Downregulation of erythropoietin receptor by overexpression of phospholipase C-gamma 1 is critical for decrease on focal adhesion in transformed cells.

BACKGROUND

Phospholipase C-γl (PLC-γl) is known to play a critical role in cell adhesion and migration and is highly expressed in metastatic tumors. In the current study, we found that cells transformed by PLC overexpression (PLC-γl cells) exhibited a marked decrease in expression of the Epo receptor (EpoR). Here, we assessed the role of EpoR-dependent signaling pathways in PLC-γl-dependent regulation of cell adhesion and migration.

METHODS

Expression and phosphorylation of EpoR and its functional role in PLC-γl cells were evaluated by immunoblot analysis or cell adhesion assay. The mechanism for PLC-γ1-induced EpoR downregulation was analyzed by blockage of proteosomal degradation with MG132. EpoR expression was also confirmed in colorectal cancer tissues in which PLC-γl was highly expressed.

RESULTS

EpoR was present on rat fibroblasts, where it functionally active and capable of increasing cell adhesion and migratory activity. However, PLC-γl cells significantly decreased the Epo-dependent effects via ubiquitination-proteosomal degradation of EpoR. A marked decrease of EpoR expression was confirmed in colorectal cancer tissues that showed high-level of PLC-γl expression.

CONCLUSION

The Epo/EpoR complex plays a critical role in the adhesion and migration of rat fibroblasts, and its functional inactivation is associated with PLC-γl-dependent reduction of cell-matrix adhesion and this also affects cell migration.