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Kordowitzki P, Kranc W, Bryl R, Kempisty B, Skowronska A, Skowronski MT. The Relevance of Aquaporins for the Physiology, Pathology, and Aging of the Female Reproductive System in Mammals. Cells 2020; 9:cells9122570. [PMID: 33271827 PMCID: PMC7760214 DOI: 10.3390/cells9122570] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 11/23/2020] [Accepted: 11/29/2020] [Indexed: 12/26/2022] Open
Abstract
Aquaporins constitute a group of water channel proteins located in numerous cell types. These are pore-forming transmembrane proteins, which mediate the specific passage of water molecules through membranes. It is well-known that water homeostasis plays a crucial role in different reproductive processes, e.g., oocyte transport, hormonal secretion, completion of successful fertilization, blastocyst formation, pregnancy, and birth. Further, aquaporins are involved in the process of spermatogenesis, and they have been reported to be involved during the storage of spermatozoa. It is noteworthy that aquaporins are relevant for the physiological function of specific parts in the female reproductive system, which will be presented in detail in the first section of this review. Moreover, they are relevant in different pathologies in the female reproductive system. The contribution of aquaporins in selected reproductive disorders and aging will be summarized in the second section of this review, followed by a section dedicated to aquaporin-related proteins. Since the relevance of aquaporins for the male reproductive system has been reviewed several times in the recent past, this review aims to provide an update on the distribution and impact of aquaporins only in the female reproductive system. Therefore, this paper seeks to determine the physiological and patho-physiological relevance of aquaporins on female reproduction, and female reproductive aging.
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Affiliation(s)
- Paweł Kordowitzki
- Department of Basic and Preclinical Sciences, Institute for Veterinary Medicine, Nicolaus Copernicus University, 87-100 Torun, Poland;
- Institute of Animal Reproduction and Food Research of Polish Academy of Sciences, 10-243 Olsztyn, Poland
| | - Wiesława Kranc
- Department of Anatomy, Poznan University of Medical Sciences, 60-781 Poznan, Poland; (W.K.); (R.B.); (B.K.)
| | - Rut Bryl
- Department of Anatomy, Poznan University of Medical Sciences, 60-781 Poznan, Poland; (W.K.); (R.B.); (B.K.)
| | - Bartosz Kempisty
- Department of Anatomy, Poznan University of Medical Sciences, 60-781 Poznan, Poland; (W.K.); (R.B.); (B.K.)
- Department of Histology and Embryology, Poznan University of Medical Sciences, 60-781 Poznan, Poland
- Department of Veterinary Surgery, Institute for Veterinary Medicine, Nicolaus Copernicus University, 87-100 Torun, Poland
| | - Agnieszka Skowronska
- Department of Human Physiology and Pathophysiology, School of Medicine, Collegium Medicum, University of Warmia and Mazury, Warszawska Street 30, 10-082 Olsztyn, Poland;
| | - Mariusz T. Skowronski
- Department of Basic and Preclinical Sciences, Institute for Veterinary Medicine, Nicolaus Copernicus University, 87-100 Torun, Poland;
- Correspondence: ; Tel.: +48-56-611-2231
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Association of the VDAC3 gene polymorphism with sperm count in Han-Chinese population with idiopathic male infertility. Oncotarget 2018; 8:45242-45248. [PMID: 28431403 PMCID: PMC5542182 DOI: 10.18632/oncotarget.16891] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 03/27/2017] [Indexed: 11/25/2022] Open
Abstract
Voltage-dependent anion channel (VDAC) is a multifunctional channel protein across the outer mitochondrial membrane of somatic cells and participates in many physiological and pathophysiological processes. Up to now, only a few studies, including our previous studies, showed that VDAC exists in mammalian spermatozoa and is involved in spermatogenesis and sperm functions. There is no report about VDAC genetic variants in germinal tissues or cells. To investigate the possible association between VDAC genetic variants and human sperm quality, we performed semen analysis and variant Genotyping of VDAC3 subtype (rs7004637, rs16891278 and rs6773) of 523 Han-Chinese males with idiopathic infertility respectively by computer assisted semen analysis (CASA) and single nucleotide polymorphism (SNP) Genotyping assay. No significant association was found between rs7004637 and rs6773 genotypes and semen quality. However, the AG genotype of rs16891278 showed a significantly lower sperm concentration compared with the AA genotype (P = 0.044). Our findings suggest that VDAC3 genetic variants may be associated with human sperm count.
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Xu A, Hua Y, Zhang J, Chen W, Zhao K, Xi W, Wang H, Fang J, Su S, Tang M, Liu B, Wang Z. Abnormal Hypermethylation of the VDAC2 Promoter is a Potential Cause of Idiopathic Asthenospermia in Men. Sci Rep 2016; 6:37836. [PMID: 27892527 PMCID: PMC5124954 DOI: 10.1038/srep37836] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 11/02/2016] [Indexed: 12/26/2022] Open
Abstract
This study aimed to explore the association between the methylation status of the VDAC2 gene promoter region and idiopathic asthenospermia (IAS). Twenty-five IAS patients and 27 fertile normozoospermia (NZ) were involved. GC-2spd cells were treated with different concentrations of 5-aza-2′-deoxycytidine (5-Aza-CdR) for 24 h and 48 h. qRT-PCR was conducted to reveal whether or not VDAC2 expression was regulated by methylated modification. A dual-luciferase activity detection was used to verify VDAC2 promoter activity in GC-2spd cells. Bisulphite genomic sequence was used to analyse DNA methylation of the VDAC2 promoter. The results showed that VDAC2 expression was significantly increased after treated with 5-Aza-CdR. A strong activity of the promoter (−2000 bp to +1000 bp) was detected by dual-luciferase activity detection (P < 0.05). The bisulphite genomic sequencing and correlation analysis showed that sperm motility was positively associated with the methylation pattern of uncomplete methylation and mild hypermethylation, and negatively related to the percentage of moderate methylation. In conclusion, high methylation of the VDAC2 promoter CpGs could be positively correlated with low sperm motility. Abnormal methylation of VDAC2 promoter may be a potential cause to idiopathic asthenospermia.
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Affiliation(s)
- Aiming Xu
- Department of Urology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China
| | - Yibo Hua
- Department of Urology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China
| | - Jianzhong Zhang
- Department of Urology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China
| | - Wei Chen
- Department of Urology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China
| | - Kai Zhao
- Department of Urology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China
| | - Wei Xi
- Department of Urology, Zhongshan Hospital affiliated to Fudan University, Shanghai 200032, China
| | - Hainan Wang
- Department of Urology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China
| | - Jianzheng Fang
- Department of Urology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China
| | - Shifeng Su
- Department of Urology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China
| | - Min Tang
- Department of Urology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China
| | - Bianjiang Liu
- Department of Urology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China.,State Key Laboratory of Reproductive Medicine, Nanjing medical University, Nanjing 210029, China
| | - Zengjun Wang
- Department of Urology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China.,State Key Laboratory of Reproductive Medicine, Nanjing medical University, Nanjing 210029, China
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Ido Y, Yoshitomi T, Ohkura K, Yamamoto T, Shinohara Y. Utility of syntenic relationships of VDAC1 pseudogenes for not only an understanding of the phylogenetic divergence history of rodents, but also ascertaining possible pseudogene candidates as genuine pseudogenes. Genomics 2014; 104:128-33. [PMID: 24858958 DOI: 10.1016/j.ygeno.2014.05.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 05/06/2014] [Accepted: 05/14/2014] [Indexed: 11/20/2022]
Abstract
Rodent and human genomes were screened to identify pseudogenes of the type 1 voltage-dependent anion channel (VDAC1) in mitochondria. In addition to the 16 pseudogenes of rat VDAC1 identified in our recent study, 15 and 13 sequences were identified as pseudogenes of VDAC1 in mouse and human genome, respectively; and 4, 2, and 1 sequences, showing lower similarities with the VDAC1 sequence, were identified as "possible pseudogene candidates" in rat, mouse, and human, respectively. No syntenic combination was observed between rodent and human pseudogenes, but 2 and 1 possible pseudogene candidates of VDAC1 of rat and mouse, respectively, were found to have syntenic counterparts in mouse and rat genome, respectively; and these syntenic counterparts were genuine VDAC1 pseudogenes. Therefore, syntenic combinations of pseudogenes of VDAC1 were useful not only for a better understanding of the phylogenetic divergence history of rodents but also for ascertaining possible pseudogene candidates as genuine pseudogenes.
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Affiliation(s)
- Yusuke Ido
- Institute for Genome Research, University of Tokushima, Kuramoto-cho-3, Tokushima 770-8503, Japan; Faculty of Pharmaceutical Sciences, University of Tokushima, Shomachi-1, Tokushima 770-8505, Japan
| | - Tatsuki Yoshitomi
- Institute for Genome Research, University of Tokushima, Kuramoto-cho-3, Tokushima 770-8503, Japan; Faculty of Pharmaceutical Sciences, University of Tokushima, Shomachi-1, Tokushima 770-8505, Japan
| | - Kazuto Ohkura
- Faculty of Pharmaceutical Science, Suzuka University of Medical Science, Minamitamagaki-cho, Suzuka 513-8670, Japan
| | - Takenori Yamamoto
- Institute for Genome Research, University of Tokushima, Kuramoto-cho-3, Tokushima 770-8503, Japan; Faculty of Pharmaceutical Sciences, University of Tokushima, Shomachi-1, Tokushima 770-8505, Japan
| | - Yasuo Shinohara
- Institute for Genome Research, University of Tokushima, Kuramoto-cho-3, Tokushima 770-8503, Japan; Faculty of Pharmaceutical Sciences, University of Tokushima, Shomachi-1, Tokushima 770-8505, Japan.
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Kwon WS, Park YJ, Mohamed ESA, Pang MG. Voltage-dependent anion channels are a key factor of male fertility. Fertil Steril 2013; 99:354-61. [DOI: 10.1016/j.fertnstert.2012.09.021] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Revised: 09/10/2012] [Accepted: 09/10/2012] [Indexed: 10/27/2022]
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Pseudogenes of rat VDAC1: 16 gene segments in the rat genome show structural similarities with the cDNA encoding rat VDAC1, with 8 slightly expressed in certain tissues. Mamm Genome 2011; 23:286-93. [DOI: 10.1007/s00335-011-9375-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2011] [Accepted: 10/15/2011] [Indexed: 11/26/2022]
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Voltage-dependant anion channels: novel insights into isoform function through genetic models. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:1477-85. [PMID: 22051019 DOI: 10.1016/j.bbamem.2011.10.019] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Revised: 10/12/2011] [Accepted: 10/18/2011] [Indexed: 11/24/2022]
Abstract
Voltage-dependant Anion Channels, also known as mitochondrial porins, are pore-forming proteins located in the mitochondrial outer membrane (MOM) that, in addition to forming complexes with other proteins that localize to the MOM, also function as the main conduit for transporting metabolites between the cytoplasm and mitochondria. VDACs are encoded by a multi-member gene family, and the number of isoforms and specific functions of VDACs varies between species. Translating the well-described in vitro characteristics of the VDAC isoforms into in vivo functions has been a challenge, with the generation of animal models of VDAC deficiency providing much of the available information about isoform-specific roles in biology. Here, we review the approaches used to create these insect and mammalian animal models, and the conclusions reached by studying the consequences of loss of function mutations on the genetic, physiologic, and biochemical properties of the resulting models. This article is part of a Special Issue entitled: VDAC structure, function, and regulation of mitochondrial metabolism.
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Rui H, Lee KI, Pastor RW, Im W. Molecular dynamics studies of ion permeation in VDAC. Biophys J 2011; 100:602-610. [PMID: 21281574 DOI: 10.1016/j.bpj.2010.12.3711] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Revised: 12/13/2010] [Accepted: 12/16/2010] [Indexed: 11/19/2022] Open
Abstract
The voltage-dependent anion channel (VDAC) in the outer membrane of mitochondria serves an essential role in the transport of metabolites and electrolytes between the cell matrix and mitochondria. To examine its structure, dynamics, and the mechanisms underlying its electrophysiological properties, we performed a total of 1.77 μs molecular dynamics simulations of human VDAC isoform 1 in DOPE/DOPC mixed bilayers in 1 M KCl solution with transmembrane potentials of 0, ±25, ±50, ±75, and ±100 mV. The calculated conductance and ion selectivity are in good agreement with the experimental measurements. In addition, ion density distributions inside the channel reveal possible pathways for different ion species. Based on these observations, a mechanism underlying the anion selectivity is proposed; both ion species are transported across the channel, but the rate for K(+) is smaller than that for Cl(-) because of the attractive interactions between K(+) and residues on the channel wall. This difference leads to the anion selectivity of VDAC.
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Affiliation(s)
- Huan Rui
- Department of Molecular Biosciences and Center for Bioinformatics, The University of Kansas, Lawrence, Kansas
| | - Kyu Il Lee
- Department of Molecular Biosciences and Center for Bioinformatics, The University of Kansas, Lawrence, Kansas
| | - Richard W Pastor
- Laboratory of Computational Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Wonpil Im
- Department of Molecular Biosciences and Center for Bioinformatics, The University of Kansas, Lawrence, Kansas.
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Anflous-Pharayra K, Lee N, Armstrong DL, Craigen WJ. VDAC3 has differing mitochondrial functions in two types of striated muscles. BIOCHIMICA ET BIOPHYSICA ACTA 2011; 1807:150-6. [PMID: 20875390 PMCID: PMC2998388 DOI: 10.1016/j.bbabio.2010.09.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2010] [Revised: 09/16/2010] [Accepted: 09/20/2010] [Indexed: 10/19/2022]
Abstract
Voltage-dependent anion channel (VDAC) is an abundant mitochondrial outer membrane protein. In mammals, three VDAC isoforms have been characterized. We have previously reported alterations in the function of mitochondria when assessed in situ in different muscle types in VDAC1 deficient mice (Anflous et al., 2001). In the present report we extend the study to VDAC3 deficient muscles and measure the respiratory enzyme activity in both VDAC1 and VDAC3 deficient muscles. While in the heart the absence of VDAC3 causes a decrease in the apparent affinity of in situ mitochondria for ADP, in the gastrocnemius, a mixed glycolytic/oxidative muscle, the affinity of in situ mitochondria for ADP remains unchanged. The absence of VDAC1 causes multiple defects in respiratory complex activities in both types of muscle. However, in VDAC3 deficient mice the defect is restricted to the heart and only to complex IV. These functional alterations correlate with structural aberrations of mitochondria. These results demonstrate that, unlike VDAC1, there is muscle-type specificity for VDAC3 function and therefore in vivo these two isoforms may fulfill different physiologic functions.
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Affiliation(s)
- Keltoum Anflous-Pharayra
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
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Liu B, Wang P, Wang Z, Jia Y, Niu X, Wang W, Zhang W. Analysis and difference of voltage-dependent anion channel mRNA in ejaculated spermatozoa from normozoospermic fertile donors and infertile patients with idiopathic asthenozoospermia. J Assist Reprod Genet 2010; 27:719-24. [PMID: 20809416 DOI: 10.1007/s10815-010-9466-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2010] [Accepted: 08/12/2010] [Indexed: 11/25/2022] Open
Abstract
PURPOSE to analyze the abundance and difference of voltage-dependent anion channel (VDAC) mRNA in ejaculated spermatozoa from normozoospermic fertile donors and infertile patients with idiopathic asthenozoospermia. METHODS high motile and low motile spermatozoa were separated respectively from ejaculates of 36 donors and 40 patients using a discontinuous Percoll gradient centrifugation. Real-Time PCR was performed to detect mRNA abundance and difference of three VDAC subtypes between two groups with different sperm motility. RESULTS real-Time PCR demonstrated that three VDAC mRNAs were present in mature spermatozoa. The VDAC2 mRNA level in ejaculated spermatozoa of patients was significantly higher than that of donors. No significant differences of VDAC1 and VDAC3 mRNA levels were found between two groups. CONCLUSION the high abundance of VDAC2 mRNA seemed to have a positive correlation with low sperm motility. The abnormal expression of VDAC might be related to male infertility with idiopathic asthenozoospermia.
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Affiliation(s)
- Bianjiang Liu
- Laboratory of Reproductive Medicine, Department of Urology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China
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Liu B, Zhang W, Wang Z. Voltage-dependent anion channel in mammalian spermatozoa. Biochem Biophys Res Commun 2010; 397:633-6. [DOI: 10.1016/j.bbrc.2010.06.025] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2010] [Accepted: 06/05/2010] [Indexed: 10/19/2022]
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Liu B, Wang Z, Zhang W, Wang X. Expression and localization of voltage-dependent anion channels (VDAC) in human spermatozoa. Biochem Biophys Res Commun 2008; 378:366-70. [PMID: 19013129 DOI: 10.1016/j.bbrc.2008.10.177] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2008] [Accepted: 10/30/2008] [Indexed: 11/24/2022]
Abstract
Voltage-dependent anion channels (VDAC), also known as mitochondrial porins, are a group of proteins first identified in the mitochondrial outer membrane that are able to form hydrophilic pore structures. VDAC allow the passage of the metabolites across the mitochondrial outer membrane, and are involved in metabolite transport and signal transduction. Several recent studies have indicated the important roles of VDAC in maintaining normal structure and motility of mammalian spermatozoa. To study the expression and localization of VDAC in human spermatozoa, different experimental approaches were applied: (1) specific primers were designed and VDAC gene sequences were cloned by PCR amplification from human testis cDNA library; (2) recombinant VDAC proteins were produced in the expression vector Escherichia coli BL21 (DE3); (3) human sperm VDAC proteins were extracted, separated and analyzed by Western blotting; (4) the localization of VDAC in human spermatozoa were detected using immunofluorescence. The three gene sequences and recombinant VDAC proteins were obtained, respectively. VDAC proteins were detected to be located in human spermatozoa, especially in sperm flagella. Our study elucidated for the first time that VDAC were synthesized and secreted at the testis level and eventually became an integral part of sperm proteins.
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Affiliation(s)
- Bianjiang Liu
- Department of Urology, First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210029, China
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Graham BH, Craigen WJ. Genetic approaches to analyzing mitochondrial outer membrane permeability. Curr Top Dev Biol 2004; 59:87-118. [PMID: 14975248 DOI: 10.1016/s0070-2153(04)59004-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Affiliation(s)
- Brett H Graham
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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Shi Y, Jiang C, Chen Q, Tang H. One-step on-column affinity refolding purification and functional analysis of recombinant human VDAC1. Biochem Biophys Res Commun 2003; 303:475-82. [PMID: 12659842 DOI: 10.1016/s0006-291x(03)00359-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The outer mitochondrial membrane porin, voltage-dependent anion-selective channel (VDAC), is believed to play an important role in mediating mitochondria-dependent apoptosis. However, detailed structure-function studies of VDAC have been hindered by the difficulties to obtain a soluble, correctly folded, and fully active form of the recombinant VDAC and its mutant variants due to its transmembrane nature. Here we report a high-throughput one-step chromatographic procedure in purification of recombinant human VDAC1 (rhVDAC1) protein overexpressed in bacteria. The improved methodology could generate a large quantity of rhVDAC1 with correct folding in terms of the secondary structure, with full biological activities in mediating cytochrome c release and in interaction with Bcl-X(L). The method will significantly benefit genetic, biochemical, and structural studies of this critical channel protein.
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Affiliation(s)
- Yong Shi
- The Center for Molecular Microbiology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100080, China
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Sampson MJ, Decker WK, Beaudet AL, Ruitenbeek W, Armstrong D, Hicks MJ, Craigen WJ. Immotile sperm and infertility in mice lacking mitochondrial voltage-dependent anion channel type 3. J Biol Chem 2001; 276:39206-12. [PMID: 11507092 DOI: 10.1074/jbc.m104724200] [Citation(s) in RCA: 179] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Voltage-dependent anion channels (VDACs), also known as mitochondrial porins, are small channel proteins involved in the translocation of metabolites across the mitochondrial outer membrane. A single channel-forming protein is found in yeast, whereas higher eukaryotes express multiple VDACs, with humans and mice each harboring three distinct channels (VDAC1-3) encoded by separate genes. To begin to assess the functions of each of the three isoforms, the VDAC3 gene was inactivated by targeted disruption in embryonic stem cells. Here we show that mice lacking VDAC3 are healthy, but males are infertile. Although there are normal sperm numbers, the sperm exhibit markedly reduced motility. Structural defects were found in two-thirds of epididymal axonemes, with the most common abnormality being loss of a single microtubule doublet at a conserved position within the axoneme. In testicular sperm, the defect was only rarely observed, suggesting that instability of a normally formed axoneme occurs with sperm maturation. In contrast, tracheal epithelial cilia showed no structural abnormalities. In addition, skeletal muscle mitochondria were abnormally shaped, and activities of the respiratory chain complexes were reduced. These results demonstrate that axonemal defects may be caused by associated nonaxonemal components such as mitochondrial channels and illustrate that normal mitochondrial function is required for stability of the axoneme.
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Affiliation(s)
- M J Sampson
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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Decker WK, Craigen WJ. The tissue-specific, alternatively spliced single ATG exon of the type 3 voltage-dependent anion channel gene does not create a truncated protein isoform in vivo. Mol Genet Metab 2000; 70:69-74. [PMID: 10833333 DOI: 10.1006/mgme.2000.2987] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Voltage-dependent anion channels (VDACs) are small, integral membrane proteins that traverse the outer mitochondrial membrane and conduct ATP and other small metabolites. They are known to bind several kinases of intermediary metabolism in a tissue-specific fashion, have been found in close association with the adenine nucleotide translocator of the inner mitochondrial membrane, and are hypothesized to form part of the mitochondrial permeability transition pore, which results in the release of cytochrome c at the onset of apoptotic cell death. VDACs are found throughout all strata of eukaryotic evolution and exhibit biophysical characteristics that are well conserved from yeast to mammals. The mammalian VDAC gene family consists of three isoforms, each of which shares approximately 70% sequence identity with the other two family members. Recently, we reported that a single codon (ATG) exon is alternatively spliced into the transcript of the type 3 voltage-dependent anion channel (VDAC3) in a tissue-specific fashion. This unusual splicing event was shown to be conserved between mouse and human, and we theorized that the spliced exon could lead to the creation of an alternative translational initiation site. Here we report that a highly specific polyclonal VDAC3 antibody was unable to detect the truncated protein isoform indicative of this putative downstream start site. From these in vivo studies, we conclude that the alternatively spliced exon results in the insertion of a single methionine residue at amino acid position 39 of the mature VDAC3 protein. Additionally, we have used a cross-species genomic sequence comparison to identify conserved regions that may be involved in the regulation of small exon splicing.
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Affiliation(s)
- W K Decker
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
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