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Updated: Jan 26, 2026

Quantifying Agonist Activity at G Protein-coupled Receptors
Published on: December 26, 2011
A novel sponge-derived protein thrombocorticin is a new agonist for thrombopoietin receptor
Hiromi Watari1, Hiroya Nakajima1, Wataru Atsuumi1
1Hokkaido University, Graduate School and Faculty of Fisheries Sciences, 3-1-1 Minato-cho, Hakodate 041-8611, Japan.
Abstract:
We screened 868 marine extracts in search of hematopoietic molecules resulted in findings of several extracts that proliferated Ba/F3-HuMpl cells but not the cells expressed with other hematopoietic cytokine receptors, EPO and G-CSF. Separation of the most potent extract of a Micronesian sponge Corticium sp., guided by the cell proliferation assay using Ba/F3-HuMpl cells resulted in an isolation of thrombocorticin (ThC), a novel 14 kDa protein as an active principal. ThC displayed concentration-dependent proliferation of Ba/F3-HuMpl cells, and had a stronger activity than that of eltrombopag, a small molecule drug used to treat thrombocytopenia. ThC induced phosphorylation of STAT5, suggesting that it activates Jak/STAT pathway as in the case of TPO. These results together indicated that ThC is a specific agonist for c-Mpl, although the size and shape differs largely from TPO. Here we present isolation, characterization and biological activity of ThC.
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