Tissue distribution and subcellular localization of a variant form of the human ST2 gene product, ST2V

The human ST2 gene has been known to encode three splice variants; namely, a soluble secreted form of ST2, a transmembrane form of ST2L, and ST2V of undetermined localization. Therefore, analysis of tissue distribution and subcellular localization of ST2V is important to elucidate functional relationships among the three splice variants of the human ST2 gene. RT-PCR procedure revealed that ST2V is predominantly expressed in the stomach, small intestine, and colon. Transfection of ST2V cDNA into COS7 cells in the presence of [(35)S] methionine and cysteine produced radiolabeled 40 kDa protein, which is recognized by specific monoclonal antibody against human ST2. Subcellular fractionation analysis showed that ST2V protein was distributed in the insoluble fraction of the cell lysate. Finally, ST2V protein was detected on the plasma membrane of COS7 cells, which had been transfected with ST2V cDNA, by confocal laser microscopic analysis. These findings taken together, indicate that ST2V protein localizes on the plasma membrane, suggesting its possible role in modification of the ST2L-signaling pathways.