Immunological evidence of a P-glycoprotein in the microorganism Dictyostelium

Starting from the observation of an efficient resistance to the vital dye Hoechst 33342, we postulated the presence of a P-glycoprotein in Dictyostelium discoïdeum cells. This hypothesis is supported by the present data obtained by immunoblotting, using the murine JSB-1 monoclonal antibody. Two components of 170 and 115 kDa were recognized in lysates and crude plasma membrane of Dictyostelium cells grown in the presence of Hoechst 33342. Control experiments conducted without Hoechst 33342 demonstrated in these cells a constitutive expression of the P-glycoprotein, which was compared to its anthracycline-induced expression in a resistant human leukemic cell line, K562.