ENDOSOMES - ANOTHER EXTRA-MITOCHONDRIAL LOCATION OF TYPE-1 PORIN VOLTAGE-DEPENDENT ANION-SELECTIVE CHANNELS (VDAC)

Endocytotic vesicles (EV) isolated from rat renal cortex were subjecte d to SDS-polyacrylamide electrophoresis and Western blotting. A monocl onal antibody against human type-1 porin (31 kDa) detected a. strong b and of 31 kDa. The same antibody has been used as the primary antibody in indirect immunocytochemistry Light microscopy of cryostat sections of rat renal carter showed a heavy staining of EV underneath the brus h-border membrane. Electron microscopy was performed by ''preembedding immunogold staining'' of rat renal cortex, the sections of which show ed an extensive labelling of EV with gold particles. These results dem onstrate that the expression of type-1 porin is not restricted to oute r mitochondrial membranes. The biological function of endosomal type-1 porin has as yet to be ascertained.