Stanniocalcin from an ancient teleost: a monomeric form of the hormone and a possible extracorpuscular distribution

Abstract

Stanniocalcin (STC) is a homodimeric glycoprotein hormone implicated in calcium and phosphate regulation in both teleost fish and mammals. In the present study, immunostaining with salmon STC antiserum demonstrated that STC cells were localized in both the corpuscles of Stannius (CS) and in specific cells of the distal renal tubules of the silver arawana, Osteoglossum bicirrhosum, an ancient ray-finned fish (actinoptergian) and basal teleost (Order Osteoglossiforme). The morphology of these STC-immunoreactive kidney cells was similar to renal 'chloride' (mitochondrial-rich) cells. The immunoreactive renal cells were present in two of three other osteoglossiformes and absent in the gar, a nonteleost actinopterygian and the eel, another basal teleost. The arawana STC cDNA encodes a prehormone of 249 amino acids (aa) with a signal peptide of 31 aa and a mature protein of 218 aa. The deduced aa sequence of arawana STC shows 54 -66% identity with other teleost STCs and 51 -52% identity with mammalian STC-1. The deduced aa sequence of arawana STC contains ten cysteines, compared with 11 in teleost STC and in mammalian STC-1. The cysteine substitution occurs at the site of inter-monomeric disulfide linkage. Western blot analysis revealed a single 21 kDa band under non-reducing conditions, and a single band of 25 kDa under reducing conditions. These data indicate that arawana STC exists as a monomeric peptide. Northern blot analysis detected a 3.3 kb STC mRNA confined to the CS, with no hybridization signal in either the remaining kidney or in gut, muscle, brain and heart. The significance of the STC signal in cells of the renal tubules of arawana and two other Osteoglossiforme species requires further investigation. This is the first report of a monomeric form of STC in any vertebrate and the first evidence of STC in renal tubules of adult fish.

Endocrine regulation of carbonate precipitate formation in marine fish intestine by Stanniocalcin and PTHrP

“…The apparent size of the immunoreactive band under denaturing reducing conditions is 3 kDa smaller than the purified STC (26 kDa). This apparent disparity in size is probably related to the removal of the 30 amino acid signal peptide in the N-terminus of STC, as previously described for other fish species (Amemiya et al, 2006;Amemiya et al, 2002). Preabsorption of the sea bream anti-STC sera with a protein extract of isolated Stannius corpuscles ablated the immunoreactive band obtained in western blots of serum and purified STC, and confirms antisera specificity.…”

Mammalian stanniocalcins and cancer.

“…This is supported by evidence that STC is preferentially expressed in early-stage oocytes, with levels diminishing as oocytes develop (McCudden et al 2001b). Another group has also reported STC localization in renal tubules (Amemiya et al 2002). It is unclear at present whether STC produced in sites apart from the CS has a local action or is released systemically as from the CS.…”

The Multifunctional Fish Gill: Dominant Site of Gas Exchange, Osmoregulation, Acid-Base Regulation, and Excretion of Nitrogenous Waste

“…Each filament is supplied with blood from an afferent radial artery that begins near the excurrent duct of a pouch. Blood traverses medially across the filament where it encounters lamellae FIG. 4. Scanning electron micrographs of gill filaments.…”