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Pituitary |
Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110
LH, FSH, and chorionic gonadotropin (CG) are comprised of a common
subunit and a hormone-specific ß subunit. Using Madin-Darby canine kidney (MDCK) epithelial cells to examine the polarized secretion of human CG/LH, we previously reported that CG and LH were detected in the apical and basolateral compartments, respectively, and the carboxyl terminal end of the CGß subunit contains a strong apical signal. Here we show that the carboxyl seven amino acids in the LHß subunit contribute to the basolateral secretion of LH, and an LH chimera bearing the CGß apical signal is redirected from the basolateral to the apical compartments. Because LH and FSH are synthesized in the same cell, we also compared the secretion polarity of LH with FSH. MDCK cells expressing the FSH dimer displayed an almost equal distribution of protein into the apical and basolateral compartments. Given that the LHß and CGß carboxy terminal sequences, which differ from that in the FSHß subunit, occupy a pivotal role in their polarized behavior, the results support the hypothesis that pituitary exit of LH and FSH occur via different secretion pathways, and are released spatially from the pituitary via different circulatory routes.
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S. Nakav, A. Jablonka-Shariff, S. Kaner, P. Chadna-Mohanty, H. E. Grotjan, and D. Ben-Menahem The LH{beta} Gene of Several Mammals Embeds a Carboxyl-terminal Peptide-like Sequence Revealing a Critical Role for Mucin Oligosaccharides in the Evolution of Lutropin to Chorionic Gonadotropin in the Animal Phyla J. Biol. Chem., April 29, 2005; 280(17): 16676 - 16684. [Abstract] [Full Text] [PDF] |
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