Role of tomoregulin, a novel EGF like molecule containing follistatin modules, in the gastrointestinal mucosa

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We have isolated a gene from stomach fibroblasts encoding novel proteins containing two follistatin modules and a single EGF-like domain. We designated the protein products of a gene tomoregulin (TR). Highly purified TR by using affinity chromatography with a monoclonal antibody from Sf9 cells stimulated tyrosine phosphorylation of erbB4, but not erbB2, erbB3, and EGF receptors in MKN28 gastric cancer cells, while TR inhibited MKN-1 gastric cancer cell growth without affecting erbB4 phosphorylation. TR-EGF domain also inhibited MKN-1 growth, suggesting that EGF domain of TR, but not follistatin modules, plays a role for the inhibition. TR or TR-EGF domain stimulated phosphorylation of MAP kinase p44 and p42 in MKN-1 gastric cancer cells without affecting erbB4 phosphorylation, suggesting that TR binds to another erbB receptor not yet known, exerting its effect on cell growth inhibition and MAP-kinase phosphorylation.