1
|
Olsen LF, Lunding A. On the coupling of intracellular K + ${{\rm{K}}}^{+}$ to glycolytic oscillations in yeast. Yeast 2024. [PMID: 39031655 DOI: 10.1002/yea.3972] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Revised: 05/06/2024] [Accepted: 06/05/2024] [Indexed: 07/22/2024] Open
Abstract
We have investigated the interplay between glycolytic oscillations and intracellularK + ${{\rm{K}}}^{+}$ concentration in the yeast Saccharomyces cerevisiae. IntracellularK + ${{\rm{K}}}^{+}$ concentration was measured using the fluorophore potassium-binding benzofuranisophthalate (PBFI). We found thatK + ${{\rm{K}}}^{+}$ is an essential ion for the occurrence of glycolytic oscillations and that intracellularK + ${{\rm{K}}}^{+}$ concentration oscillates synchronously with other variables such as nicotinamide adenine dinucleotide hydride (NADH), intracellular adenosine triphosphate (ATP), and mitochondrial membrane potential. We also investigated if glycolysis and intracellularK + ${{\rm{K}}}^{+}$ concentration oscillate in a number of yeast strains with mutations inK + ${{\rm{K}}}^{+}$ transporters in the plasma membrane, mitochondrial membrane and in the vacuolar membrane. Most of these strains are still capable of showing glycolytic oscillations, but two strains are not: (i) a strain with a deletion in the mitochondrial Mdm38pK + ∕ H + ${{\rm{K}}}^{+}\unicode{x02215}{{\rm{H}}}^{+}$ transporter and (ii) a strain with deletion of the late endosomal Nhx1pK + ∕ H + ${{\rm{K}}}^{+}\unicode{x02215}{{\rm{H}}}^{+}$ (Na + ∕ H + ${\text{Na}}^{+}\unicode{x02215}{{\rm{H}}}^{+}$ ) transporter. In these two mutant strains intracellularK + ${{\rm{K}}}^{+}$ concentration seems to be low, indicating that the two transporters may be involved in transport ofK + ${{\rm{K}}}^{+}$ into the cytosol. In the strain, Mdm38pΔ ${\rm{\Delta }}$ oscillations in glycolysis could be restored by addition of theK + ∕ H + ${{\rm{K}}}^{+}\unicode{x02215}{{\rm{H}}}^{+}$ exchange ionophore nigericin. Furthermore, in two nonoscillating mutant strains with a defective V-ATPase and deletion of the Arp1p protein the intracellularK + ${{\rm{K}}}^{+}$ is relatively high, suggesting that the V-ATPase is essential for transport ofK + ${{\rm{K}}}^{+}$ out of the cytosol and that the cytoskeleton may be involved in bindingK + ${{\rm{K}}}^{+}$ to reduce the concentration of free ion in the cytosol. Analyses of the time series of oscillations of NADH, ATP, mitochondrial membrane potential, and potassium concentration using data-driven modeling corroborate the conjecture thatK + ${{\rm{K}}}^{+}$ ion is essential for the emergence of oscillations and support the experimental findings using mutant strains.
Collapse
Affiliation(s)
- Lars F Olsen
- PhyLife, Institute of Biochemistry and Molecular Biology, University of Southern Denmark, Odense M, Denmark
| | - Anita Lunding
- PhyLife, Institute of Biochemistry and Molecular Biology, University of Southern Denmark, Odense M, Denmark
| |
Collapse
|
2
|
The paradigm of prophylactic viral outbreaks measures by microbial biosurfactants. J Infect Public Health 2023; 16:575-587. [PMID: 36840992 PMCID: PMC9940476 DOI: 10.1016/j.jiph.2023.02.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 01/19/2023] [Accepted: 02/16/2023] [Indexed: 02/22/2023] Open
Abstract
The recent emergence and outbreak of the COVID-19 pandemic confirmed the incompetence of countries across the world to deal with a global public health emergency. Although the recent advent of vaccines is an important prophylactic measure, effective clinical therapy for SARS-Cov-2 is yet to be discovered. With the increasing mortality rate, research has been focused on understanding the pathogenic mechanism and clinical parameters to comprehend COVID-19 infection and propose new avenues for naturally occurring molecules with novel therapeutic properties to alleviate the current situation. In accordance with recent clinical studies and SARS-CoV-2 infection markers, cytokine storm and oxidative stress are entwined pathogenic processes in COVID-19 progression. Lately, Biosurfactants (BSs) have been studied as one of the most advanced biomolecules of microbial origin with anti-inflammatory, antioxidant, antiviral properties, antiadhesive, and antimicrobial properties. Therefore, this review inspects available literature and proposes biosurfactants with these properties to be encouraged for their extensive study in dealing with the current pandemic as new pharmaceutics in the prevention and control of viral spread, treating the symptoms developed after the incubation period through different therapeutic approaches and playing a potential drug delivery model.
Collapse
|
3
|
Donor Splice Site Variant in SLC9A6 Causes Christianson Syndrome in a Lithuanian Family: A Case Report. MEDICINA (KAUNAS, LITHUANIA) 2022; 58:medicina58030351. [PMID: 35334527 PMCID: PMC8949093 DOI: 10.3390/medicina58030351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 02/17/2022] [Accepted: 02/24/2022] [Indexed: 11/16/2022]
Abstract
Background and Objectives: The pathogenic variants of SLC9A6 are a known cause of a rare, X-linked neurological disorder called Christianson syndrome (CS). The main characteristics of CS are developmental delay, intellectual disability, and neurological findings. This study investigated the genetic basis and explored the molecular changes that led to CS in two male siblings presenting with intellectual disability, epilepsy, behavioural problems, gastrointestinal dysfunction, poor height, and weight gain. Materials and Methods: Next-generation sequencing of a tetrad was applied to identify the DNA changes and Sanger sequencing of proband’s cDNA was used to evaluate the impact of a splice site variant on mRNA structure. Bioinformatical tools were used to investigate SLC9A6 protein structure changes. Results: Sequencing and bioinformatical analysis revealed a novel donor splice site variant (NC_000023.11(NM_001042537.1):c.899 + 1G > A) that leads to a frameshift and a premature stop codon. Protein structure modelling showed that the truncated protein is unlikely to form any functionally relevant SLC9A6 dimers. Conclusions: Molecular and bioinformatical analysis revealed the impact of a novel donor splice site variant in the SLC9A6 gene that leads to truncated and functionally disrupted protein causing the phenotype of CS in the affected individuals.
Collapse
|
4
|
Cao B, Xia Z, Hao Z, Liu C, Long D, Fan W, Zhao A. The C-terminal tail of the plant endosomal-type NHXs plays a key role in its function and stability. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2021; 303:110791. [PMID: 33487365 DOI: 10.1016/j.plantsci.2020.110791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 12/03/2020] [Accepted: 12/07/2020] [Indexed: 06/12/2023]
Abstract
Typically, Na+/H+ antiporters (NHXs) possess a conserved N-terminus for cation binding and exchange and a hydrophilic C-terminus for regulating the antiporter activity. Plant endosomal-type NHXs play important roles in protein trafficking, as well as K+ and vesicle pH homeostasis, however the role of the C-terminal tail remains unclear. Here, the function of MnNHX6, an endosomal-type NHX in mulberry, was investigated using heterologous expression in yeast. Functional and localization analyses of C-terminal truncation and mutations in MnNHX6 revealed that the C-terminal conserved region was responsible for the function and stability of the protein and its hydrophobicity, which is a key domain requirement. Nuclear magnetic resonance spectroscopy provided direct structural evidence and yeast two-hybrid screening indicated that this functional domain was also necessary for interaction with sorting nexin 1. Our findings demonstrate that although the C-terminal tail of MnNHX6 is intrinsically disordered, the C-terminal conserved region may be an important part of the external mouth of this transporter, which controls protein function and stability by serving as an inter-molecular cork with a chain mechanism. These findings improve our understanding of the roles of the C-terminal tail of endosomal-type NHXs in plants and the ion transport mechanism of NHX-like antiporters.
Collapse
Affiliation(s)
- Boning Cao
- State Key Laboratory of Silkworm Genome Biology, Key Laboratory for Sericulture Functional Genomics and Biotechnology of Agricultural Ministry, Southwest University, Chongqing, 400716, China
| | - Zhongqiang Xia
- State Key Laboratory of Silkworm Genome Biology, Key Laboratory for Sericulture Functional Genomics and Biotechnology of Agricultural Ministry, Southwest University, Chongqing, 400716, China
| | - Zhanzhang Hao
- State Key Laboratory of Silkworm Genome Biology, Key Laboratory for Sericulture Functional Genomics and Biotechnology of Agricultural Ministry, Southwest University, Chongqing, 400716, China
| | - Changying Liu
- State Key Laboratory of Silkworm Genome Biology, Key Laboratory for Sericulture Functional Genomics and Biotechnology of Agricultural Ministry, Southwest University, Chongqing, 400716, China
| | - Dingpei Long
- State Key Laboratory of Silkworm Genome Biology, Key Laboratory for Sericulture Functional Genomics and Biotechnology of Agricultural Ministry, Southwest University, Chongqing, 400716, China
| | - Wei Fan
- State Key Laboratory of Silkworm Genome Biology, Key Laboratory for Sericulture Functional Genomics and Biotechnology of Agricultural Ministry, Southwest University, Chongqing, 400716, China
| | - Aichun Zhao
- State Key Laboratory of Silkworm Genome Biology, Key Laboratory for Sericulture Functional Genomics and Biotechnology of Agricultural Ministry, Southwest University, Chongqing, 400716, China.
| |
Collapse
|
5
|
Pedersen SF, Counillon L. The SLC9A-C Mammalian Na +/H + Exchanger Family: Molecules, Mechanisms, and Physiology. Physiol Rev 2019; 99:2015-2113. [PMID: 31507243 DOI: 10.1152/physrev.00028.2018] [Citation(s) in RCA: 103] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Na+/H+ exchangers play pivotal roles in the control of cell and tissue pH by mediating the electroneutral exchange of Na+ and H+ across cellular membranes. They belong to an ancient family of highly evolutionarily conserved proteins, and they play essential physiological roles in all phyla. In this review, we focus on the mammalian Na+/H+ exchangers (NHEs), the solute carrier (SLC) 9 family. This family of electroneutral transporters constitutes three branches: SLC9A, -B, and -C. Within these, each isoform exhibits distinct tissue expression profiles, regulation, and physiological roles. Some of these transporters are highly studied, with hundreds of original articles, and some are still only rudimentarily understood. In this review, we present and discuss the pioneering original work as well as the current state-of-the-art research on mammalian NHEs. We aim to provide the reader with a comprehensive view of core knowledge and recent insights into each family member, from gene organization over protein structure and regulation to physiological and pathophysiological roles. Particular attention is given to the integrated physiology of NHEs in the main organ systems. We provide several novel analyses and useful overviews, and we pinpoint main remaining enigmas, which we hope will inspire novel research on these highly versatile proteins.
Collapse
Affiliation(s)
- S F Pedersen
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark; and Université Côte d'Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, LP2M, France, and Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| | - L Counillon
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark; and Université Côte d'Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, LP2M, France, and Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| |
Collapse
|
6
|
Ulmschneider B, Grillo-Hill BK, Benitez M, Azimova DR, Barber DL, Nystul TG. Increased intracellular pH is necessary for adult epithelial and embryonic stem cell differentiation. J Cell Biol 2017; 215:345-355. [PMID: 27821494 PMCID: PMC5100294 DOI: 10.1083/jcb.201606042] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Revised: 08/18/2016] [Accepted: 10/05/2016] [Indexed: 12/19/2022] Open
Abstract
Despite extensive knowledge about the transcriptional regulation of stem cell differentiation, less is known about the role of dynamic cytosolic cues. We report that an increase in intracellular pH (pHi) is necessary for the efficient differentiation of Drosophila adult follicle stem cells (FSCs) and mouse embryonic stem cells (mESCs). We show that pHi increases with differentiation from FSCs to prefollicle cells (pFCs) and follicle cells. Loss of the Drosophila Na+-H+ exchanger DNhe2 lowers pHi in differentiating cells, impairs pFC differentiation, disrupts germarium morphology, and decreases fecundity. In contrast, increasing pHi promotes excess pFC cell differentiation toward a polar/stalk cell fate through suppressing Hedgehog pathway activity. Increased pHi also occurs with mESC differentiation and, when prevented, attenuates spontaneous differentiation of naive cells, as determined by expression of microRNA clusters and stage-specific markers. Our findings reveal a previously unrecognized role of pHi dynamics for the differentiation of two distinct types of stem cell lineages, which opens new directions for understanding conserved regulatory mechanisms.
Collapse
Affiliation(s)
- Bryne Ulmschneider
- Department of Anatomy, University of California, San Francisco, San Francisco, CA 94143.,Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, San Francisco, CA 94143
| | - Bree K Grillo-Hill
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94143.,Department of Biological Sciences, San Jose State University, San Jose, CA 95192
| | - Marimar Benitez
- Department of Anatomy, University of California, San Francisco, San Francisco, CA 94143.,Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, San Francisco, CA 94143
| | - Dinara R Azimova
- Department of Anatomy, University of California, San Francisco, San Francisco, CA 94143.,Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, San Francisco, CA 94143
| | - Diane L Barber
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94143
| | - Todd G Nystul
- Department of Anatomy, University of California, San Francisco, San Francisco, CA 94143 .,Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, San Francisco, CA 94143
| |
Collapse
|
7
|
Short B. A basic guide to stem cell differentiation. J Biophys Biochem Cytol 2016. [DOI: 10.1083/jcb.2153if] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Increasing intracellular pH promotes the differentiation of adult and embryonic stem cells.
Collapse
|
8
|
Ejzykowicz DE, Locken KM, Ruiz FJ, Manandhar SP, Olson DK, Gharakhanian E. Hygromycin B hypersensitive (hhy) mutants implicate an intact trans-Golgi and late endosome interface in efficient Tor1 vacuolar localization and TORC1 function. Curr Genet 2016; 63:531-551. [PMID: 27812735 DOI: 10.1007/s00294-016-0660-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Revised: 10/20/2016] [Accepted: 10/22/2016] [Indexed: 12/18/2022]
Abstract
Saccharomyces cerevisiae vacuoles are functionally analogous to mammalian lysosomes. Both also serve as physical platforms for Tor Complex 1 (TORC1) signal transduction, the master regulator of cellular growth and proliferation. Hygromycin B is a eukaryotic translation inhibitor. We recently reported on hygromycin B hypersensitive (hhy) mutants that fail to grow at subtranslation inhibitory concentrations of the drug and exhibit vacuolar defects (Banuelos et al. in Curr Genet 56:121-137, 2010). Here, we show that hhy phenotype is not due to increased sensitivity to translation inhibition and establish a super HHY (s-HHY) subgroup of genes comprised of ARF1, CHC1, DRS2, SAC1, VPS1, VPS34, VPS45, VPS52, and VPS54 that function exclusively or inclusively at trans-Golgi and late endosome interface. Live cell imaging of s-hhy mutants revealed that hygromycin B treatment disrupts vacuolar morphology and the localization of late endosome marker Pep12, but not that of late endosome-independent vacuolar SNARE Vam3. This, along with normal post-late endosome trafficking of the vital dye FM4-64, establishes that severe hypersensitivity to hygromycin B correlates specifically with compromised trans-Golgi and late endosome interface. We also show that Tor1p vacuolar localization and TORC1 anabolic functions, including growth promotion and phosphorylation of its direct substrate Sch9, are compromised in s-hhy mutants. Thus, an intact trans-Golgi and late endosome interface is a requisite for efficient Tor1 vacuolar localization and TORC1 function.
Collapse
Affiliation(s)
- Daniele E Ejzykowicz
- Department of Biological Sciences, California State University Long Beach, 1250 Bellflower Blvd, Long Beach, CA, 90840, USA
| | - Kristopher M Locken
- Department of Biological Sciences, California State University Long Beach, 1250 Bellflower Blvd, Long Beach, CA, 90840, USA
| | - Fiona J Ruiz
- Department of Biological Sciences, California State University Long Beach, 1250 Bellflower Blvd, Long Beach, CA, 90840, USA.,Department of Radiation Oncology, Cancer Biology Division, Washington University School of Medicine, Saint Louis, MO, 63108, USA
| | - Surya P Manandhar
- Department of Biological Sciences, California State University Long Beach, 1250 Bellflower Blvd, Long Beach, CA, 90840, USA
| | - Daniel K Olson
- Department of Biological Sciences, California State University Long Beach, 1250 Bellflower Blvd, Long Beach, CA, 90840, USA.,Inouye Center for Microbial Oceanography, Research and Education, University of Hawaii, Manoa, Honolulu, HI, 96822, USA
| | - Editte Gharakhanian
- Department of Biological Sciences, California State University Long Beach, 1250 Bellflower Blvd, Long Beach, CA, 90840, USA.
| |
Collapse
|
9
|
Zhu J, Ying SH, Feng MG. The Na + /H + antiporter Nhx1 controls vacuolar fusion indispensible for life cycles in vitro and in vivo in a fungal insect pathogen. Environ Microbiol 2016; 18:3884-3895. [PMID: 27112237 DOI: 10.1111/1462-2920.13359] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 04/21/2016] [Indexed: 01/10/2023]
Abstract
The sole Na+ /H+ antiporter Nhx1 has been generally unexplored in filamentous fungi. We characterized Nhx1 in the entomopathogenic fungus Beauveria bassiana. An eGFP-tagged Nhx1 fusion accumulated in small punctuate structures, presumably endosomal and trans-Golgi network compartments, between septum and tubular vacuole of each wild-type cell stained with a vacuole-specific dye. Deletion of nhx1 resulted in significant acidification and severe fusion defect in vacuoles, which were fragmented and distinct from large or tubular wild-type vacuoles. The deletion also caused a drastic reduction in aerial conidiation or submerged blastospore production and more severe defect in vegetative growth than in conidial germination. The Δnhx1 mutant became more sensitive to high osmolarity, heat shock and several metal ions during growth but its conidia showed increased UV-B tolerance. Intriguingly, Δnhx1 was unable to infect a model insect through cuticle penetration or intrahaemocoel injection because it produced much less biomass and cuticle-degrading enzymes in a minimal broth and failed to form blastospores in the insect haemolymph. All changes were completely or largely restored by targeted nhx1 complementation. Our results provide novel insight into an indispensability of Nhx1 for not only vacuolar fusion but also life cycles in vitro and in vivo in B. bassiana.
Collapse
Affiliation(s)
- Jing Zhu
- Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, People's Republic of China
| | - Sheng-Hua Ying
- Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, People's Republic of China
| | - Ming-Guang Feng
- Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, People's Republic of China
| |
Collapse
|
10
|
Yenush L. Potassium and Sodium Transport in Yeast. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 892:187-228. [DOI: 10.1007/978-3-319-25304-6_8] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
11
|
Kondapalli KC, Hack A, Schushan M, Landau M, Ben-Tal N, Rao R. Functional evaluation of autism-associated mutations in NHE9. Nat Commun 2013; 4:2510. [PMID: 24065030 PMCID: PMC3815575 DOI: 10.1038/ncomms3510] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Accepted: 08/23/2013] [Indexed: 12/23/2022] Open
Abstract
NHE9 (SLC9A9) is an endosomal cation/proton antiporter with orthologues in yeast and bacteria. Rare, missense substitutions in NHE9 are genetically linked with autism but have not been functionally evaluated. Here we use evolutionary conservation analysis to build a model structure of NHE9 based on the crystal structure of bacterial NhaA and use it to screen autism-associated variants in the human population first by phenotype complementation in yeast, followed by functional analysis in primary cortical astrocytes from mouse. NHE9-GFP localizes to recycling endosomes, where it significantly alkalinizes luminal pH, elevates uptake of transferrin and the neurotransmitter glutamate, and stabilizes surface expression of transferrin receptor and GLAST transporter. In contrast, autism-associated variants L236S, S438P and V176I lack function in astrocytes. Thus, we establish a neurobiological cell model of a candidate gene in autism. Loss-of-function mutations in NHE9 may contribute to autistic phenotype by modulating synaptic membrane protein expression and neurotransmitter clearance.
Collapse
Affiliation(s)
- Kalyan C. Kondapalli
- Department of Physiology, Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA
| | - Anniesha Hack
- Department of Physiology, Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA
| | - Maya Schushan
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv, 69978 Tel-Aviv, Israel
| | - Meytal Landau
- Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - Nir Ben-Tal
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv, 69978 Tel-Aviv, Israel
| | - Rajini Rao
- Department of Physiology, Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA
| |
Collapse
|
12
|
Matsye PD, Lawrence GW, Youssef RM, Kim KH, Lawrence KS, Matthews BF, Klink VP. The expression of a naturally occurring, truncated allele of an α-SNAP gene suppresses plant parasitic nematode infection. PLANT MOLECULAR BIOLOGY 2012; 80:131-55. [PMID: 22689004 DOI: 10.1007/s11103-012-9932-z] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Accepted: 05/17/2012] [Indexed: 05/23/2023]
Abstract
Transcriptional mapping experiments of the major soybean cyst nematode resistance locus, rhg1, identified expression of the vesicular transport machinery component, α soluble NSF attachment protein (α-SNAP), occurring during defense. Sequencing the α-SNAP coding regions from the resistant genotypes G. max ([Peking/PI 548402]) and G. max ([PI 437654]) revealed they are identical, but differ from the susceptible G. max ([Williams 82/PI 518671]) by the presence of several single nucleotide polymorphisms. Using G. max ([Williams 82/PI 518671]) as a reference, a G → T(2,822) transversion in the genomic DNA sequence at a functional splice site of the α-SNAP([Peking/PI 548402]) allele produced an additional 17 nucleotides of mRNA sequence that contains an in-frame stop codon caused by a downstream G → A(2,832) transition. The G. max ([Peking/PI 548402]) genotype has cell wall appositions (CWAs), structures identified as forming as part of a defense response by the activity of the vesicular transport machinery. In contrast, the 17 nt α-SNAP([Peking/PI 548402]) mRNA motif is not found in G. max ([PI 88788]) that exhibits defense to H. glycines, but lack CWAs. The α-SNAP([PI 88788]) promoter contains sequence elements that are nearly identical to the α-SNAP([Peking/PI 548402]) allele, but differs from the G. max ([Williams 82/PI 518671]) ortholog. Overexpressing the α-SNAP([Peking/PI 548402]) allele in the susceptible G. max ([Williams 82/PI 518671]) genotype suppressed H. glycines infection. The experiments indicate a role for the vesicular transport machinery during infection of soybean by the soybean cyst nematode. However, increased GmEREBP1, PR1, PR2, PR5 gene activity but suppressed PR3 expression accompanied the overexpression of the α-SNAP([Peking/PI 548402]) allele prior to infection.
Collapse
Affiliation(s)
- Prachi D Matsye
- Department of Biological Sciences, Mississippi State University, Mississippi State, MS 39762, USA
| | | | | | | | | | | | | |
Collapse
|
13
|
Pineda Rodó A, Váchová L, Palková Z. In vivo determination of organellar pH using a universal wavelength-based confocal microscopy approach. PLoS One 2012; 7:e33229. [PMID: 22470445 PMCID: PMC3310042 DOI: 10.1371/journal.pone.0033229] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Accepted: 02/12/2012] [Indexed: 11/19/2022] Open
Abstract
Many essential cellular processes are affected by transmembrane H(+) gradients and intracellular pH (pHi). The research of such metabolic events calls for a non-invasive method to monitor pHi within individual subcellular compartments. We present a novel confocal microscopy approach for the determination of organellar pHi in living cells expressing pH-dependent ratiometric fluorescent proteins. Unlike conventional intensity-based fluorometry, our method relies on emission wavelength scans at single-organelle resolution to produce wavelength-based pH estimates both accurate and robust to low-signal artifacts. Analyses of Ato1p-pHluorin and Ato1p-mCherry yeast cells revealed previously unreported wavelength shifts in pHluorin emission which, together with ratiometric mCherry, allowed for high-precision quantification of actual physiological pH values and evidenced dynamic pHi changes throughout the different stages of yeast colony development. Additionally, comparative pH quantification of Ato1p-pHluorin and Met17p-pHluorin cells implied the existence of a significant pHi gradient between peripheral and internal cytoplasm of cells from colonies occurring in the ammonia-producing alkali developmental phase. Results represent a step forward in the study of pHi regulation and subcellular metabolic functions beyond the scope of this study.
Collapse
Affiliation(s)
- Albert Pineda Rodó
- Department of Genetics and Microbiology, Charles University, Prague, Czech Republic
| | - Libuše Váchová
- Department of Genetics and Microbiology, Charles University, Prague, Czech Republic
- Institute of Microbiology, Academy of Sciences, Prague, Czech Republic
| | - Zdena Palková
- Department of Genetics and Microbiology, Charles University, Prague, Czech Republic
| |
Collapse
|
14
|
Kallay LM, Brett CL, Tukaye DN, Wemmer MA, Chyou A, Odorizzi G, Rao R. Endosomal Na+ (K+)/H+ exchanger Nhx1/Vps44 functions independently and downstream of multivesicular body formation. J Biol Chem 2011; 286:44067-44077. [PMID: 21998311 DOI: 10.1074/jbc.m111.282319] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The multivesicular body (MVB) is an endosomal intermediate containing intralumenal vesicles destined for membrane protein degradation in the lysosome. In Saccharomyces cerevisiae, the MVB pathway is composed of 17 evolutionarily conserved ESCRT (endosomal sorting complex required for transport) genes grouped by their vacuole protein sorting Class E mutant phenotypes. Only one integral membrane protein, the endosomal Na+ (K+)/H+ exchanger Nhx1/Vps44, has been assigned to this class, but its role in the MVB pathway has not been directly tested. Herein, we first evaluated the link between Nhx1 and the ESCRT proteins and then used an unbiased phenomics approach to probe the cellular role of Nhx1. Select ESCRT mutants (vps36Δ, vps20Δ, snf7Δ, and bro1Δ) with defects in cargo packaging and intralumenal vesicle formation shared multiple growth phenotypes with nhx1Δ. However, analysis of cellular trafficking and ultrastructural examination by electron microscopy revealed that nhx1Δ cells retain the ability to sort cargo into intralumenal vesicles. In addition, we excluded a role for Nhx1 in Snf7/Bro1-mediated cargo deubiquitylation and Rim101 response to pH stress. Genetic epistasis experiments provided evidence that NHX1 and ESCRT genes function in parallel. A genome-wide screen for single gene deletion mutants that phenocopy nhx1Δ yielded a limited gene set enriched for endosome fusion function, including Rab signaling and actin cytoskeleton reorganization. In light of these findings and the absence of the so-called Class E compartment in nhx1Δ, we eliminated a requirement for Nhx1 in MVB formation and suggest an alternative post-ESCRT role in endosomal membrane fusion.
Collapse
Affiliation(s)
- Laura M Kallay
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Christopher L Brett
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Department of Biology, Concordia University, Montréal, Quebec H3G 1M8, Canada
| | - Deepali N Tukaye
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Megan A Wemmer
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309
| | - Anthony Chyou
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Greg Odorizzi
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309
| | - Rajini Rao
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
| |
Collapse
|
15
|
Chanroj S, Lu Y, Padmanaban S, Nanatani K, Uozumi N, Rao R, Sze H. Plant-specific cation/H+ exchanger 17 and its homologs are endomembrane K+ transporters with roles in protein sorting. J Biol Chem 2011; 286:33931-41. [PMID: 21795714 PMCID: PMC3190763 DOI: 10.1074/jbc.m111.252650] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Revised: 07/08/2011] [Indexed: 11/30/2022] Open
Abstract
The complexity of intracellular compartments in eukaryotic cells evolved to provide distinct environments to regulate processes necessary for cell proliferation and survival. A large family of predicted cation/proton exchangers (CHX), represented by 28 genes in Arabidopsis thaliana, are associated with diverse endomembrane compartments and tissues in plants, although their roles are poorly understood. We expressed a phylogenetically related cluster of CHX genes, encoded by CHX15-CHX20, in yeast and bacterial cells engineered to lack multiple cation-handling mechanisms. Of these, CHX16-CHX20 were implicated in pH homeostasis because their expression rescued the alkaline pH-sensitive growth phenotype of the host yeast strain. A smaller subset, CHX17-CHX19, also conferred tolerance to hygromycin B. Further differences were observed in K(+)- and low pH-dependent growth phenotypes. Although CHX17 did not alter cytoplasmic or vacuolar pH in yeast, CHX20 elicited acidification and alkalization of the cytosol and vacuole, respectively. Using heterologous expression in Escherichia coli strains lacking K(+) uptake systems, we provide evidence for K(+) ((86)Rb) transport mediated by CHX17 and CHX20. Finally, we show that CHX17 and CHX20 affected protein sorting as measured by carboxypeptidase Y secretion in yeast mutants grown at alkaline pH. In plant cells, CHX20-RFP co-localized with an endoplasmic reticulum marker, whereas RFP-tagged CHX17-CHX19 co-localized with prevacuolar compartment and endosome markers. Together, these results suggest that in response to environmental cues, multiple CHX transporters differentially modulate K(+) and pH homeostasis of distinct intracellular compartments, which alter membrane trafficking events likely to be critical for adaptation and survival.
Collapse
Affiliation(s)
- Salil Chanroj
- From the Department of Cell Biology and Molecular Genetics and the Maryland Agricultural Experiment Station, University of Maryland, College Park, Maryland 20742
| | - Yongxian Lu
- From the Department of Cell Biology and Molecular Genetics and the Maryland Agricultural Experiment Station, University of Maryland, College Park, Maryland 20742
| | - Senthilkumar Padmanaban
- From the Department of Cell Biology and Molecular Genetics and the Maryland Agricultural Experiment Station, University of Maryland, College Park, Maryland 20742
| | - Kei Nanatani
- the Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan
| | - Nobuyuki Uozumi
- the Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan
| | - Rajini Rao
- the Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, and
| | - Heven Sze
- From the Department of Cell Biology and Molecular Genetics and the Maryland Agricultural Experiment Station, University of Maryland, College Park, Maryland 20742
| |
Collapse
|
16
|
Grefen C, Honsbein A, Blatt MR. Ion transport, membrane traffic and cellular volume control. CURRENT OPINION IN PLANT BIOLOGY 2011; 14:332-9. [PMID: 21507708 DOI: 10.1016/j.pbi.2011.03.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Revised: 03/09/2011] [Accepted: 03/23/2011] [Indexed: 05/21/2023]
Abstract
Throughout their development, plants balance cell surface area and volume with ion transport and turgor. This balance lies at the core of cellular homeostatic networks and is central to the capacity to withstand abiotic as well as biotic stress. Remarkably, very little is known of its mechanics, notably how membrane traffic is coupled with osmotic solute transport and its control. Here we outline recent developments in the understanding of so-called SNARE proteins that form part of the machinery for membrane vesicle traffic in all eukaryotes. We focus on SNAREs active at the plasma membrane and the evidence for specialisation in enhanced, homeostatic and stress-related traffic. Recent studies have placed a canonical SNARE complex associated with the plasma membrane in pathogen defense, and the discovery of the first SNARE as a binding partner with ion channels has demonstrated a fundamental link to inorganic osmotic solute uptake. Work localising the channel binding site has now identified a new and previously uncharacterised motif, yielding important clues to a plausible mechanism coupling traffic and transport. We examine the evidence that this physical interaction serves to balance enhanced osmotic solute uptake with membrane expansion through mutual control of the two processes. We calculate that even during rapid cell expansion only a minute fraction of SNAREs present at the membrane need be engaged in vesicle traffic at any one time, a number surprisingly close to the known density of ion channels at the plant plasma membrane. Finally, we suggest a framework of alternative models coupling transport and traffic, and approachable through direct, experimental testing.
Collapse
Affiliation(s)
- Christopher Grefen
- Laboratory of Plant Physiology and Biophysics, Institute of Molecular, Cellular and Systems Biology, University of Glasgow, Glasgow, UK
| | | | | |
Collapse
|
17
|
Honsbein A, Blatt MR, Grefen C. A molecular framework for coupling cellular volume and osmotic solute transport control. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:2363-2370. [PMID: 21115662 DOI: 10.1093/jxb/erq386] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Eukaryotic cells expand using vesicle traffic to increase membrane surface area. Expansion in walled eukaryotes is driven by turgor pressure which depends fundamentally on the uptake and accumulation of inorganic ions. Thus, ion uptake and vesicle traffic must be controlled coordinately for growth. How this coordination is achieved is still poorly understood, yet is so elemental to life that resolving the underlying mechanisms will have profound implications for our understanding of cell proliferation, development, and pathogenesis, and will find applications in addressing the mineral and water use by plants in the face of global environmental change. Recent discoveries of interactions between trafficking and ion transport proteins now open the door to an entirely new approach to understanding this coordination. Some of the advances to date in identifying key protein partners in the model plant Arabidopsis and in yeast at membranes vital for cell volume and turgor control are outlined here. Additionally, new evidence is provided of a wider participation among Arabidopsis Kv-like K(+) channels in selective interaction with the vesicle-trafficking protein SYP121. These advances suggest some common paradigms that will help guide further exploration of the underlying connection between ion transport and membrane traffic and should transform our understanding of cellular homeostasis in eukaryotes.
Collapse
Affiliation(s)
- Annegret Honsbein
- Laboratory of Plant Physiology and Biophysics, Institute of Molecular, Cellular and Systems Biology, Bower Building, University of Glasgow, Glasgow G12 8QQ, UK
| | | | | |
Collapse
|
18
|
Orij R, Brul S, Smits GJ. Intracellular pH is a tightly controlled signal in yeast. Biochim Biophys Acta Gen Subj 2011; 1810:933-44. [PMID: 21421024 DOI: 10.1016/j.bbagen.2011.03.011] [Citation(s) in RCA: 162] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Revised: 03/15/2011] [Accepted: 03/15/2011] [Indexed: 11/25/2022]
Abstract
BACKGROUND Nearly all processes in living cells are pH dependent, which is why intracellular pH (pH(i)) is a tightly regulated physiological parameter in all cellular systems. However, in microbes such as yeast, pH(i) responds to extracellular conditions such as the availability of nutrients. This raises the question of how pH(i) dynamics affect cellular function. SCOPE OF REVIEW We discuss the control of pH(i,) and the regulation of processes by pH(i), focusing on the model organism Saccharomyces cerevisiae. We aim to dissect the effects of pH(i) on various aspects of cell physiology, which are often intertwined. Our goal is to provide a broad overview of how pH(i) is controlled in yeast, and how pH(i) in turn controls physiology, in the context of both general cellular functioning as well as of cellular decision making upon changes in the cell's environment. MAJOR CONCLUSIONS Besides a better understanding of the regulation of pH(i), evidence for a signaling role of pH(i) is accumulating. We conclude that pH(i) responds to nutritional cues and relays this information to alter cellular make-up and physiology. The physicochemical properties of pH allow the signal to be fast, and affect multiple regulatory levels simultaneously. GENERAL SIGNIFICANCE The mechanisms for regulation of processes by pH(i) are tightly linked to the molecules that are part of all living cells, and the biophysical properties of the signal are universal amongst all living organisms, and similar types of regulation are suggested in mammals. Therefore, dynamic control of cellular decision making by pH(i) is therefore likely a general trait. This article is part of a Special Issue entitled: Systems Biology of Microorganisms.
Collapse
Affiliation(s)
- Rick Orij
- Swammerdam Institute for Life Sciences, University of Amsterdam, the Netherlands.
| | | | | |
Collapse
|
19
|
Qiu QS, Fratti RA. The Na+/H+ exchanger Nhx1p regulates the initiation of Saccharomyces cerevisiae vacuole fusion. J Cell Sci 2010; 123:3266-75. [DOI: 10.1242/jcs.067637] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Nhx1p is a Na+(K+)/H+ antiporter localized at the vacuolar membrane of the yeast Saccharomyces cerevisiae. Nhx1p regulates the acidification of cytosol and vacuole lumen, and is involved in membrane traffic from late endosomes to the vacuole. Deletion of the gene leads to aberrant vacuolar morphology and defective vacuolar protein sorting. These phenotypes are hallmarks of malfunctioning vacuole homeostasis and indicate that membrane fusion is probably altered. Here, we investigated the role of Nhx1p in the regulation of homotypic vacuole fusion. Vacuoles isolated from nhx1Δ yeast showed attenuated fusion. Assays configured to differentiate between the first round of fusion and ongoing rounds showed that nhx1Δ vacuoles were only defective in the first round of fusion, suggesting that Nhx1p regulates an early step in the pathway. Although fusion was impaired on nhx1Δ vacuoles, SNARE complex formation was indistinguishable from wild-type vacuoles. Fusion could be rescued by adding the soluble SNARE Vam7p. However, Vam7p only activated the first round of nhx1Δ vacuole fusion. Once fusion was initiated, nhx1Δ vacuoles appeared behave in a wild-type manner. Complementation studies showed that ion transport function was required for Nhx1p-mediated support of fusion. In addition, the weak base chloroquine restored nhx1Δ fusion to wild-type levels. Together, these data indicate that Nhx1p regulates the initiation of fusion by controlling vacuole lumen pH.
Collapse
Affiliation(s)
- Quan-Sheng Qiu
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- School of Life Sciences, Lanzhou University, Lanzhou City, Tianshui Road 222, 730000, China
| | - Rutilio A. Fratti
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| |
Collapse
|
20
|
Sodium or potassium efflux ATPase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:1841-53. [DOI: 10.1016/j.bbamem.2010.07.009] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2010] [Revised: 07/06/2010] [Accepted: 07/13/2010] [Indexed: 12/20/2022]
|
21
|
Cagnac O, Aranda-Sicilia MN, Leterrier M, Rodriguez-Rosales MP, Venema K. Vacuolar cation/H+ antiporters of Saccharomyces cerevisiae. J Biol Chem 2010; 285:33914-22. [PMID: 20709757 DOI: 10.1074/jbc.m110.116590] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We previously demonstrated that Saccharomyces cerevisiae vnx1Δ mutant strains displayed an almost total loss of Na(+) and K(+)/H(+) antiporter activity in a vacuole-enriched fraction. However, using different in vitro transport conditions, we were able to reveal additional K(+)/H(+) antiporter activity. By disrupting genes encoding transporters potentially involved in the vnx1 mutant strain, we determined that Vcx1p is responsible for this activity. This result was further confirmed by complementation of the vnx1Δvcx1Δ nhx1Δ triple mutant with Vcx1p and its inactivated mutant Vcx1p-H303A. Like the Ca(2+)/H(+) antiporter activity catalyzed by Vcx1p, the K(+)/H(+) antiporter activity was strongly inhibited by Cd(2+) and to a lesser extend by Zn(2+). Unlike as previously observed for NHX1 or VNX1, VCX1 overexpression only marginally improved the growth of yeast strain AXT3 in the presence of high concentrations of K(+) and had no effect on hygromycin sensitivity. Subcellular localization showed that Vcx1p and Vnx1p are targeted to the vacuolar membrane, whereas Nhx1p is targeted to prevacuoles. The relative importance of Nhx1p, Vnx1p, and Vcx1p in the vacuolar accumulation of monovalent cations will be discussed.
Collapse
Affiliation(s)
- Olivier Cagnac
- Departamento de Bioquímica, Biología Celular y Molecular de Plantas, Estacion Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Apartado 419, E-18080 Granada, Spain.
| | | | | | | | | |
Collapse
|
22
|
Abstract
The maintenance of appropriate intracellular concentrations of alkali metal cations, principally K(+) and Na(+), is of utmost importance for living cells, since they determine cell volume, intracellular pH, and potential across the plasma membrane, among other important cellular parameters. Yeasts have developed a number of strategies to adapt to large variations in the concentrations of these cations in the environment, basically by controlling transport processes. Plasma membrane high-affinity K(+) transporters allow intracellular accumulation of this cation even when it is scarce in the environment. Exposure to high concentrations of Na(+) can be tolerated due to the existence of an Na(+), K(+)-ATPase and an Na(+), K(+)/H(+)-antiporter, which contribute to the potassium balance as well. Cations can also be sequestered through various antiporters into intracellular organelles, such as the vacuole. Although some uncertainties still persist, the nature of the major structural components responsible for alkali metal cation fluxes across yeast membranes has been defined within the last 20 years. In contrast, the regulatory components and their interactions are, in many cases, still unclear. Conserved signaling pathways (e.g., calcineurin and HOG) are known to participate in the regulation of influx and efflux processes at the plasma membrane level, even though the molecular details are obscure. Similarly, very little is known about the regulation of organellar transport and homeostasis of alkali metal cations. The aim of this review is to provide a comprehensive and up-to-date vision of the mechanisms responsible for alkali metal cation transport and their regulation in the model yeast Saccharomyces cerevisiae and to establish, when possible, comparisons with other yeasts and higher plants.
Collapse
|
23
|
Banuelos MG, Moreno DE, Olson DK, Nguyen Q, Ricarte F, Aguilera-Sandoval CR, Gharakhanian E. Genomic analysis of severe hypersensitivity to hygromycin B reveals linkage to vacuolar defects and new vacuolar gene functions in Saccharomyces cerevisiae. Curr Genet 2009; 56:121-37. [PMID: 20043226 DOI: 10.1007/s00294-009-0285-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Revised: 11/30/2009] [Accepted: 12/16/2009] [Indexed: 12/19/2022]
Abstract
The vacuole of Saccharomyces cerevisiae has been a seminal model for studies of lysosomal trafficking, biogenesis, and function. Several yeast mutants defective in such vacuolar events have been unable to grow at low levels of hygromycin B, an aminoglycoside antibiotic. We hypothesized that such severe hypersensitivity to hygromycin B (hhy) is linked to vacuolar defects and performed a genomic screen for the phenotype using a haploid deletion strain library of non-essential genes. Fourteen HHY genes were initially identified and were subjected to bioinformatics analyses. The uncovered hhy mutants were experimentally characterized with respect to vesicular trafficking, vacuole morphology, and growth under various stress and drug conditions. The combination of bioinformatics analyses and phenotypic characterizations implicate defects in vesicular trafficking, vacuole fusion/fission, or vacuole function in all hhy mutants. The collection was enriched for sensitivity to monensin, indicative of vacuolar trafficking defects. Additionally, all hhy mutants showed severe sensitivities to rapamycin and caffeine, suggestive of TOR kinase pathway defects. Our experimental results also establish a new role in vacuolar and vesicular functions for two genes: PAF1, encoding a RNAP II-associated protein required for expression of cell cycle-regulated genes, and TPD3, encoding the regulatory subunit of protein phosphatase 2A. Thus, our results support linkage between severe hypersensitivity to hygromycin B and vacuolar defects.
Collapse
Affiliation(s)
- M G Banuelos
- Department of Biological Sciences, California State University at Long Beach, 1250 Bellflower Blvd, Long Beach, CA 90840, USA
| | | | | | | | | | | | | |
Collapse
|
24
|
Donowitz M, Mohan S, Zhu CX, Chen TE, Lin R, Cha B, Zachos NC, Murtazina R, Sarker R, Li X. NHE3 regulatory complexes. ACTA ACUST UNITED AC 2009; 212:1638-46. [PMID: 19448074 DOI: 10.1242/jeb.028605] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The epithelial brush border Na/H exchanger NHE3 is active under basal conditions and functions as part of neutral NaCl absorption in the intestine and renal proximal tubule, where it accounts for the majority of total Na absorbed. NHE3 is highly regulated. Both stimulation and inhibition occur post-prandially. This digestion related regulation of NHE3 is mimicked by multiple extracellular agonists and intracellular second messengers. The regulation of NHE3 depends on its C-terminal cytoplasmic domain, which acts as a scaffold to bind multiple regulatory proteins and links NHE3 to the cytoskeleton. The cytoskeletal association occurs by both direct binding to ezrin and by indirect binding via ezrin binding to the C-terminus of the multi-PDZ domain containing proteins NHERF1 and NHERF2. This is a review of the domain structure of NHE3 and of the scaffolding function and role in the regulation of NHE3 of the NHE3 C-terminal domain.
Collapse
Affiliation(s)
- Mark Donowitz
- Johns Hopkins University School of Medicine, 720 Rutland Avenue Baltimore, MD 21205, USA.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Hernández A, Jiang X, Cubero B, Nieto PM, Bressan RA, Hasegawa PM, Pardo JM. Mutants of the Arabidopsis thaliana cation/H+ antiporter AtNHX1 conferring increased salt tolerance in yeast: the endosome/prevacuolar compartment is a target for salt toxicity. J Biol Chem 2009; 284:14276-85. [PMID: 19307188 PMCID: PMC2682876 DOI: 10.1074/jbc.m806203200] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2008] [Revised: 03/19/2009] [Indexed: 01/13/2023] Open
Abstract
Mutants of the plant cation/H(+) antiporter AtNHX1 that confer greater halotolerance were generated by random mutagenesis and selected in yeast by phenotypic complementation. The amino acid substitutions that were selected were conservative and occurred in the second half of the membrane-associated N terminus. AtNHX1 complemented the lack of endogenous ScNHX1 in endosomal protein trafficking assays. Growth enhancement on hygromycin B and vanadate media agreed with a generally improved endosomal/prevacuolar function of the mutated proteins. In vivo measurements by (31)P NMR revealed that wild-type and mutant AtNHX1 transporters did not affect cytosolic or vacuolar pH. Surprisingly, when yeast cells were challenged with lithium, a tracer for sodium, the main effect of the mutations in AtNHX1 was a reduction in the amount of compartmentalized lithium. When purified and reconstituted into proteoliposomes or assayed in intact vacuoles isolated from yeast cells, a representative mutant transporter (V318I) showed a greater cation discrimination favoring potassium transport over that of sodium or lithium. Together, our data suggest that the endosome/prevacuolar compartment is a target for salt toxicity. Poisoning by toxic cations in the endosome/prevacuolar compartment is detrimental for cell functions, but it can be alleviated by improving the discrimination of transported alkali cations by the resident cation/H(+) antiporter.
Collapse
Affiliation(s)
- Agustín Hernández
- Instituto de Recursos Naturales y Agrobiología, Consejo Superior de Investigaciones Científicas (IRNASE-CSIC), Avda. Reina Mercedes 10, Seville 41012, Spain
| | | | | | | | | | | | | |
Collapse
|
26
|
Rodríguez-Rosales MP, Gálvez FJ, Huertas R, Aranda MN, Baghour M, Cagnac O, Venema K. Plant NHX cation/proton antiporters. PLANT SIGNALING & BEHAVIOR 2009; 4:265-76. [PMID: 19794841 PMCID: PMC2664485 DOI: 10.4161/psb.4.4.7919] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Accepted: 01/23/2009] [Indexed: 05/18/2023]
Abstract
Although physiological and biochemical data since long suggested that Na(+)/H(+) and K(+)/H(+) antiporters are involved in intracellular ion and pH regulation in plants, it has taken a long time to identify genes encoding antiporters that could fulfil these roles. Genome sequencing projects have now shown that plants contain a very large number of putative Cation/Proton antiporters, the function of which is only beginning to be studied. The intracellular NHX transporters constitute the first Cation/Proton exchanger family studied in plants. The founding member, AtNHX1, was identified as an important salt tolerance determinant and suggested to catalyze Na(+) accumulation in vacuoles. It is, however, becoming increasingly clear, that this gene and other members of the family also play crucial roles in pH regulation and K(+) homeostasis, regulating processes from vesicle trafficking and cell expansion to plant development.
Collapse
|
27
|
Chen S, Tarsio M, Kane PM, Greenberg ML. Cardiolipin mediates cross-talk between mitochondria and the vacuole. Mol Biol Cell 2008; 19:5047-58. [PMID: 18799619 DOI: 10.1091/mbc.e08-05-0486] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Cardiolipin (CL) is an anionic phospholipid with a dimeric structure predominantly localized in the mitochondrial inner membrane, where it is closely associated with mitochondrial function, biogenesis, and genome stability (Daum, 1985; Janitor and Subik, 1993; Jiang et al., 2000; Schlame et al., 2000; Zhong et al., 2004). Previous studies have shown that yeast mutant cells lacking CL due to a disruption in CRD1, the structural gene encoding CL synthase, exhibit defective colony formation at elevated temperature even on glucose medium (Jiang et al., 1999; Zhong et al., 2004), suggesting a role for CL in cellular processes apart from mitochondrial bioenergetics. In the current study, we present evidence that the crd1Delta mutant exhibits severe vacuolar defects, including swollen vacuole morphology and loss of vacuolar acidification, at 37 degrees C. Moreover, vacuoles from crd1Delta show decreased vacuolar H(+)-ATPase activity and proton pumping, which may contribute to loss of vacuolar acidification. Deletion mutants in RTG2 and NHX1, which mediate vacuolar pH and ion homeostasis, rescue the defective colony formation phenotype of crd1Delta, strongly suggesting that the temperature sensitivity of crd1Delta is a consequence of the vacuolar defects. Our results demonstrate the existence of a novel mitochondria-vacuole signaling pathway mediated by CL synthesis.
Collapse
Affiliation(s)
- Shuliang Chen
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA
| | | | | | | |
Collapse
|
28
|
A novel immunodetection screen for vacuolar defects identifies a unique allele of VPS35 in S. cerevisiae. Mol Cell Biochem 2008; 311:121-36. [PMID: 18224426 DOI: 10.1007/s11010-008-9703-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2007] [Accepted: 01/10/2008] [Indexed: 12/11/2022]
Abstract
The late endosome and vacuole of yeast Saccharomyces cerevisiae are functionally equivalent to the mammalian late endosome and lysosome. The late endosome is the convergence point of the biosynthetic and endocytic trafficking to the vacuole. Here, we describe a novel immunodetection screen to isolate mutants defective in trafficking the soluble hydrolase carboxypeptidase Y (CPY) at the late endosome to vacuole interface (env mutants). Mutants exhibit vacuolar morphology and endocytosis defects as assayed by electron, fluorescent, and nomarski microscopy. In biochemical assays, they internally accumulate p2CPY in a dense membrane compartment lacking vacuolar properties yet display normal secretion phenotypes. The results suggest vacuolar morphology and function defects that are exclusively at the late endosome/vacuole interface. env mutants define five complementation groups. The first gene of the collection to be cloned, ENV1 is allelic to VPS35 whose established function is in retrograde trafficking from late endosome to trans-Golgi network (TGN). Microscopic, biochemical, and growth analyses establish that env1 is distinct from other alleles of VPS35 in vacuolar morphology, growth characteristics, and internal accumulation of p2CPY. Our results indicate that ENV genes may define new gene functions at the late endosome to vacuole interface.
Collapse
|
29
|
Abstract
NHE3 is the brush-border (BB) Na+/H+exchanger of small intestine, colon, and renal proximal tubule which is involved in large amounts of neutral Na+absorption. NHE3 is a highly regulated transporter, being both stimulated and inhibited by signaling that mimics the postprandial state. It also undergoes downregulation in diarrheal diseases as well as changes in renal disorders. For this regulation, NHE3 exists in large, multiprotein complexes in which it associates with at least nine other proteins. This review deals with short-term regulation of NHE3 and the identity and function of its recognized interacting partners and the multiprotein complexes in which NHE3 functions.
Collapse
Affiliation(s)
- Mark Donowitz
- Department of Medicine, GI Division, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
| | | |
Collapse
|
30
|
Current awareness on yeast. Yeast 2007. [DOI: 10.1002/yea.1324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
|
31
|
Hill JK, Brett CL, Chyou A, Kallay LM, Sakaguchi M, Rao R, Gillespie PG. Vestibular hair bundles control pH with (Na+, K+)/H+ exchangers NHE6 and NHE9. J Neurosci 2006; 26:9944-55. [PMID: 17005858 PMCID: PMC6674470 DOI: 10.1523/jneurosci.2990-06.2006] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
In hair cells of the inner ear, robust Ca2+/H+ exchange mediated by plasma-membrane Ca2+-ATPase would rapidly acidify mechanically sensitive hair bundles without efficient removal of H+. We found that, whereas the basolateral membrane of vestibular hair cells from the frog saccule extrudes H+ via an Na+-dependent mechanism, bundles rapidly remove H+ in the absence of Na+ and HCO3(-), even when the soma is acidified. K+ was fully effective and sufficient for H+ removal; in contrast, Rb+ failed to support pH recovery. Na+/H+-exchanger isoform 1 (NHE1) was present on hair-cell soma membranes and was likely responsible for Na+-dependent H+ extrusion. NHE6 and NHE9 are organellar isoforms that can appear transiently on plasma membranes and have been proposed to mediate K+/H+ exchange. We identified NHE6 in a subset of hair bundles; NHE9 was present in all bundles. Heterologous expression of these isoforms in yeast strains lacking endogenous exchangers conferred pH-dependent tolerance to high levels of KCl and NaCl. NHE9 preferred cations in the order K+, Na+ >> Rb+, consistent with the relative efficacies of these ions in promoting pH recovery in hair bundles. Electroneutral K+/H+ exchange, which we propose is performed by NHE9 in hair bundles, exploits the high-K+ endolymph, responds only to pH imbalance across the bundle membrane, is unaffected by the +80 mV endocochlear potential, and uses mechanisms already present in the ear for K+ recycling. This mechanism allows the hair cell to remove H+ generated by Ca2+ pumping without ATP hydrolysis in the cell.
Collapse
Affiliation(s)
- Jennifer K. Hill
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239
| | - Christopher L. Brett
- Department of Physiology, Johns Hopkins University, Baltimore, Maryland 21205, and
| | - Anthony Chyou
- Department of Physiology, Johns Hopkins University, Baltimore, Maryland 21205, and
| | - Laura M. Kallay
- Department of Physiology, Johns Hopkins University, Baltimore, Maryland 21205, and
| | - Masao Sakaguchi
- Graduate School of Life Science, University of Hyogo, Ako, Hyogo 678-1297, Japan
| | - Rajini Rao
- Department of Physiology, Johns Hopkins University, Baltimore, Maryland 21205, and
| | - Peter G. Gillespie
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239
| |
Collapse
|