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Peña A, Sánchez NS, Ramiro-Cortés Y, Calahorra M. Effects of medium pH on the yeast plasma membrane potential. Arch Biochem Biophys 2024:110131. [PMID: 39173699 DOI: 10.1016/j.abb.2024.110131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2024] [Revised: 05/24/2024] [Accepted: 08/19/2024] [Indexed: 08/24/2024]
Abstract
The effects of different pH incubation values and K+ on yeast plasma membrane potential (PMP) were studied both by the fluorescence changes and the accumulation of thioflavin T (ThT), a method that has been shown most adequate for both procedures. By the changes in fluorescence of ThT, the qualitative observation of PMP at the 3 evaluated pHs indicated that cells at pH 4.0 maintain a PMP lower, but close to the observed at pH 6.0 and 7.0. By measuring the accumulation of ThT and applying the Nernst equation on the different concentrations in and out, the values of PMP could also be estimated at the different pHs, resulting in values in mV, in agreement with our observations by following the fluorescence. Yeast cells at their native niches, or during fermentations must cope with low pHs, so the importance to maintain a robust PMP to survive. The contribution of bicarbonate, derived from the fermentation to the establishment of the PMP is also described. The experiments showed once more the efficacy of the methods used with this dye.
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Affiliation(s)
- Antonio Peña
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, 04510 México City, México.
| | - Norma Silvia Sánchez
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, 04510 México City, México.
| | - Yazmín Ramiro-Cortés
- Departamento de Neurodesarrollo y Fisiología, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, 04510 México City, México
| | - Martha Calahorra
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, 04510 México City, México
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4
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Verweij FJ, Bebelman MP, Jimenez CR, Garcia-Vallejo JJ, Janssen H, Neefjes J, Knol JC, de Goeij-de Haas R, Piersma SR, Baglio SR, Verhage M, Middeldorp JM, Zomer A, van Rheenen J, Coppolino MG, Hurbain I, Raposo G, Smit MJ, Toonen RFG, van Niel G, Pegtel DM. Quantifying exosome secretion from single cells reveals a modulatory role for GPCR signaling. J Cell Biol 2018; 217:1129-1142. [PMID: 29339438 PMCID: PMC5839777 DOI: 10.1083/jcb.201703206] [Citation(s) in RCA: 189] [Impact Index Per Article: 31.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 10/18/2017] [Accepted: 12/01/2017] [Indexed: 11/22/2022] Open
Abstract
All mammalian cells release small endosome-derived exosomes that function in intercellular communication, but the secretion process is poorly understood. Verweij et al. developed a live-imaging approach and demonstrate that external cues can trigger exosome release from a subpopulation of multivesicular bodies by phosphorylating the target membrane SNARE SNAP23 at serine residue 110. Exosomes are small endosome-derived extracellular vesicles implicated in cell–cell communication and are secreted by living cells when multivesicular bodies (MVBs) fuse with the plasma membrane (PM). Current techniques to study exosome physiology are based on isolation procedures after secretion, precluding direct and dynamic insight into the mechanics of exosome biogenesis and the regulation of their release. In this study, we propose real-time visualization of MVB–PM fusion to overcome these limitations. We designed tetraspanin-based pH-sensitive optical reporters that detect MVB–PM fusion using live total internal reflection fluorescence and dynamic correlative light–electron microscopy. Quantitative analysis demonstrates that MVB–PM fusion frequency is reduced by depleting the target membrane SNAREs SNAP23 and syntaxin-4 but also can be induced in single cells by stimulation of the histamine H1 receptor (H1HR). Interestingly, activation of H1R1 in HeLa cells increases Ser110 phosphorylation of SNAP23, promoting MVB–PM fusion and the release of CD63-enriched exosomes. Using this single-cell resolution approach, we highlight the modulatory dynamics of MVB exocytosis that will help to increase our understanding of exosome physiology and identify druggable targets in exosome-associated pathologies.
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Affiliation(s)
- Frederik Johannes Verweij
- Department of Pathology, Cancer Center Amsterdam, VU University Medical Center, Amsterdam, Netherlands .,Institut Curie, Paris Sciences et Lettres Research University, Centre National de la Recherché Scientifique, UMR 144, Paris, France.,Cell and Tissue Imaging Core Facility PICT-IBiSA, Institut Curie, Paris, France
| | - Maarten P Bebelman
- Department of Pathology, Cancer Center Amsterdam, VU University Medical Center, Amsterdam, Netherlands.,Division of Medicinal Chemistry, Amsterdam Institute for Molecules Medicines and Systems, VU University Amsterdam, Amsterdam, Netherlands
| | - Connie R Jimenez
- Department of Medical Oncology, Cancer Center Amsterdam, VU University Medical Center, Amsterdam, Netherlands
| | - Juan J Garcia-Vallejo
- Department of Molecular Cell Biology and Immunology, VU University Medical Center, Amsterdam, Netherlands
| | - Hans Janssen
- Division of Cell Biology, Netherlands Cancer Institute, Amsterdam, Netherlands
| | - Jacques Neefjes
- Department of Chemical Immunology, Leiden University Medical Center, Leiden, Netherlands
| | - Jaco C Knol
- Department of Medical Oncology, Cancer Center Amsterdam, VU University Medical Center, Amsterdam, Netherlands
| | - Richard de Goeij-de Haas
- Department of Medical Oncology, Cancer Center Amsterdam, VU University Medical Center, Amsterdam, Netherlands
| | - Sander R Piersma
- Department of Medical Oncology, Cancer Center Amsterdam, VU University Medical Center, Amsterdam, Netherlands
| | - S Rubina Baglio
- Department of Pathology, Cancer Center Amsterdam, VU University Medical Center, Amsterdam, Netherlands
| | - Matthijs Verhage
- Department of Clinical Genetics, VU University Medical Center, Amsterdam, Netherlands.,Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam, Netherlands
| | - Jaap M Middeldorp
- Department of Pathology, Cancer Center Amsterdam, VU University Medical Center, Amsterdam, Netherlands
| | - Anoek Zomer
- Cancer Genomics Netherlands-Hubrecht Institute-Koninklijke Nederlandse Akademie van Wetenschappen, Utrecht, Netherlands.,University Medical Centre Utrecht, Utrecht, Netherlands
| | - Jacco van Rheenen
- Cancer Genomics Netherlands-Hubrecht Institute-Koninklijke Nederlandse Akademie van Wetenschappen, Utrecht, Netherlands.,University Medical Centre Utrecht, Utrecht, Netherlands
| | - Marc G Coppolino
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Canada
| | - Ilse Hurbain
- Institut Curie, Paris Sciences et Lettres Research University, Centre National de la Recherché Scientifique, UMR 144, Paris, France.,Centre National de la Recherché Scientifique, UMR 144, Paris, France.,Cell and Tissue Imaging Core Facility PICT-IBiSA, Institut Curie, Paris, France
| | - Graça Raposo
- Institut Curie, Paris Sciences et Lettres Research University, Centre National de la Recherché Scientifique, UMR 144, Paris, France.,Centre National de la Recherché Scientifique, UMR 144, Paris, France.,Cell and Tissue Imaging Core Facility PICT-IBiSA, Institut Curie, Paris, France
| | - Martine J Smit
- Division of Medicinal Chemistry, Amsterdam Institute for Molecules Medicines and Systems, VU University Amsterdam, Amsterdam, Netherlands
| | - Ruud F G Toonen
- Department of Clinical Genetics, VU University Medical Center, Amsterdam, Netherlands.,Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam, Netherlands
| | - Guillaume van Niel
- Institut Curie, Paris Sciences et Lettres Research University, Centre National de la Recherché Scientifique, UMR 144, Paris, France.,Centre National de la Recherché Scientifique, UMR 144, Paris, France.,Cell and Tissue Imaging Core Facility PICT-IBiSA, Institut Curie, Paris, France
| | - D Michiel Pegtel
- Department of Pathology, Cancer Center Amsterdam, VU University Medical Center, Amsterdam, Netherlands
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Sun Y, O'Riordan MXD. Regulation of bacterial pathogenesis by intestinal short-chain Fatty acids. ADVANCES IN APPLIED MICROBIOLOGY 2013; 85:93-118. [PMID: 23942149 PMCID: PMC4029053 DOI: 10.1016/b978-0-12-407672-3.00003-4] [Citation(s) in RCA: 197] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The human gut microbiota is inextricably linked to health and disease. One important function of the commensal organisms living in the intestine is to provide colonization resistance against invading enteric pathogens. Because of the complex nature of the interaction between the microbiota and its host, multiple mechanisms likely contribute to resistance. In this review, we dissect the biological role of short-chain fatty acids (SCFA), which are fermentation end products of the intestinal microbiota, in host-pathogen interactions. SCFA exert an extensive influence on host physiology through nutritional, regulatory, and immunomodulatory functions and can also affect bacterial fitness as a form of acid stress. Moreover, SCFA act as a signal for virulence gene regulation in common enteric pathogens. Taken together, these studies highlight the importance of the chemical environment where the biology of the host, the microbiota, and the pathogen intersects, which provides a basis for designing effective infection prevention and control.
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Affiliation(s)
- Yvonne Sun
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA.
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Raven JA, Hurd CL. Ecophysiology of photosynthesis in macroalgae. PHOTOSYNTHESIS RESEARCH 2012; 113:105-25. [PMID: 22843100 DOI: 10.1007/s11120-012-9768-z] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Accepted: 07/04/2012] [Indexed: 05/07/2023]
Abstract
Macroalgae occur in the marine benthos from the upper intertidal to depths of more than 200 m, contributing up to 1 Pg C per year to global primary productivity. Freshwater macroalgae are mainly green (Chlorophyta) with some red (Rhodophyta) and a small contribution of brown (Phaeophyceae) algae, while in the ocean all three higher taxa are important. Attempts to relate the depth distribution of three higher taxa of marine macroalgae to their photosynthetic light use through their pigmentation in relation to variations in spectral quality of photosynthetically active radiation (PAR) with depth (complementary chromatic adaptation) and optical thickness (package effect) have been relatively unsuccessful. The presence (Chlorophyta, Phaeophyceae) or absence (Rhodophyta) of a xanthophyll cycle is also not well correlated with depth distribution of marine algae. The relative absence of freshwater brown algae does not seem to be related to their photosynthetic light use. Photosynthetic inorganic carbon acquisition in some red and a few green macroalgae involves entry of CO(2) by diffusion. Other red and green macroalgae, and brown macroalgae, have CO(2) concentrating mechanisms; these frequently involve acid and alkaline zones on the surface of the alga with CO(2) (produced from HCO(3) (-)) entering in the acid zones, while some macroalgae have CCMs based on active influx of HCO(3) (-). These various mechanisms of carbon acquisition have different responses to the thickness of the diffusion boundary layer, which is determined by macroalgal morphology and water velocity. Energetic predictions that macroalgae growing at or near the lower limit of PAR for growth should rely on diffusive CO(2) entry without acid and alkaline zones, and on NH(4) (+) rather than NO(3) (-) as nitrogen source, are only partially borne out by observation. The impact of global environmental change on marine macroalgae mainly relates to ocean acidification and warming with shoaling of the thermocline and decreased nutrient flux to the upper mixed layer. Predictions of the impact on macroalgae requires further experiments on interactions among increased inorganic carbon, increased temperature and decreased nitrogen and phosphorus supply, and, when possible, studies of genetic adaptation to environmental change.
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Affiliation(s)
- John A Raven
- Division of Plant Sciences, University of Dundee at the James Hutton Institute, Invergowrie, Dundee, DD2 5DA, Scotland, UK.
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Abstract
All of the photoreceptors involved in the absorption and transduction of light energy in photosynthesis are integral (carotenoid, chlorophyll) or peripheral (phycobilin) membrane proteins. The informational photoreceptors (phytochrome) and the flavoprotein (carotenoprotein?) cryptochrome, could be integral (carotenoprotein, flavoprotein) or peripheral or soluble (phytochrome, flavoprotein) pigment-protein complexes. The primary activity of the informational photoreceptors is unlikely to involve energization of primary active transport: the solute fluxes produced in this way would not form a quantitatively significant link in the perception-transduction-response sequence. By contrast, regulation of mediated solute fluxes at the plasmalemma could effect a substantial amplification of the absorbed photon signal, i.e. a large change in moles of solute transported could result from the absorption of 1 mol of photons. Modulation of the passive influx (or active efflux) of protons or calcium ions at the plasmalemma are likely targets for regulation by photoreceptors. Calcium flux regulation is particularly attractive in view of the ubiquity of calmodulin activity in eukaryotes, although problems could arise in maintaining the uniqueness of phytochrome messages
vis-à-vis
cryptochrome messages. Temporal analysis of the relation between photoreceptor changes and electrical effects resulting from changes in ion fluxes cannot, in general, rule out the involvement of intermediates between the redox or conformational change in the photoreceptor and the observed change in ion flux. Although slow in terms of the potential rate of change on solute fluxes resulting from direct interaction of a photoreceptor and a solute porter, the observed rates of signal transduction are well in excess of any obvious ‘need’ on the part of the plant in terms of rates of response to environmental changes.
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Gutknecht J. Proton conductance caused by long-chain fatty acids in phospholipid bilayer membranes. J Membr Biol 1988; 106:83-93. [PMID: 2852256 DOI: 10.1007/bf01871769] [Citation(s) in RCA: 104] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Mechanisms of proton conductance (GH) were investigated in phospholipid bilayer membranes containing long-chain fatty acids (lauric, myristic, palmitic, oleic or phytanic). Membranes were formed from diphytanoyl phosphatidylcholine in decane plus chlorodecane (usually 30% vol/vol). Fatty acids were added either to the aqueous phase or to the membrane-forming solution. Proton conductance was calculated from the steady-state total conductance and the H+ diffusion potential produced by a transmembrane pH gradient. Fatty acids caused GH to increase in proportion to the first power of the fatty acid concentration. The GH induced by fatty acids was inhibited by phloretin, low pH and serum albumin. GH was increased by chlorodecane, and the voltage dependence of GH was superlinear. The results suggest that fatty acids act as simple (A- type) proton carriers. The membrane: water partition coefficient (Kp) and adsorption coefficient (beta) were estimated by finding the membrane and aqueous fatty acid concentrations which gave identical values of GH. For palmitic and oleic acids Kp was about 10(5) and beta was about 10(-2) cm. The A- translocation or "flip-flop" rate (ka) was estimated from the value of GH and the fatty acid concentration in the membrane, assuming that A- translocation was the rate limiting step in H+ transport. The kA's were about 10(-4) sec-1, slower than classical weak-acid uncouplers by a factor of 10(5). Although long-chain fatty acids are relatively inefficient H+ carriers, they may cause significant biological H- conductance when present in the membrane at high concentrations, e.g., in ischemia, hypoxia, hormonally induced lipolysis, or certain hereditary disorders, e.g., Refsum's (phytanic acid storage) disease.
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Affiliation(s)
- J Gutknecht
- Department of Physiology, Duke University Medical Center, Durham, North Carolina 27706
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