Initiation sites for Ca2+ signals in endothelial cells

Area of Science:

• Cellular Biology
• Calcium Signaling
• Endothelial Cell Function

Background:

• Intracellular calcium (Ca2+) signals, often manifesting as oscillations and waves, are crucial for cellular processes.
• These signals are frequently initiated at discrete sites and propagate throughout the cell.
• Understanding the spatial organization of Ca2+ signals is key to deciphering cellular responses.

Purpose of the Study:

• To investigate the spatial organization and initiation of intracellular Ca2+ signals in CPAE endothelial cells.
• To determine the role of cell processes versus the cell body in Ca2+ wave generation and propagation.
• To explore the dependence of Ca2+ signaling on external calcium.

Main Methods:

• Stimulation of single CPAE endothelial cells with adenosine triphosphate (ATP).
• Microscopic observation of intracellular Ca2+ dynamics.
• Manipulation of external calcium concentrations to assess signal dependence.

Main Results:

• Ca2+ waves preferentially initiated in the long, thin cell processes of CPAE cells.
• Cell processes exhibited higher agonist sensitivity, faster Ca2+ rise, and quicker wave propagation rates compared to the cell body.
• External calcium removal progressively inhibited signaling in processes but not the cell body, suggesting localized store unit control.

Conclusions:

• CPAE cells possess numerous individual store units capable of initiating Ca2+ release.
• A diffusing messenger coordinates these units to generate propagating Ca2+ waves, initiated in cell processes.
• External calcium is essential for sustained Ca2+ wave propagation, particularly in the cell processes.