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MBP-1 mediated apoptosis involves cytochrome c release from mitochondria
Asish K Ghosh1, Mainak Majumder, Robert Steele
1Department of Pathology, Saint Louis University, St. Louis, Missouri, MO 63104, USA.
Abstract:
MBP-1, a cellular factor, appears to be involved in multiple functions, including transcriptional modulation, apoptosis and cell growth regulation. In this study, we have investigated the signaling pathway involved in MBP-1 mediated apoptotic cell death. Human carcinoma cells infected with a replication deficient adenovirus expressing MBP-1 (AdMBP-1) induced apoptosis, when compared with cells infected by replication-defective adenovirus (dl312) as a negative control. Transduction of MBP-1 in carcinoma cells releases cytochrome c from mitochondria into the cytosol leading to activation of procaspase-9, procaspase-3 and PARP cleavage. We previously observed that MBP-1 mediated apoptosis can be protected by Bcl-2, although MBP-1 does not share a homology with the BH domain of the Bcl-2 family member of proteins. To further understand the mechanism of MBP-1 mediated apoptosis, we examined whether MBP-1 modulates the Bcl-2 gene family. Our results demonstrated that human breast carcinoma cells infected with AdMBP-1 selectively reduced Bcl-xL mRNA and protein expression when compared with dl312 infected negative control cells. An in vitro transient reporter assay also suggested repression of the Bcl-x promoter activity by MBP-1. Additional studies indicated that MBP-1 modulates Ets family protein function, thereby downregulating Bcl-xL expression. Taken together, our results suggest that MBP-1 selectively represses Bcl-xL expression in MCF-7 cells and induces mitochondrial involvement in the apoptotic process.
Insights
The cellular factor MBP-1 induces apoptosis in human carcinoma cells by downregulating Bcl-xL expression, leading to mitochondrial cytochrome c release and caspase activation.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- MBP-1 is a cellular factor implicated in transcriptional modulation, apoptosis, and cell growth.
- Understanding the precise signaling pathways of MBP-1-mediated apoptosis is crucial for cancer therapy.
Purpose of the Study:
- To investigate the signaling pathway of MBP-1-mediated apoptotic cell death.
- To elucidate the mechanism by which MBP-1 induces apoptosis, focusing on its interaction with the Bcl-2 gene family.
Main Methods:
- Human carcinoma cells were infected with adenovirus expressing MBP-1 (AdMBP-1) or a control adenovirus.
- Apoptosis was assessed by monitoring cytochrome c release, caspase activation (procaspase-9, procaspase-3), and PARP cleavage.
- Bcl-xL mRNA and protein expression levels were quantified.
- In vitro transient reporter assays were used to evaluate Bcl-x promoter activity.
Main Results:
- AdMBP-1 infection induced apoptosis in human carcinoma cells, evidenced by cytochrome c release and caspase activation.
- MBP-1 selectively reduced Bcl-xL mRNA and protein expression in MCF-7 cells.
- Reporter assays indicated that MBP-1 represses Bcl-x promoter activity.
- MBP-1 was found to modulate Ets family protein function, contributing to Bcl-xL downregulation.
Conclusions:
- MBP-1 induces apoptosis through a mitochondrial pathway involving cytochrome c release and caspase activation.
- MBP-1 selectively represses Bcl-xL expression in breast carcinoma cells, suggesting a novel mechanism of apoptotic induction.
- The findings highlight MBP-1 as a potential target for cancer treatment by modulating Bcl-xL expression.