Background:

We have shown before that Cx43 enhances the migration of HeLa cells in a gap junction independent manner. We have also found that Cx43 mediated increase in cell migration is associated with enhanced filopodia formation. Increased migration and filopodia formation of HeLa-Cx43 cells are dependent on p38 MAPK activation. We analysed now the role of the p38 downstream molecule Hsp27 which is known to act as an actin-capping protein.

Methods:

HeLa cells expressing Cx43 or empty-vector transfected (CTL) cells were stimulated with 10% FCS in the presence or absence of a p38 inhibitor (SB203580). Phosphorylation of Hsp27 was analysed by Western blot. The potential binding of Hsp27 to Cx43 was investigated by immunoprecipitation.

Results:

Phosphorylation of Hsp27 which reportedly regulates the actin-capping in a negative manner was indeed significantly higher in HeLa-Cx43 compared to HeLa-CTL cells. The inhibition of p38 activation resulted in decreased phosphorylation levels of Hsp27 in both Cx43-expressing and HeLa-CTL cells. Immunoprecipitation studies showed interaction with phosphorylated Hsp27 and Cx43 which was enhanced in the presence of the migratory stimulus.

Conclusion:

Our results show that the actin-capping protein Hsp27 is phosphorylated in a p38-dependent manner. Phosphorylated Hsp27 co-precipitates with Cx43. The findings suggest that an increased binding of Hsp27 to Cx43 might be one of the mechanisms of enhanced actin-dependent filopodia formation. Further analyses are necessary to clarify if an inhibition of the binding of Hsp27 to Cx43 indeed decreases the migration and filopodia formation of Cx43 expressing cells.