title: High Cell Density Upregulates Calcium Oscillation by Increasing Calcium Store Content via Basal Mitogen-Activated Protein Kinase Activity.
abstract: Calcium releases of non-excitable cells are generally a combination of oscillatory and non-oscillatory patterns, and factors affecting the calcium dynamics are still to be determined. Here we report the influence of cell density on calcium increase patterns of clonal cell lines. The majority of HeLa cells seeded at 1.5 x 104/cm2 showed calcium oscillations in response to histamine and ATP, whereas cells seeded at 0.5 x 104/cm2 largely showed transient and sustained calcium increases. Cell density also affected the response of HEK293 cells to ATP in a similar manner. High cell density increased the basal activity of the mitogen-activated protein (MAP) kinase and calcium store content, and both calcium oscillation and calcium store content were down-regulated by a MAP kinase inhibitor, U0126. Thus, MAP kinase-mediated regulation of calcium store likely underlie the effect of cell density on calcium oscillation. Calcium increase patterns of HeLa cells were conserved at any histamine concentrations tested, whereas the overexpression of histamine H1 receptor, which robustly increased histamine-induced inositol phospholipid hydrolysis, converted calcium oscillations to sustained calcium increases only at high histamine concentrations. Thus, the consequence of modulating inositol phospholipid metabolism was distinct from that of changing cell density, suggesting the effect of cell density is not attributed to inositol phospholipid metabolism. Collectively, our results propose that calcium increase patterns of non-excitable cells reflect calcium store, which is regulated by the basal MAP kinase activity under the influence of cell density.
authors.affiliation: Department of Biology, Kobe University Graduate School of Science, Kobe, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Morita
authors.affiliation: Laboratory of Cellular Neurobiology, School of Life Science, Tokyo University of Pharmacy and Life Science, Tokyo, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Nakane
authors.affiliation: Department of Biology, Kobe University Graduate School of Science, Kobe, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Fujii
authors.affiliation: Department of Biology, Kobe University Graduate School of Science, Kobe, Japan.
authors.forename: Shohei
authors.initials: S
authors.lastname: Maekawa
authors.affiliation: Laboratory of Cellular Neurobiology, School of Life Science, Tokyo University of Pharmacy and Life Science, Tokyo, Japan.
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Kudo
mesh_terms: D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002452:Cell Count; D049109:Cell Proliferation; D057809:HEK293 Cells; D006367:HeLa Cells; D006632:Histamine / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism; D047428:Protein Kinase Inhibitors
chemical_list: D010716:Phosphatidylinositols; D047428:Protein Kinase Inhibitors; D006632:Histamine; D020928:Mitogen-Activated Protein Kinases; D002118:Calcium