Activities of the EM10 protein from Echinococcus multilocularis in cultured mammalian cells demonstrate functional relationships to ERM family members.

The ezrin-radixin-moesin (ERM) homolog EM10 is expressed by the larval stage of the parasite E. multilocularis and shows 46.9% overall identity in the primary structure with human ezrin. To determine whether EM10 has similar activities to ERM proteins, we investigated properties of the protein expressed in mammalian cells. In particular, we transiently expressed haemagglutinin-tagged (HA-tagged) versions of the full-length EM10 as well as the amino- and the carboxy-terminal halves of EM10 in HtTA-1 cells. In addition we stably transfected NIH-3T3 cells with untagged full-length EM10. The data demonstrate that EM10 polypeptides behave like their corresponding portions of radixin when transiently expressed in mammalian cells. The full-length and amino-terminal EM10 polypeptides were localized to cortical structures. Cells expressing the carboxy-terminal polypeptide of EM10 showed long actin-filled protrusions. Cells expressing full-length EM10 showed a reduction in endogenous moesin-staining at cortical structures. In stably transfected NIH-3T3 cells EM10 was not crisply localized but rather was diffuse throughout the cytoplasm. These cells showed a conspicuous loss of stress-fibers, a phenotype that was not seen in analogous experiments with ERM proteins. The results demonstrate both similarities and differences between the functional properties of EM10 and ERM proteins expressed in vertebrate cells.