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Modulation of endoplasmic reticulum calcium pump by Bcl-2
1Department of Pathology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
Abstract:
Members of the bcl-2 gene family encode proteins that function either to promote or to inhibit apoptosis. Despite numerous efforts, the mechanism of action of Bcl-2, an anti-apoptotic protein, is still not clear. In particular, the relation between Bcl-2 and the endoplasmic reticulum (ER) calcium store is not well-understood. In the present work, we examined the effect of Bcl-2 on the ER store. We demonstrate that overexpression of Bcl-2 in breast epithelial cells modulates ER store by upregulating calcium pump (SERCA) expression without affecting the release channel (IP3R). The steady state levels of SERCA2 mRNA and protein were both increased in Bcl-2 expression clones. The increase in SERCA2 protein leads to accelerated calcium uptake and enhanced Ca2+ loading. In addition, we also show the detection of intracellular interaction between Bcl-2 and SERCA molecules by co-immunoprecipitation. Since high lumenal Ca2+ concentration of ER is essential for normal cell functions, the results suggest that Bcl-2 preserves the ER Ca2+ store by upregulating SERCA gene expression as well as by a possible interaction with the pump.
Insights
The anti-apoptotic protein Bcl-2 preserves endoplasmic reticulum (ER) calcium stores by upregulating the calcium pump SERCA. Bcl-2 also interacts with SERCA, enhancing cellular calcium loading and function.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- The Bcl-2 gene family regulates apoptosis, but Bcl-2's mechanism, especially its ER calcium interaction, remains unclear.
- Understanding Bcl-2's role in calcium homeostasis is crucial for cell function.
Purpose of the Study:
- To investigate the effect of Bcl-2 on endoplasmic reticulum (ER) calcium stores.
- To elucidate the molecular mechanisms underlying Bcl-2's modulation of ER calcium.
Main Methods:
- Overexpression of Bcl-2 in breast epithelial cells.
- Analysis of SERCA2 mRNA and protein levels.
- Co-immunoprecipitation to detect protein interactions.
- Measurement of intracellular calcium uptake and loading.
Main Results:
- Bcl-2 overexpression upregulates SERCA2 gene and protein expression.
- Increased SERCA2 leads to accelerated calcium uptake and enhanced ER Ca2+ loading.
- Direct intracellular interaction between Bcl-2 and SERCA molecules was detected.
Conclusions:
- Bcl-2 preserves ER calcium stores by increasing SERCA expression.
- Bcl-2 may also interact directly with SERCA to maintain ER calcium homeostasis.
- These findings highlight a novel role for Bcl-2 in regulating cellular calcium signaling.