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Contreras RG, Torres-Carrillo A, Flores-Maldonado C, Shoshani L, Ponce A. Na +/K +-ATPase: More than an Electrogenic Pump. Int J Mol Sci 2024; 25:6122. [PMID: 38892309 PMCID: PMC11172918 DOI: 10.3390/ijms25116122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 05/20/2024] [Accepted: 05/23/2024] [Indexed: 06/21/2024] Open
Abstract
The sodium pump, or Na+/K+-ATPase (NKA), is an essential enzyme found in the plasma membrane of all animal cells. Its primary role is to transport sodium (Na+) and potassium (K+) ions across the cell membrane, using energy from ATP hydrolysis. This transport creates and maintains an electrochemical gradient, which is crucial for various cellular processes, including cell volume regulation, electrical excitability, and secondary active transport. Although the role of NKA as a pump was discovered and demonstrated several decades ago, it remains the subject of intense research. Current studies aim to delve deeper into several aspects of this molecular entity, such as describing its structure and mode of operation in atomic detail, understanding its molecular and functional diversity, and examining the consequences of its malfunction due to structural alterations. Additionally, researchers are investigating the effects of various substances that amplify or decrease its pumping activity. Beyond its role as a pump, growing evidence indicates that in various cell types, NKA also functions as a receptor for cardiac glycosides like ouabain. This receptor activity triggers the activation of various signaling pathways, producing significant morphological and physiological effects. In this report, we present the results of a comprehensive review of the most outstanding studies of the past five years. We highlight the progress made regarding this new concept of NKA and the various cardiac glycosides that influence it. Furthermore, we emphasize NKA's role in epithelial physiology, particularly its function as a receptor for cardiac glycosides that trigger intracellular signals regulating cell-cell contacts, proliferation, differentiation, and adhesion. We also analyze the role of NKA β-subunits as cell adhesion molecules in glia and epithelial cells.
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Affiliation(s)
| | | | | | | | - Arturo Ponce
- Department of Physiology, Biophysics and Neurosciences, CINVESTAV-IPN, Mexico City 07360, Mexico; (R.G.C.); (A.T.-C.); (C.F.-M.); (L.S.)
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Maňásková-Postlerová P, Davidová N, Sulc M, Philimonenko A, Hozák P, Jonáková V. Reproductive tissue expression and sperm localization of porcine beta-microseminoprotein. Cell Tissue Res 2011; 344:341-53. [PMID: 21384183 DOI: 10.1007/s00441-011-1149-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Accepted: 02/07/2011] [Indexed: 11/28/2022]
Abstract
Beta-microseminoprotein (MSP) is a predominant protein of human seminal plasma and originates from prostate secretions. MSP from boar seminal plasma has been sequenced and shows only 50%-52% homology with that of human. Porcine MSP is synthesized by the post-natal prostate gland and is identical with the sperm motility inhibitor. Although MSP is a protein characteristic of the prostate gland, we have established the presence of its mRNA transcript not only in boar prostate but also in other reproductive organ tissues. In extracts of all these organs, specific polyclonal antiMSP antibody recognizes a 12-kDa protein band identified by mass spectrometry as MSP. Immunofluorescence (IMF) has revealed the occurrence of MSP in the epithelial tissue of the prostate, epididymis, seminal vesicles and Cowper's glands. MSP has been localized on epididymal spermatozoa in the acrosomal region and on the flagellum of ejaculated spermatozoa. The absence of MSP on the surface of capacitated spermatozoa together with the antibody detection of MSP in the sperm acidic extract after in vitro capacitation indicates its acrosomal origin. Additionally, MSP has been localized by IMF in the sperm acrosome in capacitated spermatozoa with a permeabilized plasma membrane and by electron microscopy in ejaculated spermatozoa. The function of MSP in seminal plasma and spermatozoa is not fully understood. Nevertheless, the secretion of porcine MSP by various reproductive organs indicates its multiple roles in the reproductive process. For the first time in mammalian species, MSP has been localized in various physiological stages of sperm.
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Kumar A, Jagtap DD, Mahale SD, Kumar M. Crystal structure of prostate secretory protein PSP94 shows an edge-to-edge association of two monomers to form a homodimer. J Mol Biol 2010; 397:947-56. [PMID: 20184897 DOI: 10.1016/j.jmb.2010.02.035] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2009] [Revised: 02/17/2010] [Accepted: 02/18/2010] [Indexed: 12/17/2022]
Abstract
Several recent genome-wide association studies have linked the human MSMB gene, encoding prostate secretory protein of 94 residues (PSP94), with prostate cancer susceptibility. PSP94 is one of the most abundant proteins from prostatic secretions and a primary constituent of human semen. PSP94 suppresses tumor growth and metastasis, and its expression gradually decreases during progression of the prostate cancer. It is a rapidly evolving protein with homologues present in several species with 10 conserved cysteine residues. PSP94 homologues show high-affinity binding with different proteins from the cysteine-rich secretory protein family, some of which have been shown to be ion channel blockers. Here, we report the crystal structure of human PSP94 at 2.3 A resolution. The structure shows that the amino and the carboxyl ends of the polypeptide chain are held in close proximity facing each other. A strong hydrogen bond between these ends, which are located respectively on the first and the last beta-strands, leads to formation of an almost straight edge in PSP94 structure. Crystal structure shows that these edges from two PSP94 monomers associate in antiparallel fashion, leading to formation of a dimer. Our studies further show that dimers dissociate into monomers at acidic pH, possibly through distortion of the straight edge. Further, based on several observations, we propose that PSP94 binds to cysteine-rich secretory proteins and immunoglobulin G through the same edge, which is involved in the formation of PSP94 dimeric interface.
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Affiliation(s)
- Ashwani Kumar
- High Pressure Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
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Kumar V, Roske Y, Singh N, Heinemann U, Singh TP, Yadav S. Purification and preliminary X-ray crystallographic studies of beta-microseminoprotein from human seminal plasma. Acta Crystallogr Sect F Struct Biol Cryst Commun 2009; 65:518-21. [PMID: 19407392 DOI: 10.1107/s1744309109013670] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2009] [Accepted: 04/11/2009] [Indexed: 11/11/2022]
Abstract
beta-Microseminoprotein (beta-MSP) is a small cysteine-rich protein with a molecular mass of 10 kDa. It was first isolated from human seminal plasma and has subsequently been identified from several species. Comparison of the amino-acid sequences of beta-MSP proteins suggests that the protein is a rapidly evolving protein. The function of beta-MSP is poorly understood. Furthermore, no crystal structure has been reported of any beta-MSP; therefore, determination of the crystal structure of beta-MSP is the foremost task in order to understand the function of this protein completely. Here, the purification, crystallization and preliminary X-ray diffraction analysis of beta-MSP from human seminal plasma are described. The protein was purified using anion-exchange and size-exclusion chromatography and the purified protein was crystallized using 0.1 M ammonium sulfate, 0.1 M HEPES buffer pH 7.0 and 20%(w/v) PEG 3350. The crystals belonged to the tetragonal space group P4(3)22 and contained three beta-MSP molecules in the asymmetric unit. X-ray intensity data were collected to 2.4 A resolution.
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Affiliation(s)
- Vijay Kumar
- Department of Biophysics, All India Institute of Medical Sciences, New Delhi, India
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Kumar M, Jagtap DD, Mahale SD, Prashar V, Kumar A, Das A, Bihani SC, Ferrer JL, Hosur MV, Ramanadham M. Crystallization and preliminary X-ray diffraction analysis of human seminal plasma protein PSP94. Acta Crystallogr Sect F Struct Biol Cryst Commun 2009; 65:389-91. [PMID: 19342788 PMCID: PMC2664768 DOI: 10.1107/s1744309109008549] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2009] [Accepted: 03/09/2009] [Indexed: 11/10/2022]
Abstract
The human seminal plasma protein PSP94 is a small protein of 94 residues that contains ten cysteines. Since its discovery about 25 years ago, several potential biological functions have been reported for this protein. Many PSP94 homologues have also been identified since then from various species, but no crystal structure has been determined to date. PSP94 has been purified from human seminal plasma and crystallized. These crystals diffracted to approximately 2.3 A resolution and belonged to space group P4(1)2(1)2, with unit-cell parameters a = 107.9, b = 107.9, c = 92.1 A. There are four molecules in the asymmetric unit. Structure solution by the heavy-atom method is currently in progress.
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Affiliation(s)
- Mukesh Kumar
- Solid State Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India.
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Anahí Franchi N, Avendaño C, Molina RI, Tissera AD, Maldonado CA, Oehninger S, Coronel CE. beta-Microseminoprotein in human spermatozoa and its potential role in male fertility. Reproduction 2008; 136:157-66. [PMID: 18469041 DOI: 10.1530/rep-08-0032] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
beta-Microseminoprotein (MSMB) is one of the most abundant proteins in human seminal plasma. The objectives of this study were: (1) to purify MSMB from seminal plasma (SP) and generate antibodies against the pure protein; (2) to investigate the interaction of MSMB with ejaculated spermatozoa and its possible effect on the spontaneous acrosome reaction (AR); and (3) to quantify MSMB content in SP and examine its relationship with the clinical sperm parameters. MSMB was purified from SP and its presence on the sperm surface was examined by indirect immunofluorescence using a specific polyclonal antibody. The effect of MSMB on the AR was evaluated using guinea pig epididymal spermatozoa as a model. MSMB quantification assay was performed with a two-site binding ELISA using two polyclonal antibodies against MSMB. MSMB was assessed in semen samples from fertile donors (controls) and subfertile patients according to World Health Organization criteria. MSMB was detected on the sperm surface and mainly localized to the acrosomal region of the head and neck. A significant spontaneous AR inhibition was observed when guinea pig epididymal spermatozoa were preincubated with MSMB. Finally, MSMB was significantly increased in subfertile patients when compared with fertile controls (P<0.02). The association of MSMB to the sperm surface, the inhibitor effect on the spontaneous AR and the increased MSMB levels found in SP in subfertile men suggests a relationship between this protein and semen quality and a possible role in the process of fertilization.
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Affiliation(s)
- N Anahí Franchi
- Laboratorio de Bioquímica y Biología Reproductiva, Instituto de Ciencia y Tecnología de Alimentos, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Córdoba 5000, Argentina.
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Aoki N, Sakiyama A, Deshimaru M, Terada S. Identification of novel serum proteins in a Japanese viper: Homologs of mammalian PSP94. Biochem Biophys Res Commun 2007; 359:330-4. [PMID: 17543280 DOI: 10.1016/j.bbrc.2007.05.091] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2007] [Accepted: 05/16/2007] [Indexed: 11/15/2022]
Abstract
Three small serum proteins (SSP-1, -2, and -3), with molecular masses of 6.5-10kDa, were isolated from Habu (Trimeresurus flavoviridis) serum, and the amino acid sequences were determined by protein and cDNA analysis. Despite only limited sequence identity to any mammalian prostatic secretory protein of 94 amino acids (PSP94), all of the Cys residues in these SSPs were well conserved. SSPs are the first PSP94 family proteins to be identified in reptiles. SSP-1 and -3 weakly inhibited the proteolytic activity of a snake venom metalloproteinase. On the other hand, SSP-2 formed a tight complex with triflin, a snake venom-derived Ca(2+) channel blocker that suppresses the smooth muscle contraction. This suggests a role for SSP-2 in the self defense system of venomous snakes.
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Affiliation(s)
- Narumi Aoki
- Department of Chemistry, Faculty of Science, Fukuoka University, 8-19-1 Nanakuma, Fukuoka, Japan
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Jagtap DD, Narahari A, Swamy MJ, Mahale SD. Disulphide bond reduction and S-carboxamidomethylation of PSP94 affects its conformation but not the ability to bind immunoglobulin. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2007; 1774:723-31. [PMID: 17493883 DOI: 10.1016/j.bbapap.2007.03.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2007] [Revised: 03/20/2007] [Accepted: 03/30/2007] [Indexed: 12/17/2022]
Abstract
Prostate secretory protein of 94 amino acids (PSP94) is a small non-glycosylated, cysteine rich protein with a molecular mass of 10 kDa. It has also been referred to as beta-microseminoprotein (beta-MSP) and proteins homologous to it have been reported in a number of species. Comparison of the amino acid sequence of these proteins suggests that, it is a rapidly evolving protein. However, all the ten cysteine residues are well conserved in these homologues, indicating their possible role in maintaining the structure and function of these proteins. In the present study, PSP94 was purified from human seminal plasma and characterized further and it showed the presence of five disulfide bonds. Reduction of disulphide bonds of PSP94 led to significant changes in the secondary and tertiary structure of PSP94. CD of disulphide bond reduced PSP94 indicates an overall decrease in the beta sheet content from 79.8% to 46.4%. Tertiary structural changes as monitored by fluorescence quenching reveal that reduction of disulphide bonds of PSP94 followed by the modification of the free thiol groups leads to complete exposure of Trp32 and Trp92 and that one or more side chain carboxyl groups move closer to their indole side chains. Antibodies against native and modified PSP94 demonstrated that the changes following reduction of disulphide linkages are within the immunodominant region of the protein. Changes induced in the functional properties of PSP94, if any, by modification were investigated with respect to IgG binding as PSP94 has been reported to be similar to immunoglobulin binding factor purified from seminal plasma. A novel finding from this study is that both native PSP94 as well as modified protein have the ability to bind human IgG, suggesting the involvement of sequential epitopes of PSP94 in IgG binding.
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Affiliation(s)
- Dhanashree D Jagtap
- Division of Structural Biology, National Institute for Research in Reproductive Health (Indian Council of Medical Research), Jehangir Merwanji Street, Parel, Mumbai-400012, India
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Ghasriani H, Teilum K, Johnsson Y, Fernlund P, Drakenberg T. Solution Structures of Human and Porcine β-Microseminoprotein. J Mol Biol 2006; 362:502-15. [PMID: 16930619 DOI: 10.1016/j.jmb.2006.07.029] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2006] [Revised: 07/10/2006] [Accepted: 07/13/2006] [Indexed: 11/21/2022]
Abstract
Beta-microseminoprotein (MSP) is a small cysteine-rich protein (molecular mass about 10 kDa) first isolated from human seminal plasma and later identified in several other organisms. The function of MSP is not known, but a recent study has shown MSP to bind CRISP-3, a protein present in neutrophilic granulocytes. The amino acid sequence is highly variable between species raising the question of the evolutionary conservation of the 3D structure. Here we present NMR solution structures of both the human and the porcine MSP. The two proteins (sequence identity 51%) have a very similar 3D structure with the secondary structure elements well conserved and with most of the amino acid substitutions causing a change of charge localized to one side of the molecule. MSP is a beta-sheet-rich protein with two distinct domains. The N-terminal domain is composed of a four-stranded beta-sheet, with the strands arranged according to the Greek key-motif, and a less structured part. The C-terminal domain contains two two-stranded beta-sheets with no resemblance to known structural motifs. The two domains, connected to each other by the peptide backbone, one disulfide bond, and interactions between the N and C termini, are oriented to give the molecule a rather extended structure. This global fold differs markedly from that of a previously published structure for porcine MSP, in which the two domains have an entirely different orientation to each other. The difference probably stems from a misinterpretation of ten specific inter-domain NOEs.
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Affiliation(s)
- Houman Ghasriani
- Department of Biophysical Chemistry, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
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Clark NL, Swanson WJ. Pervasive adaptive evolution in primate seminal proteins. PLoS Genet 2006; 1:e35. [PMID: 16170411 PMCID: PMC1201370 DOI: 10.1371/journal.pgen.0010035] [Citation(s) in RCA: 136] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2005] [Accepted: 08/04/2005] [Indexed: 11/30/2022] Open
Abstract
Seminal fluid proteins show striking effects on reproduction, involving manipulation of female behavior and physiology, mechanisms of sperm competition, and pathogen defense. Strong adaptive pressures are expected for such manifestations of sexual selection and host defense, but the extent of positive selection in seminal fluid proteins from divergent taxa is unknown. We identified adaptive evolution in primate seminal proteins using genomic resources in a tissue-specific study. We found extensive signatures of positive selection when comparing 161 human seminal fluid proteins and 2,858 prostate-expressed genes to those in chimpanzee. Seven of eight outstanding genes yielded statistically significant evidence of positive selection when analyzed in divergent primates. Functional clues were gained through divergent analysis, including several cases of species-specific loss of function in copulatory plug genes, and statistically significant spatial clustering of positively selected sites near the active site of kallikrein 2. This study reveals previously unidentified positive selection in seven primate seminal proteins, and when considered with findings in Drosophila, indicates that extensive positive selection is found in seminal fluid across divergent taxonomic groups. Proteins found in seminal fluid accompanying sperm show dramatic effects on reproduction, such as manipulating female behavior. Even in primates they participate in competition between sperm of different males, and serve to protect sperm from infection by pathogens. These types of roles require the proteins to constantly adapt to stay ahead of the competition. Such adaptive pressures on proteins leave characteristic signatures in the DNA sequences that encode them. The authors used these signatures to identify adaptive evolution in primate seminal proteins and found extensive signs of adaptation when comparing thousands of seminal genes between human and chimpanzee. They further characterized outstanding genes in several primate species, including a diversity of apes and monkeys. Several of these proteins have no known function, yet by visualizing the adaptation on their three-dimensional surfaces, the authors uncovered clues to what is driving their evolution. In addition, they found several cases in which certain species lost their functional copies of these genes. Interestingly, species that showed loss of function do not participate in sperm competition. Past studies found widespread adaptation in fruit fly seminal fluid, and this study reveals extensive adaptation in primate seminal proteins. Could this be a phenomenon common among animals?
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Affiliation(s)
- Nathaniel L Clark
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA.
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