title: Identification of the novel autoantigen candidate Rab GDP dissociation inhibitor alpha in isolated adrenocorticotropin deficiency.
abstract: Isolated adrenocorticotropin deficiency (IAD) is characterized by low or absent adrenocorticotropic hormone (ACTH) production. IAD is presumed to be caused in part by an autoimmune mechanism, and several lines of evidence have suggested the presence of anti-pituitary antibodies in IAD. However, the exact autoantigens remain unknown. The present study was designed to identify the autoantigen(s) in IAD using chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Rat anterior pituitary lysate was subjected to SDS-PAGE, and immunoblotting was performed using the sera from two patients with IAD and from a healthy subject. The bands detected by the patient serum samples, but not by the healthy subject sample, were excised, in-gel digested using trypsin, and subjected to LC-MS/MS analysis. On immunoblots, a 51-kDa band in the insoluble pellet was detected by the sera from the IAD patients but not from the healthy subject. Mass spectrometric analysis revealed the 51-kDa band contained Rab guanine nucleotide dissociation inhibitor (GDI) alpha. Consistent with the mass spectrometric analysis, a recombinant full-length human Rab GDI alpha was recognized by the two IAD patient samples but not by the healthy subject sample using immunoblotting. In total, anti-Rab GDI alpha antibodies were detected in serum samples from three of five patients with IAD (60%) but were absent in 5 healthy subjects. In addition, Rab GDI alpha was expressed in the anterior pituitary. In conclusion, it appears that Rab GDI alpha is a candidate autoantigen involved in IAD, and that anti-Rab GDI alpha antibodies are present predominantly in patients with IAD.
authors.affiliation: Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kiyota
authors.forename: Shintaro
authors.initials: S
authors.lastname: Iwama
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Sugimura
authors.forename: Seiji
authors.initials: S
authors.lastname: Takeuchi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takagi
authors.forename: Naoko
authors.initials: N
authors.lastname: Iwata
authors.forename: Kohtaro
authors.initials: K
authors.lastname: Nakashima
authors.forename: Haruyuki
authors.initials: H
authors.lastname: Suzuki
authors.forename: Tomoki
authors.initials: T
authors.lastname: Nishioka
authors.forename: Takuya
authors.initials: T
authors.lastname: Kato
authors.forename: Atsushi
authors.initials: A
authors.lastname: Enomoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Arima
authors.forename: Kozo
authors.initials: K
authors.lastname: Kaibuchi
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Oiso
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood / Q000172:deficiency* / Q000276:immunology / Q000378:metabolism; D000328:Adult; D000368:Aged; D000818:Animals; D000918:Antibody Specificity; D001323:Autoantibodies / Q000032:analysis*; D001324:Autoantigens / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001327:Autoimmune Diseases / Q000097:blood / Q000276:immunology / Q000378:metabolism*; D015551:Autoimmunity; D004700:Endocrine System Diseases / Q000097:blood / Q000276:immunology / Q000378:metabolism*; D005260:Female; D030342:Genetic Diseases, Inborn / Q000097:blood / Q000276:immunology / Q000378:metabolism*; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007003:Hypoglycemia / Q000097:blood / Q000276:immunology / Q000378:metabolism*; D007564:Japan; D008297:Male; D008875:Middle Aged; D008970:Molecular Weight; D010449:Peptide Mapping; D010903:Pituitary Gland, Anterior / Q000276:immunology / Q000378:metabolism*; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013047:Specific Pathogen-Free Organisms
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; C086796:GDP dissociation inhibitor 1; D020730:Guanine Nucleotide Dissociation Inhibitors; D011994:Recombinant Proteins; D000324:Adrenocorticotropic Hormone