Adrenalectomy facilitates ATAT1 expression and α-tubulin acetylation in ACTH-producing corticotrophs

Microtubules play an important role in the intracellular transport of secretory granules in endocrine cells and in mitosis and the maintenance of cell morphology and are composed of heterodimers of α- and β-tubulin. α-Tubulin N-acetyltransferase 1 (ATAT1), which acetylates the lysine residue at position 40 of α-tubulin, functions not only in stabilizing microtubule structures and forming the primary cilium assembly but also in vesicular trafficking in neurons. However, the localization of ATAT1 and the role of α-tubulin acetylation in endocrine cells in the pituitary are still poorly understood. Corticotrophs in the anterior lobe of the pituitary produce and secrete adrenocorticotropin (ACTH). Although removal of the adrenal gland, a target organ of ACTH, is reported to promote the synthesis and secretion of ACTH in corticotrophs and to induce structural alterations in their organelles, uncertainty remains as to whether the acetylation of α-tubulin is involved in such intracellular events of corticotrophs. We investigate the expression and localization of ATAT1 and the acetylation of α-tubulin in the pituitary of normal and adrenalectomized rats. We find that ATAT1 is localized to the Golgi apparatus of endocrine cells in the anterior lobe of normal pituitary and that the expression levels of ATAT1 and acetylation levels of α-tubulin increase following adrenalectomy. These results agree with the hypothesis that the acetylation of α-tubulin by ATAT1 regulates the intracellular transport of secretory granules in corticotrophs.