title: Fluorescent Visualization of Cellular Proton Fluxes.
abstract: Cells use plasma membrane proton fluxes to maintain cytoplasmic and extracellular pH and to mediate the co-transport of metabolites and ions. Because proton-coupled transport often involves movement of multiple substrates, traditional electrical measurements provide limited information about proton transport at the cell surface. Here we visualize voltage-dependent proton fluxes over the entire landscape of a cell by covalently attaching small-molecule fluorescent pH sensors to the cell's glycocalyx. We found that the extracellularly facing sensors enable real-time detection of proton accumulation and depletion at the plasma membrane, providing an indirect readout of channel and transporter activity that correlated with whole-cell proton current. Moreover, the proton wavefront emanating from one cell was readily visible as it crossed over nearby cells. Given that any small-molecule fluorescent sensor can be covalently attached to a cell's glycocalyx, our approach is readily adaptable to visualize most electrogenic and non-electrogenic transport events at the plasma membrane.
authors.affiliation: Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605-2324, USA; Programs in Neuroscience and Chemical Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605-2324, USA.
authors.forename: Lejie
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Biomedical Imaging Group, Molecular Medicine, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605-2324, USA.
authors.forename: Karl
authors.initials: K
authors.lastname: Bellve
authors.affiliation: Biomedical Imaging Group, Molecular Medicine, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605-2324, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Fogarty
authors.affiliation: Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605-2324, USA; Programs in Neuroscience and Chemical Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605-2324, USA. Electronic address: william.kobertz@umassmed.edu.
authors.forename: William R
authors.initials: WR
authors.lastname: Kobertz
keywords: glycocalyx; membrane transport; pH; proton-coupled transport; voltage-gatedion channels