title: Cystinosin-LKG rescues cystine accumulation and decreases apoptosis rate in cystinotic proximal tubular epithelial cells.
abstract: Nephropathic cystinosis is a lysosomal storage disease that is caused by mutations in the CTNS gene encoding a cystine/proton symporter cystinosin and an isoform cystinosin-LKG which is generated by an alternative splicing of exon 12. We have investigated the physiological role of the cystinosin-LKG that is widely expressed in epithelial tissues.
  
  
  
  We have analyzed the intracellular localization and the function of the cystinosin-LKG conjugated with DsRed (cystinosin-LKG-RFP) in Madin-Darby canine kidney cells (MDCK II) and in proximal tubular epithelial cells carrying a deletion of the CTNS gene (cystinotic PTEC), respectively.
  
  
  
  Cystinosin-LKG-RFP colocalized with markers of lysosomes, late endosomes and was also expressed on the apical surface of polarized MDCK II cells. Moreover, immune-electron microscopy images of MDCK II cells overexpressing cystinosin-LKG-RFP showed stacked lamellar membranes inside perinuclear lysosomal structures. To study the role of LKG-isoform, we have investigated cystine accumulation and apoptosis that have been described in cystinotic cells. Cystinosin-LKG decreased cystine levels by approximately 10-fold similarly to cystinosin-RFP. The levels of TNFα- and actinomycin D-inducted apoptosis dropped in cystinotic cells expressing LKG-isoform. This effect was also similar to the main isoform.
  
  
  
  Our results suggest that cystinosin-LKG and cystinosin move similar functional activities in cells.
authors.affiliation: Department of Nephrology and Urology, Division of Nephrology, Bambino Gesù Children's Hospital and Research Institute, Rome, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Taranta
authors.affiliation: Department of Nephrology and Urology, Division of Nephrology, Bambino Gesù Children's Hospital and Research Institute, Rome, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Bellomo
authors.affiliation: Confocal Microscopy core facility, Research Center, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Petrini
authors.affiliation: Telethon Institute of Genetics and Medicine, Naples, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Polishchuk
authors.affiliation: Department of Nephrology and Urology, Division of Nephrology, Bambino Gesù Children's Hospital and Research Institute, Rome, Italy.
authors.forename: Ester
authors.initials: E
authors.lastname: De Leo
authors.affiliation: Department of Nephrology and Urology, Division of Nephrology, Bambino Gesù Children's Hospital and Research Institute, Rome, Italy.
authors.forename: Laura Rita
authors.initials: LR
authors.lastname: Rega
authors.affiliation: Laboratory of Metabolomics and Proteomics, Bambino Gesù Children's Hospital and Research Institute, Rome, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Pastore
authors.affiliation: Telethon Institute of Genetics and Medicine, Naples, Italy.
authors.forename: Roman
authors.initials: R
authors.lastname: Polishchuk
authors.affiliation: Telethon Institute of Genetics and Medicine, Naples, Italy.
authors.forename: Maria Antonietta
authors.initials: MA
authors.lastname: De Matteis
authors.affiliation: Department of Nephrology and Urology, Division of Nephrology, Bambino Gesù Children's Hospital and Research Institute, Rome, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Emma
mesh_terms: D017398:Alternative Splicing; D026921:Amino Acid Transport Systems, Neutral / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis; D002478:Cells, Cultured; D003553:Cystine / Q000378:metabolism*; D003554:Cystinosis / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D004285:Dogs; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000378:metabolism / Q000473:pathology; D008247:Lysosomes / Q000378:metabolism; D061985:Madin Darby Canine Kidney Cells; D046529:Microscopy, Electron, Transmission; D009154:Mutation; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D026921:Amino Acid Transport Systems, Neutral; C111445:CTNS protein, human; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D014409:Tumor Necrosis Factor-alpha; D003553:Cystine