Evidence for cross-talk between stanniocalcins

• Published in: Canadian journal of physiology and pharmacology Vol. 83; no. 11; pp. 953 - 956
• Main Authors: Paciga, Mark, James, Kathi, Gillespie, J Ryan J, Wagner, Graham F
• Format: Journal Article
• Language: English
• Published: Ottawa, Canada NRC Research Press 01.11.2005; National Research Council of Canada; Canadian Science Publishing NRC Research Press
• Subjects: Animals; Binding, Competitive; Biological and medical sciences; Cattle; Cell Membrane - metabolism; Cells, Cultured; Cellular biology; Chemicals; Corpus Luteum - cytology; Corpus Luteum - metabolism; Female; Fundamental and applied biological sciences. Psychology; Glycoproteins - metabolism; Hormone metabolism and regulation; Humans; Mammalian female genital system; Microsomes - metabolism; Peptides; Pharmacology; Progesterone; Progesterone - metabolism; Vertebrates: reproduction; Ligand; Ovarian hormone; Ovary; Vertebrata; Mammalia; Polypeptide; Female genital system; Corpus luteum; Peptidergic receptor; Progesterone; Sex steroid hormone; Mechanism of action; Release
• ISSN: 0008-4212; 1205-7541
• DOI: 10.1139/y05-055

There are 2 forms of stanniocalcin (STC) produced by the STC-1 gene; a 50 kDa polypeptide known as STC50 and a recently discovered group of higher molecular weight variants that are collectively referred to as big STC. Both have different tissue patterns of expression and different intracellular targeting pathways. STC50 functions locally in tissues such as muscle, liver, and kidney and is targeted to mitochondria. Big STC, on the other hand, is made by the ovaries. It signals both locally on nearby corpus luteal cells and systemically. Interestingly, however, receptor binding assays employing STC50 as the tracer have shown that the smaller ligand can bind equally to tissue receptors targeted by either form of the hormone. This suggests there may be cross-talk between ligands. The present study provides credence to this notion by demonstrating how the 2 hormones can compete for tissue receptors normally targeted by 1 form of the hormone (big STC). The results also reveal how STC50 can completely block the inhibitory effects of big STC on luteal cell progesterone release when added simultaneously. The findings therefore add credence to the possibility that there may be circumstances during which the 2 ligands functionally antagonize each other's actions.Key words: stanniocalcin (STC), STC50, big STC, receptor, antagonism, progesterone release.