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.

Fluorescent and Bioluminescent Calcium Indicators with Tuneable Colors and Affinities

“…The occurrence of successive calcium spikes upon ATP perfusion has been described previously. 27 HT = HaloTag.…”

Astrocyte arborization enhances Ca2+ but not cAMP signaling plasticity

“…The predominant type of Ca 2+ response ( Table S2 , see also Figure S7 ) was sustained in NB+ astrocytes and oscillatory in DMEM+ astrocytes. Besides ATP, histamine, glutamate, and noradrenaline (Morita et al, 2003 ; Morita et al 2015a ; Pasti et al, 1995 ) trigger [Ca 2+ ] i oscillations in astrocytes and other cells (Morita et al, 2003 ; Morita, Nakane, Fujii, et al, 2015 ; Piazza et al, 2007 ). The majority (77%) of oscillatory responses in DMEM+ astrocytes had a characteristic oscillation period of 11–20 s, which is in agreement with the oscillation period reported for responses evoked by NA or glutamate (Horvat et al, 2016 ; Morita et al, 2003 ; Pasti et al, 1995 ).…”

Role of intracellular Ca2+–based mechanotransduction of human periodontal ligament fibroblasts

“…Multiple patterns of [Ca 2+ ] i have been reported to be induced by physical and biochemical stimuli in other cell types ( e.g. , Hela cells and osteoblasts) (32, 36). Nevertheless, the causality of these multiple [Ca 2+ ] i patterns remains unclear.…”

“…This suggests that the other signaling pathways, including paracrine communication and ATP, may also induce hPDL cells to synchronize the MS-induced signals (35). Multiple patterns of [Ca 2+ ] i have been reported to be induced by physical and biochemical stimuli in other cell types (e.g., Hela cells and osteoblasts) (32,36). Nevertheless, the causality of these multiple [Ca 2+ ] i patterns remains unclear.…”