title: Identification of a receptor for extracellular renalase.
abstract: BACKGROUND
  An increased risk for developing essential hypertension, stroke and diabetes is associated with single nucleotide gene polymorphisms in renalase, a newly described secreted flavoprotein with oxidoreductase activity. Gene deletion causes hypertension, and aggravates acute ischemic kidney (AKI) and cardiac injury. Independent of its intrinsic enzymatic activities, extracellular renalase activates MAPK signaling and prevents acute kidney injury (AKI) in wild type (WT) mice. Therefore, we sought to identity the receptor for extracellular renalase.
  
  
  RESULTS
  RP-220 is a previously identified, 20 amino acids long renalase peptide that is devoid of any intrinsic enzymatic activity, but it is equally effective as full-length recombinant renalase at protecting against toxic and ischemic injury. Using biotin transfer studies with RP-220 in the human proximal tubular cell line HK-2 and protein identification by mass spectrometry, we identified PMCA4b as a renalase binding protein. This previously characterized plasma membrane ATPase is involved in cell signaling and cardiac hypertrophy. Co-immunoprecipitation and co-immunolocalization confirmed protein-protein interaction between endogenous renalase and PMCA4b. Down-regulation of endogenous PMCA4b expression by siRNA transfection, or inhibition of its enzymatic activity by the specific peptide inhibitor caloxin1b each abrogated RP-220 dependent MAPK signaling and cytoprotection. In control studies, these maneuvers had no effect on epidermal growth factor mediated signaling, confirming specificity of the interaction between PMCA4b and renalase.
  
  
  CONCLUSIONS
  PMCA4b functions as a renalase receptor, and a key mediator of renalase dependent MAPK signaling.
authors.affiliation: Department of Medicine, VACHS, Yale University, New Haven, Connecticut, United States of America; Renal Division, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Medicine, VACHS, Yale University, New Haven, Connecticut, United States of America.
authors.forename: Heino
authors.initials: H
authors.lastname: Velazquez
authors.affiliation: Department of Medicine, VACHS, Yale University, New Haven, Connecticut, United States of America.
authors.forename: John
authors.initials: J
authors.lastname: Chang
authors.affiliation: Department of Medicine, VACHS, Yale University, New Haven, Connecticut, United States of America.
authors.forename: Robert
authors.initials: R
authors.lastname: Safirstein
authors.affiliation: Department of Medicine, VACHS, Yale University, New Haven, Connecticut, United States of America.
authors.forename: Gary V
authors.initials: GV
authors.lastname: Desir
mesh_terms: D058186:Acute Kidney Injury / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D019610:Cytoprotection / Q000235:genetics; D015536:Down-Regulation / Q000235:genetics; D004815:Epidermal Growth Factor / Q000235:genetics / Q000378:metabolism; D000075222:Essential Hypertension; D006801:Humans; D006973:Hypertension / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D008995:Monoamine Oxidase / Q000235:genetics / Q000378:metabolism*; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D054730:Protein Interaction Domains and Motifs / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics
chemical_list: D004815:Epidermal Growth Factor; D008995:Monoamine Oxidase; C521557:renalase; D020928:Mitogen-Activated Protein Kinases; C507517:ATP2B4 protein, human; D053499:Plasma Membrane Calcium-Transporting ATPases