TY - JOUR
T1 - Inhibition of ezrin causes PKC-mediated internalization of erbb2/HER2 tyrosine kinase in breast cancer cells
AU - Jeong, Jaekwang
AU - Choi, Jungmin
AU - Kim, Wonnam
AU - Dann, Pamela
AU - Takyar, Farzin
AU - Gefter, Julia V.
AU - Friedman, Peter A.
AU - Wysolmerski, John J.
N1 - Funding Information:
This work was supported by National Institutes of Health Grants CA153702 and HD076248 (to J. J. W.). The authors declare that they have no conflicts of interest with the contents of this article. The content is solely the respon-sibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Publisher Copyright:
© 2019 Jeong et al.
PY - 2019/1/18
Y1 - 2019/1/18
N2 - Unlike other ErbB family members, HER2 levels are maintained on the cell surface when the receptor is activated, allowing prolonged signaling and contributing to its transforming ability. Interactions between HER2, HSP90, PMCA2, and NHERF1 within specialized plasma membrane domains contribute to the membrane retention of HER2. We hypothesized that the scaffolding protein ezrin, which has been shown to interact with NHERF1, might also help stabilize the HER2–PMCA2–NHERF1 complex at the plasma membrane. Therefore, we examined ezrin expression and its relationship with HER2, NHERF1, and PMCA2 levels in murine and human breast cancers. We also used genetic knockdown and/or pharmacologic inhibition of ezrin, HSP90, NHERF1, PMCA2, and HER2 to examine the functional relationships between these factors and membrane retention of HER2. We found ezrin to be expressed at low levels at the apical surface of normal mammary epithelial cells, but its expression is up-regulated and correlates with HER2 expression in hyperplasia and tumors in murine mammary tumor virus-Neu mice, in human HER2-positive breast cancer cell lines, and in ductal carcinoma in situ and invasive breast cancers from human patients. In breast cancer cells, ezrin co-localizes and interacts with HER2, NHERF1, PMCA2, and HSP90 in specialized membrane domains, and inhibiting ezrin disrupts interactions between HER2, PMCA2, NHERF1, and HSP90, inhibiting HER2 signaling and causing PKC-me-diated internalization and degradation of HER2. Inhibition of ezrin synergizes with lapatinib in a PKC-dependent fashion to inhibit proliferation and promote apoptosis in HER2-positive breast cancer cells. We conclude that ezrin stabilizes a multiprotein complex that maintains active HER2 at the cell surface.
AB - Unlike other ErbB family members, HER2 levels are maintained on the cell surface when the receptor is activated, allowing prolonged signaling and contributing to its transforming ability. Interactions between HER2, HSP90, PMCA2, and NHERF1 within specialized plasma membrane domains contribute to the membrane retention of HER2. We hypothesized that the scaffolding protein ezrin, which has been shown to interact with NHERF1, might also help stabilize the HER2–PMCA2–NHERF1 complex at the plasma membrane. Therefore, we examined ezrin expression and its relationship with HER2, NHERF1, and PMCA2 levels in murine and human breast cancers. We also used genetic knockdown and/or pharmacologic inhibition of ezrin, HSP90, NHERF1, PMCA2, and HER2 to examine the functional relationships between these factors and membrane retention of HER2. We found ezrin to be expressed at low levels at the apical surface of normal mammary epithelial cells, but its expression is up-regulated and correlates with HER2 expression in hyperplasia and tumors in murine mammary tumor virus-Neu mice, in human HER2-positive breast cancer cell lines, and in ductal carcinoma in situ and invasive breast cancers from human patients. In breast cancer cells, ezrin co-localizes and interacts with HER2, NHERF1, PMCA2, and HSP90 in specialized membrane domains, and inhibiting ezrin disrupts interactions between HER2, PMCA2, NHERF1, and HSP90, inhibiting HER2 signaling and causing PKC-me-diated internalization and degradation of HER2. Inhibition of ezrin synergizes with lapatinib in a PKC-dependent fashion to inhibit proliferation and promote apoptosis in HER2-positive breast cancer cells. We conclude that ezrin stabilizes a multiprotein complex that maintains active HER2 at the cell surface.
UR - http://www.scopus.com/inward/record.url?scp=85060163282&partnerID=8YFLogxK
U2 - 10.1074/jbc.RA118.004143
DO - 10.1074/jbc.RA118.004143
M3 - Article
C2 - 30463939
AN - SCOPUS:85060163282
SN - 0021-9258
VL - 294
SP - 887
EP - 901
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 3
ER -