title: Cyclophilin C-associated protein/Mac-2 binding protein colocalizes with calnexin and regulates the expression of tissue transglutaminase.
abstract: Cyclophilin C-associated protein (CyCAP) or Mac-2 binding protein has been identified as a binding protein for cyclophilin C in mice and for Mac-2 (galectin-3) in human, suggesting its multiple binding activity to proteins. In the present study, using specific anti-rat-CyCAP antibody, we found that CyCAP colocalizes with calnexin at the location near the nuclear envelope, however CyCAP does not have colocalization with calreticulin. In senescent fibroblasts and interferon-gamma (IFNgamma) treated fibroblasts, both calnexin and CyCAP form larger polymers and are released from the endoplasmic reticulum (ER) through the cellular membrane to the extracellular area. Immunoprecipitation studies further confirm that the release of calnexin is through binding to CyCAP. Further, we found that tissue transglutaminase (tTG) protein is decreased, however not at the RNA level, in CyCAP null fibroblasts, which suggests that CyCAP is involved in tTG post-translational modification. Our data give novel evidence that CyCAP regulates the post-translational modification of tTG through its colocalization with calnexin in ER.
authors.affiliation: Children's Surgical Research Program, Stanford University School of Medicine, Stanford, California 94305-5148, USA. wkong@stanford.edu
authors.forename: Wuyi
authors.initials: W
authors.lastname: Kong
authors.forename: Bryan W
authors.initials: BW
authors.lastname: Lin
authors.forename: Shaowei
authors.initials: S
authors.lastname: Li
authors.forename: Michael T
authors.initials: MT
authors.lastname: Longaker
authors.forename: H Peter
authors.initials: HP
authors.lastname: Lorenz
mesh_terms: D000818:Animals; D037281:Calnexin / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D016922:Cellular Senescence; D004261:DNA Replication; D004721:Endoplasmic Reticulum / Q000201:enzymology; D016326:Extracellular Matrix Proteins; D005347:Fibroblasts / Q000201:enzymology* / Q000473:pathology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006023:Glycoproteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D007371:Interferon-gamma / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D009685:Nuclear Envelope / Q000378:metabolism; D011485:Protein Binding; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011499:Protein Processing, Post-Translational; D051381:Rats; D017207:Rats, Sprague-Dawley; D055647:Rats, Transgenic; D012867:Skin / Q000201:enzymology* / Q000293:injuries / Q000473:pathology; D011503:Transglutaminases / Q000378:metabolism*; D022161:Transport Vesicles / Q000201:enzymology; D014945:Wound Healing
chemical_list: D002352:Carrier Proteins; D016326:Extracellular Matrix Proteins; D006023:Glycoproteins; C492608:Lgals3bp protein, rat; D009419:Nerve Tissue Proteins; C082349:Ppicap protein, mouse; D037281:Calnexin; D007371:Interferon-gamma; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins