title: A genetically encoded ratiometric sensor to measure extracellular pH in microdomains bounded by basolateral membranes of epithelial cells.
abstract: Extracellular pH, especially in relatively inaccessible microdomains between cells, affects transport membrane protein activity and might have an intercellular signaling role. We have developed a genetically encoded extracellular pH sensor capable of detecting pH changes in basolateral spaces of epithelial cells. It consists of a chimerical membrane protein displaying concatenated enhanced variants of cyan fluorescence protein (ECFP) and yellow fluorescence protein (EYFP) at the external aspect of the cell surface. The construct, termed pHCECSensor01, was targeted to basolateral membranes of Madin-Darby canine kidney (MDCK) cells by means of a sequence derived from the aquaporin AQP4. The fusion of pH-sensitive EYFP with pH-insensitive ECFP allows ratiometric pH measurements. The titration curve of pHCECSensor01 in vivo had a pK (a) value of 6.5 +/- 0.04. Only minor effects of extracellular chloride on pHCECSensor01 were observed around the physiological concentrations of this anion. In MDCK cells, the sensor was able to detect changes in pH secondary to H(+) efflux into the basolateral spaces elicited by an ammonium prepulse or lactate load. This genetically encoded sensor has the potential to serve as a noninvasive tool for monitoring changes in extracellular pH microdomains in epithelial and other tissues in vivo.
authors.affiliation: Centro de Estudios Científicos, Av. Arturo Prat 514, Valdivia, Chile.
authors.forename: Javier
authors.initials: J
authors.lastname: Urra
authors.forename: Moisés
authors.initials: M
authors.lastname: Sandoval
authors.forename: Isabel
authors.initials: I
authors.lastname: Cornejo
authors.forename: L Felipe
authors.initials: LF
authors.lastname: Barros
authors.forename: Francisco V
authors.initials: FV
authors.lastname: Sepúlveda
authors.forename: L Pablo
authors.initials: LP
authors.lastname: Cid
mesh_terms: D000818:Animals; D051401:Aquaporin 4 / Q000378:metabolism / Q000502:physiology; D001426:Bacterial Proteins / Q000737:chemistry; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism; D003627:Data Interpretation, Statistical; D004285:Dogs; D004847:Epithelial Cells / Q000502:physiology*; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins / Q000737:chemistry; D006859:Hydrogen / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000494:pharmacology; D008164:Luminescent Proteins / Q000737:chemistry; D050506:Mutant Chimeric Proteins / Q000378:metabolism / Q000502:physiology; D010957:Plasmids; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D011994:Recombinant Proteins / Q000235:genetics*
chemical_list: D051401:Aquaporin 4; D001426:Bacterial Proteins; D002712:Chlorides; C485182:Cyan Fluorescent Protein; D008164:Luminescent Proteins; D050506:Mutant Chimeric Proteins; D000644:Quaternary Ammonium Compounds; D011994:Recombinant Proteins; C054562:yellow fluorescent protein, Bacteria; D049452:Green Fluorescent Proteins; D019344:Lactic Acid; D006859:Hydrogen