Figure 2.

The rate of apoptosis is dependent on the Cx type expressed and correlates to the GJ permeability. (a) Western blot analysis for the expression of Cx37, Cx40 and Cx43 in stably transfected HeLa cells compared with empty vector-transfected HeLa (CTL). (b) Immunofluorescence stainings of Cx proteins in stably transfected HeLa cells demonstrate typical localisation at the membrane of adjacent cells. HeLa-CTL cells were used as controls and showed no Cx43 expression by staining for Cx43. (c) Apoptosis (induced by 1 μM SN, 3 h) of stably transfected HeLa cells is dependent on the Cx type expressed and significantly increased by expression of Cx40 or Cx43 compared with HeLa-CTL. Apoptosis was determined by annexin V-FITC/PI labelling and fold increase of apoptotic cells is expressed as mean±S.E.M.; *P<0.05 versus CTL; ^#P<0.05 versus Cx37; n≥5 in at least three different cell cultures. (d) Gap junctional cell coupling of HeLa cells varies with the Cx type expressed and correlates with the rate of apoptosis. Cell coupling was measured by dye spreading (Alexa Fluor 488). The number of dye-stained cells is displayed as mean±S.E.M. (n≥18 dye injections in ≥3 different cell cultures; *P<0.05 versus CTL; ^#P<0.05 versus Cx37; NG). GAPDH, glyceraldehyde 3-phosphate dehydrogenase