title: Cellular colocalization and coregulation between hypothalamic pro-TRH and prohormone convertases in hypothyroidism.
abstract: The prohormone convertases (PCs), PC1/3 and PC2, are involved in the tissue-specific endoproteolytic posttranslational processing of many hormonal precursors within the secretory pathway. One important prohormone, pro-thyrotropin-releasing hormone (TRH), is expressed in both hypophysiotropic (where it regulates the secretion of thyroid-stimulating hormone) and nonhypophysiotropic regions of the brain. Pro-TRH is processed at specific sites in the secretory pathway, primarily by PC1/3 followed by PC2. We hypothesized that thyroid hormone status in specific nuclei of the brain would alter pro-TRH processing by inducing changes in PC1/3 and PC2 expression. Therefore, we examined pro-TRH, PC1/3, and PC2 coexpression and coregulation in the paraventricular nucleus (PVN), lateral hypothalamus (LH), and ventromedial nucleus (VMN) of hypothyroid and euthyroid rats. Our results show that 6-n-propyl-2-thiouracil (PTU) treatment producing hypothyroidism induced a significant increase in the expression of PC1/3, PC2, and pro-TRH in the PVN and LH, but not VMN. When confocal studies were performed, an increase in colocalization of PC1/3 or PC2 in pro-TRH was observed only in PVN, a response that was especially prominent in the ventral and medial areas of the PVN. PTU did not regulate colocalization in the VMH or LH. Regulation of colocalization of processing enzyme and prohormone expression is a novel mechanism to alter hormonal biosynthesis.
authors.affiliation: Charles R. Drew Univ. of Medicine & Sciences, Division of Endocrinology, 1731 E. 120th St., Los Angeles, CA 90059, USA.
authors.forename: Veronica Paez
authors.initials: VP
authors.lastname: Espinosa
authors.forename: Monica
authors.initials: M
authors.lastname: Ferrini
authors.forename: Xiaoxiong
authors.initials: X
authors.lastname: Shen
authors.forename: Kabirullah
authors.initials: K
authors.lastname: Lutfy
authors.forename: Eduardo A
authors.initials: EA
authors.lastname: Nillni
authors.forename: Theodore C
authors.initials: TC
authors.lastname: Friedman
mesh_terms: D000818:Animals; D005786:Gene Expression Regulation; D007037:Hypothyroidism / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D008954:Models, Biological; D009474:Neurons / Q000378:metabolism; D010286:Paraventricular Hypothalamic Nucleus / Q000378:metabolism; D045664:Proprotein Convertase 1 / Q000378:metabolism; D045706:Proprotein Convertase 2 / Q000378:metabolism; D043484:Proprotein Convertases / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: D011498:Protein Precursors; D013973:Thyrotropin-Releasing Hormone; C046418:pro-thyrotropin releasing hormone; D043484:Proprotein Convertases; D045664:Proprotein Convertase 1; D045706:Proprotein Convertase 2; D011761:Pyrrolidonecarboxylic Acid