Localization of connexin 43 in mitochondria of ovarian cancer cells

Abstract

Connexin 43 (Cx43) is a gap junctional protein typically known for its channel forming role in intercellular communication between many types of cells. It has been reported that Cx43 proteins are localized in mitochondrial membranes from cardiovascular cells, Sca‐1+ stem cells, and rat brain tissues. In those various cell types Cx43 seemingly has a cytoprotective role during physiological stress. The present studies were undertaken to determine whether Cx43 protein is present in mitochondria and could possibly play a similar role in human ovarian cancer cells (OVCAR‐3 and SK‐OV‐3 cell lines). Western blot analysis demonstrated that the relative amount of Cx43 in mitochondrial pellets was enriched over that in other fractions. This was validated by comparison with patterns of established mitochondrial proteins such as voltage‐dependent anion channel and cytochrome c oxidase subunit IV. Immunogold transmission electron microscopy confirmed localization of Cx43 in the mitochondria. Additional findings that the level of mitochondrial Cx43 channel protein was specifically reduced with induction of apoptosis by etoposide are compatible with the possibility that it has a role in mitochondrial homeostasis in these ovarian cancer cells. This project was funded by the TTUHSC Department of Cell Biology and Biochemistry and the South Plains Oncology Consortium.