EXPRESSION OF MTDNA AND NDNA ENCODED RESPIRATORY-CHAIN PROTEINS IN CHEMICALLY AND GENETICALLY-DERIVED RHO0 HUMAN FIBROBLASTS - A COMPARISONOF SUBUNIT PROTEINS IN NORMAL FIBROBLASTS TREATED WITH ETHIDIUM-BROMIDE AND FIBROBLASTS FROM A PATIENT WITH MTDNA DEPLETION SYNDROME

Although much progress has been made in identifying genetic defects as sociated with mitochondrial diseases, the protein expression patterns of most disorders are poorly understood. Here we use immunochemical te chniques to describe subunit expression patterns of respiratory chain enzyme complexes II (succinate dehydrogenase: SD) and IV (cytochrome c oxidase: COX) in cultured cells lacking mtDNA (RhoO cells) derived ei ther chemically by exposure of normal cells to ethidium bromide, or ge netically in cells derived from a patient with mtDNA depletion syndrom e. Both control cells and early passage patient-derived cells express a normal complement of SD and COX subunit proteins. Ethidium bromide t reatment of normal cells and in vitro cell proliferation of patient-de rived cells caused both populations to acquire identical RhoO phenotyp es. As expected, they lack mtDNA-encoded subunits COX-I and COX-II. In contrast, nDNA-encoded subunits are affected differentially, with som e (COX-VIc) lacking and others (COX-IV, COX-Va, SD 30 and SD 70) maint ained at somewhat reduced levels. We suggest chat the differential sta bility of nDNA-encoded subunits in the absence of intact enzyme comple xes is due to the ability of some, but not all, subunits to associate as partial complexes in the absence of mtDNA-encoded subunits. (C) 199 7 Elsevier Science B.V.