CABYR binds to AKAP3 and Ropporin in the human sperm fibrous sheath

Homozygous variants in AKAP3 induce asthenoteratozoospermia and male infertility

BACKGROUND

As a common type of asthenoteratozoospermia, multiple morphological abnormalities of the sperm flagella (MMAF) can cause male infertility. Previous studies have revealed genetic factors as a major cause of MMAF. The known MMAF-associated genes are involved in the mitochondrial sheath, outer dense fibre or axoneme of the sperm flagella. These findings indicate the genetic heterogeneity of MMAF.

METHODS AND RESULTS

Here, we conducted genetic analyses using whole-exome sequencing in a cohort of 150 Han Chinese men with asthenoteratozoospermia. Homozygous deleterious variants of AKAP3 (A-kinase anchoring protein 3) were identified in two MMAF-affected men from unrelated families. One AKAP3 variant was a frameshift (c.2286_2287del, p.His762Glnfs*22) and the other variant was a missense mutation (c.44G>A, p.Cys15Tyr), which was predicted to be damaging by multiple bioinformatics tools. Further western blotting and immunofluorescence assays revealed the absence of AKAP3 in the spermatozoa from the man harbouring the homozygous frameshift variant, whereas the expression of AKAP3 was markedly reduced in the spermatozoa of the man with the AKAP3 missense variant p.Cys15Tyr. Notably, the clinical outcomes after intracytoplasmic sperm injection (ICSI) were divergent between these two cases, suggesting a possibility of AKAP3 dosage-dependent prognosis of ICSI treatment.

CONCLUSIONS

Our study revealed AKAP3 as a novel gene involved in human asthenoteratozoospermia.

Tomato spotted wilt orthotospovirus shifts sex ratio toward males in the western flower thrips, Frankliniella occidentalis, by down-regulating a FSCB-like gene

BACKGROUND

Plant viruses can facilitate their transmission by modulating the sex ratios of their insect vectors. Previously, we found that exposure to tomato spotted wilt orthotospovirus (TSWV) in the western flower thrips, Frankliniella occidentalis, led to a male-biased sex ratio in the offspring. TSWV, a generalist pathogen with a broad host range, is transmitted primarily by F. occidentalis in a circulative-propagative manner. Here, we integrated proteomic tools with RNAi to comprehensively investigate the genetic basis underlying the shift in vector sex ratio induced by the virus.

RESULTS

Proteomic analysis exhibited 104 differentially expressed proteins between F. occidentalis adult males with and without TSWV. The expression of the fiber sheath CABYR-binding-like (FSCB) protein, namely FoFSCB-like, a sperm-specific protein associated with sperm capacitation and motility, was decreased by 46%. The predicted FoFSCB-like protein includes 10 classic Pro-X-X-Pro motifs and 42 phosphorylation sites, which are key features for sperm capacitation. FoFSCB-like expression was gradually increased during the development and peaked at the pupal stage. After exposure to TSWV, FoFSCB-like expression was substantially down-regulated. Nanoparticle-mediated RNAi substantially suppressed FoFSCB-like expression and led to a significant male bias in the offspring.

CONCLUSION

These combined results suggest that down-regulation of FoFSCB-like in virus-exposed thrips leads to a male-biased sex ratio in the offspring. This study not only advances our understanding of virus-vector interactions, but also identifies a potential target for the genetic management of F. occidentalis, the primary vector of TSWV, by manipulating male fertility. © 2022 Society of Chemical Industry.

Quantitative phosphoproteomics analyses reveal the regulatory mechanisms related to frozen-thawed sperm capacitation and acrosome reaction in yak (Bos grunniens)

Mammalian spermatozoa are not mature after ejaculation and must undergo additional functional and structural changes within female reproductive tracts to achieve subsequent fertilization, including both capacitation and acrosome reaction (AR), which are dominated by post-translational modifications (PTMs), especially phosphorylation. However, the mechanism of protein phosphorylation during frozen-thawed sperm capacitation and AR has not been well studied. In this study, the phosphoproteomics approach was employed based on tandem mass tag (TMT) labeling combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) strategy to analyze frozen-thawed sperm in Ashidan yak under three sequential conditions (density gradient centrifugation-based purification, incubation in the capacitation medium and induction of AR processes by the calcium ionophore A23187 treatment). The identification of 1,377 proteins with 5,509 phosphorylation sites revealed changes in phosphorylation levels of sperm-specific proteins involved in regulation of spermatogenesis, sperm motility, energy metabolism, cilium movement, capacitation and AR. Some phosphorylated proteins, such as AKAP3, AKAP4, SPA17, PDMD11, CABYR, PRKAR1A, and PRKAR2A were found to regulate yak sperm capacitation and AR though the cAMP/PKA signaling pathway cascades. Notably, the phosphorylation level of SPA17 at Y156 increased in capacitated sperm, suggesting that it is also a novel functional protein besides AKAPs during sperm capacitation. Furthermore, the results of this study suggested that the phosphorylation of PRKAR1A and PRKAR2A, and the dephosphorylation of CABYR both play key regulatory role in yak sperm AR process. Protein-protein interaction analysis revealed that differentially phosphorylated proteins (AKAP3, AKAP4, FSIP2, PSMD11, CABYR, and TPPP2) related to capacitation and AR process played a key role in protein kinase A binding, sperm motility, reproductive process, cytoskeleton and sperm flagella function. Taken together, these data provide not only a solid foundation for further exploring phosphoproteome of sperm in yak, but an efficient way to identify sperm fertility-related marker phosphorylated proteins.

Structural modeling of human AKAP3 protein and in silico analysis of single nucleotide polymorphisms associated with sperm motility

AKAP3 is a member of the A-kinase anchoring proteins and it is a constituent of the sperm fibrous sheath. AKAP3 is needed for the formation of sperm flagellum structure, sperm motility, and male fertility. This study aims to model the AKAP3 tertiary structure and identify the probable impact of four mutations characterized in infertile men on the AKAP3 structure. The T464S, I500T, E525K, and I661T substitutions were analyzed using in silico methods. The secondary structure and three-dimensional model of AKAP3 were determined using PSI-BLAST based secondary structure prediction and Robetta servers. The TM-score was used to quantitatively measure the structural similarities between native and mutated models. All of the desired substitutions were classified as benign. I-Mutant results showed all of the substitutions decreased AKAP3 stability; however, the I500T and I661T were more effective. Superposition and secondary structure comparisons between native and mutants showed no dramatic deviations. Our study provided an appropriate model for AKAP3. Destabilization of AKAP3 caused by these substitutions did not appear to induce structural disturbances. As AKAP3 is involved in male infertility, providing more structural insights and the impact of mutations that cause protein functional diversity could elucidate the etiology of male fertility problems at molecular level.

Characterization of the Testis-Specific Angiotensin Converting Enzyme (tACE)-Interactome during Bovine Sperm Capacitation

A comprehensive understanding of molecular and biochemical changes during sperm capacitation is critical to the success of assisted reproductive technologies. We reported involvement of the testis-specific isoform of Angiotensin Converting Enzyme (tACE) in bovine sperm capacitation. The objective of this study was to characterize the tACE interactome in fresh and heparin-capacitated bovine sperm through immunoprecipitation coupled with mass spectrometry. These interactions were validated by co-localization of tACE with beta-tubulin as an identified interactome constituent. Although interactions between tACE and several proteins remained unchanged in fresh and capacitated sperm, mitochondrial aldehyde dehydrogenase 2 (ALDH2), inactive serine/threonine protein-kinase 3 (VRK3), tubulin-beta-4B chain (TUBB4B), and tubulin-alpha-8 chain (TUBA8) were recruited during capacitation, with implications for cytoskeletal and membrane reorganization, vesicle-mediated transport, GTP-binding, and redox regulation. A proposed tACE interactional network with identified interactome constituents was generated. Despite tACE function being integral to capacitation, the relevance of interactions with its binding partners during capacitation and subsequent events leading to fertilization remains to be elucidated.

Protein Identification of Spermatozoa and Seminal Plasma in Bottlenose Dolphin (Tursiops truncatus)

Proteins play an important role in many reproductive functions such as sperm maturation, sperm transit in the female genital tract or sperm-oocyte interaction. However, in general, little information concerning reproductive features is available in the case of aquatic animals. The present study aims to characterize the proteome of both spermatozoa and seminal plasma of bottlenose dolphins (Tursiops truncatus) as a model organism for cetaceans. Ejaculate samples were obtained from two trained dolphins housed in an aquarium. Spermatozoa and seminal plasma were analyzed by means of proteomic analyses using an LC-MS/MS, and a list with the gene symbols corresponding to each protein was submitted to the DAVID database. Of the 419 proteins identified in spermatozoa and 303 in seminal plasma, 111 proteins were shared by both. Furthermore, 70 proteins were identified as involved in reproductive processes, 39 in spermatozoa, and 31 in seminal plasma. The five most abundant proteins were also identified in these samples: AKAP3, ODF2, TUBB, GSTM3, ROPN1 for spermatozoa and CST11, LTF, ALB, HSP90B1, PIGR for seminal plasma. In conclusion, this study provides the first characterization of the proteome in cetacean sperm and seminal plasma, opening the way to future research into new biomarkers, the analysis of conservation capacity or possible additional applications in the field of assisted reproductive technologies.

Comparative Proteomics and Phosphoproteomics Analysis Reveal the Possible Breed Difference in Yorkshire and Duroc Boar Spermatozoa

Sperm cells are of unique elongated structure and function, the development of which is tightly regulated by the existing proteins and the posttranslational modifications (PTM) of these proteins. Based on the phylogenetic relationships of various swine breeds, Yorkshire boar is believed to be distinctly different from Duroc boar. The comprehensive differential proteomics and phosphoproteomics profilings were performed on spermatozoa from both Yorkshire and Duroc boars. By both peptide and PTM peptide quantification followed by statistical analyses, 167 differentially expressed proteins were identified from 1,745 proteins, and 283 differentially expressed phosphopeptides corresponding to 102 unique differentially phosphorylated proteins were measured from 1,140 identified phosphopeptides derived from 363 phosphorylated proteins. The representative results were validated by Western blots. Pathway enrichment analyses revealed that majority of differential expression proteins and differential phosphorylation proteins were primarily concerned with spermatogenesis, male gamete generation, sperm motility, energy metabolism, cilium morphogenesis, axonemal dynein complex assembly, sperm–egg recognition, and capacitation. Remarkably, axonemal dynein complex assembly related proteins, such as SMCP, SUN5, ODF1, AKAP3, and AKAP4 that play a key regulatory role in the sperm physiological functions, were significantly higher in Duroc spermatozoa than that of Yorkshire. Furthermore, phosphorylation of sperm-specific proteins, such as CABYR, ROPN1, CALM1, PRKAR2A, and PRKAR1A, participates in regulation of the boar sperm motility mainly through the cAMP/PKA signal pathway in different breeds, demonstrating that protein phosphorylation may be an important mechanism underlying the sperm diversity. Protein–protein interaction analysis revealed that the 14 overlapped proteins between differential expression proteins and differential phosphorylation proteins potentially played a key role in sperm development and motility of the flagellum, including the proteins ODF1, SMCP, AKAP4, FSIP2, and SUN5. Taken together, these physiologically and functionally differentially expressed proteins (DEPs) and differentially expressed phosphorylated proteins (DPPs) may constitute the proteomic backgrounds between the two different boar breeds. The validation will be performed to delineate the roles of these PTM proteins as modulators of Yorkshire and Duroc boar spermatozoa.

Beyond PKA: Evolutionary and structural insights that define a docking and dimerization domain superfamily

Protein-interaction domains can create unique macromolecular complexes that drive evolutionary innovation. By combining bioinformatic and phylogenetic analyses with structural approaches, we have discovered that the docking and dimerization (D/D) domain of the PKA regulatory subunit is an ancient and conserved protein fold. An archetypal function of this module is to interact with A-kinase-anchoring proteins (AKAPs) that facilitate compartmentalization of this key cell-signaling enzyme. Homology searching reveals that D/D domain proteins comprise a superfamily with 18 members that function in a variety of molecular and cellular contexts. Further in silico analyses indicate that D/D domains segregate into subgroups on the basis of their similarity to type I or type II PKA regulatory subunits. The sperm autoantigenic protein 17 (SPA17) is a prototype of the type II or R2D2 subgroup that is conserved across metazoan phyla. We determined the crystal structure of an extended D/D domain from SPA17 (amino acids 1–75) at 1.72 Å resolution. This revealed a four-helix bundle-like configuration featuring terminal β-strands that can mediate higher order oligomerization. In solution, SPA17 forms both homodimers and tetramers and displays a weak affinity for AKAP18. Quantitative approaches reveal that AKAP18 binding occurs at nanomolar affinity when SPA17 heterodimerizes with the ropporin-1-like D/D protein. These findings expand the role of the D/D fold as a versatile protein-interaction element that maintains the integrity of macromolecular architectures within organelles such as motile cilia.

Hypomorphic and hypermorphic mouse models of Fsip2 indicate its dosage-dependent roles in sperm tail and acrosome formation

Loss-of-function mutations in multiple morphological abnormalities of the sperm flagella (MMAF)-associated genes lead to decreased sperm motility and impaired male fertility. As an MMAF gene, the function of fibrous sheath-interacting protein 2 (FSIP2) remains largely unknown. In this work, we identified a homozygous truncating mutation of FSIP2 in an infertile patient. Accordingly, we constructed a knock-in (KI) mouse model with this mutation. In parallel, we established an Fsip2 overexpression (OE) mouse model. Remarkably, KI mice presented with the typical MMAF phenotype, whereas OE mice showed no gross anomaly except for sperm tails with increased length. Single-cell RNA sequencing of the testes uncovered altered expression of genes related to sperm flagellum, acrosomal vesicle and spermatid development. We confirmed the expression of Fsip2 at the acrosome and the physical interaction of this gene with Acrv1, an acrosomal marker. Proteomic analysis of the testes revealed changes in proteins sited at the fibrous sheath, mitochondrial sheath and acrosomal vesicle. We also pinpointed the crucial motifs of Fsip2 that are evolutionarily conserved in species with internal fertilization. Thus, this work reveals the dosage-dependent roles of Fsip2 in sperm tail and acrosome formation.

Testis developmental related gene 1 (TDRG1) encodes a progressive motility-associated protein in human spermatozoa

STUDY QUESTION

Is there an association between the human testis-specific gene, testis developmental related gene 1 (TDRG1) and human sperm motility?

SUMMARY ANSWER

TDRG1 is associated with asthenozoospermia and involved in regulating human sperm motility.

WHAT IS KNOWN ALREADY

Many testis-specific proteins potentially regulate spermatogenesis and sperm motility. We have identified a novel human testis-specific gene, TDRG1, which encodes a 100-amino-acid protein localized in the human sperm tail, yet little is known about its role in human spermatozoa.

STUDY DESIGN, SIZE, DURATION

Sperm samples were obtained from normozoospermic men and asthenozoospermic men who visited the reproductive medical center at Jiangxi Maternal and Child Health Hospital, Nanchang, Jiangxi, China between February 2018 and January 2019. In total, 27 normozoospermic men and 25 asthenozoospermic men were recruited to participate in the study.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The level of TDRG1 in sperm of normozoospermic and asthenozoospermic men was examined by immunoblotting and immunofluorescence assays. Progressive motility was examined by computer-aided sperm analysis. The correlation between the TDRG1 protein level and progressive motility was analyzed by linear regression. TDRG1 was imported into the sperm of normozoospermic and asthenozoospermic men using a cell-penetrating peptide (CPP)-fused TDRG1 recombinant protein (CPP-TDRG1), and the progressive motility was examined. Also, the altered proteins associated with TDRG1 in asthenozoospermic sperm were detected using label-free quantification method-based quantitative proteomic technology. TDRG1-interacting proteins were identified by co-immunoprecipitation coupled with tandem mass spectrometry analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

The mean level of TDRG1 was significantly decreased in sperm of asthenozoospermic men compared with normozoospermic men (P < 0.05) and was positively correlated with percentage of progressively motile sperm (r2 = 0.75, P = 0.0001). The introduction of TDRG1 into human sperm, using CPP, significantly increased progressive motility (P < 0.05) and improved the progressive motility of sperm from asthenozoospermic men to the normal level. TDRG1 forms a protein complex with sperm-motility related proteins in human sperm and its downregulation was associated with a decrease in other motility-related proteins.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

The sample size was limited and larger cohorts are needed for verifying the positive effect of CPP-TDRG1 on human sperm motility. Furthermore, the caution should be paid that a comprehensive safety examination would be performed to evaluate whether CPP-TDRG1 is a possible treatment approach for asthenozoospermia.

WIDER IMPLICATIONS OF THE FINDINGS

Our results provide new insights into the mechanisms of sperm motility which may contribute to the diagnosis and treatment for asthenozoospermia.

STUDY FUNDING/COMPETING INTEREST(S)

National Natural Science Foundation of China (81501317 and 81871207 to H.C.; 81771644 to T.L.; 31671204 to X.Z.; 81571432 to Y.T.). The authors have no conflicts of interest to declare.

Loss of CEP70 function affects acrosome biogenesis and flagella formation during spermiogenesis

The spermatogenesis process is complex and delicate, and any error in a step may cause spermatogenesis arrest and even male infertility. According to our previous transcriptomic data, CEP70 is highly expressed throughout various stages of human spermatogenesis, especially during the meiosis and deformation stages. CEP70 is present in sperm tails and that it exists in centrosomes as revealed by human centrosome proteomics. However, the specific mechanism of this protein in spermatogenesis is still unknown. In this study, we found a heterozygous site of the same mutation on CEP70 through mutation screening of patients with clinical azoospermia. To further verify, we deleted CEP70 in mice and found that it caused abnormal spermatogenesis, leading to male sterility. We found that the knockout of CEP70 did not affect the prophase of meiosis I, but led to male germ-cell apoptosis and abnormal spermiogenesis. By transmission electron microscopy (TEM) and scanning electron microscopy (SEM) analysis, we found that the deletion of CEP70 resulted in the abnormal formation of flagella and acrosomes during spermiogenesis. Tandem mass tag (TMT)-labeled quantitative proteomic analysis revealed that the absence of CEP70 led to a significant decrease in the proteins associated with the formation of the flagella, head, and acrosome of sperm, and the microtubule cytoskeleton. Taken together, our results show that CEP70 is essential for acrosome biogenesis and flagella formation during spermiogenesis.

Prediction of 3D Protein Structure Based on The Mutation of AKAP3 and PLOD3 Genes in The Case of Non-Obstructive Azoospermia

Background

The present study has been designed with the aim of evaluating A-kinase anchoring proteins 3 (AKAP3) and Procollagen-Lysine, 2-Oxoglutarate 5-Dioxygenase 3 (PLOD3) gene mutations and prediction of 3D protein structure for ligand binding activity in the cases of non-obstructive azoospermic male.

Materials and Methods

Clinically diagnosed cases of non-obstructive azoospermia (n=111) with age matched controls (n=42) were included in the present case-control study for genetics analysis and confirmation of diagnosis. The sample size was calculated using Epi info software version 6 with 90 power and 95% confidence interval. Genomic DNA was isolated from blood (2.0 ml) and a selected case was used for whole exome sequencing (WES) using Illumina Hiseq for identification of the genes. Bioinformatic tools were used for decode the amino acid sequence from biological database (www.ncbi.nlm.nih.gov/protein). 3D protein structure of AKAP3 and PLOD3 genes was predicted using I-TASSER server and binding energy was calculated by Ramachandran plot.

Results

Present study revealed the mutation of AKAP3 gene, showing frameshift mutation at rs67512580 (ACT → -CT) and loss of adenine in homozygous condition, where, leucine changed into serine. Similarly, PLOD3 gene shows missense mutation in heterozygous condition due to loss of guanine in the sequence AGG→A-G and it is responsible for the change in post-translational event of amino acid where arginine change into lysine. 3D structure shows 8 and 4 pockets binding site in AKAP3 and PLOD3 gene encoded proteins with MTX respectively, but only one site bound to the receptor with less binding energy representing efficient model of protein structure.

Conclusion

These genetic variations are responsible for alteration of translational events of amino acid sequences, leading to protein synthesis change following alteration in the predicted 3D structure and functions during spermiogen- esis, which might be a causative “risk” factor for male infertility.

Lack of AKAP3 disrupts integrity of the subcellular structure and proteome of mouse sperm and causes male sterility

The development and maintenance of the correct morphology of sperm is important for their functions. Cellular morphogenesis of sperm occurs during the post-meiotic developmental stage; however, little is known about what coordinates this process. In the present study, we investigated the role of A-kinase anchoring protein 3 (AKAP3) during mouse spermiogenesis, using both mouse genetics and proteomics. It was found that AKAP3 is essential for the formation of the specific subcellular structure of the sperm flagellum, motility of sperm and male fertility. Additionally, lack of AKAP3 caused global changes of the sperm proteome and mislocalization of sperm proteins, including accumulation of RNA metabolism and translation factors and displacement of PKA subunits in mature sperm, which may underlie misregulated PKA activity and immotility in sperm. Interestingly, sperm lacking a complete fibrous sheath from both Akap3 and Akap4 null mice accumulated F-actin filaments and morphological defects during post-testicular maturation in the epididymis. These results suggest that the subcellular structures of sperm could be formed via independent pathways, and elucidate the roles of AKAP3 during the coordinated synthesis and organization of the sperm proteome and sperm morphology.

Characterization and functional roles of paternal RNAs in 2-4 cell bovine embryos

Embryos utilize oocyte-donated RNAs until they become capable of producing RNAs through embryonic genome activation (EGA). The sperm's influence over pre-EGA RNA content of embryos remains unknown. Recent studies have revealed that sperm donate non-genomic components upon fertilization. Thus, sperm may also contribute to RNA presence in pre-EGA embryos. The first objective of this study was to investigate whether male fertility status is associated with the RNAs present in the bovine embryo prior to EGA. A total of 65 RNAs were found to be differentially expressed between 2-4 cell bovine embryos derived from high and low fertility sires. Expression patterns were confirmed for protein phosphatase 1 regulatory subunit 36 (PPP1R36) and ataxin 2 like (ATXN2L) in three new biological replicates. The knockdown of ATXN2L led to a 22.9% increase in blastocyst development. The second objective of this study was to characterize the parental origin of RNAs present in pre-EGA embryos. Results revealed 472 sperm-derived RNAs, 2575 oocyte-derived RNAs, 2675 RNAs derived from both sperm and oocytes, and 663 embryo-exclusive RNAs. This study uncovers an association of male fertility with developmentally impactful RNAs in 2-4 cell embryos. This study also provides an initial characterization of paternally-contributed RNAs to pre-EGA embryos. Furthermore, a subset of 2-4 cell embryo-specific RNAs was identified.

Voltage-dependent anion channel isoform 3 as a potential male contraceptive drug target

Voltage-dependent anion channel isoform 3 (VDAC3), a channel in the mitochondrial outer membrane, has been suggested to play a role in the regulation of ATP transport and Ca²⁺ homeostasis. These processes are regarded as important for spermatozoa motility. Accordingly, in previous years, mutations in the VDAC3-encoding gene were detected in spermatozoa with low motility from infertile patients. Therefore, it can be assumed that these mutations would cause alteration of the structure and/or charge of the VDAC3 channel. The review is focused on current knowledge about contribution of VDAC3 activity to human spermatozoa motility and morphology. We also discuss the possibility of designing new molecules that could specifically block the VDAC3 channel and consequently act as male contraceptives.

Testis-specific calcium-binding protein CBP86-IV (CABYR) binds with phosphoglycerate kinase 2 in vitro and in vivo experiment

The investigation of the interacting proteins with testis-specific calcium-binding protein CBP86-IV (CABYR) was carried out in human spermatozoa. The total RNA from human spermatozoa was extracted, and the ORF sequence of TSCBP86-IV gene was amplified and cloned into expression vector pET-28a. The positive recombinant clones were transformed into Escherichia coli strain BL21 (DE3) to express fusion protein. Then, co-immunoprecipitation (Co-IP) of TSCBP86-IV was performed in BL21 cell lysate expressing CBP86-IV recombinant protein. The immune complex was captured and identified by mass spectrometry. Reverse Co-IP of potential interacting proteins was performed in human sperm cell lysate. The potential protein interactions were confirmed by yeast two-hybrid system. Thirteen proteins were successfully identified in immune complex from E. coli cell lysate. Phosphoglycerate kinase 2 (PGK2) further showed positive results both in reverse Co-IP and yeast two-hybrid experiments and was confirmed to be interacted with TSCBP86-IV in human sperm cells.

Phosphoproteomic and Functional Analyses Reveal Sperm-specific Protein Changes Downstream of Kappa Opioid Receptor in Human Spermatozoa

G-protein coupled receptors (GPCRs) belong to the seven transmembrane receptor superfamily that transduce signals via G proteins in response to external stimuli to initiate different intracellular signaling pathways which culminate in specific cellular responses. The expression of diverse GPCRs at the plasma membrane of human spermatozoa suggests their involvement in the regulation of sperm fertility. However, the signaling events downstream of many GPCRs in spermatozoa remain uncharacterized. Here, we selected the kappa-opioid receptor (KOR) as a study model and applied phosphoproteomic approach based on TMT labeling and LC-MS/MS analyses. Quantitative coverage of more than 5000 proteins with over 3500 phosphorylation sites revealed changes in the phosphorylation levels of sperm-specific proteins involved in the regulation of the sperm fertility in response to a specific agonist of KOR, U50488H. Further functional studies indicate that KOR could be involved in the regulation of sperm fertile capacity by modulation of calcium channels. Our findings suggest that human spermatozoa possess unique features in the molecular mechanisms downstream of GPCRs which could be key regulators of sperm fertility and improved knowledge of these specific processes may contribute to the development of useful biochemical tools for diagnosis and treatment of male infertility.

Modification of Crocodile Spermatozoa Refutes the Tenet That Post-testicular Sperm Maturation Is Restricted To Mammals

Competition to achieve paternity has contributed to the development of a multitude of elaborate male reproductive strategies. In one of the most well-studied examples, the spermatozoa of all mammalian species must undergo a series of physiological changes, termed capacitation, in the female reproductive tract before realizing their potential to fertilize an ovum. However, the evolutionary origin and adaptive advantage afforded by capacitation remains obscure. Here, we report the use of comparative and quantitative proteomics to explore the biological significance of capacitation in an ancient reptilian species, the Australian saltwater crocodile (Crocodylus porosus,). Our data reveal that exposure of crocodile spermatozoa to capacitation stimuli elicits a cascade of physiological responses that are analogous to those implicated in the functional activation of their mammalian counterparts. Indeed, among a total of 1119 proteins identified in this study, we detected 126 that were differentially phosphorylated (± 1.2 fold-change) in capacitated versus, noncapacitated crocodile spermatozoa. Notably, this subset of phosphorylated proteins shared substantial evolutionary overlap with those documented in mammalian spermatozoa, and included key elements of signal transduction, metabolic and cellular remodeling pathways. Unlike mammalian sperm, however, we noted a distinct bias for differential phosphorylation of serine (as opposed to tyrosine) residues, with this amino acid featuring as the target for ∼80% of all changes detected in capacitated spermatozoa. Overall, these results indicate that the phenomenon of sperm capacitation is unlikely to be restricted to mammals and provide a framework for understanding the molecular changes in sperm physiology necessary for fertilization.

Loss-of-function mutations in QRICH2 cause male infertility with multiple morphological abnormalities of the sperm flagella

Aberrant sperm flagella impair sperm motility and cause male infertility, yet the genes which have been identified in multiple morphological abnormalities of the flagella (MMAF) can only explain the pathogenic mechanisms of MMAF in a small number of cases. Here, we identify and functionally characterize homozygous loss-of-function mutations of QRICH2 in two infertile males with MMAF from two consanguineous families. Remarkably, Qrich2 knock-out (KO) male mice constructed by CRISPR-Cas9 technology present MMAF phenotypes and sterility. To elucidate the mechanisms of Qrich2 functioning in sperm flagellar formation, we perform proteomic analysis on the testes of KO and wild-type mice. Furthermore, in vitro experiments indicate that QRICH2 is involved in sperm flagellar development through stabilizing and enhancing the expression of proteins related to flagellar development. Our findings strongly suggest that the genetic mutations of human QRICH2 can lead to male infertility with MMAF and that QRICH2 is essential for sperm flagellar formation.

Biallelic mutations in PMFBP1 cause acephalic spermatozoa

The majority of men with defects in spermatogenesis remain undiagnosed. Acephalic spermatozoa is one of the diseases causing primary infertility. However, the causes underlying over half of affected cases remain unclear. Here, we report by whole-exome sequencing the identification of homozygous and compound heterozygous truncating mutations in PMFBP1 of two unrelated individuals with acephalic spermatozoa. PMFBP1 was highly and specifically expressed in human and mouse testis. Furthermore, immunofluorescence staining in sperm from a normal control showed that PMFBP1 localizes to the head-flagella junction region, and the absence of PMFBP1 was confirmed in patients harboring PMFBP1 mutations. In addition, we generated Pmfbp1 knock-out (KO) mice, which we found recapitulate the acephalic sperm phenotype. Label-free quantitative proteomic analysis of testicular sperm from Pmfbp1 KO and control mice showed 124 and 35 proteins, respectively, increased or decreased in sperm from KO mice compared to that found in control mice. Gene ontology analysis indicates that the biological process of Golgi vesicle transport was the most highly enriched in differentially expressed proteins, indicating process defects related to Golgi complex function may disturb formation of the head-neck junction. Collectively, our data indicate that PMFBP1 is necessary for sperm morphology in both humans and mice, and that biallelic truncating mutations in PMFBP1 cause acephalic spermatozoa.

Molecular study of human sperm RNA: Ropporin and CABYR in asthenozoospermia

BACKGROUND

Sperm motility is an essential aspect of human fertility. Sperm contain an abundance of transcripts, thought to be remnants of mRNA, which comprise a genetic fingerprint and can be considered a historic record of gene expression during spermatogenesis. The aberrant expression of numerous genes has been found to contribute to impaired sperm motility; these include ROPN1 (rhophilin associated tail protein 1), which encodes a component of the fibrous sheath of the mammalian sperm flagella, and CABYR (calcium-binding tyrosine-(Y)-phosphorylation-regulated protein), which plays an important role in calcium activation and modulation. The aim of this study was to investigate ROPN1 and CABYR gene co-expression in asthenozoospermic semen samples in comparison with normozoospermic samples.

METHODS

We studied 120 semen samples (60 normozoospermic and 60 asthenozoospermic) from Caucasian patients attending our centre for an andrological check-up. Total RNA was extracted from purified spermatozoa with RNeasy mini kit. ROPN1 and CABYR mRNA expression was analysed using RT-qPCR. Continuous variables were described as means ± standard deviations.

RESULTS

ROPN1 and CABYR mRNA were simultaneously downregulated in asthenozoospermic in comparison with normozoospermic samples. There was also a positive correlation between total progressive motility and ROPN1 and CABYR gene expression and between total motile sperm number and ROPN1 and CABYR gene expression.

CONCLUSIONS

The results demonstrated downregulation of both ROPN1 and CABYR in asthenozoospermic samples and importantly, a positive correlation between the expression of the two genes, suggesting that ROPN1 and CABYR co-expression is a prerequisite for normal flagellar function and sperm motility.

Sperm RNA elements as markers of health

Idiopathic infertility, an etiology not identified as part of standard clinical assessment, represents approximately 20% of all infertility cases. Current male infertility diagnosis focuses on the concentration, motility, and morphology of spermatozoa. This is of limited value when predicting birth success and of limited utility when selecting the optimum treatment. At fertilization, spermatozoa provide their genomic contribution, as well as a set of RNAs and proteins that have distinct roles in development. The potential of spermatozoal RNAs to be used as a prognostic of live birth has been shown [Jodar et al. (2015) Science Translational Medicine 7(295):295re6]. This relied on a set of 648 sperm RNA elements derived from 285 genes that are perhaps indicative of future health status. To address this tenet, the present study correlated the levels of each transcript among all samples to assess linkage between transcript absence, birth success, and possible disease association. Correlations between transcript levels of the 285 genes were analyzed amongst themselves, and within the context of the entire transcript population for these samples. The transcripts ACE, GIGYF2, and ODF2 had many negative correlations and form the majority of correlations, suggesting an important function for these transcripts. Eleven of the 285 queried genes had disease-associated variants within a sperm RNA element. Three genes, GPX4, NDRG1, and RPS24 had SREs were absent in at least one individual from the test cohort. GPX4 and RPS24 are associated with developmental defects and/or neonatal lethality. This leaves the intriguing possibility that, while sperm RNAs delivered to the oocyte inform the success of live birth, they may also be predictors of human health.

ABBREVIATIONS

GO: Gene Ontology; ART: assisted reproductive technology; IVF: in vitro fertilization; ICSI: intra-cytoplasmic sperm injection; RNA-seq: RNA-sequencing; TIC: timed intercourse; IUI: intrauterine insemination; SRE: sperm RNA elements; HPA: Human Protein Atlas; SMDS: sedaghatian-type spondylometaphyseal dysplasia; DBA: Diamond-Blackfan anemia; RPKM: reads per kilobase per million; TPM: transcripts per million; IPA: Ingenuity Pathway Analysis; OMIM: Online Mendelian Inheritance in Man.

Proteomic analysis of mature and immature ejaculated spermatozoa from fertile men

Dysfunctional spermatozoa maturation is the main reason for the decrease in sperm motility and morphology in infertile men. Ejaculated spermatozoa from healthy fertile men were separated into four fractions using three-layer density gradient. Proteins were extracted and bands were digested on a LTQ-Orbitrap Elite hybrid mass spectrometer system. Functional annotations of proteins were obtained using bioinformatics tools and pathway databases. Western blotting was performed to verify the expression levels of the proteins of interest. 1469 proteins were identified in four fractions of spermatozoa. The number of detected proteins decreased according to the maturation level of spermatozoa. During spermatozoa maturation, proteins involved in gamete generation, cell motility, energy metabolism and oxidative phosphorylation processes showed increasing expression levels and those involved in protein biosynthesis, protein transport, protein ubiquitination, and response to oxidative stress processes showed decreasing expression levels. We validated four proteins (HSP 70 1A, clusterin, tektin 2 and tektin 3) by Western blotting. The study shows protein markers that may provide insight into the ejaculated spermatozoa proteins in different stages of sperm maturation that may be altered or modified in infertile men.

CABYR is essential for fibrous sheath integrity and progressive motility in mouse spermatozoa

Ca²⁺-binding tyrosine-phosphorylation-regulated protein (CABYR) has been implicated in sperm physiological function in several in vitro studies. It has also been implicated as a potential cause of and diagnostic tool in asthenozoospermic human males. CABYR is known to be localized to the fibrous sheath, an accessory structure in the flagellar principal piece. Utilizing the CRISPR-Cas9 technology, we have knocked out this gene in mice to understand its role in male fertility. Cabyr-knockout male mice showed severe subfertility with a defect in sperm motility as well as a significant disorganization in the fibrous sheath. Further, abnormal configuration of doublet microtubules was observed in the Cabyr-knockout spermatozoa, suggesting that the fibrous sheath is important for the correct organization of the axoneme. Our results show that it is the role of CABYR in the formation of the fibrous sheath that is essential for male fertility.

A proteomic analysis on human sperm tail: comparison between normozoospermia and asthenozoospermia

PURPOSE

Asthenozoospermia is a common cause of human male infertility characterized by reduced sperm motility. The molecular mechanism that impairs sperm motility is not fully understood. This study proposed to identify novel biomarkers by focusing on sperm tail proteomic analysis of asthenozoospermic patients.

METHODS

Sperm were isolated from normozoospermic and asthenozoospermic semen samples. Tail fractions were obtained by sonication followed by Percoll gradient. The proteins were extracted by solubilization and subjected to two-dimensional gel electrophoresis (2-DE); then, the spots were analyzed using Image Master 2D Platinum software. The significantly increased/decreased amounts of proteins in the two groups were exploited by matrix-assisted laser desorption-ionization time-of-flight/time-of-flight (MALDI-TOF-TOF) mass spectrometry.

RESULTS

Three hundred ninety protein spots were detected in both groups. Twenty-one protein spots that had significantly altered amounts (p < 0.05) were excised and exploited using MALDI-TOF-TOF mass spectrometry. They led to the identification of the following 14 unique proteins: Tubulin beta 2B; glutathione S-transferase Mu 3; keratin, type II cytoskeletal 1; outer dense fiber protein 2; voltage-dependent anion-selective channel protein 2; A-kinase anchor protein 4; cytochrome c oxidase subunit 6B; sperm protein associated with the nucleus on the X chromosome B; phospholipid hydroperoxide glutathione peroxidase-mitochondrial; isoaspartyl peptidase/L-asparaginase; heat shock-related 70 kDa protein 2; stress-70 protein, mitochondrial; glyceraldehyde-3-phosphate dehydrogenase, testis-specific and clusterin.

CONCLUSION

Fourteen proteins present in different amounts in asthenozoospermic sperm tail samples were identified, four of which are reported here for the first time. These proteins might be used as markers for the better diagnosis of sperm dysfunctions, targets for male contraceptive development, and to predict embryo quality.

Low-expressed testis-specific calcium-binding protein CBP86-IV (CABYR) is observed in idiopathic asthenozoospermia

OBJECTIVES

To investigate the expression level of testis-specific calcium-binding protein CBP86-IV in normal and asthenozoospermic human sperm.

METHODS

The total RNA was extracted from human sperm, and target cDNA was obtained by reverse transcription-polymerase chain reaction. Then the cDNA was used for quantitative PCR analysis and cloned into the prokaryotic expression vector pET-28a, respectively. The fusion protein was induced and expressed as inclusion body which was used to produce the polyclonal antibody against TSCBP86-IV. The protein expression level of TSCBP86-IV from normal human sperm and idiopathic asthenozoospermic samples was detected by the purified antibody.

RESULTS

The experimental results showed that the protein expression of TSCBP86-IV was reduced in idiopathic asthenozoospermia and consistent with the transcriptional changing tendency which was detected by quantitative PCR analysis.

CONCLUSIONS

The stable and reliable change of TSCBP86-IV may be taken as a new molecular marker for clinical diagnosis of idiopathic asthenozoospermia.

Major protein alterations in spermatozoa from infertile men with unilateral varicocele

BACKGROUND

The etiology of varicocele, a common cause of male factor infertility, remains unclear. Proteomic changes responsible for the underlying pathology of unilateral varicocele have not been evaluated. The objective of this prospective study was to employ proteomic techniques and bioinformatic tools to identify and analyze proteins of interest in infertile men with unilateral varicocele.

METHODS

Spermatozoa from infertile men with unilateral varicocele (n=5) and from fertile men (control; n=5) were pooled in two groups respectively. Proteins were extracted and separated by 1-D SDS-PAGE. Bands were digested and identified on a LTQ-Orbitrap Elite hybrid mass spectrometer system. Bioinformatic analysis identified the pathways and functions of the differentially expressed proteins (DEP).

RESULTS

Sperm concentration, motility and morphology were lower, and reactive oxygen species levels were higher in unilateral varicocele patients compared to healthy controls. The total number of proteins identified were 1055, 1010 and 1042 in the fertile group, and 795, 713 and 763 proteins in the unilateral varicocele group. Of the 369 DEP between both groups, 120 proteins were unique to the fertile group and 38 proteins were unique to the unilateral varicocele group. Compared to the control group, 114 proteins were overexpressed while 97 proteins were underexpressed in the unilateral varicocele group. We have identified 29 proteins of interest that are involved in spermatogenesis and other fundamental reproductive events such as sperm maturation, acquisition of sperm motility, hyperactivation, capacitation, acrosome reaction and fertilization. The major functional pathways of the 359 DEP related to the unilateral varicocele group involve metabolism, disease, immune system, gene expression, signal transduction and apoptosis. Functional annotations showed that unilateral varicocele mostly affected small molecule biochemistry and post-translational modification proteins. Proteins expressed uniquely in the unilateral varicocele group were cysteine-rich secretory protein 2 precursor (CRISP2) and arginase-2 (ARG2).

CONCLUSIONS

The expression of these proteins of interest are altered and possibly functionally compromised in infertile men with unilateral varicocele. If validated, these proteins may lead to potential biomarker(s) and help better understand the mechanism involved in the pathophysiology of unilateral varicocele in infertile men.

Cancer testis antigens: a novel target in lung cancer

Lung cancer is the main cause of cancer mortality worldwide. This is mainly due to the fact that it is diagnosed in advanced stage patients, which are no more surgically curable. Consequently, searching for novel treatments and new modalities for early diagnosis offers great promise to improve the clinical outcome. Recently, a new group of antigens, the cancer testis antigens, have been described as possible early diagnostic tools and therapeutic targets in cancer therapy.This review will report emerging evidences of cancer testis antigens deregulation in lung cancer and explore the state of the art of their currently known role and potential as markers for early diagnosis and disease progression and targets of an immunotherapeutic approach aiming to improve the cure rate of this tumor.

Loss of R2D2 proteins ROPN1 and ROPN1L causes defects in murine sperm motility, phosphorylation, and fibrous sheath integrity

The fibrous sheath (FS) is a flagellar cytoskeletal structure unique to sperm that surrounds the outer dense fibers and axoneme. Its primary components are A-kinase anchoring proteins (AKAPs) 3 and 4, which suggests that the FS affects flagellar beating via the scaffolding of signaling pathways necessary for motility. Sperm proteins ROPN1 and ROPN1L bind AKAP3. To determine the role of ROPN1 and ROPN1L in sperm function, we created mice deficient in ROPN1 (RKO), mice deficient in ROPN1L (RLKO), and double knockout mice (DKO). All three strains of mice had normal testicular morphology and spermatogenesis. Only the DKOs had obvious defects in sperm morphology (thinning and shredding of the principal piece), which was accompanied by a reduction in AKAP3 levels. RLKO mice had slightly reduced sperm motility and increased levels of ROPN1. RKO mice had moderately impaired motility and increased levels of ROPN1L. DKO sperm were immotile. We have previously determined that RKO male mice are subfertile, and DKO males are infertile. Together these data indicate that ROPN1L and ROPN1 compensate for each other in the absence of the opposing protein, possibly to maintain AKAP3 incorporation in the FS. Sperm from mice lacking ROPN1L exhibited reductions in both cAMP-dependent protein kinase (PKA) phosphorylation of a 270-kDa protein (perhaps FSCB), and in capacitation-induced tyrosine phosphorylation. Sperm from mice lacking ROPN1 had reduced levels of FSCB and increased tyrosine phosphorylation of noncapacitated sperm. These data demonstrate that mutations in ROPN1 and ROPN1L can cause defects in FS integrity, sperm motility, and PKA-dependent signaling processes, leading to male infertility.