title: Serendipitous discovery of a novel protein signaling mechanism in heart failure.
abstract: A number of protein signaling mechanisms are known to be involved in the progression of heart failure, yet the mechanism(s) by which the heart fails remains poorly understood. Therefore, we undertook a global approach to this question and used an antibody microarray to identify proteins differentially expressed in dysfunctional right ventricles in a bovine model of heart failure and the results were validated using cardiac tissue from both bovine and human heart failure. We found that protein disulfide isomerase 3, PDIA3, a protein that resides in the lumen of the endoplasmic reticulum, is significantly upregulated in both animal and human models of right and left heart failure. Altered expression of this protein has not previously been described in models of heart failure. In our initial microarray analysis, we found that CSK (c-Src kinase) was among the proteins upregulated in failing bovine ventricle. To further elucidate the role of CSK in heart failure, we studied the expression of its downstream target, Src, and found that Src expression and phosphorylation were markedly upregulated in failing ventricles. However, we also noted a smaller immunologically reactive protein that was only seen in experimental animals. In order to positively identify the smaller, Src-reactive protein, we used 2-dimensional gel electrophoresis and mass spectrophotometry. Surprisingly, we identified this protein as PDIA3, a protein that did not belong to the Src family of proteins. Upon sequence examination we found that PDIA3 contains a short C-terminal sequence with strong homology to Src and that it was this short sequence to which the antibody was generated. PDIA3 participates in MHC class I presentation and is implicated in the progression of valvular dysfunction in rheumatic heart disease, as well as calcium modulation in the sarcoplasmic reticulum. The molecule resides in the lumen of the endoplasmic reticulum and participates in disulfide bond formation during protein folding by interacting with calnexin and calreticulin. This interaction may indirectly effect SERCA (sarco/endoplasmic reticulum Ca(2+)-transport ATPase) activity and by extension contribute to the calcium dysregulation that characterizes progressive heart failure. Further studies are needed to elucidate the role that PDIA3 may play in the progression of heart failure.
authors.affiliation: University of Colorado, Department of Medicine, Division of Cardiology, Aurora, CO 80045, USA.
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Vitello
authors.forename: Yanmei
authors.initials: Y
authors.lastname: Du
authors.forename: Peter M
authors.initials: PM
authors.lastname: Buttrick
authors.forename: Lori A
authors.initials: LA
authors.lastname: Walker
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D017951:Antigen Presentation; D002417:Cattle; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004721:Endoplasmic Reticulum / Q000201:enzymology; D006333:Heart Failure / Q000201:enzymology* / Q000276:immunology; D006352:Heart Ventricles / Q000201:enzymology*; D015395:Histocompatibility Antigens Class I / Q000276:immunology; D006801:Humans; D016056:Immunodominant Epitopes / Q000737:chemistry / Q000276:immunology; D008969:Molecular Sequence Data; D040081:Protein Array Analysis; D019704:Protein Disulfide-Isomerases / Q000096:biosynthesis* / Q000737:chemistry / Q000276:immunology; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism; D015398:Signal Transduction; D018487:Ventricular Dysfunction, Left / Q000201:enzymology*; D018497:Ventricular Dysfunction, Right / Q000201:enzymology*; D019061:src-Family Kinases / Q000276:immunology / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D015395:Histocompatibility Antigens Class I; D016056:Immunodominant Epitopes; D019061:src-Family Kinases; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D019704:Protein Disulfide-Isomerases; C085868:PDIA3 protein, human