for sperm motility, epididymal sperm density, and abnormal sperm rates. Additionally, their testicular tissues were examined histologically and immunohistochemically. This study underscores the potential hazards of cyfluthrin exposure on male reproductive health and highlights the protective role of benfotiamine in mitigating these effects. It emphasizes the importance of careful pesticide usage and dosage considerations to prevent potential public health issues, including infertility, associated with long-term exposure to pesticides like cyfluthrin.

The human testis-enriched HSPA2 interacts with HIF-1α in epidermal keratinocytes, yet HIF-1α stability and HIF-1-dependent gene expression rely on the HSPA (HSP70) activity

The Hypoxia-Inducible Factor 1 (HIF-1) is essential for cellular adaptation to reduced oxygen levels. It also facilitates the maintenance and re-establishment of skin homeostasis. Among others, it is involved in regulating keratinocyte differentiation. The stability of the oxygen-liable HIF-1α subunit is regulated by various non-canonical oxygen-independent mechanisms, which among others involve Heat Shock Proteins of the A family (HSPA/HSP70). This group of highly homologous chaperones and proteostasis-controlling factors includes HSPA2, a unique member crucial for spermatogenesis and implicated in the regulation of keratinocyte differentiation. HIF-1 can control the HSPA2 gene expression. In this study, we revealed that HIF-1α is the first confirmed client of HSPA2 in human somatic cells. It colocalises and interacts directly with HSPA2 in the epidermis in situ and immortalised keratinocytes in vitro. Using an in vitro model based on HSPA2-overexpressing and HSPA2-deficient variants of immortalised keratinocytes we showed that changes in HSPA2 levels do not affect the levels and intracellular localisation of HIF-1α or influence the ability of HIF-1 to modulate target gene expression. However, HIF-1α stability in keratinocytes appears critically reliant on HSPAs as a group of functionally overlapping chaperones. In addition to HSPA2, HIF-1α colocalises and forms complexes with HSPA8 and HSPA1, representing housekeeping and stress-inducible HSPA family paralogs, respectively. Chemical inhibition of HSPA activity, but not paralog-specific knockdown of HSPA8 or HSPA1 expression reduced HIF-1α levels and HIF-1-dependent gene expression. These observations suggest that pharmacological targeting of HSPAs could prevent excessive HIF-1 signalling in pathological skin conditions.

Phenotypic and transcriptome profiling of spikes reveals the regulation of light regimens on spike growth and fertile floret number in wheat

The spike growth phase is critical for the establishment of fertile floret (grain) numbers in wheat (Triticum aestivum L.). Then, how to shorten the spike growth phase and increase grain number synergistically? Here, we showed high-resolution analyses of floret primordia (FP) number, morphology and spike transcriptomes during the spike growth phase under three light regimens. The development of all FP in a spike could be divided into four distinct stages: differentiation (Stage I), differentiation and morphology development concurrently (Stage II), morphology development (Stage III), and polarization (Stage IV). Compared to the short photoperiod, the long photoperiod shortened spike growth and stimulated early flowering by shortening Stage III; however, this reduced assimilate accumulation, resulting in fertile floret loss. Interestingly, long photoperiod supplemented with red light shortened the time required to complete Stages I-II, then raised assimilates supply in the spike and promoted anther development before polarization initiation, thereby increasing fertile FP number during Stage III, and finally maintained fertile FP development during Stage IV until they became fertile florets via a predicted dynamic gene network. Our findings proposed a light regimen, critical stages and candidate regulators that achieved a shorter spike growth phase and a higher fertile floret number in wheat.

Proteomic biomarkers in seminal plasma as predictors of reproductive potential in azoospermic men

Introduction

Azoospermia, characterized by an absence of sperm in the ejaculate, represents the most severe form of male infertility. While surgical sperm retrieval in obstructive azoospermia (OA) is successful in the majority of cases, patients with non-obstructive azoospermia (NOA) show retrieval rates of only about 50% and thus frequently have unnecessary surgery. Surgical intervention could be avoided if patients without preserved spermatogenesis are identified preoperatively. This prospective study aimed to discover biomarkers in seminal plasma that could be employed for a non-invasive differential diagnosis of OA/NOA in order to rationalize surgery recommendations and improve success rates.

Methods

All patients signed written informed consent, underwent comprehensive andrological evaluation, received human genetics to exclude relevant pathologies, and patients with azoospermia underwent surgical sperm retrieval. Using label-free LC-MS/MS, we compared the proteomes of seminal plasma samples from fertile men (healthy controls (HC), n=8) and infertile men diagnosed with 1) OA (n=7), 2) NOA with successful sperm retrieval (mixed testicular atrophy (MTA), n=8), and 3) NOA without sperm retrieval (Sertoli cell-only phenotype (SCO), n=7). Relative abundance changes of two candidate markers of sperm retrieval, HSPA2 and LDHC, were confirmed by Western Blot.

Results

We found the protein expression levels of 42 proteins to be significantly down-regulated (p ≤ 0.05) in seminal plasma from SCO NOA patients relative to HC whereas only one protein was down-regulated in seminal plasma from MTA patients. Analysis of tissue and cell expression suggested that the testis-specific proteins LDHC, PGK2, DPEP3, and germ-cell enriched heat-shock proteins HSPA2 and HSPA4L are promising biomarkers of spermatogenic function. Western blotting revealed a significantly lower abundance of LDHC and HSPA2 in the seminal plasma of men with NOA (SCO and MTA) compared to controls.

Discussion

The results indicate that certain testis-specific proteins when measured in seminal plasma, could serve as indicators of the presence of sperm in the testis and predict the success of sperm retrieval. Used in conjunction with conventional clinical assessments, these proteomic biomarkers may assist in the non-invasive diagnosis of idiopathic male infertility.

Human Hsp70 Substrate-Binding Domains Recognize Distinct Client Proteins

The 13 Hsp70 proteins in humans act on unique sets of substrates with diversity often being attributed to J-domain-containing protein (Hsp40 or JDP) cofactors. We were therefore surprised to find drastically different binding affinities for Hsp70-peptide substrates, leading us to probe substrate specificity among the 8 canonical Hsp70s from humans. We used peptide arrays to characterize Hsp70 binding and then mined these data using machine learning to develop an algorithm for isoform-specific prediction of Hsp70 binding sequences. The results of this algorithm revealed recognition patterns not predicted based on local sequence alignments. We then showed that none of the human isoforms can complement heat-shocked DnaK knockout Escherichia coli cells. However, chimeric Hsp70s consisting of the human nucleotide-binding domain and the substrate-binding domain of DnaK complement during heat shock, providing further evidence in vivo of the divergent function of the Hsp70 substrate-binding domains. We also demonstrated that the differences in heat shock complementation among the chimeras are not due to loss of DnaJ binding. Although we do not exclude JDPs as additional specificity factors, our data demonstrate substrate specificity among the Hsp70s, which has important implications for inhibitor development in cancer and neurodegeneration.

Decreased AKAP4/PKA signaling pathway in high DFI sperm affects sperm capacitation

The sperm DNA fragmentation index (DFI) is a metric used to assess DNA fragmentation within sperm. During in vitro fertilization-embryo transfer (IVF-ET), high sperm DFI can lead to a low fertilization rate, poor embryo development, early miscarriage, etc. A kinase anchoring protein (AKAP) is a scaffold protein that can bind protein kinase A (PKA) to subcellular sites of specific substrates and protects the biophosphorylation reaction. Sperm protein antigen 17 (SPA17) can also bind to AKAP. This study intends to explore the reason for the decreased fertilization rate observed in high sperm DFI (H-DFI) patients during IVF-ET. In addition, the study investigates the expression of AKAP, protein kinase A regulatory subunit (PKARII), and SPA17 between H-DFI and low sperm DFI (L-DFI) patients. SPA17 at the transcriptional level is abnormal, the translational level increases in H-DFI patients, and the expression of AKAP4/PKARII protein decreases. H 2 O 2 has been used to simulate oxidative stress damage to spermatozoa during the formation of sperm DFI. It indicates that H 2 O 2 increases the expression of sperm SPA17 protein and suppresses AKAP4/PKARII protein expression. These processes inhibit sperm capacitation and reduce acrosomal reactions. Embryo culture data and IVF outcomes have been documented. The H-DFI group has a lower fertilization rate. Therefore, the results indicate that the possible causes for the decreased fertilization rate in the H-DFI patients have included loss of sperm AKAP4/PKARII proteins, blocked sperm capacitation, and reduced occurrence of acrosome reaction.

Sperm proteostasis: Can-nabinoids be chaperone's partners?

The male gamete is a highly differentiated cell that aims to fuse with the oocyte in fertilization. Sperm have silenced the transcription and translational processes, maintaining proteostasis to guarantee male reproductive health. Despite the information about the implication of molecular chaperones as orchestrators of protein folding or aggregation, and the handling of body homeostasis by the endocannabinoid system, there is still a lack of basic investigation and random controlled clinical trials that deliver more evidence on the involvement of cannabinoids in reproductive function. Besides, we noticed that the information regarding whether recreational marijuana affects male fertility is controversial and requires further investigation. In other cell models, it has recently been evidenced that chaperones and cannabinoids are intimately intertwined. Through a literature review, we aim to explore the interaction between chaperones and cannabinoid signaling in sperm development and function. To untangle how or whether this dialogue happens within the sperm proteostasis. We discuss the action of chaperones, the endocannabinoid system and phytocannabinoids in sperm proteostasis. Reports of some heat shock and lipid proteins interacting with cannabinoid receptors prove that chaperones and the endocannabinoid system are in an intimate dialogue. Meanwhile, advancing the evidence to decipher these mechanisms for introducing innovative interventions into routine clinical settings becomes crucial. We highlight the potential interaction between chaperones and cannabinoid signaling in regulating proteostasis in male reproductive health.

Circular RNAs and Their Role in Male Infertility: A Systematic Review

Male infertility is a global health problem that is on the rise. Today, many noncoding RNAs (ncRNAs) are associated with male infertility. Circular RNAs (circRNAs) have recently drawn attention, but a comprehensive understanding of the role of circRNAs in male infertility is limited. This systematic review investigates the differential expression of circRNAs in male infertility or circRNAs that could serve as candidate biomarkers. The PRISMA guidelines were used to search PubMed and Web of Science on 11 January 2023. Inclusion criteria were human participants, experimental studies aiming to associate circRNAs with male infertility reporting differentially expressed circRNAs, and the English language. A total of 156 articles were found, and after the screening and eligibility stages, 13 studies were included in the final sample. Many circRNAs are deregulated in male infertility, and their interactions with miRNAs play an important role in affecting cellular processes and pathways. CircRNAs could also be used as biomarkers to screen patients before sperm retrieval. However, most studies focus on the role of circRNAs in azoospermia, and there is a knowledge gap regarding other subtypes of male infertility. Future research is needed to explore the exact mechanism of action of circRNAs and investigate their use as biomarkers.

New horizons in human sperm selection for assisted reproduction

Male infertility is a commonly encountered pathology that is estimated to be a contributory factor in approximately 50% of couples seeking recourse to assisted reproductive technologies. Upon clinical presentation, such males are commonly subjected to conventional diagnostic andrological practices that rely on descriptive criteria to define their fertility based on the number of morphologically normal, motile spermatozoa encountered within their ejaculate. Despite the virtual ubiquitous adoption of such diagnostic practices, they are not without their limitations and accordingly, there is now increasing awareness of the importance of assessing sperm quality in order to more accurately predict a male's fertility status. This realization raises the important question of which characteristics signify a high-quality, fertilization competent sperm cell. In this review, we reflect on recent advances in our mechanistic understanding of sperm biology and function, which are contributing to a growing armory of innovative approaches to diagnose and treat male infertility. In particular we review progress toward the implementation of precision medicine; the robust clinical adoption of which in the setting of fertility, currently lags well behind that of other fields of medicine. Despite this, research shows that the application of advanced technology platforms such as whole exome sequencing and proteomic analyses hold considerable promise in optimizing outcomes for the management of male infertility by uncovering and expanding our inventory of candidate infertility biomarkers, as well as those associated with recurrent pregnancy loss. Similarly, the development of advanced imaging technologies in tandem with machine learning artificial intelligence are poised to disrupt the fertility care paradigm by advancing our understanding of the molecular and biological causes of infertility to provide novel avenues for future diagnostics and treatments.

Implications of sperm heat shock protein 70-2 in bull fertility

Heat shock protein 70 (HSP70) is one of the most abundant chaperone proteins. Their function is well documented in facilitating the protein synthesis, translocation, de novo folding, and ordering of multiprotein complexes. HSP70 in bovine consists of four genes: HSP70-1, HSP70-2, HSP70-3, and HSP70-4. HSP70-2 was found to be involved in fertility. Current knowledge implicates HSP70-2 in sperm quality, sperm capacitation, sperm–egg recognition, and fertilization essential for bull reproduction. HSP70-2 is also involved in the biological processes of spermatogenesis, as it protects cells from the effects of apoptosis and oxidative stress. Fertilization success is not only determined by the amount of sperm found in the female reproductive tract but also by the functional ability of the sperm. However, subfertility is more likely to be associated with changes in sperm molecular dynamics not detectable using conventional methods. As such, molecular analyses and omics methods have been developed to monitor crucial aspects of sperm molecular morphology that are important for sperm functions, which are the objectives of this review.

How thermal challenges change gene regulation in the songbird brain and gonad: implications for sexual selection in our changing world

In a rapidly warming world, exposure to high temperatures may impact fitness, but the gene regulatory mechanisms that link sublethal heat to sexually selected traits are not well understood, particularly in endothermic animals. Our experiment used zebra finches (Taeniopygia guttata), songbirds that experience extreme temperature fluctuations in their native Australia. We exposed captive males to an acute thermal challenge (43°C) compared with thermoneutral (35°C) and lower (27°C) temperatures. We found significantly more heat dissipation behaviors at 43°C, a temperature previously shown to reduce song production and fertility, and more heat retention behaviors at 27°C. Next, we characterized transcriptomic responses in tissues important for mating effort - the posterior telencephalon, for its role in song production, and the testis, for its role in fertility and hormone production. Differential expression of hundreds of genes in the testes, but few in the brain, suggest the brain is less responsive to extreme temperatures. Nevertheless, gene network analyses revealed that expression related to dopaminergic signaling in the brain co-varied with heat dissipation behaviors, providing a mechanism by which temporary thermal challenges may alter motivational circuits for song production. In both brain and testis, we observed correlations between thermally sensitive gene networks and individual differences in thermoregulatory behavior. Although we cannot directly relate these gene regulatory changes to mating success, our results suggest that individual variation in response to thermal challenges could impact sexually selected traits in a warming world.

Fetal exposure of Aristolochic Acid I undermines ovarian reserve by disturbing primordial folliculogenesis

The primordial follicle pool established in early life determines the ovarian reserve in the female reproductive lifespan. Premature exhaustion of primordial follicles contributes to primary ovarian insufficiency (POI), that is dependent by the initial size of the primordial follicle pool and by the rate of its activation and depletion. AAI, a powerful nephrotoxin with carcinogenic potential, is present in the Aristolochiaceae species, which can release AAI into soil as a persistent pollutant. In order to assess the potential risk of Aristolochic Acid I (AAI) exposure on mammalian oogenesis, we uncovered its adverse effect on primordial folliculogenesis in the neonatal mouse ovary and its effect on female fertility in adulthood. Pregnant mice were orally administrated with doses of AAI without hepatic or renal toxicity during late-gestation. Ovaries from offspring of administered female displayed gross aberrations during primordial folliculogenesis. Also, unenclosed oocytes in germ-cell cysts showed increased DNA damage. Furthermore, several key factors, including NANOS3, SOX9, KLF4, that govern early gonad's differentiation were abnormally expressed in the exposed ovary, while the follicle formation was partially restored by knockdown of Nanos3 or sox9. In adulthood, these aberrations evolved into a significant reduction in offspring number and impaired ovarian reserve. Together, our results show that AAI influences primordial folliculogenesis and, importantly, affected female fertility. This study shows that administration of drugs herbs or consumption of vegetables that contain AAs during pregnancy may adversely influence the fertility of offspring.

Sperm Phosphoproteome: Unraveling Male Infertility

Infertility affects approximately 15% of couples worldwide of childbearing age, and in many cases the etiology of male infertility is unknown. The current standard evaluation of semen is insufficient to establish an accurate diagnosis. Proteomics techniques, such as phosphoproteomics, applied in this field are a powerful tool to understand the mechanisms that regulate sperm functions such as motility, which is essential for successful fertilization. Among the post-translational modifications of sperm proteins, this review summarizes, from a proteomic perspective, the updated knowledge of protein phosphorylation, in human spermatozoa, as a relevant molecular mechanism involved in the regulation of sperm physiology. Specifically, the role of sperm protein phosphorylation in motility and, consequently, in sperm quality is highlighted. Additionally, through the analysis of published comparative phosphoproteomic studies, some candidate human sperm phosphoproteins associated with low sperm motility are proposed. Despite the remarkable advances in phosphoproteomics technologies, the relatively low number of studies performed in human spermatozoa suggests that phosphoproteomics has not been applied to its full potential in studying male infertility yet. Therefore, further studies will improve the application of this procedure and overcome the limitations, increasing the understanding of regulatory mechanisms underlying protein phosphorylation in sperm motility and, consequently, in male fertility.

Transcriptomic signatures responding to PKM2 activator TEPP-46 in the hyperglycemic human renal proximal epithelial tubular cells

Pyruvate kinase M2 (PKM2), as the terminal and last rate-limiting enzyme of the glycolytic pathway, is an ideal enzyme for regulating metabolic phenotype. PKM2 tetramer activation has shown a protective role against diabetic kidney disease (DKD). However, the molecular mechanisms involved in diabetic tubular have not been investigated so far. In this study, we performed transcriptome gene expression profiling in human renal proximal tubular epithelial cell line (HK-2 cells) treated with 25 mM high D-glucose (HG) for 7 days before the addition of 10 μM TEPP-46, an activator of PKM2 tetramerization, for a further 1 day in the presence of HG. Afterwards, we analyzed the differentially expressed (DE) genes and investigated gene relationships based on weighted gene co-expression network analysis. The results showed that 2,902 DE genes were identified (adjusted P-value ≤ 0.05), where 2,509 DE genes (86.46%) were co-expressed in the key module. Four extremely downregulated DE genes (HSPA8, HSPA2, HSPA1B, and ARRB1) and three extremely upregulated DE genes (GADD45A, IGFBP3, and SIAH1) enriched in the downregulated endocytosis (hsa04144) and upregulated p53 signaling pathway (hsa04115), respectively, were validated by qRT-PCR experiments. The qRT-PCR results showed that the relative expression levels of HSPA8 [adjusted P-value = 4.45 × 10^-34 and log₂(FC) = -1.12], HSPA2 [adjusted P-value = 6.09 × 10^-14 and log₂(FC) = -1.27], HSPA1B [adjusted P-value = 1.14 × 10^-11 and log₂(FC) = -1.02], and ARRB1 [adjusted P-value = 2.60 × 10^-5 and log₂(FC) = -1.13] were significantly different (P-value < 0.05) from the case group to the control group. Furthermore, the interactions and predicted microRNAs of the key genes (HSPA8, HSPA2, HSPA1B, and ARRB1) were visualized in networks. This study identified the key candidate transcriptomic biomarkers and biological pathways in hyperglycemic HK-2 cells responding to the PKM2 activator TEPP-46 that can highlight a possibility of PKM2 tetramerization reshaping the interplay among endocytic trafficking through the versatile networks of Hsp70s and rewiring the crosstalk between EGFR signal transduction circuits and metabolic stress to promote resilience, which will be valuable for further research on PKM2 in DKD.

Cellular Stress Responses in Oocytes: Molecular Changes and Clinical Implications

The oocyte may be exposed to several sources of stress during its growth and maturation, which may lead to reduced fertility. Unfolded protein responses (UPRs) play a central role to maintain cell survival and repair. Transcription of heat shock proteins (HSPs) is a key element to facilitate reestablishment of cellular homeostasis. Unlike somatic cells, cellular mechanisms by which oocytes can sense and respond to stress are not well described. In here, we provide an overview about the impact of cellular stress, particularly due to lipotoxicity, oxidative stress, and heat stress on oocyte developmental competence. Next, we focus on the expression of HSPs in oocytes and their potential role in UPRs in oocytes and embryos. This is based on a comprehensive shotgun proteomic analysis of mature bovine oocytes performed in our laboratory, as well as a literature review. The topic is discussed in light of our understanding of similar mechanisms in other cell types and the limited transcriptional activity in oocytes. More fundamental research is needed both at the transcriptomic and proteomic levels to further understand cell stress response mechanisms in oocytes and early developing embryos, their critical interactions, and their long-term effects. Strategies to provide targeted external support to prevent or reduce cell stress levels during oocyte maturation or early embryo development under maternal metabolic stress conditions should be developed to maximize the odds of producing good quality embryos and guarantee optimal viability.

HSP70s in Breast Cancer: Promoters of Tumorigenesis and Potential Targets/Tools for Therapy

The high frequency of breast cancer worldwide and the high mortality among women with this malignancy are a serious challenge for modern medicine. A deeper understanding of the mechanisms of carcinogenesis and emergence of metastatic, therapy-resistant breast cancers would help development of novel approaches to better treatment of this disease. The review is dedicated to the role of members of the heat shock protein 70 subfamily (HSP70s or HSPA), mainly inducible HSP70, glucose-regulated protein 78 (GRP78 or HSPA5) and GRP75 (HSPA9 or mortalin), in the development and pathogenesis of breast cancer. Various HSP70-mediated cellular mechanisms and pathways which contribute to the oncogenic transformation of mammary gland epithelium are reviewed, as well as their role in the development of human breast carcinomas with invasive, metastatic traits along with the resistance to host immunity and conventional therapeutics. Additionally, intracellular and cell surface HSP70s are considered as potential targets for therapy or sensitization of breast cancer. We also discuss a clinical implication of Hsp70s and approaches to targeting breast cancer with gene vectors or nanoparticles downregulating HSP70s, natural or synthetic (small molecule) inhibitors of HSP70s, HSP70-binding antibodies, HSP70-derived peptides, and HSP70-based vaccines.

eIF4E3 forms an active eIF4F complex during stresses (eIF4FS) targeting mTOR and re-programs the translatome

The eIF4E are a family of initiation factors that bind the mRNA 5′ cap, regulating the proteome and the cellular phenotype. eIF4E1 mediates global translation and its activity is controlled via the PI3K/AKT/mTOR pathway. mTOR down-regulation results in eIF4E1 sequestration into an inactive complex with the 4E binding proteins (4EBPs). The second member, eIF4E2, regulates the translatome during hypoxia. However, the exact function of the third member, eIF4E3, has remained elusive. We have dissected its function using a range of techniques. Starting from the observation that it does not interact with 4EBP1, we demonstrate that eIF4E3 recruitment into an eIF4F complex occurs when Torin1 inhibits the mTOR pathway. Ribo-seq studies demonstrate that this complex (eIF4F^S) is translationally active during stress and that it selects specific mRNA populations based on 5′ TL (UTR) length. The interactome reveals that it associates with cellular proteins beyond the cognate initiation factors, suggesting that it may have ‘moon-lighting’ functions. Finally, we provide evidence that cellular metabolism is altered in an eIF4E3 KO background but only upon Torin1 treatment. We propose that eIF4E3 acts as a second branch of the integrated stress response, re-programming the translatome to promote ‘stress resistance’ and adaptation.

Function, Therapeutic Potential, and Inhibition of Hsp70 Chaperones

Hsp70s are among the most highly conserved proteins in all of biology. Through an iterative binding and release of exposed hydrophobic residues on client proteins, Hsp70s can prevent aggregation and promote folding to the native state of their client proteins. The human proteome contains eight canonical Hsp70s. Because Hsp70s are relatively promiscuous they play a role in folding a large proportion of the proteome. Hsp70s are implicated in disease through their ability to regulate protein homeostasis. In recent years, researchers have attempted to develop selective inhibitors of Hsp70 isoforms to better understand the role of individual isoforms in biology and as potential therapeutics. Selective inhibitors have come from rational design, forced localization, and serendipity, but the development of completely selective inhibitors remains elusive. In the present review, we discuss the Hsp70 structure and function, the known Hsp70 client proteins, the role of Hsp70s in disease, and current efforts to discover Hsp70 modulators.

Testicular localization of activating transcription factor 1 and its potential function during spermatogenesis

Activating transcription factor 1 (ATF1), belonging to the CREB/ATF family of transcription factors, is highly expressed in the testes. However, its role in spermatogenesis has not yet been established. Here, we aimed to elucidate the impact of ATF1 in spermatogenesis by examining the expression pattern of ATF1 in mice and the effect of ATF1 knockdown in the mouse testes. We found that ATF1 is expressed in various organs, with very high levels in the testes. Immunohistochemical staining showed that ATF1 was localized in the nuclei of spermatogonia and co-localized with proliferating cell nuclear antigen. In ATF1-deficient mice, the seminiferous tubules of the testis contained cells at all developmental stages; however, the number of spermatocytes was decreased. Proliferating cell nuclear antigen expression was decreased and apoptotic cells were rare in the seminiferous tubules. These results indicate that ATF1 plays a role in male germ cell proliferation and sperm production.

Association of heat shock protein A2 expression and sperm quality after N-acetyl-cysteine supplementation in astheno-terato-zoospermic infertile men

In infertile men, reduced expression of heat shock protein A2 (HSPA2) is related to reduced sperm quality and function. The present study has aimed to investigate the effects of N-acetyl-cysteine (NAC) supplementation on expression of heat shock protein A2 (HSPA2). In this study in continuation of previous study, semen samples from 50 astheno-terato-zoospermic men who have received NAC (600 mg/day) orally for three months were evaluated for expression HSPA2 using RT-PCR, and Western blot analysis. In addition, semen samples of these individuals were assessed for sperm parameters, DNA fragmentation (TUNEL), protamine deficiency (CMA3), lipid peroxidation index (MDA) and total antioxidant capacity (TCA). All assessment was carried out before and after NAC treatment. In addition to improved sperm parameters and aforementioned functional parameters, the presented results revealed the significant increase in relative expression levels of HSPA2 was obtained after using NAC treatment (p < .05). Correlation analysis also demonstrated that HSPA2 expression is significantly related to most of the assessed parameters. NAC may directly or indecently impose its beneficial effect through increased expression of HSPA2, which plays a potential role in proper folding of element needed to counteract stress condition in infertile individuals.

Role of NLRs in the Regulation of Type I Interferon Signaling, Host Defense and Tolerance to Inflammation

Type I interferon signaling contributes to the development of innate and adaptive immune responses to either viruses, fungi, or bacteria. However, amplitude and timing of the interferon response is of utmost importance for preventing an underwhelming outcome, or tissue damage. While several pathogens evolved strategies for disturbing the quality of interferon signaling, there is growing evidence that this pathway can be regulated by several members of the Nod-like receptor (NLR) family, although the precise mechanism for most of these remains elusive. NLRs consist of a family of about 20 proteins in mammals, which are capable of sensing microbial products as well as endogenous signals related to tissue injury. Here we provide an overview of our current understanding of the function of those NLRs in type I interferon responses with a focus on viral infections. We discuss how NLR-mediated type I interferon regulation can influence the development of auto-immunity and the immune response to infection.

Circular RNAs from BOULE play conserved roles in protection against stress-induced fertility decline

Circular RNAs (circRNAs) are a large family of newly identified transcripts, and their physiological roles and evolutionary significance require further characterization. Here, we identify circRNAs generated from a conserved reproductive gene, Boule, in species from Drosophila to humans. Flies missing circular Boule (circBoule) RNAs display decreased male fertility, and sperm of circBoule knockout mice exhibit decreased fertilization capacity, when under heat stress conditions. During spermatogenesis, fly circBoule RNAs interact with heat shock proteins (HSPs) Hsc4 and Hsp60C, and mouse circBoule RNAs in sperm interact with HSPA2. circBoule RNAs regulate levels of HSPs by promoting their ubiquitination. The interaction between HSPA2 and circBoule RNAs is conserved in human sperm, and lower levels of the human circBoule RNAs circEx3-6 and circEx2-7 are found in asthenozoospermic sperm. Our findings reveal conserved physiological functions of circBoule RNAs in metazoans and suggest that specific circRNAs may be critical modulators of male reproductive function against stresses in animals.

Molecular insights into the divergence and diversity of post-testicular maturation strategies

Competition to achieve paternity has coerced the development of a multitude of male reproductive strategies. In one of the most well-studied examples, the spermatozoa of all mammalian species must undergo a series of physiological changes as they transit the male (epididymal maturation) and female (capacitation) reproductive tracts prior to realizing their potential to fertilize an ovum. However, the origin and adaptive advantage afforded by these intricate processes of post-testicular sperm maturation remain to be fully elucidated. Here, we review literature pertaining to the nature and the physiological role of epididymal maturation and subsequent capacitation in comparative vertebrate taxa including representative species from the avian, reptilian, and mammalian lineages. Such insights are discussed in terms of the framework they provide for helping to understand the evolutionary significance of post-testicular sperm maturation.

HSPA2 Chaperone Contributes to the Maintenance of Epithelial Phenotype of Human Bronchial Epithelial Cells but Has Non-Essential Role in Supporting Malignant Features of Non-Small Cell Lung Carcinoma, MCF7, and HeLa Cancer Cells

Simple Summary

Heat shock proteins A (HSPA) are molecular chaperones that play a central role in the cellular protein quality control. One of them is HSPA2 which recently was indicated as a novel cancer-related protein due to its elevated expression in various tumors and reported prognostic significance. Several previous in vitro studies have shown significant role of HSPA2 in supporting cancer cells growth and invasiveness. Our data presented in this article contradict the current belief of the essential role of HSPA2 chaperone and show that HSPA2 is not crucial for maintenance of the malignant phenotype of lung, breast, and cervical cancer cells. Instead, we revealed HSPA2’s role in supporting clonogenic potential and adhesive ability of bronchial epithelial cells. Therefore, further research should concentrate on elucidating HSPA2 roles in epithelial cells.

Abstract

Heat Shock Protein A2 (HSPA2) is a member of the HSPA (HSP70) chaperone family and has a critical role for male fertility. HSPA2 is present in a number of somatic organs. Limited evidence suggests that HSPA2 may be involved in regulating epithelial cell differentiation. HSPA2 also emerged as a cancer-related chaperone; however, no consensus on its functional significance has been reached so far. In this study, we compared the phenotypic effects of HSPA2 deficit in non-transformed human bronchial epithelial cells (HBEC), and in lung, breast, and cervical cancer cells. We used various techniques to inhibit the HSPA2 gene expression in order to examine the impact of HSPA2 deficiency on cell growth, migration, adhesion, and invasion. Our results show that HBEC but not cancer cells are sensitive to HSPA2 deficit. HSPA2 knockdown in HBEC cells impaired their clone-forming ability and adhesiveness. Thus, our results indicate that epithelial cells can rely on a specific activity of HSPA2, but such dependence can be lost in epithelial cells that have undergone malignant transformation.

A noncanonical role of NOD-like receptor NLRP14 in PGCLC differentiation and spermatogenesis

NOD-like receptors (NLRs) are traditionally recognized as key surveillance pattern recognition receptors (PRRs) during innate immune regulation. Several NLRs exhibit highly restricted expression in mammalian germline, where their physiological functions are largely unknown. Here we report that Nlrp14, an NLR specifically expressed in testis and ovary, plays a critical role in regulating germ cell differentiation and reproduction. Nlrp14 deficiency led to decreased primordial germ cell-like cell (PGCLC) differentiation in vitro and reproduction failure in both male and female mice in vivo. In the male mice, Nlrp14 knockout strongly compromised differentiation of spermatogonial stem cells and meiosis. Mechanistically, NLRP14 protected HSPA2 from proteasome-mediated degradation by recruiting BAG2, loss of which was further confirmed in a human mutation associated with male sterility.

NOD-like receptors (NLRs) are traditionally recognized as major inflammasome components. The role of NLRs in germ cell differentiation and reproduction is not known. Here, we identified the gonad-specific Nlrp14 as a pivotal regulator in primordial germ cell-like cell (PGCLC) differentiation in vitro. Physiologically, knock out of Nlrp14 resulted in reproductive failure in both female and male mice. In adult male mice, Nlrp14 knockout (KO) inhibited differentiation of spermatogonial stem cells (SSCs) and meiosis, resulting in trapped SSCs in early stages, severe oligozoospermia, and sperm abnormality. Mechanistically, NLRP14 promoted spermatogenesis by recruiting a chaperone cofactor, BAG2, to bind with HSPA2 and form the NLRP14−HSPA2−BAG2 complex, which strongly inhibited ChIP-mediated HSPA2 polyubiquitination and promoted its nuclear translocation. Finally, loss of HSPA2 protection and BAG2 recruitment by NLRP14 was confirmed in a human nonsense germline variant associated with male sterility. Together, our data highlight a unique proteasome-mediated, noncanonical function of NLRP14 in PGCLC differentiation and spermatogenesis, providing mechanistic insights of gonad-specific NLRs in mammalian germline development.

Comparative transcriptome analysis digs out genes related to antifreeze between fresh and frozen-thawed rooster sperm

The objective of this study was to investigate differences in mRNA expression between fresh and frozen–thawed sperm in roosters. In trial 1, gene expression profiles were measured using microarray with Affymetrix GeneChip Chicken Genome Arrays. The results showed that 2,115 genes were differentially expressed between the 2 groups. Among these genes, 2,086 were significantly downregulated and 29 were significantly upregulated in the frozen–thawed sperm group. Gene Ontology (GO) analysis showed that more than 1,000 differentially expressed genes (DEG) of all significantly regulated genes were involved in GO terms including biological processes, molecular function, and cellular component. Kyoto Encyclopedia of Genes and Genomes analysis showed that DEG were significantly (P < 0.05) enriched on ribosome, oxidative phosphorylation, proteasome, cell cycle, oocyte meiosis, and spliceosome pathways. In trial 2, ejaculated semen was collected from 18 roosters and divided into 5 recombinant HSP90 protein–supplemented groups (0.01, 0.1, 0.5, 1, or 2 μg/mL) and one control group with no recombinant HSP90 protein supplementation to evaluate the effect of recombinant HSP90 protein in the extender on post-thaw quality of rooster semen. The results showed that post-thaw sperm viability and motility was significantly improved (P < 0.05) in the extender containing 0.5 and 1 μg/mL of recombinant HSP90 protein compared with the control. Our preliminary results will provide a valuable basis for understanding the potential molecular mechanisms of cryodamage in frozen–thawed sperm and theoretical guidance to improve the fertility of frozen–thawed chicken sperm.

Oxidative Stress Dysregulates Protein Homeostasis Within the Male Germ Line

Aims: Oxidative stress is causally linked to male reproductive pathologies, driven primarily by lipid peroxidation and an attendant production of highly reactive lipid aldehydes, such as 4-hydroxynonenal (4HNE) within the male germ line. In somatic cells, 4HNE dysregulates proteostasis via targeting of vulnerable proteins for adduction, causing protein misfolding and eventually aggregation. The aims of this study were to explore whether oxidative stress precipitates an equivalent response in the male germ line and determine the protective mechanisms used by germ cells to prevent this cascade of protein damage. Results: We reveal a causative role for oxidative stress in the accumulation of protein deposits in male germ cells. Specifically, 4HNE treatment resulted in a significant increase in cytosolic protein aggregation within pre- and post-meiotic germ cells as measured by the aggregate-detecting fluorophores ProteoStat and Thioflavin T, and the amyloid-specific anti-A11 and anti-OC antibodies. Our data implicate nucleocytoplasmic transport machinery and molecular chaperones as potential mechanisms for the subcellular compartmentalization and/or suppression of aggregating proteins. Thus, the inhibition of karyopherin transport proteins and molecular chaperones resulted in a significant increase in the accumulation of aggregated cellular protein. Innovation: These data establish the novel paradigm that lipid peroxidation is a key contributor to a decline in proteostasis in developing germ cells. These findings will inform the development of novel strategies to protect germ cells from oxidative stress. Conclusion: Together, these results shed light on proteostasis mechanisms that may assist in the management of misfolded proteins in the male germ line under conditions of acute oxidative stress.

Heat shock proteins in the physiology and pathophysiology of epidermal keratinocytes

Heat shock proteins (HSPs), a large group of highly evolutionary conserved proteins, are considered to be main elements of the cellular proteoprotection system. HSPs are encoded by genes activated during the exposure of cells to proteotoxic factors, as well as by genes that are expressed constitutively under physiological conditions. HSPs, having properties of molecular chaperones, are involved in controlling/modulation of multiple cellular and physiological processes. In the presented review, we summarize the current knowledge on HSPs in the biology of epidermis, the outer skin layer composed of stratified squamous epithelium. This tissue has a vital barrier function preventing from dehydratation due to passive diffusion of water out of the skin, and protecting from infection and other environmental insults. We focused on HSPB1 (HSP27), HSPA1 (HSP70), HSPA2, and HSPC (HSP90), because only these HSPs have been studied in the context of physiology and pathophysiology of the epidermis. The analysis of literature data shows that HSPB1 plays a role in the regulation of final steps of keratinization; HSPA1 is involved in the cytoprotection, HSPA2 contributes to the early steps of keratinocyte differentiation, while HSPC is essential in the re-epithelialization process. Since HSPs have diverse functions in various types of somatic tissues, in spite of multiple investigations, open questions still remain about detailed roles of a particular HSP isoform in the biology of epidermal keratinocytes.

HSPA1L and HSPA1B gene polymorphisms and haplotypes are associated with idiopathic male infertility in Iranian population

OBJECTIVE

Male infertility is a multifactorial disease resulting from the interaction between the genetic and environmental factors. Spermatogenic failure accounts for more than half of male infertility cases. Heat shock proteins (HSPs) are the molecular chaperones that are involved in different developmental stages of spermatogenesis. The current study was planned to investigate the role of HSPA1L rs2227956 and HSPA1B rs1061581 gene polymorphisms in idiopathic male infertility.

STUDY DESIGN

This case-control study was conducted on 516 subjects consisted of 308 patients with idiopathic male infertility and 208 age matched-(±5) control subjects. HSPA1L rs2227956 and HSPA1B rs1061581 polymorphisms were genotyped by PCR-RFLP method.

RESULTS

A significant association with male infertility was found for HSPA1L rs2227956 in genotypes (TT vs CT: OR = 2.049, 95% CI = 1.337-3.139, P = 0.001; TT vs CC: OR = 3.028, 95% CI = 1.100-8.332, P = 0.032). In the dominant genetic model, rs2227956C allele increased the risk of male infertility (OR = 2.049, 95% CI = 1.337-3.139, P = 0.001). Also, the results showed a significant association between the HSPA1B rs1061581GG genotype and male infertility (OR = 2.638, 95% CI: 1.001-4.486, P = 0.001). The rs1061581 G allele was a risk factor for male infertility (OR = 1.657, 95% CI = 1.278-2.148, P < 0.001). Haplotype analysis showed CG and TA (rs2227956/ rs1061581) haplotype affect the risk of male infertility (P < 0.001).

CONCLUSION

HSPA1L rs2227956 and HSPA1B rs1061581 gene polymorphisms are associated with susceptibility to idiopathic male infertility in Iranian population. Further studies in different ethnicity are necessary to confirm these results.

Decreased expression of heat shock protein A4L in spermatozoa is positively related to poor human sperm quality

Heat shock protein A4L (HSPA4L), which is highly expressed in the testis, is correlated with male fertility. However, the relationship between HSPA4L expression and sperm quality remains unknown. In the present study, a systematic characterization of HSPA4L expression on spermatozoa was performed. HSPA4L is highly expressed in the human testis, characterized by abundant localization in testicular spermatocytes and round spermatids. Compared with the testis from young adults (aged 27-36 years old), downregulated expression of HSPA4L in the testis from elderly adults (aged 78-82 years old) was observed. Immunofluorescence quantification demonstrated the localization of HSPA4L in the middle piece of sperm. Compared with mature spermatozoa, a similar lower intensity and localization percentage of HSPA4L in immature and asthenozoospermic spermatozoa were observed, and the consistently decreased expression of HSPA4L in immature and asthenozoospermic spermatozoa was validated by western blot analysis. Functional analysis revealed a correlation between HSPA4L and sperm motility by Spearman correlation analysis and its involvement in sperm-oocyte penetration by the human sperm-hamster egg penetration test. The current study demonstrates that HSPA4L is a promising marker for the assessment of sperm quality and provides clues for exploring biomarkers for the molecular diagnosis and treatment of male infertility.

The serine protease testisin is present on the surface of capacitated stallion spermatozoa and interacts with key zona pellucida binding proteins

BACKGROUND AND OBJECTIVES

Serine proteases are emerging as important players in the spermatozoon's acquisition of functional competence. This study aimed to characterize the serine protease testisin (PRSS21) in stallion spermatozoa, examining its surface expression, possible origins in the testis and epididymis, and changes in response to capacitation and acrosome reaction, as well as its capacity to form high molecular weight complexes and interact with other proteins.

MATERIALS AND METHODS

The role of serine proteases in spontaneous capacitation and acrosome reaction of stallion spermatozoa was established using the serine protease inhibitor, AEBSF. Testisin localization, before and after exposure of stallion spermatozoa to capacitating conditions and calcium ionophore, was examined using live cell immunofluorescence and flow cytometry. Immunohistochemistry of testicular and epididymal tissues was used to further dissect the origins of sperm testisin. Testisin's participation in high molecular weight protein complexes and identification of its interacting partner proteins were investigated using Blue Native PAGE, co-immunoprecipitation, and mass spectrometry, with interrogation of protein-protein interaction databases and gene ontology analysis of partner proteins used to further explore the potential roles of the testisin-containing complex in sperm function.

RESULTS

Testisin surface expression increased significantly in capacitated spermatozoa (p < 0.001), increased further following acrosome reaction (p < 0.01), and was localized to the equatorial region of the sperm head. Testisin was also detected in luminal fluid within the caput and corpus regions of the epididymis, epididymal spermatozoa, and epididymal epithelial cells. Testisin formed several multiprotein complexes; co-immunoprecipitation revealed interactions of testisin with a multitude of zona pellucida-binding proteins, including ZPBP, ZAN, acrosin, several heat-shock proteins, and components of the TCP1 complex.

CONCLUSION

Testisin appears to form part of the zona pellucida-binding complex in stallion spermatozoa and may be involved in the proteolytic cascade that prepares the sperm surface for interaction with the oocyte.

Assessing the potential of HSPA2 and ADAM2 as two biomarkers for human sperm selection

Selection of the best sperm, with the least defects, is a critical factor in the success of ART especially in male factor infertility. This study assessed the potential Heat shock protein (HSPA2) and metallopeptidase domain2 (ADAM2) biomarkers for sperm selection. Sperm were obtained from 72 asthenoteratozoospermic and 42 normospermic ejaculates. The semen characteristic, DNA fragmentation (DFI), chromatin maturation index (CMI), ADAM2 and HSPA2 levels on sperm, and their correlation with embryo quality were assessed in both groups. Results showed the significant reduction in HSPA2 and ADAM2 in asthenoteratozoospermic compared to normazoospermic ejaculates regarding the cut-off value of 14 and 13% for these two biomarkers. The specificity of HSPA2 and ADAM2 separately, and the combination of these two biomarkers, were 95.2, 90.5 and 93.5%, respectively, for sperm from normozoospermic ejaculates. However, they were 48.6, 50.0 and 54.5% for asthenoteratozoospermic ones. A significant correlation was observed with HSPA2, ADAM2 and a combination of these two biomarkers with CMI, DFI and embryo quality. Although a combination of these two biomarkers have the potential to be a good choice for selecting sperm with the lowest level of chromatin damage, it seems that selection according to HSPA2 has priority over ADAM2 or a combination of the two.