Induction or suppression of expression of cytochrome C oxidase subunit II by heregulin beta 1 in human mammary epithelial cells is dependent on the levels of ErbB2 expression.
The ErbB family of receptor kinases is composed of four members: epidermal growth factor receptor (EGFR/ErbB1), ErbB2/neu, ErbB3, and ErbB4. Amplification of the ErbB2/neu is found in about 30% of breast cancer patients and is associated with a poor prognosis. Heregulin (HRG) activates the ErbB2 via induction of heterodimerization with ErbB3 and ErbB4 receptors. With suppression subtractive hybridization, we demonstrated that the expression of cytochrome c oxidase subunit II (COXII) is HRG-responsive. Two nontransformed human mammary epithelial cell lines, the HB2 and the HB2(ErbB2) (the HB2 engineered to overexpress ErbB2), displayed an opposite response to HRG-mediated regulation. HRG upregulated mRNA expression of COXII in the HB2 cells, but suppressed COXII expression in the HB2(ErbB2) cells. A human breast cancer cell line (T47D), which expresses ErbB2 at a level similar to that of the HB2 cells, also responded to HRG by increasing COXII mRNA levels. Therefore, HRG regulation of COXII expression depends on the levels of ErbB2 expression. Furthermore, the expression of COXII was inversely correlated to the levels of ErbB2, i.e., the cells overexpressing ErbB2 exhibited lower COXII levels. HRG-evoked signal transduction differed between the cells with normal ErbB expression and the cells overexpressing ErbB2. The activation of both ERK and PI3-K was essential for HRG regulation of COXII, i.e., blockage of either pathway eliminated HRG-mediated alteration. This is the first report demonstrating that the expression of mitochondria-encoded COXII is HRG-responsive. The levels of ErbB2 expression are decisive for the diverse biological activities of HRG.
Department of Microbiology, Immunology & Cell Biology, West Virginia University School of Medicine, Morgantown, West Virginia 26506-9177, USA. jluo@hsc.wvu.edu
Yanbo
Y
Sun
Hong
H
Lin
Yunfeng
Y
Zhu
Cuiling
C
Ma
Jianping
J
Ye
Jia
J
Luo
D001943:Breast Neoplasms / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D005786:Gene Expression Regulation; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D020890:Neuregulin-1 / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D003576:Electron Transport Complex IV; D020928:Mitogen-Activated Protein Kinases; D020890:Neuregulin-1; D019869:Phosphatidylinositol 3-Kinases; D010940:Plant Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; C111957:cox2 protein, Glycine soja; C087230:heregulin beta1