Crossreaction with an anti-Bax antibody reveals novel multi-endocrine cellular antigen.
We found a novel protein that has crossreactivity with a polyclonal anti-Bax antibody (SCBAX antibody). The protein was localized exclusively in the endocrine cells of hypothalamus, pituitary gland, and pancreatic islets. Immunohistochemical (IHC) double labeling revealed that the cells showing crossreactivity with this antibody corresponded precisely to oxytocin neurons and ACTH, alpha-MSH, and glucagon cells in rat and gerbil. By immunoelectron microscopy, the protein was localized predominantly in and just around the secretory granules in the cytoplasm but not in the mitochondria. Double-labeling IHC with the anti-Bax SCBAX antibody and two anti-Bax monoclonal antibodies (MAbs) showed that cells stained with the anti-Bax SCBAX antibody were not stained with anti-Bax MAbs except for very few cells (probably apoptotic cells). Western blotting analysis revealed that the molecular mass of the protein was approximately 55 kD, which differs from that of Bax protein (21 kD). These findings indicate that the anti-Bax SCBAX antibody recognizes not only pro-apoptotic Bax protein (a 21-kD mitochondrial protein) but also an unknown substance present in one endocrine cell group in each endocrine organ. Therefore, the protein is designated as multi-endocrine cellular antigen (MECA). MECA is probably a 55-kD protein secreted from the particular differentiated cell groups of endocrine tissues.
Utsunomiya
Kazuhiro
K
Department of Anatomy and Cell Science, Kansai Medical University, Moriguchi-City, Osaka, Japan.
Watanabe
Jun
J
Takamori
Yasuharu
Y
Kataoka
Yosky
Y
Kurokawa
Kiyoshi
K
Yamada
Hisao
H
D000818:Animals; D000906:Antibodies; D000941:Antigens / Q000276:immunology / Q000378:metabolism*; D015153:Blotting, Western; D003429:Cross Reactions; D004703:Endocrine System / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D005849:Gerbillinae; D007150:Immunohistochemistry; D008297:Male; D016253:Microscopy, Immunoelectron; D009928:Organ Specificity; D011518:Proto-Oncogene Proteins / Q000276:immunology* / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2; D051381:Rats; D017208:Rats, Wistar; D051028:bcl-2-Associated X Protein
D000906:Antibodies; D000941:Antigens; C494828:Bax protein, rat; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein