title: Klotho ameliorates chemically induced endoplasmic reticulum (ER) stress signaling.
abstract: BACKGROUND
  Both endoplasmic reticulum (ER) stress, a fundamental cell response associated with stress-initiated unfolded protein response (UPR), and loss of Klotho, an anti-aging hormone linked to NF-κB-induced inflammation, occur in chronic metabolic diseases such as obesity and type 2 diabetes. We investigated if the loss of Klotho is causally linked to increased ER stress.
  
  
  METHODS
  We treated human renal epithelial HK-2, alveolar epithelial A549, HEK293, and SH-SH-SY5Y neuroblastoma cells with ER stress-inducing agents, thapsigargin and/or tunicamycin. Effects of overexpression or siRNA-mediated knockdown of Klotho on UPR signaling was investigated by immunoblotting and Real-time PCR.
  
  
  RESULTS
  Elevated Klotho levels in HK-2 cells decreased expression of ER stress markers phospho--IRE1, XBP-1s, BiP, CHOP, pJNK, and phospho-p38, all of which were elevated in response to tunicamycin and/or thapsigargin. Similar results were observed using A549 cells for XBP-1s, BiP, and CHOP in response to thapsigargin. Conversely, knockdown of Klotho in HEK 293 cells using siRNA caused further thapsigargin-induced increases in pIRE-1, XBP-1s, and BiP. Klotho overexpression in A549 cells blocked thapsigargin-induced caspase and PARP cleavage and improved cell viability.
  
  
  CONCLUSIONS
  Our data indicate that Klotho has an important role in regulating ER stress and that loss of Klotho is causally linked to ER stress-induced apoptosis.
authors.affiliation: Department of Internal Medicine, University of Texas Medical Branch, Galveston, TX 77555-1060, USA.
authors.forename: Srijita
authors.initials: S
authors.lastname: Banerjee
authors.forename: Yanhua
authors.initials: Y
authors.lastname: Zhao
authors.forename: Partha S
authors.initials: PS
authors.lastname: Sarkar
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Rosenblatt
authors.forename: Ronald G
authors.initials: RG
authors.lastname: Tilton
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Choudhary
mesh_terms: D017209:Apoptosis; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects; D005966:Glucuronidase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D000090265:Klotho Proteins; D010766:Phosphorylation; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction; D019284:Thapsigargin / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014415:Tunicamycin / Q000494:pharmacology; D056811:Unfolded Protein Response; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; D034741:RNA, Small Interfering; D014157:Transcription Factors; D014415:Tunicamycin; D019284:Thapsigargin; D011065:Poly(ADP-ribose) Polymerases; D017346:Protein Serine-Threonine Kinases; D005966:Glucuronidase; D000090265:Klotho Proteins; D020169:Caspases