UVM Theses and Dissertations
Format:
Print
Author:
Hatle, Ketki Madhusudan
Dept./Program:
Cell and Molecular Biology Program
Year:
2009
Degree:
Ph. D.
Abstract:
Methylation Controlled J protein is an atypical member of the DnaJ family of co-chaperones. Hypermethylation-mediated transcriptional silencing of the MCJ gene has been associated with increased chemotherapeutic resistance in ovarian cancer. Here we show that MCJ is a type II transmembrane protein localized to the Golgi and associated vesicles and is present only in vertebrates. MCJ is expressed in drug sensitive breast cancer cells but not in multidrug resistant cells. More importantly, we also demonstrate that inhibition of MCJ expression causes multidrug resistance due to an increased expression of ABCB1 drug transporter that effluxes the drug out of the cell. Induction of ABCB1 gene expression is mediated by stabilization of cJun due to an impaired degradation of this transcription factor in the absence of MCJ. Thus, MCJ is required in breast cancer cells to prevent cJun mediated expression of ABCB1 and maintain the drug response.
The role of MCJ in normal tissues has not been previously studied. We have characterized the ortholog of human MCJ in mouse and we show that MCJ is highly expressed in the heart, liver, kidney and CD8 T cells. To investigate the physiological role of MCJ, we have generated MCJ deficient mice. Interestingly, we have observed that in vitro activated MCJ knockout CD8⁺ T cells produced increased levels of cytokines as compared with the wildtype CD8⁺ T cells. This increased cytokine production by MCJ deficient CD8⁺ T cells was not due to increased cytokine gene expression. We propose that MCJ regulates the cytokine secretion pathway specifically in CD8⁺ T cells and in the absence of MCJ causes dysregulation of this pathway, resulting in increased cytokine production. This is the first report describing MCJ protein function in breast cancer cells and examining MCJ expression in mouse and non-malignant human tissues.
The role of MCJ in normal tissues has not been previously studied. We have characterized the ortholog of human MCJ in mouse and we show that MCJ is highly expressed in the heart, liver, kidney and CD8 T cells. To investigate the physiological role of MCJ, we have generated MCJ deficient mice. Interestingly, we have observed that in vitro activated MCJ knockout CD8⁺ T cells produced increased levels of cytokines as compared with the wildtype CD8⁺ T cells. This increased cytokine production by MCJ deficient CD8⁺ T cells was not due to increased cytokine gene expression. We propose that MCJ regulates the cytokine secretion pathway specifically in CD8⁺ T cells and in the absence of MCJ causes dysregulation of this pathway, resulting in increased cytokine production. This is the first report describing MCJ protein function in breast cancer cells and examining MCJ expression in mouse and non-malignant human tissues.