title: Identification of KRT16 as a target of an autoantibody response in complex regional pain syndrome.
abstract: OBJECTIVE
  Using a mouse model of complex regional pain syndrome (CRPS), our goal was to identify autoantigens in the skin of the affected limb.
  
  
  METHODS
  A CRPS-like state was induced using the tibia fracture/cast immobilization model. Three weeks after fracture, hindpaw skin was homogenized, run on 2-d gels, and probed by sera from fracture and control mice. Spots of interest were analyzed by liquid chromatography-mass spectroscopy (LC-MS) and the list of targets validated by examining their abundance and subcellular localization. In order to measure the autoantigenicity of selected protein targets, we quantified the binding of IgM in control and fracture mice sera, as well as in control and CRPS human sera, to the recombinant protein.
  
  
  RESULTS
  We show unique binding between fracture skin extracts and fracture sera, suggesting the presence of auto-antigens. LC-MS analysis provided us a list of potential targets, some of which were upregulated after fracture (KRT16, eEF1a1, and PRPH), while others showed subcellular-redistribution and increased membrane localization (ANXA2 and ENO3). No changes in protein citrullination or carbamylation were observed. In addition to increased abundance, KRT16 demonstrated autoantigenicity, since sera from both fracture mice and CRPS patients showed increased autoantibody binding to recombinant kRT16 protein.
  
  
  CONCLUSIONS
  Pursuing autoimmune contributions to CRPS provides a novel approach to understanding the condition and may allow the development of mechanism-based therapies. The identification of autoantibodies against KRT16 as a biomarker in mice and in humans is a critical step towards these goals, and towards redefining CRPS as having an autoimmune etiology.
authors: Veterans Affairs Palo Alto Health Care System Palo Alto, CA, USA; Department of Anesthesiology, Stanford University School of Medicine, Stanford, CA, USA; Palo Alto Veterans Institute for Research, Palo Alto, CA, USA. Electronic address: maral@stanford.edu.
authors: Maral
authors: M
authors: Tajerian
authors: Veterans Affairs Palo Alto Health Care System Palo Alto, CA, USA; Palo Alto Veterans Institute for Research, Palo Alto, CA, USA.
authors: Victor
authors: V
authors: Hung
authors: Veterans Affairs Palo Alto Health Care System Palo Alto, CA, USA; Palo Alto Veterans Institute for Research, Palo Alto, CA, USA.
authors: Hamda
authors: H
authors: Khan
authors: Veterans Affairs Palo Alto Health Care System Palo Alto, CA, USA; Palo Alto Veterans Institute for Research, Palo Alto, CA, USA; Division of Immunology and Rheumatology, Stanford University, Stanford, CA, USA.
authors: Lauren J
authors: LJ
authors: Lahey
authors: Veterans Affairs Palo Alto Health Care System Palo Alto, CA, USA; Department of Anesthesiology, Stanford University School of Medicine, Stanford, CA, USA; Palo Alto Veterans Institute for Research, Palo Alto, CA, USA.
authors: Yuan
authors: Y
authors: Sun
authors: Department of Neurology, University Medical Center, Mainz, Germany.
authors: Frank
authors: F
authors: Birklein
authors: Department of Neurology, Justus Liebig University, Giessen, Germany.
authors: Heidrun H
authors: HH
authors: Krämer
authors: Veterans Affairs Palo Alto Health Care System Palo Alto, CA, USA; Palo Alto Veterans Institute for Research, Palo Alto, CA, USA; Division of Immunology and Rheumatology, Stanford University, Stanford, CA, USA.
authors: William H
authors: WH
authors: Robinson
authors: Veterans Affairs Palo Alto Health Care System Palo Alto, CA, USA; Palo Alto Veterans Institute for Research, Palo Alto, CA, USA; Physical Medicine and Rehabilitation Service, Veterans Affairs Palo Alto Health Care System, Palo Alto, CA, USA.
authors: Wade S
authors: WS
authors: Kingery
authors: Veterans Affairs Palo Alto Health Care System Palo Alto, CA, USA; Department of Anesthesiology, Stanford University School of Medicine, Stanford, CA, USA; Palo Alto Veterans Institute for Research, Palo Alto, CA, USA.
authors: J David
authors: JD
authors: Clark
mesh_terms: D000328:Adult; D000818:Animals; D017306:Annexin A2 / Q000378:metabolism; D001324:Autoantigens / Q000235:genetics / Q000378:metabolism*; D020918:Complex Regional Pain Syndromes / Q000097:blood* / Q000473:pathology*; D004195:Disease Models, Animal; D006614:Hindlimb / Q000294:innervation; D006801:Humans; D053553:Keratin-6 / Q000276:immunology* / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008875:Middle Aged; D020648:Peptide Elongation Factor 1 / Q000378:metabolism; D064531:Peripherins / Q000378:metabolism; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D012867:Skin / Q000378:metabolism* / Q000648:ultrastructure*; D013347:Subcellular Fractions / Q000378:metabolism; D013978:Tibial Fractures / Q000097:blood / Q000473:pathology; D015854:Up-Regulation / Q000502:physiology*; D055815:Young Adult
chemical_list: C472822:ANXA2 protein, human; D017306:Annexin A2; D001324:Autoantigens; C094814:EEF1A1 protein, human; C507569:KRT6A protein, human; D053553:Keratin-6; C578994:PRPH protein, human; D020648:Peptide Elongation Factor 1; D064531:Peripherins; D010751:Phosphopyruvate Hydratase
keywords: Animal models of pain; Antigen identification; Autoimmunity; Chronic pain; Complex regional pain syndrome; Keratin 16; Skin