Stanniocalcin (STC) is a hormone that was originally identified in fish, where it
inhibits calcium uptake by the gills and gut and stimulates phosphate adsorption by
the kidney [1-3]. Recently, two mammalian homologues of stanniocalcin were identified.
The first (STC1) shows 61% identity to the fish stanniocalcins and appears to have
a function similar to that of the fish stanniocalcins [4, 5]. The second homologue
(STC2) is 30-38% identical to the fish stanniocalcins, and is characterized by unique
cysteine and histidine motifs that are not found in the other stanniocalcins [6-8].
We purified both the native hamster and recombinant human STC2 proteins and obtained
a partial amino acid sequence of the hamster protein. Both proteins behave as a disulfide
bonded homodimer, which undergoes post-translational modification(s). The STC2 gene
was localized to human chromosome 5q35. Northern blot analysis revealed that the primary
site of human STC2 production is the pancreas, and immunostaining localized the STC2
protein to a subpopulation of cells in the islet. Double immunostaining for STC2 and
either insulin or glucagon revealed that STC2 protein is found in the alpha cells,
but not the beta cells. We speculate that STC2 may play a role in glucose homeostasis.
Key words
Stanniocalcin - Pancreas - Alpha Cells - Glucose Homeostasis
