High Cell Density Upregulates Calcium Oscillation by Increasing Calcium Store Content via Basal Mitogen-Activated...

Area of Science:

• Cellular Biology
• Biochemistry
• Signaling Pathways

Background:

• Calcium signaling in non-excitable cells exhibits complex oscillatory and non-oscillatory patterns.
• Factors influencing these calcium dynamics, crucial for cellular functions, remain incompletely understood.

Purpose of the Study:

• To investigate the impact of cell density on calcium release patterns in clonal cell lines.
• To elucidate the underlying molecular mechanisms, particularly the role of mitogen-activated protein (MAP) kinase.

Main Methods:

• Utilized HeLa and HEK293 cell lines seeded at varying densities (0.5 x 10^4/cm^2 and 1.5 x 10^4/cm^2).
• Stimulated cells with histamine and adenosine triphosphate (ATP) to monitor calcium release patterns.
• Assessed MAP kinase activity and calcium store content, and employed the MAP kinase inhibitor U0126.

Main Results:

• Higher cell density (1.5 x 10^4/cm^2) induced calcium oscillations in response to histamine and ATP.
• Lower cell density (0.5 x 10^4/cm^2) predominantly resulted in transient and sustained calcium increases.
• High cell density elevated basal MAP kinase activity and calcium store content; U0126 reversed these effects.

Conclusions:

• Cell density significantly modulates calcium signaling patterns in non-excitable cells.
• MAP kinase-mediated regulation of calcium stores appears to be the key mechanism underlying density-dependent calcium oscillations.
• The observed effects are distinct from alterations in inositol phospholipid metabolism, highlighting a novel regulatory pathway.