Related Experiment Video
Updated: Apr 26, 2026
Monitoring Dynamic Changes In Mitochondrial Calcium Levels During Apoptosis Using A Genetically Encoded Calcium Sensor
Published on: April 1, 2011
p32, a novel binding partner of Mcl-1, positively regulates mitochondrial Ca(2+) uptake and apoptosis
Kang Xiao1, Yinyin Wang2, Zhijie Chang2
1Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
Abstract:
Mcl-1 is a major anti-apoptotic Bcl-2 family protein. It is well known that Mcl-1 can interact with certain pro-apoptotic Bcl-2 family proteins in normal cells to neutralize their pro-apoptotic functions, thus prevent apoptosis. In addition, it was recently found that Mcl-1 can also inhibit mitochondrial calcium uptake. The detailed mechanism, however, is still not clear. Based on Yeast Two-Hybrid screening and co-immunoprecipitation, we identified a mitochondrial protein p32 (C1qbp) as a novel binding partner of Mcl-1. We found that p32 had a number of interesting properties: (1) p32 can positively regulate UV-induced apoptosis in HeLa cells. (2) Over-expressing p32 could significantly promote mitochondrial calcium uptake, while silencing p32 by siRNA suppressed it. (3) In p32 knockdown cells, Ruthenium Red treatment (an inhibitor of mitochondrial calcium uniporter) showed no further suppressive effect on mitochondrial calcium uptake. In addition, in Ruthenium Red treated cells, Mcl-1 also failed to suppress mitochondrial calcium uptake. Taken together, our findings suggest that p32 is part of the putative mitochondrial uniporter that facilitates mitochondrial calcium uptake. By binding to p32, Mcl-1 can interfere with the uniporter function, thus inhibit the mitochondrial Ca(2+) uploading. This may provide a novel mechanism to explain the anti-apoptotic function of Mcl-1.
Insights
Mcl-1, an anti-apoptotic protein, inhibits mitochondrial calcium uptake by binding to the p32 protein. This interaction disrupts calcium transport, revealing a new mechanism for Mcl-1
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Mcl-1 is a key anti-apoptotic protein in the Bcl-2 family.
- Mcl-1 neutralizes pro-apoptotic proteins and inhibits mitochondrial calcium uptake.
- The precise mechanism of Mcl-1's inhibition of mitochondrial calcium uptake remains unclear.
Purpose of the Study:
- To identify novel binding partners of Mcl-1.
- To elucidate the role of Mcl-1 in regulating mitochondrial calcium uptake.
- To uncover a new mechanism for Mcl-1's anti-apoptotic function.
Main Methods:
- Yeast Two-Hybrid screening to identify Mcl-1 binding partners.
- Co-immunoprecipitation to confirm Mcl-1 and p32 interaction.
- RNA interference (siRNA) to knockdown p32 expression.
- Measurement of mitochondrial calcium uptake in HeLa cells.
- Treatment with Ruthenium Red, a mitochondrial calcium uniporter inhibitor.
Main Results:
- The mitochondrial protein p32 (C1qbp) was identified as a novel binding partner of Mcl-1.
- p32 positively regulates UV-induced apoptosis and promotes mitochondrial calcium uptake.
- Silencing p32 suppressed mitochondrial calcium uptake.
- Mcl-1 binding to p32 interferes with mitochondrial calcium uniporter function, inhibiting calcium uptake.
- Ruthenium Red treatment abolished the suppressive effect of Mcl-1 on mitochondrial calcium uptake in p32 knockdown cells.
Conclusions:
- p32 is a component of the mitochondrial calcium uniporter complex.
- Mcl-1 inhibits mitochondrial calcium uptake by interacting with p32.
- This interaction provides a novel molecular mechanism for the anti-apoptotic activity of Mcl-1.
Related Concept Videos
01:31The Intrinsic Apoptotic Pathway
02:23Abnormal Proliferation
01:23Negative Regulator Molecules
01:16Calmodulin-dependent Signaling
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
01:19Translocation of Proteins into the Mitochondria
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
01:07MAPK Signaling Cascades