Intrinsic and acquired multidrug resistance (MDR) is an important problem in cancer therapy. MDR in human KB carcinoma cells selected for resistance to colchicine, vinblastine, or doxorubicin (former generic name adriamycin) is associated with overexpression of the "MDR] " gene, which encodes P-glycoprotein. We previously have isolated an overlapping set of cDNA clones for the (20).DNA and RNA Blot Hybridization. DNA was extracted from transfectants (13) and used for Southern blots (23). Total cellular RNA was isolated from the transfectants (20) and used for RNA blots (23). The 3.4-kilobase (kb) cDNA probe was labeled with 32P to a specific activity of 1-2 x 109 dpm/,ug by nick translation. Hybridization was done at 42°C in 50% formamide containing 5 x NaCl/Cit (lx = 0.15 M NaCl/ 0.015 M sodium citrate, pH 7), 0.2% bovine serum albumin, 0.2% polyvinylpyrrolidone, 0.2% Ficoll, 0.1% NaDodSO4, 50 mM Tris*HC, and 100 ,ug of salmon sperm DNA per ml, followed by washing with 0.2x NaCl/Cit containing 0.2% NaDodSO4 at 60°C for DNA hybridization and with O.1x NaCl/Cit containing 0.1% NaDodSO4 at 70°C for RNA hybridization at high stringency.Ribonuclease Protection Assay. Human MDR] mRNA transcribed from the retroviral promoter was detected with a ribonuclease protection assay using a uniformly labeled SP6 antisense RNA probe (785 nucleotides) derived from a 1-kb genomic fragment containing the MDR] transcription initiation site and the first intron of the MDRJ gene cloned in pGEM3 (Promega Biotec, Madison, WI). Total cellular RNA (10 ,ug) was hybridized with 6 x 105 cpm of probe, and ribonuclease digestion was performed as described (24).

Fabry disease is an X-linked inherited metabolic disorder that is caused by a deficiency of ␣-galactosidase A (␣-Gal A). Progressive deposition of neutral glycosphingolipids that have terminal ␣-linked galactosyl moieties in vascular endothelial cells causes renal failure along with premature myocardial infarctions and strokes in patients with this condition. No specific treatment is available for patients with this disorder at this time. An animal model of this condition would be valuable for exploring therapeutic strategies for patients with Fabry disease. We report here the generation of ␣-Gal A deficient mice by gene targeting and an analysis of the resulting phenotype. The knockout mice display a complete lack of ␣-Gal A activity. The mice, however, appeared clinically normal at 10 weeks of age. Ultrastructural analysis revealed concentric lamellar inclusions in the kidneys, and confocal microscopy using a f luorescent-labeled lectin specific for ␣-D-galactosyl residues showed accumulation of substrate in the kidneys as well as in cultured fibroblasts. Lipid analysis revealed a marked accumulation of ceramidetrihexoside in the liver and the kidneys. These findings indicate the similarity of the pathophysiological process in the mutant mice and in patients with Fabry disease. The deficiency of ␣-Gal A activity and the accumulation of material containing terminal ␣-galactosyl residues in cultured embryonic fibroblasts derived from ␣-Gal A(؊͞0) mice were corrected by transducing these cells with bicistronic multidrug resistance retroviruses containing human ␣-Gal A cDNA.

Multidrug-resistant human tumor cells overexpress the MDRI gene product P-glycoprotein, which is believed to function as an ATP-dependent efflux pump. In this study we demonstrate that the partially purified P-glycoprotein, when reconstituted in an artificial membrane, catalyzes drug-stimulated ATP hydrolysis. Plasma membrane proteins of a human multidrug-resistant cell line, KB-V1, were solubilized with 1.4% (wt/Vol) ocyl 3-D-glucopyranoside in the presence of 0.4% phospholipid and 20% (vol/vol) glycerol, and the crude detergent extract was chromatographed on DEAE-Sepharose CL-6B. The 0.1 M NaCi fraction, enriched in P-glycoprotein but devoid of NaK-ATPase, was reconstituted by the detergent-dilution method. P-glycoprotein constituted 25-30% of the reconstituted protein in proteoliposomes. ATP hydrolysis by proteoliposomes was stimulated 3.5-fold by the addition of vinblastine but was unaffected by the hydrophobic antitumor agent camptothecin, which is not transported by P- Several previous reports suggest the association ofATPase activity with P-glycoprotein: (i) the ATP analog 8-azido-[32-P]ATP binds to P-glycoprotein (8); (ii) the immunoaffinity-purified protein exhibits a low level of ATPase activity (9); and (iii) in vitro mutagenesis of the consensus sequences of either or both ATP-binding domains of the MDR] cDNA fails to confer drug resistance in transfected cells that express the altered protein (10, 11). In addition, the ATP-dependent transport of vinblastine by membrane vesicles of multidrugresistant cells has been demonstrated (12). Thus, it has been proposed that P-glycoprotein catalyzes ATP-dependent efflux of drugs from resistant cells. These previous studies, however, do not conclusively prove that the two functions (i.e., ATP hydrolysis and drug transport) are directly mediated by P-glycoprotein. To establish that P-glycoprotein is an ATP-dependent multidrug transporter, purification and functional reconstitution into phospholipid vesicles is essential. We describe here partial purification and reconstitution of P-glycoprotein. The data suggest that P-glycoprotein exhibits a high level of substrate-stimulatable ATPase activity similar to other ion-transporting pumps. MATERIALS AND METHODSPreparation of Plasma Membrane Vesides. The multidrugresistant human carcinoma KB-V1 cells, a subclone of KB3-1, were grown in the presence of vinblastine (1 ,g/ml) to confluence (13). The membrane vesicles were prepared by nitrogen cavitation and sucrose density gradient centrifugation as described (12). The final pellet of vesicles was resuspended and stored in vesicle buffer (10 mM Tris HCl, pH 7.4/50 mM NaCl/250 mM sucrose/0.5 mM phenylmethylsulfonyl fluoride) at -700C.Solubilization of P-Glycoprotein. The solubilization of membrane proteins followed the protocols established earlier (14,15