Retroviral vector-mediated gene transfer into human hematopoietic progenitor cells.

The transfer of the human gene for hypoxanthine phosphoribosyltransferase (HPRT) into human bone marrow cells was accomplished by use of a retroviral vector. The cells were infected in vitro with a replication-incompetent murine retroviral vector that carried and expressed a mutant HPRT complementary DNA. The infected cells were superinfected with a helper virus and maintained in long-term culture. The production of progeny HPRT virus by the bone marrow cells was demonstrated with a colony formation assay on cultured HPRT-deficient, ouabain-resistant murine fibroblasts. Hematopoietic progenitor cells able to form colonies of granulocytes or macrophages (or both) in semisolid medium in the presence of colony stimulating factor were present in the nonadherent cell population. Colony forming units cloned in agar and subsequently cultured in liquid medium produced progeny HPRT virus, indicating infection of this class of hematopoietic progenitor cell.

Studies of mutant human adenylosuccinate lyase.

We have studied the residual adenylosuccinate lyase activity in cultured lymphoblasts from a pair of siblings with infantile autism who have been previously shown to have a deficiency of the enzyme. The rates and distribution of de novo purine synthesis assessed by the utilization of radiolabeled formate by intact cells was nearly normal. We compared the steady-state kinetics and thermal stability of adenylosuccinate lyase in lysates from those cells and normal lymphoblasts. There is no evidence of inhibitory activity in the lysates of the mutant cells. The optimal pH was approximately 7.8 and was indistinguishable from that in control cells. The apparent Km in the two mutant cells lines (2.6 +/- 0.5 microM) is not significantly different from normal (3.3 +/- 0.8 microM), but the mutants displayed markedly decreased maximum steady-state velocities (6.7 +/- 1.1 compared to 13.8 +/- 0.9 nmol.mg-1.min-1). Residual activities in mutant cells show decreased thermal stability (t1/2 = 0.21 minutes at 60 degrees C as compared to 2.2 minutes), suggesting that there is a structural mutation of the adenylosuccinate lyase in the mutant cells.

Quinacrine mustard inactivates the bovine heart mitochondrial F1-ATPase with the modification of the beta subunit.

The bovine mitochondrial F1-ATPase is reversibly inhibited by quinacrine. The concentration of quinacrine which causes 50% inhibition at pH 7.0 is estimated to be 580 microM. Lineweaver-Burk plots constructed from kinetic data collected at pH 7.0 with equimolar concentrations of Mg2+ and ATP in the reaction mixtures indicate competitive inhibition by quinacrine. Uncompetitive inhibition by quinacrine is indicated by Lineweaver-Burk plots constructed from kinetic data obtained at pH 7.0 with variable ATP concentrations and a constant Mg2+ concentration of 3.0 mM. A KI of 440 microM was calculated from a replot of 1/Vmaxi versus quinacrine concentration using the intercepts of the Lineweaver-Burk plots constructed from the data obtained at a fixed concentration of 3.0 mM Mg2+. Quinacrine mustard is a potent inactivator of the F1-ATPase. The pseudo-first order rate constant, k1, for the inactivation of the enzyme by 500 microM quinacrine mustard is 0.161 min-1 at pH 7.0 and 23 degrees C. Under the same conditions in the presence of 5.0 mM ATP, 5.0 mM ADP, or 5.0 mM Mg2+ plus 5.0 mM ADP, k1 is, respectively: 0.082 min-1, 0.136 min-1, or 0.075 min-1. In the presence of 1.0 mM chlorpromazine or 5.0 mM quinacrine under the above conditions, k1, is 0.089 min-1 and 0.037 min-1, respectively. Free Mg2+ has no effect on the rate of inactivation of the enzyme by quinacrine mustard. The rate of inactivation of the F1-ATPase by quinacrine mustard as a function of pH revealed an apparent pK alpha of 8.0. Examination of the resolved subunits for fluorescence after inactivating the enzyme with quinacrine mustard demonstrated that only the beta subunit was labeled.

Detection of 5'-phosphoribosyl-4-(N-succinylcarboxamide)-5-aminoimidazole in urine by use of the Bratton-Marshall reaction: identification of patients deficient in adenylosuccinate lyase activity.

The Bratton-Marshall reaction can be used to identify patients with adenylosuccinate lyase deficiency. These patients excrete in their urine the dephosphorylated derivative of the de novo purine synthesis intermediate 5'-phosphoribosyl-4-(N-succinylcarboxamide)-5-aminoimidazole (SAICAR). The test described here depends on a coupling reaction of N-1-naphthylethylenediamine with diazotized ribosyl-4-(N-succinylcarboxamide)-5-aminoimidazole giving rise to a fast developing purple chromaphore with a maximum absorbance at 555 nm. Using the closely related compound ribosyl-5-amino-4-imidazolecarboxamide (AICA riboside) as a standard, concentrations as low as 1.0 microM produce a visible color change. The absorption at 555 nM of the azo compound increases as a linear function of the concentration of AICA riboside in the reaction. The use of a filter-paper dipstick for urine sampling and storage is also described. The two metabolites which are present in increased concentration in biological fluids of adenylosuccinate lyase deficient patients are stable on the dipstick for at least 60 days when stored at room temperature (25 degrees C).

The use of [3H]aniline to identify the essential carboxyl group in the bovine mitochondrial F1-ATPase that reacts with 1-(ethoxycarbonyl)-2-ethoxy-1,2-dihydroquinoline.

The inactivation of the bovine heart mitochondrial F1-ATPase with 1-(ethoxycarbonyl)-2-ethoxy-1,2-dihydroquinoline (EEDQ) in the presence of [3H]aniline at pH 7.0 led to the covalent incorporation of 3H into the enzyme. When the ATPase was inactivated by 94% with 0.9 mM EEDQ in the presence of 3.6 mM [3H]aniline in a large-scale experiment in which the protein concentration was 21 mg/ml, 4.2 mol [3H]anilide were formed per mol enzyme, of which 0.35 mol was incorporated per mol of the alpha subunit and 1.0 mol was incorporated per mol of the beta subunit. Examination of a tryptic digest of the isolated alpha subunit revealed that the majority of the 3H was contained in a single tryptic peptide, which, when purified, was shown to contain the [3H]anilide of a glutamic acid residue which corresponds to alpha-Glu-402 of the Escherichia coli F1-ATPase. This residue was labeled to the extent of about 1.0 mol/mol enzyme. Analysis of tryptic peptides purified from the isolated beta subunit showed that 0.8 and 1.5 mol, respectively, of the [3H]anilides of beta-Glu-341 and beta-Glu-199 were formed per mol MF1 during the inactivation of the enzyme at 21 mg/ml. When the ATPase was inactivated by 90% at a protein concentration of 1.7 mg/ml by 0.9 mM EEDQ in the presence of 1.7 mM [3H]aniline, 3.1 mol [3H]anilide were formed per mol enzyme. From the analysis of the radioactive peptides purified from a tryptic digest of the labeled ATPase from this experiment it was estimated that 0.7 mol of the [3H]anilide of alpha-Glu-402, 0.3 mol of the [3H]anilide of beta-Glu-341, and 1.5 mol of the [3H]anilide of beta-Glu-199 were formed per mol F1-ATPase. Since beta-Glu-199 is labeled to the same extent in the two experiments while alpha-Glu-402 and beta-Glu-341 were not, suggests that the modification of beta-Glu-199 is responsible for inactivation of the enzyme by EEDQ.

The varied responses of different F1-ATPases to chlorpromazine.

The effects of chlorpromazine on various properties of the F1-ATPases from bovine heart mitochondria (MF1), the plasma membranes of Escherichia coli (EF1), and plasma membranes of the thermophilic bacterium PS3 (TF1) have been examined. While chlorpromazine inhibited MF1 with an I0.5 of about 50 microM and EF1 with an I0.5 of about 150 microM at 23 degrees C, the ATPase activity of TF1 was stimulated by chlorpromazine concentrations up to 0.6 mM at this temperature. Maximal activation of about 20% was observed at 0.2 mM chlorpromazine at 23 degrees C. Chlorpromazine concentrations greater than 0.6 mM inhibited TF1 at 23 degrees C. At 37 degrees C the ATPase activity of TF1 was doubled in the presence of 0.5 mM chlorpromazine, the concentration at which maximal stimulation was observed at this temperature. Chlorpromazine inhibited the rate of inactivation of EF1 by dicyclohexylcarbodiimide (DCCD) at 23 degrees C and pH 6.5. Concentrations of chlorpromazine which inhibited the ATPase activity of TF1 at pH 7.0 accelerated the rate of inactivation of the enzyme by DCCD at pH 6.5, while lower concentrations of the phenothiazine, which stimulated the ATPase, had no effect on DCCD inactivation. Chlorpromazine concentrations up to 1.0 mM had no effect on the rate of inactivation of TF1 by DCCD at 37 degrees C and pH 6.5. Chlorpromazine at 0.5 mM accelerated the rate of inactivation of MF1 by 5'-p-fluorosulfonylbenzoyladenosine (FSBA), while it slowed the rate of inactivation of EF1 by FSBA. The inactivation of TF1 by FSBA in the absence of chlorpromazine was complex and was not included in this comparison. Chlorpromazine protected MF1 and EF1 against cold inactivation. Whereas 100 microM chlorpromazine afforded about 90% stabilization of MF1 at 4 degrees C, only about 30% stabilization of EF1 was observed under the same conditions in the presence of 400 microM chlorpromazine. Each of the ATPases was inactivated by the structural analog of chlorpromazine, quinacrine mustard. Whereas 5 mM ATP and 5 mM ADP protected MF1 and TF1 against inactivation by 0.5 mM quinacrine mustard, the rate of inactivation of EF1 by quinacrine mustard was accelerated fourfold by 5 mM ATP and slightly accelerated by 5 mM ADP.

Proton-translocating ATPase and lysosomal cystine transport.

A proton-translocating ATPase was identified in highly purified lysosomes from Epstein-Barr virus-transformed human lymphoblasts. Activity of this ATPase caused acidification of highly purified, fluorescein isothiocyanate dextran-loaded lysosomes and correlated with the ATP-dependent efflux of lysosomal cystine. The lysosomal ATPase was distinct from mitochondrial F1-ATPase in its responses to a variety of inhibitors. Although ATP-dependent lysosomal cystine efflux is not demonstrable in cultured lymphoblasts from individuals with nephropathic cystinosis, ATPase activity and acidification in lysosomes from these cells is comparable to that in noncystinotic lysosomes. ATPase activity in lymphoblasts from normal individuals was 543 +/- 79 nmol/mg/min while in lymphoblasts from cystinotic individuals this activity was 541 +/- 25 nmol/mg/min. ATP-dependent acidification of lysosomes from normals was -0.5 +/- 0.1 pH units compared to -0.5 +/- 0.1 pH units in cystinotic lysosomes. Activity of the lysosomal proton-translocating ATPase is a necessary, but not sufficient, condition for lysosomal cystine efflux.

Increased adenosine concentration in blood from ischemic myocardium by AICA riboside. Effects on flow, granulocytes, and injury.

Morbidity and mortality from acute coronary artery occlusion may be reduced if local myocardial adenosine concentration is augmented because 1) coronary collateral blood flow during ischemia increases with adenosine infusion, and 2) granulocytes that accumulate in the microcirculation during ischemia are, to a large extent, inhibited by adenosine from generating superoxide anion free radicals, from adhering to vascular endothelium, and from damaging endothelial cells in culture. Using a cultured lymphoblast model system, we found that 5-amino-4-imidazole carboxamide (AICA) riboside enhanced adenosine accumulation during ATP catabolism. Therefore, AICA riboside pretreatment was used in canine myocardium to selectively increase adenosine concentration in the ischemic area during 1 hour of ischemia. At 5 minutes of ischemia, endocardial flow to ischemic myocardium in saline-treated and AICA riboside-treated dogs was 0.06 +/- 0.03 and 0.34 +/- 0.11 ml/min/g, respectively (p less than 0.01); flow to nonischemic myocardium was not affected. Ventricular tachycardia and premature ventricular depolarizations were significantly attenuated in the AICA riboside-treated dogs. Blood pressure and heart rate were not affected by AICA riboside. In venous blood from ischemic tissue, adenosine increased from undetectable levels (less than 0.01 microM) to 0.22 +/- 0.08 microM in saline and 1.79 +/- 0.06 microM in AICA riboside-treated dogs, respectively (p less than 0.001). Coronary vein inosine concentrations were greater in saline than in AICA riboside-treated dogs. In separate in vitro studies, AICA riboside did not alter the removal rate of adenosine from canine blood. Indium-labeled granulocyte accumulation was significantly less in ischemic myocardium in AICA riboside-treated compared with saline-treated dogs. In addition, adenosine, but not AICA riboside, inhibited in vitro canine granulocyte superoxide production. We conclude that AICA riboside given before myocardial ischemia augments adenosine concentration, decreases arrhythmias, decreases granulocyte accumulation, and improves collateral flow to ischemic myocardium. One of the beneficial mechanisms could be an increased production of adenosine rather than inosine from ATP catabolism that causes vasodilation and inhibition of granulocytes. We propose a new hypothesis regarding regulation of the inflammatory reaction to ischemia in the microcirculation. Adenosine, in addition to its vasodilator action, is an anti-injury autacoid that links ATP catabolism to inhibition of granulocyte adherence, microvascular obstruction, and superoxide anion formation.