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Mapping of mouse Tpte. The human chromosome 13q14.2q21 and its homologous region on mouse chromosome 8 are shown. Gene symbols are NEK3/Nek3 (never in mitosis gene a-related kinase 3), ATP7B/Atp7b (ATPase, Cu(2+)-transporting, β polypeptide), TPTEps1 (TPTE pseudogene1)/Tpte (transmembrane phosphatase with tensin homology). The map position is based on the NCBI human genome map (http://www.ncbi.nlm.nih.gov/cgi-bin/ Entrez/hum-srch) and the mouse genome database, Jackson Laboratory Bar Harbor (http://www.informatics.jax.org/menus/map_menu. shtml)
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The human TPTE gene encodes a testis-specific protein that contains four potential transmembrane domains and a protein tyrosine phosphatase motif, and shows homology to the tumor suppressor PTEN/MMAC1. Chromosomal mapping revealed multiple copies of the TPTE gene present on the acrocentric chromosomes 13, 15, 21 and 22, and the Y chromosome. Zooblo...
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... 13&tax_id=9606), where NEK3 and ATP7B have been mapped. Analysis of the nucleotide sequence of this re- gion of human chromosome 13q allowed the identifica- tion of a presumably inactive copy of TPTE characterized by exon deletions and multiple nucleotide substitutions. This TPTE copy was named TPTEps1 for TPTE pseudo- gene 1 (Fig. 2). These data indicate that the human chro- mosome 13q14.2-q21 TPTE copy is likely to be the an- cestral human gene from which the different TPTE copies arose through duplication events that occurred after the separation of primates and ...
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... The voltage-sensor domain consists of four transmembrane (TM) segments, of which the cytoplasmic end of TM-4 contains a highly (caption on next page) T. Bhattacharyya and R. Sowdhamini conserved histidine that seems to have arisen at an early stage of radiation of eutherian mammals and is not observed in proto-or metatherian mammals considered in this study (Fig. 3A-C). The ability of the voltagesensor domain to conduct proton currents is attributed to this conserved histidine residue, and this holds even in the case of TPTE, which is phosphatase-dead [39][40][41]. Among rodents, only mice retain a single copy of the TPTE gene and interestingly, the sequence corresponding to murine TPTE does not retain a histidine at the conserved position, unlike human TPTE (Fig. 3A). ...
The age of genomics has given us a wealth of information and the tools to study whole genomes. This, in turn, has facilitated genome-wide studies among organisms that were relatively less studied in the pre-genomic era or are non-model organisms. This paves the way to the discovery of interesting evolutionary patterns, which are brought to light by genome-wide surveys of protein superfamilies. Phosphorylation is a post-translational modification that is utilised across all clades of life, and acts as an important signalling switch, regulating several cellular processes. Tyrosine phosphatases, which are found predominantly in eukaryotes, act on phosphorylated tyrosine residues and sometimes on other substrates. Extending on our previous effort to look for tyrosine phosphatases in the human genome, we have looked for sequences of the cysteine-based tyrosine phosphatase superfamily in thirty mammalian genomes from all across Mammalia and validated the sequences with the presence of the signature catalytic motif. Domain architecture annotation, followed by in-depth analysis, revealed interesting taxon-specific patterns such as subtle differences between the protein families in marsupials and early mammals versus placental mammals. Finally, we discuss an interesting case of loss of the tyrosine phosphatase domain from a gene product in the course of eutherian evolution.
... In line with the idea that VSP serves a fundamental physiological role, VSP orthologs have been identified in several tissues across diverse phyla, including ascidians, newts, salamanders, zebrafish, chicken, amphibians, mice, and humans [10,11,[20][21][22][23][24][25][26]. In particular, VSP mRNA transcripts have been found in the adult nervous systems of sea squirts and the brains of frogs, mice and humans [20,22,27,28] as well as in kidney, stomach, heart, testis and ovary [20,[22][23][24][25][27][28][29][30]. In addition to adult tissues, VSP transcripts have been detected in embryonic tissues such as the kidney and eye of zebrafish [31], the kidney, brain and stomach of chicks [21,30], and the brain, spinal cord and eye of mice [25,27,32]. ...
... A more recent study in mice used dissociated cortical neurons from P0-1 mice and the staining appears throughout the cells [32]. In addition, heterologous expression of mouse and human VSP consistently show intracellular membrane localizations [20,25,29]. In contrast, our subcellular localization of endogenous Xl-VSP protein is on the apical membrane of kidney tubule epithelia. ...
Voltage-sensing phosphatases (VSPs) are transmembrane proteins that couple changes in membrane potential to hydrolysis of inositol signaling lipids. VSPs catalyze the dephosphorylation of phosphatidylinositol phosphates (PIPs) that regulate diverse aspects of cell membrane physiology including cell division, growth and migration. VSPs are highly conserved among chordates, and their RNA transcripts have been detected in the adult and embryonic stages of frogs, fish, chickens, mice and humans. However, the subcellular localization and biological function of VSP remains unknown. Using reverse transcriptase-PCR (RT-PCR), we show that both Xenopus laevis VSPs (Xl-VSP1 and Xl-VSP2) mRNAs are expressed in early embryos, suggesting that both Xl-VSPs are involved in early tadpole development. To understand which embryonic tissues express Xl-VSP mRNA, we used in situ hybridization (ISH) and found Xl-VSP mRNA in both the brain and kidney of NF stage 32–36 embryos. By Western blot analysis with a VSP antibody, we show increasing levels of Xl-VSP protein in the developing embryo, and by immunohistochemistry (IHC), we demonstrate that Xl-VSP protein is specifically localized to the apical membrane of both embryonic and adult kidney tubules. We further characterized the catalytic activity of both Xl-VSP homologs and found that while Xl-VSP1 catalyzes 3- and 5-phosphate removal, Xl-VSP2 is a less efficient 3-phosphatase with different substrate specificity. Our results suggest that Xl-VSP1 and Xl-VSP2 serve different functional roles and that VSPs are an integral component of voltage-dependent PIP signaling pathways during vertebrate kidney tubule development and function.
... The mammalian orthologs of Ci-VSP are the PI phosphatases TPTE, TPIP, and PTEN2, which are highly expressed in the testis. 45) The VSP VSD has an architecture similar to other VSDs and consists of four helices, including the signature S4 containing multiple positively charged residues (Fig. 3). A study of the crystal structures of the VSD from Ci-VSP suggests that upon a change in membrane potential, there is a simple upward helical motion of S4 without significant motion change in the other helices. ...
The voltage sensor domain (VSD) has long been studied as a unique domain intrinsic to voltage-gated ion channels (VGICs). Within VGICs, the VSD is tightly coupled to the pore-gate domain (PGD) in diverse ways suitable for its specific function in each physiological context, including action potential generation, muscle contraction and relaxation, hormone and neurotransmitter secretion, and cardiac pacemaking. However, some VSD-containing proteins lack a PGD. Voltage-sensing phosphatase contains a cytoplasmic phosphoinositide phosphatase with similarity to phosphatase and tensin homolog (PTEN). Hv1, a voltage-gated proton channel, also lacks a PGD. Within Hv1, the VSD operates as a voltage sensor, gate, and pore for both proton sensing and permeation. Hv1 has a C-terminal coiled coil that mediates dimerization for cooperative gating. Recent progress in the structural biology of VGICs and VSD proteins provides insights into the principles of VSD coupling conserved among these proteins as well as the hierarchy of protein organization for voltage-evoked cell signaling.
... In line with the idea that VSP serves a fundamental physiological role, VSP orthologs have been identified in several tissues across diverse phyla, including ascidians, newts, salamanders, zebrafish, chicken, amphibians, mice, and humans [10,11,[20][21][22][23][24][25][26]. In particular, VSP mRNA transcripts have been found in the adult nervous systems of sea squirts and the brains of frogs, mice and humans [20,22,27,28] as well as in kidney, stomach, heart, testis and ovary [20,[22][23][24][25][27][28][29][30]. In addition to adult tissues, VSP transcripts have been detected in embryonic tissues such as the kidney and eye of zebrafish [31], the kidney, brain and stomach of chicks [21,30], and the brain, spinal cord and eye of mice [25,27,32]. ...
... A more recent study in mice used dissociated cortical neurons from P0-1 mice and the staining appears throughout the cells [32]. In addition, heterologous expression of mouse and human VSP consistently show intracellular membrane localizations [20,25,29]. In contrast, our subcellular localization of endogenous Xl-VSP protein is on the apical membrane of kidney tubule epithelia. ...
Voltage-sensing phosphatases (VSPs) are transmembrane proteins that couple changes in membrane potential to hydrolysis of inositol signaling lipids. VSPs catalyze the dephosphorylation of phosphatidylinositol phosphates (PIPs) that regulate diverse aspects of cell membrane physiology including cell division, growth and migration. VSPs are highly conserved among chordates, and their RNA transcripts have been detected in the adult and embryonic stages of frogs, fish, chickens, mice and humans. However, the subcellular localization and biological function of VSP remains unknown. Using reverse transcriptase-PCR (RT-PCR), we show that both Xenopus laevis VSP (Xl-VSP1 and Xl-VSP2) mRNAs are expressed in early embryos, suggesting that both Xl-VSPs are involved in early tadpole development. To understand which embryonic tissues express Xl-VSP mRNA, we used in situ hybridization (ISH) and found Xl-VSP mRNA in both the brain and kidney of NF stage 32-36 embryos. By Western blot analysis with a VSP antibody, we show increasing levels of Xl-VSP protein in the developing embryo, and by immunohistochemistry (IHC), we demonstrate that Xl-VSP protein is specifically localized to the apical membrane of both embryonic and adult kidney tubules. We further characterized the catalytic activity of both Xl-VSP homologs and found that while Xl-VSP1 catalyzes 3- and 5-phosphate removal, Xl-VSP2 is a less efficient 3-phosphatase with different substrate specificity. Our results suggest that Xl-VSP1 and Xl-VSP2 serve different functional roles and that VSPs are an integral component of voltage-dependent PIP signaling pathways during vertebrate kidney tubule development and function.
... VSP was first discovered as a protein showing remarkable homology with PTEN from humans and rodents (48,193,202 (127). Moreover, a variant truncated just after the fourth transmembrane segment continued to exhibit the same charge movement, and the isolated COOH-terminal cytoplasmic region of ci0100145019 showed an ability to dephosphorylate PtdIns(3,4,5)P 3 in vitro. ...
... For example, Xenopus laevis has two VSP genes (Xl-VSP1 and Xl-VSP2) due to whole genome duplication (145) (FIGURE 7). Moreover, in the human genome, there are at least eight VSP-like genes, but only two, TPTE (PTEN2) and TPIP (TPTE2), appear to be functional genes; the remaining six are pseudogenes (25,48,173,202). Several splice variants have also been reported for both TPTE and TPIP in humans. ...
... Among them, the longest isoform retains the intact VSD as well as the enzyme region. In contrast to humans, mice appear to have a single VSP gene, like most other animal species (48). Rodent VSP has greater similarity to human TPIP than to TPTE; nonetheless, mouse VSP is referred to as PTEN2 (202) or TPTE. ...
Voltage-sensing phosphatase (VSP) contains a voltage sensor domain (VSD) similar to that in voltage-gated ion channels, and a phosphoinositide phosphatase region similar to phosphatase and tensin homolog deleted on chromosome 10 (PTEN). The VSP gene is conserved from unicellular organisms to higher vertebrates. Membrane depolarization induces electrical driven conformational rearrangement in the VSD, which is translated into catalytic enzyme activity. Biophysical and structural characterization has revealed details of the mechanisms underlying the molecular functions of VSP. Coupling between the VSD and the enzyme is tight, such that enzyme activity is tuned in a graded fashion to the membrane voltage. Upon VSP activation, multiple species of phosphoinositides are simultaneously altered, and the profile of enzyme activity depends on the history of the membrane potential. VSPs have been the obvious candidate link between membrane potential and phosphoinositide regulation. However, patterns of voltage change regulating VSP in native cells remain largely unknown. This review addresses the current understanding of the biophysical biochemical properties of VSP and provides new insight into the proposed functions of VSP.
... In the time since the first charac terization of the sea squirt VSP (Ciona intestinalis VSP; Ci-VSP) [14], VSP orthologs have been characterized from a teleost [15], amphibian [16], chick [17] and mammals [18,19]. Human and rodent VSPs have also been characterized as PTEN-related phosphatases, called TPTE and TPIP [20][21][22]. ...
Voltage-sensing phosphatase (VSP) consists of a transmembrane voltage sensor and a cytoplasmic enzyme region. The enzyme region contains the phosphatase and C2 domains, is structurally similar to the tumor suppressor phosphatase PTEN, and catalyzes the dephosphorylation of phosphoinositides. The transmembrane voltage sensor is connected to the phosphatase through a short linker region, and phosphatase activity is induced upon membrane depolarization. Although the detailed molecular characteristics of the voltage sensor domain and the enzyme region have been revealed, little is known how these two regions are coupled. In addition, it is important to know whether mechanism for coupling between the voltage sensor domain and downstream effector function is shared among other voltage sensor domain-containing proteins. Recent studies in which specific amino acid sites were genetically labeled using a fluorescent unnatural amino acid have enabled detection of the local structural changes in the cytoplasmic region of Ciona intestinalis VSP that occur with a change in membrane potential. The results of those studies provide novel insight into how the enzyme activity of the cytoplasmic region of VSP is regulated by the voltage sensor domain.
... Mm-VSP expression has been reported in the testis (26,27), similarly to other VSP family members (3,(28)(29)(30). In most species, VSP expression has been detected in the central nervous system as well. ...
... Biophysical Journal 109(12) 2480-2491 band contained the expected 328 basepair sequence, whereas the lower-molecular-weight band contained a sequence lacking the 54 bases of exon 9 ( Fig. 1 B). Alternate splicing of Mm-VSP has been predicted (26), although the exclusion of exon 9 has not been previously reported. We term this novel (to our knowledge) splice variant Mm-VSP-Ex9. ...
... Consistent with previous reports on Mm-VSP, we found that the protein localized to intracellular compartments when expressed in heterologous systems (26,27). Indeed, when we expressed Mm-VSP-GFP fusion proteins in HEK293T/17 cells, we observed fluorescence in intracellular compartments (Fig. 2 B). ...
Voltage-sensitive phosphatases (VSPs) are proteins that directly couple changes in membrane electrical potential to inositol lipid phosphatase activity. VSPs thus couple two signaling pathways that are critical for cellular functioning. Although a number of nonmammalian VSPs have been characterized biophysically, mammalian VSPs are less well understood at both the physiological and biophysical levels. In this study, we aimed to address this gap in knowledge by determining whether the VSP from mouse, Mm-VSP, is expressed in the brain and contains a functional voltage-sensing domain (VSD) and a phosphatase domain. We report that Mm-VSP is expressed in neurons and is developmentally regulated. To address whether the functions of the VSD and phosphatase domain are retained in Mm-VSP, we took advantage of the modular nature of these domains and expressed each independently as a chimeric protein in a heterologous expression system. We found that the Mm-VSP VSD, fused to a viral potassium channel, was able to drive voltage-dependent gating of the channel pore. The Mm-VSP phosphatase domain, fused to the VSD of a nonmammalian VSP, was also functional: activation resulted in PI(4,5)P-2 depletion that was sufficient to inhibit the PI(4,5)P-2-regulated KCNQ2/3 channels. While testing the functionality of the VSD and phosphatase domain, we observed slight differences between the activities of Mm-VSP-based chimeras and those of nonmammalian VSPs. Although the properties of VSP chimeras may not completely reflect the properties of native VSPs, the differences we observed in voltage-sensing and phosphatase activity provide a starting point for future experiments to investigate the function of Mm-VSP and other mammalian VSPs. In conclusion, our data reveal that both the VSD and the lipid phosphatase domain of Mm-VSP are functional, indicating that Mm-VSP likely plays an important role in mouse neurophysiology.
... Voltage sensing phosphatases (VSP) are the first family of enzymes displaying a voltage sensing domain (VSD). The first member of the VSP family was described in 1999, when the human isoform TPTE (Transmembrane Phosphatase with Tensin homology) was reported as a testis-specific protein (Chen et al., 1999;Guipponi et al., 2001;Wu et al., 2001;Tapparel et al., 2003). In spite of the great similarities between the C-terminus of TPTE and members of the protein tyrosine phosphatases (PTP) family (Chen et al., 1999;Guipponi et al., 2000Guipponi et al., , 2001Walker et al., 2001;Tapparel et al., 2003), no catalytic activity was -or has been -observed to be mediated by this protein. ...
... The first member of the VSP family was described in 1999, when the human isoform TPTE (Transmembrane Phosphatase with Tensin homology) was reported as a testis-specific protein (Chen et al., 1999;Guipponi et al., 2001;Wu et al., 2001;Tapparel et al., 2003). In spite of the great similarities between the C-terminus of TPTE and members of the protein tyrosine phosphatases (PTP) family (Chen et al., 1999;Guipponi et al., 2000Guipponi et al., , 2001Walker et al., 2001;Tapparel et al., 2003), no catalytic activity was -or has been -observed to be mediated by this protein. ...
... Two years later, the findings of a second human VSP (Walker et al., 2001;Wu et al., 2001) and a murine VSP (Guipponi et al., 2001) were reported. In contrast to TPTE, the new human VSP (known as TPTE2 and originally named TPIP: TPTE and PTEN homologous Inositol lipid Phosphatase) displayed phosphoinositide phosphatase activity (Walker et al., 2001;Wu et al., 2001). ...
... February 2015 | Volume 6 | Article 20 | 4 tensin homology (TPTEs 2 ; Chen et al., 1999; Guipponi et al., 2000 Guipponi et al., , 2001 Walker et al., 2001; Wu et al., 2001; Tapparel et al., 2003). In these early studies, the research had been focused only on the biochemical characterization of the enzymatic activity, because the proteins share a high sequence homology with the tumor suppressor PTEN. ...
The transmembrane protein Ci-VSP from the ascidian Ciona intestinalis was described as first member of a fascinating family of enzymes, the voltage sensitive phosphatases (VSPs). Ci-VSP and its voltage-activated homologs from other species are stimulated by positive membrane potentials and dephosphorylate the head groups of negatively charged phosphoinositide phosphates (PIPs). In doing so, VSPs act as control centers at the cytosolic membrane surface, because they intervene in signaling cascades that are mediated by PIP lipids. The characteristic motif CX5RT/S in the active site classifies VSPs as members of the huge family of cysteine-based protein tyrosine phosphatases (PTPs). Although PTPs have already been well-characterized regarding both, structure and function, their relationship to VSPs has drawn only limited attention so far. Therefore, the intention of this review is to give a short overview about the extensive knowledge about PTPs in relation to the facts known about VSPs. Here, we concentrate on the structural features of the catalytic domain which are similar between both classes of phosphatases and their consequences for the enzymatic function. By discussing results obtained from crystal structures, molecular dynamics simulations, and mutagenesis studies, a possible mechanism for the catalytic cycle of VSPs is presented based on that one proposed for PTPs. In this way, we want to link the knowledge about the catalytic activity of VSPs and PTPs.
... Orthologous cDNAs encoding VSPs have been identified from zebrafish, Danio rerio ; chick, Gallus gallus (Kurokawa et al. 2012); and frogs, Xenopus laevis and tropicalis (Ratzan et al. 2011). Mammalian orthologs (TPTE and TPTE2/TPIP) have been shown to be expressed in spermatocytes (Guipponi et al. 2001;Walker et al. 2001;Tapparel et al. 2003) and in tumors (Pleasance et al. 2010). ...
Voltage-sensing phosphatases (VSPs) share the molecular architecture of the voltage sensor domain (VSD) with voltage-gated ion channels and the phosphoinositide phosphatase region with the phosphatase and tensin homolog (PTEN), respectively. VSPs enzymatic activities are regulated by the motions of VSD upon depolarization. The physiological role of these proteins has remained elusive, and insights may be gained by investigating biological variations in different animal species. Urodele amphibians are vertebrates with potent activities of regeneration and also show diverse mechanisms of polyspermy prevention. We cloned cDNAs of VSPs from the testes of two urodeles; Hynobius nebulosus and Cynops pyrrhogaster, and compared their expression and voltage-dependent activation. Their molecular architecture is highly conserved in both Hynobius VSP (Hn-VSP) and Cynops VSP (Cp-VSP), including the positively-charged arginine residues in the S4 segment of the VSD and the enzymatic active site for substrate binding, yet the C-terminal C2 domain of Hn-VSP is significantly shorter than that of Cp-VSP and other VSP orthologs. RT-PCR analysis showed that gene expression pattern was distinct between two VSPs. The voltage sensor motions and voltage-dependent phosphatase activities were investigated electrophysiologically by expression in Xenopus oocytes. Both VSPs showed “sensing” currents, indicating that their voltage sensor domains are functional. The phosphatase activity of Cp-VSP was found to be voltage dependent, as shown by its ability to regulate the conductance of coexpressed GIRK2 channels, but Hn-VSP lacked such phosphatase activity due to the truncation of its C2 domain.
