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AIKO KITAHARA, HARUKI MIKAWA, HITOSHI OHTSUKI, YOKO YAMAGATA, TAKASHI MURACHI, REIJI KANNAGI, Specific Localization of Tissue-Type Transglutaminase in Adrenocorticotropin-Producing Cells of the Human Pituitary Gland as Demonstrated by Immunohistochemistry, The Journal of Clinical Endocrinology & Metabolism, Volume 65, Issue 5, 1 November 1987, Pages 885–890, https://doi.org/10.1210/jcem-65-5-885
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The distribution of transglutaminases, the Ca2+-dependent protein cross-linking enzymes, in the human pituitary gland was investigated by immunohistological methods using specific antibodies. Tissue-type transglutaminase was specifically localized in ACTH-producing cells, and the cells producing GH, PRL, TSH, FSH, and LH contained no appreciable amount of the enzyme. No detectable plasma-type transglutaminase (coagulation factor XIII) was found in pituitary tissue. In a previous study we demonstrated that ACTH-producing cells contain very little Ca2+-dependent proteinases (calpain), but a remarkable amount of their inhibitor, calpastatin. Pituitary gland cells producing hormones other than ACTH contained calpains, but no detectable calpastatin. These results collectively suggest that intracellular substrate proteins in ACTH-producing cells are protected from Ca2+-dependent degradation and are substrates for Ca2+-dependent cross-linking catalyzed by the tissue-type transglutaminase. In other pituitary gland cells, conversely, the intracellular substrate proteins are more likely to undergo Ca2+-dependent degradation than cross-linking.
