Plasma membrane Ca2+-ATPase 4 in murine epididymis: secretion of splice variants in the luminal fluid and a role in sperm maturation

The biological functions and pathological mechanisms of CASK in various diseases

Background

As a scaffold protein, calcium/calmodulin-dependent serine protein kinase (CASK) has been extensively studied in a variety of tissues throughout the body. The Cask gene is ubiquitous in several tissues, such as the neurons, islets, heart, kidneys and sperm, and is mostly localised in the cytoplasm adjacent to the basement membrane. CASK binds to a variety of proteins through its domains to exerting its biological activity.

Scope of review

Here, we discuss the role of CASK in multiple tissues throughout the body. The role of different CASK domains in regulating neuronal development, neurotransmitter release and synaptic vesicle secretion was emphasised; the regulatory mechanism of CASK on the function of pancreatic islet β cells was analysed; the role of CASK in cardiac physiology, kidney and sperm development was discussed; and the role of CASK in different tumours was compared. Finally, we clarify the importance of the Cask gene in the body, and how deletion or mutation of the Cask gene can have adverse consequences.

Major conclusions

CASK is a conserved gene with similar roles in various tissues. The function of the Cask gene in the nervous system is mainly involved in the development of the nervous system and the release of neurotransmitters. In the endocrine system, an involvement of CASK has been reported in the process of insulin vesicle transport. CASK is also involved in cardiomyocyte ion channel regulation, kidney and sperm development, and tumour proliferation. CASK is an indispensable gene for the whole body, and CASK mutations can cause foetal malformations or death at birth. In this review, we summarise the biological functions and pathological mechanisms of CASK in various systems, thereby providing a basis for further in-depth studies of CASK functions.

Ca2+ homeostasis and male fertility: a target for a new male contraceptive system

Ca2+ is a key secondary messenger that determines sperm motility patterns. Mammalian sperm undergo capacitation, a process to acquire fertilizing ability, in the female reproductive tract. Capacitated sperm change their flagellar waveform to develop hyperactivated motility, which is crucial for successful sperm navigation to the eggs and fertilization. The sperm-specific channel, CATSPER, and an ATPase transporter, PMCA4, serve as major paths for Ca2+ influx and efflux, respectively, in sperm. The ionic paths coordinate Ca2+ homeostasis in the sperm, and their loss-of-function impairs sperm motility, to cause male infertility. In this review, we summarize the physiological significance of these two Ca2+ gates and suggest their potential applications in novel male contraceptives.

Microfluidics facilitating the use of small extracellular vesicles in innovative approaches to male infertility

Sperm are transcriptionally and translationally quiescent and, therefore, rely on the seminal plasma microenvironment for function, survival and fertilization of the oocyte in the oviduct. The male reproductive system influences sperm function via the binding and fusion of secreted epididymal (epididymosomes) and prostatic (prostasomes) small extracellular vesicles (S-EVs) that facilitate the transfer of proteins, lipids and nucleic acids to sperm. Seminal plasma S-EVs have important roles in sperm maturation, immune and oxidative stress protection, capacitation, fertilization and endometrial implantation and receptivity. Supplementing asthenozoospermic samples with normospermic-derived S-EVs can improve sperm motility and S-EV microRNAs can be used to predict non-obstructive azoospermia. Thus, S-EV influence on sperm physiology might have both therapeutic and diagnostic potential; however, the isolation of pure populations of S-EVs from bodily fluids with current conventional methods presents a substantial hurdle. Many conventional techniques lack accuracy, effectiveness, and practicality; yet microfluidic technology has the potential to simplify and improve S-EV isolation and detection.

Comparative proteomic analysis of seminal plasma exosomes in buffalo with high and low sperm motility

BACKGROUND

Exosomes are nanosized membranous vesicles secreted by various types of cells, which facilitate intercellular communication by transporting bioactive compounds. Exosomes are abundant in biological fluids including semen, and their protein composition and the potential of seminal plasma exosomes (SPEs) as fertility biomarkers were elucidated in humans, however, little information is available regarding buffalo (Bubalus bubalis). Here, we examined protein correlation between spermatozoa, seminal plasma (SP), and SPEs, and we compared and analyzed protein differences between high-motility (H-motility) and low-motility (L-motility) SPEs in buffalo.

RESULTS

SPEs were concentrated and purified by ultracentrifugation combined with sucrose density gradient centrifugation, followed by verification using western blotting, nanoparticle tracking analysis, and transmission electron microscopy. Protein composition in spermatozoa, SP and SPEs, and protein difference in H- and L-motility SPEs were identified by LC-MS/MS proteomic analysis and were functionally analyzed through comprehensive bioinformatics. Many SPEs proteins originated from spermatozoa and SP, and nearly one third were also present in spermatozoa and SP. A series of proteins associated with reproductive processes including sperm capacitation, spermatid differentiation, fertilization, sperm-egg recognition, membrane fusion, and acrosome reaction were integrated in a functional network. Comparative proteomic analyses showed 119 down-regulated and 41 up-regulated proteins in L-motility SPEs, compared with H-motility SPEs. Gene Ontology (GO) enrichment of differentially expressed proteins (DEPs) showed that most differential proteins were located in sperm and vesicles, with activities of hydrolase and metalloproteinase, and were involved in sperm-egg recognition, fertilization, single fertilization, and sperm-zona pellucida binding processes, etc. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that differential proteins were mainly involved in the PPRP signaling pathway, calcium signaling pathway, and cAMP signaling pathway, among others. Furthermore, 6 proteins associated with reproduction were validated by parallel reaction monitoring analysis.

CONCLUSION

This study provides a comprehensive description of the seminal plasma exosome proteome and may be of use for further screening of biomarkers associated with male infertility.

Sperm Ion Transporters and Channels in Human Asthenozoospermia: Genetic Etiology, Lessons from Animal Models, and Clinical Perspectives

In mammals, sperm fertilization potential relies on efficient progression within the female genital tract to reach and fertilize the oocyte. This fundamental property is supported by the flagellum, an evolutionarily conserved organelle that provides the mechanical force for sperm propulsion and motility. Importantly several functional maturation events that occur during the journey of the sperm cells through the genital tracts are necessary for the activation of flagellar beating and the acquisition of fertilization potential. Ion transporters and channels located at the surface of the sperm cells have been demonstrated to be involved in these processes, in particular, through the activation of downstream signaling pathways and the promotion of novel biochemical and electrophysiological properties in the sperm cells. We performed a systematic literature review to describe the currently known genetic alterations in humans that affect sperm ion transporters and channels and result in asthenozoospermia, a pathophysiological condition defined by reduced or absent sperm motility and observed in nearly 80% of infertile men. We also present the physiological relevance and functional mechanisms of additional ion channels identified in the mouse. Finally, considering the state-of-the art, we discuss future perspectives in terms of therapeutics of asthenozoospermia and male contraception.

Calcium Homeostasis in the Epididymal Microenvironment: Is Extracellular Calcium a Cofactor for Matrix Gla Protein-Dependent Scavenging Regulated by Vitamins

In the male reproductive tract, the epididymis is an essential organ for sperm maturation, in which sperm cells acquire mobility and the ability to fertilize oocytes while being stored in a protective microenvironment. Epididymal function involves a specialized luminal microenvironment established by the epithelial cells of epididymal mucosa. Low-calcium concentration is a unique feature of this epididymal luminal microenvironment, its relevance and regulation are, however, incompletely understood. In the rat epididymis, the vitamin D-related calcium-dependent TRPV6-TMEM16A channel-coupler has been shown to be involved in fluid transport, and, in a spatially complementary manner, vitamin K2-related γ-glutamyl carboxylase (GGCX)-dependent carboxylation of matrix Gla protein (MGP) plays an essential role in promoting calcium-dependent protein aggregation. An SNP in the human GGCX gene has been associated with asthenozoospermia. In addition, bioinformatic analysis also suggests the involvement of a vitamin B6-axis in calcium-dependent MGP-mediated protein aggregation. These findings suggest that vitamins interact with calcium homeostasis in the epididymis to ensure proper sperm maturation and male fertility. This review article discusses the regulation mechanisms of calcium homeostasis in the epididymis, and the potential role of vitamin interactions on epididymal calcium homeostasis, especially the role of matrix calcium in the epididymal lumen as a cofactor for the carboxylated MGP-mediated scavenging function.

FUS driven circCNOT6L biogenesis in mouse and human spermatozoa supports zygote development

Circular RNA (circRNA) biogenesis requires a backsplicing reaction, promoted by inverted repeats in cis-flanking sequences and trans factors, such as RNA-binding proteins (RBPs). Among these, FUS plays a key role. During spermatogenesis and sperm maturation along the epididymis such a molecular mechanism has been poorly explored. With this in mind, we chose circCNOT6L as a study case and wild-type (WT) as well as cannabinoid receptor type-1 knock-out (Cb1^−/−) male mice as animal models to analyze backsplicing mechanisms. Our results suggest that spermatozoa (SPZ) have an endogenous skill to circularize mRNAs, choosing FUS as modulator of backsplicing and under CB1 stimulation. A physical interaction between FUS and CNOT6L as well as a cooperation among FUS, RNA Polymerase II (RNApol2) and Quaking (QKI) take place in SPZ. Finally, to gain insight into FUS involvement in circCNOT6L biogenesis, FUS expression was reduced through RNA interference approach. Paternal transmission of FUS and CNOT6L to oocytes during fertilization was then assessed by using murine unfertilized oocytes (NF), one-cell zygotes (F) and murine oocytes undergoing parthenogenetic activation (PA) to exclude a maternal contribution. The role of circCNOT6L as an active regulator of zygote transition toward the 2-cell-like state was suggested using the Embryonic Stem Cell (ESC) system. Intriguingly, human SPZ exactly mirror murine SPZ.

The Role of Extracellular Vesicles in Sperm Function and Male Fertility

Within the reproductive tract, distinct cell types must have precisely controlled communication for complex processes such as gamete production, fertilisation and implantation. Intercellular communication in many physiological processes involves extracellular vesicles (EVs). In reproductive systems, EVs have been implicated in many aspects, from gamete maturation to embryo development. Sperm develop within the testis and then exit into the epididymis in an immature form, lacking motility and fertilising capabilities. Due to their small size, compact nature of the nucleus and the lack of specific organelles, sperm are unable to perform de novo protein synthesis, and thus rely on extrinsic signals delivered from the external milieu to gain full function. Mounting evidence points to EVs as being a major provider of these signals, not just within the male reproductive tract but also within the female as the sperm make their way through a seemingly hostile environment to the oocyte. In this chapter, we review the current knowledge on EVs as mediators of sperm maturation and function and highlight their potential roles in male fertility.

PMCA4 gene expression is regulated by the androgen receptor in the mouse testis during spermatogenesis

The present study aimed to investigate the expression of ATPase Ca⁺⁺ transporting plasma membrane 4 (PMCA4) in mouse testis and to determine its role in spermatogenesis. Reverse transcription-quantitative PCR, western blotting and immunofluorescence were performed to evaluate the expression levels of PMCA4 in mouse testes at various weeks postnatal in wild type mice, and in testes from Sertoli cell-specific androgen receptor knockout and androgen receptor knockout (ARKO) mice. Luciferase assay, androgen receptor (AR) overexpression and AR antagonist experiments were used to confirm that AR regulated the expression of PMCA4. The results demonstrated that PMCA4 was highly expressed in mouse testes at 3–8 weeks postnatal. PMCA4 expression levels in ARKO mouse testes were decreased compared with wild type. In addition, activation of AR by testosterone administration resulted in an increase in the activity of the PMCA4 promoter. Cells transfected with an AR-overexpressing plasmid exhibited increased expression levels of the PMCA4 protein. Finally, the increase in PMCA4 protein levels induced by testosterone was prevented by pre-treatment with the AR antagonist flutamide. The present results confirmed that PMCA4 was upregulated during mouse testis development and that PMCA4 mRNA and protein expression levels were regulated by androgens and AR. The present findings suggest that PMCA4 may be involved in the regulation of spermatogenesis.

Extracellular Vesicles, the Road toward the Improvement of ART Outcomes

Nowadays, farm animal industries use assisted reproductive technologies (ART) as a tool to manage herds' reproductive outcomes, for a fast dissemination of genetic improvement as well as to bypass subfertility issues. ART comprise at least one of the following procedures: collection and handling of oocytes, sperm, and embryos in in vitro conditions. Therefore, in these conditions, the interaction with the oviductal environment of gametes and early embryos during fertilization and the first stages of embryo development is lost. As a result, embryos obtained in in vitro fertilization (IVF) have less quality in comparison with those obtained in vivo, and have lower chances to implant and develop into viable offspring. In addition, media currently used for IVF are very similar to those empirically developed more than five decades ago. Recently, the importance of extracellular vesicles (EVs) in the fertility process has flourished. EVs are recognized as effective intercellular vehicles for communication as they deliver their cargo of proteins, lipids, and genetic material. Thus, during their transit through the female reproductive tract both gametes, oocyte and spermatozoa (that previously encountered EVs produced by male reproductive tract) interact with EVs produced by the female reproductive tract, passing them important information that contributes to a successful fertilization and embryo development. This fact highlights that the reproductive tract EVs cargo has an important role in reproductive events, which is missing in current ART media. This review aims to recapitulate recent advances in EVs functions on the fertilization process, highlighting the latest proposals with an applied approach to enhance ART outcome through EV utilization as an additive to the media of current ART procedures.

Membrane insertion and intercellular transfer of glycosylphosphatidylinositol-anchored proteins: potential therapeutic applications

Anchorage of a subset of cell surface proteins in eukaryotic cells is mediated by a glycosylphosphatidylinositol (GPI) moiety covalently attached to the carboxy-terminus of the protein moiety. Experimental evidence for the potential of GPI-anchored proteins (GPI-AP) of being released from cells into the extracellular environment has been accumulating, which involves either the loss or retention of the GPI anchor. Release of GPI-AP from donor cells may occur spontaneously or in response to endogenous or environmental signals. The experimental evidence for direct insertion of exogenous GPI-AP equipped with the complete anchor structure into the outer plasma membrane bilayer leaflets of acceptor cells is reviewed as well as the potential underlying molecular mechanisms. Furthermore, promiscuous transfer of certain GPI-AP between plasma membranes of different cells in vivo under certain (patho)physiological conditions has been reported. Engineering of target cell surfaces using chimeric GPI-AP with complete GPI anchor may be useful for therapeutic applications.

Alternative splicing of the Izumo1 gene ensures triggering gamete fusion in mice

IZUMO1 is a sperm acrosomal membrane protein that is essential for mammalian fertilization through recognition of JUNO on the oocyte surface and accompanying IZUMO1-JUNO complex formation. Here, we report a new Izumo1 gene splicing variant (IZUMO1_v2) with a unique 52-amino-acid-long signal sequence transcribed from Exon 1b. Although the mRNA amount of Izumo1_v2 is 76 times lower than that of the original Izumo1 (IZUMO1_v1) in the testis, the cell-oocyte assay indicates that IZUMO1_v2-expressing COS-7 cells have the ability to attach to the oocyte equivalent of IZUMO1_v1. To clarify the physiological function of IZUMO1_v2, we produced an IZUMO1_v1-specific knockout mouse line with a nine-base deletion adjacent to the initial methionine codon of IZUMO1_v1 by the CRISPR/Cas9 system. The IZUMO1_v1 knockout male mice carry 0.19-fold lower level of IZUMO1 protein in the spermatozoon; however, reduction in fertility was only minimally affected compared to the wild-type mice, suggesting that only a small fraction of IZUMO1 is sufficient for triggering sperm-egg fusion. We propose that the alternative splicing generating IZUMO1_v2 might function as a fail-safe in mouse for when splicing is disturbed.

Oviductal extracellular vesicles (oviductosomes, OVS) are conserved in humans: murine OVS play a pivotal role in sperm capacitation and fertility

STUDY QUESTIONS

Are extracellular vesicles (EVs) in the murine oviduct (oviductosomes, OVS) conserved in humans and do they play a role in the fertility of Pmca4-/- females?

SUMMARY ANSWER

OVS and their fertility-modulating proteins are conserved in humans, arise via the apocrine pathway, and mediate a compensatory upregulation of PMCA1 (plasma membrane Ca2+-ATPase 1) in Pmca4-/- female mice during proestrus/estrus, to account for their fertility.

WHAT IS KNOWN ALREADY

Recently murine OVS were identified and shown during proestrus/estrus to express elevated levels of PMCA4 which they can deliver to sperm. PMCA4 is the major Ca2+ efflux pump in murine sperm and Pmca4 deletion leads to loss of sperm motility and male infertility as there is no compensatory upregulation of the remaining Ca2+ pump, PMCA1. Of the four family members of PMCAs (PMCA1-4), PMCA1 and PMCA4 are ubiquitous, and to date there have been no reports of one isoform being upregulated to compensate for another in any organ/tissue. Since Pmca4-/- females are fertile, despite the abundant expression of PMCA4 in wild-type (WT) OVS, we propose that OVS serve a role of packaging and delivering to sperm elevated levels of PMCA1 in Pmca4-/- during proestrus/estrus to compensate for PMCA4's absence.

STUDY DESIGN, SIZE, DURATION

Fallopian tubes from pre-menopausal women undergoing hysterectomy were used to study EVs in the luminal fluid. Oviducts from sexually mature WT mice were sectioned after perfusion fixation to detect EVs in situ. Oviducts were recovered from WT and Pmca4-/- after hormonally induced estrus and sectioned for PMCA1 immunofluorescence (IF) (detected with confocal microscopy) and hematoxylin and eosin staining. Reproductive tissues, luminal fluids and EVs were recovered after induced estrus and after natural cycling for western blot analysis of PMCA1 and qRT-PCR of Pmca1 to compare expression levels in WT and Pmca4-/-. OVS, uterosomes, and epididymal luminal fluid were included in the comparisons. WT and Pmca4-/- OVS were analyzed for the presence of known PMCA4 partners in sperm and their ability to interact with PMCA1, via co-immunoprecipitation. In vitro uptake of PMCA1 from OVS was analyzed in capacitated and uncapacitated sperm via quantitative western blot analysis, IF localization and flow cytometry. Caudal sperm were also assayed for uptake of tyrosine-phosphorylated proteins which were shown to be present in OVS. Finally, PMCA1 and PMCA4 in OVS and that delivered to sperm were assayed for enzymatic activity.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Human fallopian tubes were flushed to recover luminal fluid which was processed for OVS via ultracentrifugation. Human OVS were negatively stained for transmission electron microscopy (TEM) and subjected to immunogold labeling, to detect PMCA4. Western analysis was used to detect HSC70 (an EV biomarker), PMCA1 and endothelial nitric oxide synthase (eNOS) which is a fertility-modulating protein delivered to human sperm by prostasomes. Oviducts of sexually mature female mice were sectioned after perfusion fixation for TEM tomography to obtain 3D information and to distinguish cross-sections of EVs from those of microvilli and cilia. Murine tissues, luminal fluids and EVs were assayed for PMCA1 (IF and western blot) or qRT-PCR. PMCA1 levels from western blots were quantified, using band densities and compared in WT and Pmca4-/- after induced estrus and in proestrus/estrus and metestrus/diestrus in cycling females. In vitro uptake of PMCA1 and tyrosine-phosphorylated proteins was quantified with flow cytometry and/or quantitative western blot. Ca2+-ATPase activity in OVS and sperm before and after PMCA1 and PMCA4 uptake was assayed, via the enzymatic hydrolysis rate of ATP.

MAIN RESULTS AND THE ROLE OF CHANCE

TEM revealed that human oviducts contain EVs (exosomal and microvesicular). These EVs contain PMCA4 (immunolabeling), eNOS and PMCA1 (western blot) in their cargo. TEM tomography showed the murine oviduct with EV-containing blebs which typify the apocrine pathway for EV biogenesis. Western blots revealed that during proestrus/estrus PMCA1 was significantly elevated in the oviductal luminal fluid (OLF) (P = 0.02) and in OVS (P = 0.03) of Pmca4-/-, compared to WT. Further, while PMCA1 levels did not fluctuate in OLF during the cycle in WT, they were significantly (P = 0.02) higher in proestrus/estrus than at metestrus/diestrus in Pmca4-/-. The elevated levels of PMCA1 in proestrus/estrus, which mimics PMCA4 in WT, is OLF/OVS-specific, and is not seen in oviductal tissues, uterosomes or epididymal luminal fluid of Pmca4-/-. However, qRT-PCR revealed significantly elevated levels of Pmca1 transcript in Pmca4-/- oviductal tissues, compared to WT. PMCA1 could be transferred from OVS to sperm and the levels were significantly higher for capacitated vs uncapacitated sperm, as assessed by flow cytometry (P = 0.001) after 3 h co-incubation, quantitative western blot (P < 0.05) and the frequency of immuno-labeled sperm (P < 0.001) after 30 min co-incubation. Tyrosine phosphorylated proteins were discovered in murine OVS and could be delivered to sperm after their co-incubation with OVS, as detected by western, immunofluorescence localization, and flow cytometry. PMCA1 and PMCA4 in OVS were shown to be enzymatically active and this activity increased in sperm after OVS interaction.

LARGE SCALE DATA

None.

LIMITATIONS REASONS FOR CAUTION

Although oviductal tissues of WT and Pmca4-/- showed no significant difference in PMCA1 levels, Pmca4-/- levels of OVS/OLF during proestrus/estrus were significantly higher than in WT. We have attributed this enrichment or upregulation of PMCA1 in Pmca4-/- partly to selective packaging in OVS to compensate for the lack of PMCA4. However, in the absence of a difference between WT and Pmca4-/- in the PMCA1 levels in oviductal tissues as a whole, we cannot rule out significantly higher PMCA1 expression in the oviductal epithelium that gives rise to the OVS as significantly higher Pmca1 transcripts were detected in Pmca4-/-.

WIDER IMPLICATIONS OF THE FINDINGS

Since OVS and fertility-modulating cargo components are conserved in humans, it suggests that murine OVS role in regulating the expression of proteins required for capacitation and fertility is also conserved. Secondly, OVS may explain some of the differences in in vivo and in vitro fertilization for mouse mutants, as seen in mice lacking the gene for FER which is the enzyme required for sperm protein tyrosine phosphorylation. Our observation that murine OVS carry and can modulate sperm protein tyrosine phosphorylation by delivering them to sperm provides an explanation for the in vivo fertility of Fer mutants, not seen in vitro. Finally, our findings have implications for infertility treatment and exosome therapeutics.

STUDY FUNDING AND COMPETING INTEREST(S)

The work was supported by National Institute of Health (RO3HD073523 and 5P20RR015588) grants to P.A.M.-D. There are no conflicts of interests.

Murine Oviductosomes (OVS) microRNA profiling during the estrous cycle: Delivery of OVS-borne microRNAs to sperm where miR-34c-5p localizes at the centrosome

Oviductosomes (OVS) are nano-sized extracellular vesicles secreted in the oviductal luminal fluid by oviductal epithelial cells and known to be involved in sperm capacitation and fertility. Although they have been shown to transfer encapsulated proteins to sperm, cargo constituents other than proteins have not been identified. Using next-generation sequencing, we demonstrate that OVS are carriers of microRNAs (miRNAs), with 272 detected throughout the estrous cycle. Of the 50 most abundant, 6 (12%) and 2 (4%) were expressed at significantly higher levels (P < 0.05) at metestrus/diestrus and proestrus/estrus. RT-qPCR showed that selected miRNAs are present in oviductal epithelial cells in significantly (P < 0.05) lower abundance than in OVS, indicating selective miRNA packaging. The majority (64%) of the top 25 OVS miRNAs are present in sperm. These miRNAs’ potential target list is enriched with transcription factors, transcription regulators, and protein kinases and there are several embryonic developmentally-related genes. Importantly, OVS can deliver to sperm miRNAs, including miR-34c-5p which is essential for the first cleavage and is solely sperm-derived in the zygote. Z-stack of confocal images of sperm co-incubated with OVS loaded with labeled miRNAs showed the intracellular location of the delivered miRNAs. Interestingly, individual miRNAs were predominantly localized in specific head compartments, with miR-34c-5p being highly concentrated at the centrosome where it is known to function. These results, for the first time, demonstrate OVS’ ability to contribute to the sperm’s miRNA repertoire (an important role for solely sperm-derived zygotic miRNAs) and the physiological relevance of an OVS-borne miRNA that is delivered to sperm.

Central and Peripheral Nervous System Progenitors Derived from Human Pluripotent Stem Cells Reveal a Unique Temporal and Cell-Type Specific Expression of PMCAs

The P-type ATPases family consists of ion and lipid transporters. Their unique diversity in function and expression is critical for normal development. In this study we investigated human pluripotent stem cells (hPSC) and different neural progenitor states to characterize the expression of the plasma membrane calcium ATPases (PMCAs) during human neural development and in mature mesencephalic dopaminergic (mesDA) neurons. Our RNA sequencing data identified a dynamic change in ATPase expression correlating with the differentiation time of the neural progenitors, which was independent of the neuronal progenitor type. Expression of ATP2B1 and ATP2B4 were the most abundantly expressed, in accordance with their main role in Ca²⁺ regulation and we observed all of the PMCAs to have a subcellular punctate localization. Interestingly in hPSCs ATP2B1 and ATP2B3 were highly expressed in a cell cycle specific manner and ATP2B2 and ATP2B4 were highly expressed in a hPSC sub-population. In neural rosettes a strong apical PMCA expression was identified in the luminal region. Lastly, we confirmed all PMCAs to be expressed in mesDA neurons, however at varying levels. Our results reveal that PMCA expression dynamically changes during stem cell differentiation and highlights the diverging needs of cell populations to regulate and properly integrate Ca²⁺ changes, which can ultimately correspond to changes in specific stem cell transcription states.

Junctional adhesion molecule A: expression in the murine epididymal tract and accessory organs and acquisition by maturing sperm

STUDY QUESTION

Is junctional adhesion molecule A (JAM-A), a sperm protein essential for normal motility, expressed in the murine post-testicular pathway and involved in sperm maturation?

SUMMARY ANSWER

JAM-A is present in the prostate and seminal vesicles and in all three regions of the epididymis where it is secreted in epididymosomes in the luminal fluid and can be delivered to sperm in vitro.

WHAT IS KNOWN ALREADY

JAM-A shares with the plasma membrane Ca2+ATPase 4 (PMCA4, the major Ca2+ efflux pump in murine sperm) a common interacting partner, CASK (Ca2+/CaM-dependent serine kinase). JAM-A, like PMCA4, plays a role in Ca2+ regulation, since deletion of Jam-A results in significantly elevated intracellular Ca2+ levels and reduced sperm motility. Recently, PMCA4 was reported to be expressed in the epididymis and along with CASK was shown to be in a complex on epididymosomes where it was transferred to sperm. Because of the association of JAM-A with CASK in sperm and because of the presence of PMCA4 and CASK in the epididymis, the present study was performed to determine whether JAM-A is expressed in the epididymis and delivered to sperm during their maturation.

STUDY DESIGN, SIZE, DURATION

The epididymides, prostate and seminal vesicles were collected from sexually mature C57BL/6J and Institute for Cancer Research mice and antibodies specific for JAM-A and Ser285 -phosphorylated JAM-A (pJAM-A) were used for the analysis. Tissues, sperm and epididymal luminal fluid (ELF) were studied. Epididymosomes were also isolated for study. Caput and caudal sperm were co-incubated with ELF individually to determine their abilities to acquire JAM-A in vitro.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Sections of all three regions of the epididymis were subjected to indirect immunofluorescence analysis. Epididymal tissues, fluid, sperm, prostate and seminal vesicle tissues were analyzed for JAM-A and/or pJAM-A via western blotting analysis. The relative amounts of JAM-A and pJAM-A among epididymal tissues, ELF and sperm were detected by western blot via quantification of band intensities. Epididymosomes were isolated by ultracentrifugation of the ELF after it was clarified to remove cells and tissue fragments, and the proteins western blotted for JAM-A and pJAM-A, and exosomal biochemical markers. FACS analysis was used to quantify the amount of JAM-A present on caput and caudal sperm, as well as the amount of JAM-A acquired in vitro after their co-incubation with ELF.

MAIN RESULTS AND THE ROLE OF CHANCE

Western blots revealed that JAM-A is expressed in all three regions of the epididymis, the prostate and seminal vesicles. As confirmed by indirect immunofluorescence, a western blot showed that JAM-A has a higher expression in the corpus and caudal regions, where it is significantly (P < 0.01) more abundant than in the caput. Both JAM-A and Ser285-phosphorylated JAM-A (pJAM-A) are secreted into the ELF where it is highest in the distal regions. In the ELF, both JAM-A and pJAM-A were detected in epididymosomes. Western blotting of sperm proteins showed a significant (P < 0.01) increase of JAM-A and pJAM-A in caudal, compared with caput, sperm. Flow-cytometric analysis confirmed the increase in JAM-A in caudal sperm where it was 1.4-fold higher than in caput ones. Co-incubation of caput and caudal sperm with ELF demonstrated ~2.3- and ~1.3-fold increases, respectively, in JAM-A levels indicating that epididymosomes transfer more JAM-A to caput sperm that are less saturated with the protein than caudal ones.

LARGE SCALE DATA

Not applicable.

LIMITATIONS, REASONS FOR CAUTION

First, although the ELF was clarified prior to ultracentrifugation for epididymosome isolation, we cannot rule out contamination of the epididymosomal proteins by those from epididymal epithelial cells. Second, the JAM-A detected in the prostate and seminal vesicles might not necessarily be secreted from those organs and may only be present within the tissues, where it would be unable to impact sperm in the ejaculate.

WIDER IMPLICATIONS OF THE FINDINGS

Although performed in the mouse the study has implications for humans, as the highly conserved JAM-A is a signaling protein in human sperm. There is physiological significance to the finding that JAM-A, which regulates sperm motility and intracellular Ca2+, exists in elevated levels in the cauda where sperm gain motility and fertilizing ability. The study suggests that the acquisition of JAM-A in the epididymal tract is involved in the mechanism by which sperm gain their motility during epididymal maturation. This increased understanding of sperm physiology is important for aspects of ART.

STUDY FUNDING AND COMPETING INTEREST(S)

The work was supported by NIH-RO3HD073523 and NIH-5P20RR015588 grants to P.A.M.-D. The authors declare there are no conflicts of interests.

Characteristics of the Epididymal Luminal Environment Responsible for Sperm Maturation and Storage

The testicular spermatozoa of all mammalian species are considered functionally immature owing to their inability to swim in a progressive manner and engage in productive interactions with the cumulus-oocyte complex. The ability to express these key functional attributes develops progressively during the cells' descent through the epididymis, a highly specialized ductal system that forms an integral part of the male reproductive tract. The functional maturation of the spermatozoon is achieved via continuous interactions with the epididymal luminal microenvironment and remarkably, occurs in the complete absence of de novo gene transcription or protein translation. Compositional analysis of the luminal fluids collected from the epididymis of a variety of species has revealed the complexity of this milieu, with a diversity of inorganic ions, proteins, and small non-coding RNA transcripts having been identified to date. Notably, both the quantitative and qualitative profile of each of these different luminal elements display substantial segment-to-segment variation, which in turn contribute to the regionalized functionality of this long tubule. Thus, spermatozoa acquire functional maturity in the proximal segments before being stored in a quiescent state in the distal segment in preparation for ejaculation. Such marked division of labor is achieved via the combined secretory and absorptive activity of the epithelial cells lining each segment. Here, we review our current understanding of the molecular mechanisms that exert influence over the unique intraluminal environment of the epididymis, with a particular focus on vesicle-dependent mechanisms that facilitate intercellular communication between the epididymal soma and maturing sperm cell population.

Dyslipidemia alters sperm maturation and capacitation in LXR-null mice

Lipid metabolism disorders (dyslipidemia) are causes of male infertility, but little is known about their impact on male gametes when considering post-testicular maturation events, given that studies concentrate most often on endocrine dysfunctions and testicular consequences. In this study, three-month-old wild-type (wt) and Liver-X-Receptors knock out (Lxrα;β−/−) males were fed four weeks with a control or a lipid-enriched diet containing 1.25% cholesterol (high cholesterol diet (HCD)). The HCD triggered a dyslipidemia leading to sperm post-testicular alterations and infertility. Sperm lipids were analyzed by LC–MS and those fromLxrα;β−/−males fed the HCD showed higher chol/PL and PC/PE ratios compared towt-HCD (P < 0.05) and lower oxysterol contents compared to wt (P < 0.05) orLxrα;β−/−(P < 0.05). These modifications impaired membrane-associated events triggering the tyrosine phosphorylation normally occurring during the capacitation process, as shown by phosphotyrosine Western blots. Using flow cytometry, we showed that a smaller subpopulation of spermatozoa fromLxrα;β−/−-HCD males could raise their membrane fluidity during capacitation (P < 0.05 vswtorwt-HCD) as well as their intracellular calcium concentration (P < 0.05 vsLxrα;β−/−andP < 0.001 vswt). The accumulation of the major sperm calcium efflux pump (PMCA4) was decreased inLxrα;β−/−males fed the HCD (P < 0.05 vsLxrα;β−/−andP < 0.001 vswt). This study is the first showing an impact of dyslipidemia on post-testicular sperm maturation with consequences on the capacitation signaling cascade. It may lead to the identification of fertility prognostic markers in this pathophysiological situation, which could help clinicians to better understand male infertilities which are thus far classified as idiopathic.

The serum protein renalase reduces injury in experimental pancreatitis

Acute pancreatitis is a disease associated with inflammation and tissue damage. One protein that protects against acute injury, including ischemic injury to both the kidney and heart, is renalase, which is secreted into the blood by the kidney and other tissues. However, whether renalase reduces acute injury associated with pancreatitis is unknown. Here, we used both in vitro and in vivo murine models of acute pancreatitis to study renalase's effects on this condition. In isolated pancreatic lobules, pretreatment with recombinant human renalase (rRNLS) blocked zymogen activation caused by cerulein, carbachol, and a bile acid. Renalase also blocked cerulein-induced cell injury and histological changes. In the in vivo cerulein model of pancreatitis, genetic deletion of renalase resulted in more severe disease, and administering rRNLS to cerulein-exposed WT mice after pancreatitis onset was protective. Because pathological increases in acinar cell cytosolic calcium levels are central to the initiation of acute pancreatitis, we also investigated whether rRNLS could function through its binding protein, plasma membrane calcium ATPase 4b (PMCA4b), which excretes calcium from cells. We found that PMCA4b is expressed in both murine and human acinar cells and that a PMCA4b-selective inhibitor worsens pancreatitis-induced injury and blocks the protective effects of rRNLS. These findings suggest that renalase is a protective plasma protein that reduces acinar cell injury through a plasma membrane calcium ATPase. Because exogenous rRNLS reduces the severity of acute pancreatitis, it has potential as a therapeutic agent.

The Plasma Membrane Calcium ATPases and Their Role as Major New Players in Human Disease

The Ca²⁺ extrusion function of the four mammalian isoforms of the plasma membrane calcium ATPases (PMCAs) is well established. There is also ever-increasing detail known of their roles in global and local Ca²⁺ homeostasis and intracellular Ca²⁺ signaling in a wide variety of cell types and tissues. It is becoming clear that the spatiotemporal patterns of expression of the PMCAs and the fact that their abundances and relative expression levels vary from cell type to cell type both reflect and impact on their specific functions in these cells. Over recent years it has become increasingly apparent that these genes have potentially significant roles in human health and disease, with PMCAs1-4 being associated with cardiovascular diseases, deafness, autism, ataxia, adenoma, and malarial resistance. This review will bring together evidence of the variety of tissue-specific functions of PMCAs and will highlight the roles these genes play in regulating normal physiological functions and the considerable impact the genes have on human disease.

Plasma membrane calcium ATPase 4 (PMCA4) co-ordinates calcium and nitric oxide signaling in regulating murine sperm functional activity

Reduced sperm motility (asthenospermia) and resulting infertility arise from deletion of the Plasma Membrane Ca²⁺ -ATPase 4 (Pmca4) gene which encodes the highly conserved Ca²⁺ efflux pump, PMCA4. This is the major Ca²⁺ clearance protein in murine sperm. Since the mechanism underlying asthenospermia in PMCA4's absence or reduced activity is unknown, we investigated if sperm PMCA4 negatively regulates nitric oxide synthases (NOSs) and when absent NO, peroxynitrite, and oxidative stress levels are increased. Using co-immunoprecipitation (Co-IP) and Fluorescence Resonance Energy Transfer (FRET), we show an association of PMCA4 with the NOSs in elevated cytosolic [Ca²⁺ ] in capacitated and Ca²⁺ ionophore-treated sperm and with neuronal (nNOS) at basal [Ca²⁺ ] (ucapacitated sperm). FRET efficiencies for PMCA4-eNOS were 35% and 23% in capacitated and uncapacitated sperm, significantly (p < 0.01) different, with the molecules being <10 nm apart. For PMCA4-nNOS, this interaction was seen only for capacitated sperm where FRET efficiency was 24%, significantly (p < 0.05) higher than in uncapacitated sperm (6%). PMCA4 and the NOSs were identified as interacting partners in a quaternary complex that includes Caveolin1, which co-immunoprecipitated with eNOS in a Ca²⁺ -dependent manner. In Pmca4^-/- sperm NOS activity was elevated twofold in capacitated/uncapacitated sperm (vs. wild-type), accompanied by a twofold increase in peroxynitrite levels and significantly (p < 0.001) increased numbers of apoptotic germ cells. The data support a quaternary complex model in which PMCA4 co-ordinates Ca²⁺ and NO signaling to maintain motility, with increased NO levels resulting in asthenospermia in Pmca4^-/- males. They suggest the involvement of PMCA4 mutations in human asthenospermia, with diagnostic relevance.

Effectiveness of a walnut-enriched diet on murine sperm: involvement of reduced peroxidative damage

A walnut supplement for a Western-style diet in men was shown to improve sperm motility, vitality, and morphology. To gain further insights into factors underlying this improvement, we administered a parallel walnut-enriched diet to mice [including those with a defect in sperm motility due to deletion of Plasma Membrane Ca²⁺-ATPase 4 (Pmca4^-/- )] to determine if there is a similar improvement that is accompanied by reduced sperm membrane peroxidative damage. Although sperm vitality and acrosome reaction rate were unaffected, the diet led to a significant improvement in motility (P < 0.05) and morphology (P < 0.04) in wild-type sperm and in morphology (P < 0.01) in Pmca4^-/- , confirming the diet's efficacy, which appeared to be more modest in mice than in humans. In both strains of mice, the diet resulted in a significant decrease in sperm lipid peroxidation (oxidative stress) levels, but did not rescue the significantly increased apoptotic levels seen in the testis and epididymis of Pmca4 nulls. Our findings support the effectiveness of walnuts on sperm quality, associated with reduced peroxidative damage; and suggest that oxidative stress is involved in the mechanism(s) underlying male reproductive defects in Pmca4^-/- .

Epididymosomes: transfer of fertility-modulating proteins to the sperm surface

A variety of glycosylphosphatidylinositol (GPI)-linked proteins are acquired on spermatozoa from epididymal luminal fluids (ELF) during sperm maturation. These proteins serve roles in immunoprotection and in key steps of fertilization such as capacitation, acrosomal exocytosis and sperm-egg interactions. Their acquisition on sperm cells is mediated both by membrane vesicles (epididymosomes, EP) which were first reported to dock on the sperm surface, and by lipid carriers which facilitate the transfer of proteins associated with the membrane-free fraction of ELF. While the nonvesicular fraction is more efficient, both pathways are dependent on hydrophobic interactions between the GPI-anchor and the external lipid layer of the sperm surface. More recently proteomic and hypothesis-driven studies have shown that EP from several mammals carry transmembrane (TM) proteins, including plasma membrane Ca 2 + -ATPase 4 (PMCA4). Synthesized in the testis, PMCA4 is an essential protein and the major Ca 2 + efflux pump in murine spermatozoa. Delivery of PMCA4 to spermatozoa from bovine and mouse EP during epididymal maturation and in vitro suggests that the docking of EP on the sperm surface precedes fusion, and experimental evidence supports a fusogenic mechanism for TM proteins. Fusion is facilitated by CD9, which generates fusion-competent sites on membranes. On the basis of knowledge of PMCA4's interacting partners a number of TM and membrane-associated proteins have been identified or are predicted to be present, in the epididymosomal cargo deliverable to spermatozoa. These Ca 2 + -dependent proteins, undetected in proteomic studies, play essential roles in sperm motility and fertility, and their detection highlights the usefulness of the hypothesis-driven approach.

Plasma membrane Ca2+-ATPase 4: interaction with constitutive nitric oxide synthases in human sperm and prostasomes which carry Ca2+/CaM-dependent serine kinase

Deletion of the gene encoding the widely conserved plasma membrane calcium ATPase 4 (PMCA4), a major Ca(2+) efflux pump, leads to loss of sperm motility and male infertility in mice. PMCA4's partners in sperm and how its absence exerts its effect on fertility are unknown. We hypothesize that in sperm PMCA4 interacts with endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS) which are rapidly activated by Ca(2+), and that these fertility-modulating proteins are present in prostasomes, which deliver them to sperm. We show that in human sperm PMCA4 is present on the acrosome, inner acrosomal membrane, posterior head, neck, midpiece and the proximal principal piece. PMCA4 localization showed inter- and intra-individual variation and was most abundant at the posterior head/neck junction, co-localizing with NOSs. Co-immunoprecipitations (Co-IP) revealed a close association of PMCA4 and the NOSs in Ca(2+) ionophore-treated sperm but much less so in uncapacitated untreated sperm. Fluorescence resonance energy transfer (FRET) showed a similar Ca(2+)-related association: PMCA4 and the NOSs are within 10 nm apart, and preferentially so in capacitated, compared with uncapacitated, sperm. FRET efficiencies varied, being significantly (P < 0.001) higher at high cytosolic Ca(2+) concentration ([Ca(2+)]c) in capacitated sperm than at low [Ca(2+)]c in uncapacitated sperm for the PMCA4-eNOS complex. These dynamic interactions were not seen for PMCA4-nNOS complexes, which had the highest FRET efficiencies. Further, along with Ca(2+)/CaM-dependent serine kinase (CASK), PMCA4 and the NOSs are present in the seminal plasma, specifically in prostasomes where Co-IP showed complexes similar to those in sperm. Finally, flow cytometry demonstrated that following co-incubation of sperm and seminal plasma, PMCA4 and the NOSs can be delivered in vitro to sperm via prostasomes. Our findings indicate that PMCA4 interacts simultaneously with the NOSs preferentially at high [Ca(2+)]c in sperm to down-regulate them, and thus prevent elevated levels of NO, known to induce asthenozoospermia via oxidative stress. Our studies point to the potential underlying cause of infertility in PMCA4's absence, and suggest that inactivating mutations of PMCA4 could lead to asthenozoospermia and human infertility. Screening for these mutations may serve both diagnostic and therapeutic purposes.

Oviductosome-Sperm Membrane Interaction in Cargo Delivery: DETECTION OF FUSION AND UNDERLYING MOLECULAR PLAYERS USING THREE-DIMENSIONAL SUPER-RESOLUTION STRUCTURED ILLUMINATION MICROSCOPY (SR-SIM)

Oviductosomes ((OVS), exosomes/microvesicles), which deliver the Ca(2+) efflux pump, plasma membrane Ca(2+)ATPase 4 (PMCA4), to sperm are likely to play an important role in sperm fertilizing ability (Al-Dossary, A. A., Strehler, E. E., and Martin-DeLeon, P. A. (2013) PloS one 8, e80181). It is unknown how exosomes/microvesicles deliver transmembrane proteins such as PMCA4 to sperm. Here we define a novel experimental approach for the assessment of the interaction of OVS with sperm at a nanoscale level, using a lipophilic dye (FM4-64FX) and three-dimensional SR/SIM, which has an 8-fold increase in volumetric resolution, compared with conventional confocal microscopy. Coincubation assays detected fusion of prelabeled OVS with sperm, primarily over the head and midpiece. Immunofluorescence revealed oviductosomal delivery of PMCA4a to WT and Pmca4 KO sperm, and also endogenous PMCA4a on the inner acrosomal membrane. Fusion was confirmed by transmission immunoelectron microscopy, showing immunogold particles in OVS, and fusion stalks on sperm membrane. Immunofluorescence colocalized OVS with the αv integrin subunit which, along with CD9, resides primarily on the sperm head and midpiece. In capacitated and acrosome reacted sperm, fusion was significantly (p < 0.001) inhibited by blocking integrin/ligand interactions via antibodies, exogenous ligands (vitronectin and fibronectin), and their RGD recognition motif. Our results provide evidence that receptor/ligand interactions, involving αvβ3 and α5β1integrins on sperm and OVS, facilitate fusion of OVS in the delivery of transmembrane proteins to sperm. The mechanism uncovered is likely to be also involved in cargo delivery of prostasomes, epididymosomes, and uterosomes.

ATPases, ion exchangers and human sperm motility

Human sperm has several mechanisms to control its ionic milieu, such as the Na,K-ATPase (NKA), the Ca-ATPase of the plasma membrane (PMCA), the Na+/Ca2+-exchanger (NCX) and the Na+/H+-exchanger (NHE). On the other hand, the dynein-ATPase is the intracellular motor for sperm motility. In this work, we evaluated NKA, PMCA, NHE, NCX and dynein-ATPase activities in human sperm and investigated their correlation with sperm motility. Sperm motility was measured by Computer Assisted Semen Analysis. It was found that the NKA activity is inhibited by ouabain with twoKi(7.9×10−9and 9.8×10−5 M), which is consistent with the presence of two isoforms of α subunit of the NKA in the sperm plasma membranes (α1 and α4), being α4 more sensitive to ouabain. The decrease in NKA activity is associated with a reduction in sperm motility. In addition, sperm motility was evaluated in the presence of known inhibitors of NHE, PMCA and NCX, such as amiloride, eosin, and KB-R7943, respectively, as well as in the presence of nigericin after incubation with ouabain. Amiloride, eosin and KB-R7943 significantly reduced sperm motility. Nigericin reversed the effect of ouabain and amiloride on sperm motility. Dynein-ATPase activity was inhibited by acidic pH and micromolar concentrations of Ca2+. We explain our results in terms of inhibition of the dynein-ATPase in the presence of higher cytosolic H+and Ca2+, and therefore inhibition of sperm motility.

Hyaluronidase 2: a novel germ cell hyaluronidase with epididymal expression and functional roles in mammalian sperm

To initiate the crucial cell adhesion events necessary for fertilization, sperm must penetrate extracellular matrix barriers containing hyaluronic acid (HA), a task thought to be accomplished by neutral-active hyaluronidases. Here we report that the ~57 kDa hyaluronidase 2 (HYAL2) that in somatic tissues has been highly characterized to be acid-active is present in mouse and human sperm, as detected by Western blot, flow cytometric, and immunoprecipitation assays. Immunofluorescence revealed its presence on the plasma membrane over the acrosome, the midpiece, and proximal principal piece in mice where protein fractionation demonstrated a differential distribution in subcellular compartments. It is significantly more abundant in the acrosome-reacted (P = 0.04) and soluble acrosomal fractions (P = 0.006) (microenvironments where acid-active hyaluronidases function) compared to that of the plasma membrane where neutral hyaluronidases mediate cumulus penetration. Using HA substrate gel electrophoresis, immunoprecipitated HYAL 2 was shown to have catalytic activity at pH 4.0. Colocalization and coimmunoprecipitation assays reveal that HYAL2 is associated with its cofactor, CD44, consistent with CD44-dependent HYAL2 activity. HYAL2 is also present throughout the epididymis, where Hyal2 transcripts were detected, and in the epididymal luminal fluids. In vitro assays demonstrated that HYAL2 can be acquired on the sperm membrane from epididymal luminal fluids, suggesting that it plays a role in epididymal maturation. Because similar biphasic kinetics are seen for HYAL2 and SPAM1 (Sperm adhesion molecule 1), it is likely that HYAL2 plays a redundant role in the catalysis of megadalton HA to its 20 kDa intermediate during fertilization.

Expression and secretion of plasma membrane Ca2+-ATPase 4a (PMCA4a) during murine estrus: association with oviductal exosomes and uptake in sperm

PMCA4, a membrane protein, is the major Ca²⁺ efflux pump in murine sperm where its deletion leads to a severe loss of hyperactivated motility and to male infertility. We have previously shown that the PMCA4b splice variant interacts with CASK (Ca^2+/CaM-dependent serine kinase) in regulating sperm Ca²⁺. More recently we detected that PMCA4a isoform, in addition to its presence in testis, is secreted in the epididymal luminal fluid and transferred to sperm. Here we show that Pmca4 mRNA is expressed in both the 4a and 4b variants in the vagina, uterus, and oviduct. Immunofluorescence reveals that PMCA4a is similarly expressed and is elevated during estrus, appearing in the glandular and luminal epithelia. Western analysis detected PMCA4a in all tissues and in the luminal fluids (LF) of the vagina (VLF), uterus (ULF), and the oviduct (OLF) collected during estrus. It was ~9- and 4-fold higher in OLF than in VLF and ULF, and only marginally present in LF collected at metestrus/diestrus. Fractionation of the LF collected at estrus, via ultracentrifugation, revealed that 100% of the PMCA4a resides in the vesicular fraction of the ULF and OLF. Transmission electron microscopy (TEM) revealed that OLF vesicles have an exosomal orientation (with the cytoplasmic-side inward), a size range of 25-100 nm, with the characteristic CD9 biomarker. Thus, we dubbed these vesicles “oviductosomes”, to which PMCA4a was immunolocalized. Incubation of caudal sperm in the combined LF or exosomes resulted in up to a ~3-fold increase of sperm PMCA4a, as detected by flow cytometry, indicating in vitro uptake. Our results are consistent with the increased requirement of Ca²⁺ efflux in the oviduct. They show for the first time the presence of oviductal exosomes and highlight their role, along with uterosomes and vaginal exosomes, in post-testicular sperm acquisition of PMCA4a which is essential for hyperactivated motility and fertility.