Correlation between Ca2+ oscillation and cell proliferation via CCKB/gastrin receptor

Gastrin stimulates cell proliferation through the CCKB receptor coupled to Gq-protein, whereas the m3 muscarinic receptor, which also couples to Gq, has no trophic effects. In order to elucidate the cause of the difference, we stably transfected CHO cells with human CCKB and m3 receptors. Stimulation of the CCKB, but not the m3 receptor increased cell growth. Activation of MAP kinase via the m3 receptor was to the same extent as that via CCKB, indicating that there is an initial signaling common to both receptors. Stimulation of either receptor induced a transient increase in [Ca2+](i) followed by a sustained plateau phase. After 2 h of stimulation, the [Ca2+](i) response to the m3 receptor disappeared, whereas that to the CCKB receptor remained as a [Ca2+](i) oscillation. Removal of extracellular Ca2+, which abolished [Ca2+](i) oscillation, completely inhibited DNA synthesis via CCKB. When the C-terminal part of the CCKB receptor was truncated, the trophic effect as well as the [Ca2+](i) response after 2 h of stimulation disappeared, whereas the chimeric CCKB receptor with the C-terminal region of the m3 receptor preserved its ability to elicit both DNA synthesis and [Ca2+](i) oscillation. These results suggest that desensitization might be a principal determinant of cell proliferation, and the persistence of the [Ca2+](i) response as [Ca2+](i) oscillation could be essential for this type of signal transduction, (C) 1999 Elsevier Science B.V. All rights reserved.