Bcl-2-mediated alterations in endoplasmic reticulum Ca2+ analyzed with an improved genetically encoded fluorescent...

Area of Science:

• Cellular Biology
• Molecular Imaging
• Biochemistry

Background:

• The endoplasmic reticulum (ER) is a critical cellular storehouse for calcium (Ca2+).
• ER-released Ca2+ ions are vital for numerous signaling pathways, including apoptosis, metabolism, and fertilization.
• Directly imaging intracellular Ca2+ concentrations within the ER ([Ca2+]ER) is essential for understanding these processes.

Purpose of the Study:

• To develop a novel genetically encoded Ca2+ indicator for improved imaging of [Ca2+]ER in individual cells.
• To investigate the role of the antiapoptotic protein B cell lymphoma 2 (Bcl-2) in regulating ER Ca2+ homeostasis.
• To examine the effects of inhibiting Bcl-2 on ER Ca2+ dynamics.

Main Methods:

• Engineered a genetically encoded Ca2+ sensor by modifying calmodulin and a calmodulin-binding peptide interfaces.
• Optimized sensor kinetics and binding affinity (Kd) for accurate ER Ca2+ imaging.
• Utilized the sensor in MCF-7 breast cancer cells to monitor [Ca2+]ER under various conditions, including ATP stimulation and Bcl-2 inhibition.

Main Results:

• The novel Ca2+ sensor demonstrated improved performance for monitoring [Ca2+]ER compared to existing methods.
• Bcl-2 was shown to decrease resting [Ca2+]ER by enhancing Ca2+ leakage and to modify ATP-induced Ca2+ oscillations.
• Inhibition of Bcl-2 using epigallocatechin gallate led to increased [Ca2+]ER, confirming Bcl-2's role in Ca2+ leakage.

Conclusions:

• The developed genetically encoded Ca2+ indicator provides a significant advancement for studying ER Ca2+ signaling.
• Bcl-2 plays a crucial role in maintaining ER Ca2+ homeostasis by regulating Ca2+ leakage.
• Targeting Bcl-2 offers a potential strategy for modulating cellular Ca2+ signaling pathways.