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J. Biol. Chem., Vol. 277, Issue 2, 879-882, January 11, 2002

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ACCELERATED PUBLICATION
Evolution of Lutropin to Chorionic Gonadotropin Generates a Specific Routing Signal for Apical Release in Vivo^*

Albina Jablonka-Shariff, Vicenta Garcia-Campayo, and Irving Boime^§

From the Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110

One of the fundamental differences among mammals is the mechanism of maintaining the corpus luteum of pregnancy. Placentation in primates is associated with the production of the glycoprotein hormone chorionic gonadotropin (CG), which is secreted into the maternal serum and stimulates progesterone synthesis from the corpus luteum, which is essential for early development of the embryo. CG together with the pituitary hormones lutropin (LH), follitropin, and thyrotropin constitute the family of glycoprotein hormones comprised of a common  subunit and a hormone-specific  subunit. The LH and CG subunits share 85% amino acid sequence identity, and functionally LH and CG are interchangeable. CG evolved by a recent gene duplication event from the LH locus, and despite the close relationship between them, their modes of secretion are quite different. CG release from the placenta is apically directed, whereas LH is released from the basal side of the cell, and the determinant(s) for this redirected trafficking are unknown. Here, using the polarized Madin-Darby canine kidney (MDCK) cell line, we provide evidence for the molecular basis of the different secretory patterns of LH and CG in vivo. The apical targeting of CG is programmed by a carboxyl-terminal sequence, which encodes a novel sorting signal. It is also apparent that the presence of the O-linked oligosaccharides in the CTP sequence contributes to this apical routing. The CTP, which is absent in LH, redirects CG to the maternal serum and permits the unique arrangement for primate placentation. Our data also show that the MDCK cells can distinguish the different secretory pathways for the gonadotropins and will be a valuable model for elucidating the determinants associated with the unique sorting of these functionally related hormones.

This article has been cited by other articles:

				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]

				A. Jablonka-Shariff and I. Boime Luteinizing Hormone and Follicle-Stimulating Hormone Exhibit Different Secretion Patterns from Cultured Madin-Darby Canine Kidney Cells Biol Reprod, March 1, 2004; 70(3): 649 - 655. [Abstract] [Full Text] [PDF]

				M. M. Matzuk, F. J. DeMayo, L. A. Hadsell, and T. R. Kumar Overexpression of Human Chorionic Gonadotropin Causes Multiple Reproductive Defects in Transgenic Mice Biol Reprod, July 1, 2003; 69(1): 338 - 346. [Abstract] [Full Text] [PDF]