[Construction of human glioma cDNA library]

Total RNA from a human glioma was extracted by acid guanidinium-thiocyanate-chloroform one step method, and poly(A+)RNA was separated by affinity chromatography on oligo (dT) cellulose. The cDNA was synthesized by using poly (A+) RNA as template, the length of cDNA being 0.2-5 kb. The glioma cDNA inserts could be cloned into lambda gt11 vector, the resulting recombinant DNA was packaged in vitro. The cDNA library of 1.12 x 10(5) pfu/ml was obtained, and the cloning efficiency was 4.8 x 10(3)/ng cDNA. This library might contribute an important basis to study of the structure and function of human glioma genes.

Transformation of human osteoblasts to anchorage-independent growth by insoluble nickel particles

Nickel compounds are well established by epidemiologic studies as human carcinogens. Although the carcinogenicity of nickel compounds has been studied in experimental animals and in a variety of cultured mammalian cells, there are only sporadic reports of nickel-induced transformation of human cells. In attempts to study the mechanisms of nickel-induced carcinogenesis in human cells, an immortalized human osteoblastic cell line (HOS) that could not grow in soft agar or form tumors in athymic nude mouse was repeatedly treated with a water-soluble nickel compound (NiCl2) or a less water-soluble nickel compound crystalline (NiS). After three rounds of NiS treatment, there was an increase in anchorage-independent (AI) colony formation. This was not found in untreated or NiCl2-treated cells. Ten AI colonies obtained from NiS-treated cells were isolated. All of these clones showed changes in cell morphology, including the appearance of uniform polygon shape, growth in multilayers, and heavy staining with Giemsa. Most of these clones were retested for their ability to grow in soft agar and showed growth efficiencies of 5 to 50%. It has been shown by other investigators that aggregate growth is well correlated with tumorigenic potential in viral or chemical transformants of HOS cells. Four of seven tested NiS-transformed clones were able to form large aggregates compared to their untransformed counterparts, and continued to proliferate in aggregate form when they were plated on 0.9% agar. Current investigations focus on the molecular and genetic changes induced by nickel compounds in these human cells.

Engineering aspartic proteases to probe structure and function relationships

Recently, protein engineering has been used to interconvert homodimeric and homologous single-chain aspartic proteases, with some success. The independent folding of the domains of these proteases has also permitted the engineering of domain-rearranged protease zymogens and the use of individual domains as probes for structural denaturation. In addition, site-directed mutagenesis has provided insights into the catalytic mechanism and specificity of this family of proteases.

Time-dependent thermodynamics during early electron transfer in reaction centers from Rhodobacter sphaeroides

The temperature dependence of fluorescence on the picosecond to nanosecond time scale from the reaction centers of Rhodobacter sphaeroides strain R-26 and two mutants with elevated P/P+ midpoint potentials has been measured with picosecond time resolution. In all three samples, the kinetics of the fluorescence decay is complex and can only be well described with four or more exponential decay terms spanning the picosecond to nanosecond time range. Multiexponential fits are needed at all temperatures between 295 and 20 K. The complex decay kinetics are explained in terms of a dynamic solvation model in which the charge-separated state is stabilized after formation by protein conformational changes. Many of these motions have not had time to occur on the time scale of initial electron transfer and/or are frozen out at low temperature. This results in a time- and temperature-dependent enthalpy change between the excited singlet state and the charge-separated state that is the dominant term in the free energy difference between these states. Long-lived fluorescence is still observed even at 20 K, particularly for the high-potential mutants. This implies that the driving force for electron transfer on the nanosecond time scale at low temperature is less than 200 cm-1 (25 meV) in R-26 reaction centers and even smaller on the picosecond time scale or in the high-potential mutants.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between thermodynamics and mechanism during photoinduced charge separation in reaction centers from Rhodobacter sphaeroides

Detailed fast transient absorption measurements have been performed at low temperature on reaction centers from Rhodobacter sphaeroides strain R-26 and on a double mutant, [LH(L131) + LH-(M160)], in which the P/P+ oxidation potential is roughly 140 mV (1100 cm-1) above that of wild-type reaction centers. In both samples, the decay of the excited singlet state of the initial electron donor is not well described by a single-exponential decay term. This is particularly true for reaction centers from the double mutant where at least three exponential kinetic components are required to describe the decay, with time constants ranging from a few picoseconds to hundreds of picoseconds. However, singular value decomposition analysis of the time-dependent absorption change spectra indicates the presence of only two spectrally distinct states in reaction centers from both R-26 and the double mutant. Thus, the complex decay of P* at low temperature does not appear to be due to formation of either the state P+BA- as a distinct intermediate in electron transfer or P+BB- as an equilibrated side product of electron transfer. Instead, the decay kinetics are modeled by assuming dynamic solvation of the charge-separated state, as was done for the long-lived fluorescence decay in the accompanying paper [Peloquin, J. M., Williams, J. C., Lin, X., Alden, R. G., Taguchi, A. K. W., Allen, J.P., & Woodbury, N. W. (1994) Biochemistry 33, 8089-8100]. The results of assuming a static distribution of electron-transfer rates at early times followed by dynamic solvation of the charge-separated states on longer time scales are also presented. Regardless of which model is used to describe the early time kinetics of excited-state decay, the time-dependent excited-state population on the 100-ps or longer time scale is best described in terms of thermal repopulation of P* from the charge-separated state, even at 20 K. This results in a time- and temperature-dependent driving force estimated for initial electron transfer of less than 200 cm-1 on all time scales from picoseconds to nanoseconds. Assuming a nonzero internal reorganization energy associated with charge separation, the small driving force does not appear to be consistent with the lack of temperature dependence of electron transfer and the fact that a mutant with a P/P+ oxidation potential 140 mV (1100 cm-1) higher than wild type is still able to undergo electron transfer, even at low temperature.(ABSTRACT TRUNCATED AT 400 WORDS)

Diuretic therapy for hypertension and the risk of primary cardiac arrest

BACKGROUND

The results of trials of the primary prevention of coronary heart disease have suggested that treating hypertension with high doses of thiazide diuretic drugs might increase the risk of sudden death from cardiac causes. In contrast, treatment with low doses of thiazide reduces the risk of coronary heart disease.

METHODS

To examine the association between thiazide treatment for hypertension and the occurrence of primary cardiac arrest, we conducted a population-based case-control study among enrollees of a health maintenance organization. The case patients were 114 persons with hypertension who had a primary cardiac arrest from 1977 through 1990. The control patients were a stratified random sample of 535 persons with hypertension. The patients' treatment was assessed with the use of a computerized pharmacy data base. Records of their ambulatory care were reviewed to determine other clinical characteristics.

RESULTS

The risk of primary cardiac arrest among patients receiving combined thiazide and potassium-sparing diuretic therapy was lower than that among patients treated with a thiazide without potassium-sparing therapy (odds ratio, 0.3; 95 percent confidence interval, 0.1 to 0.7). As compared with low-dose thiazide therapy (25 mg daily), moderate-dose therapy (50 mg daily) was associated with a moderate increase in risk (odds ratio, 1.7; 95 percent confidence interval, 0.7 to 4.5), and high-dose therapy (100 mg daily) was associated with a larger increase in risk (odds ratio, 3.6; 95 percent confidence interval, 1.2 to 10.8) (P value for trend, 0.02). The addition of a potassium-sparing drug to low-dose thiazide therapy was associated with a reduced risk of cardiac arrest (odds ratio, 0.4; 95 percent confidence interval, 0.1 to 1.5).

CONCLUSIONS

Both the dose of thiazide drugs and the addition of potassium-sparing drugs influence the risk of primary cardiac arrest. These results may explain the differences in the effect of antihypertensive therapy on mortality from coronary heart disease in previous clinical trials.

The presence but not the sequence of the N-terminal peptide in cardiac TnC is important for function

The most diverged region of the primary amino acid sequence between cardiac (cTnC) and fast skeletal troponin C is the N-terminal ten amino acids. We report here that major changes in the primary sequence of this region in cTnC had a minimal effect on the ability of the mutant proteins to recover maximal activity in TnC-extracted cardiac and fast skeletal muscle myofibrils. However, deletion of the N-terminal nine amino acids resulted in a 60% decrease in maximal Ca(2+)-dependent ATPase activity with only a small change in the pCa50 of activation. Deletion of the N-terminal peptide did not appear to appreciably affect the Ca(2+)-binding properties of cTnC, but it did alter the interaction with hydrophobic fluorescent probes. Thus, the presence but not the sequence, of the N-terminal extension is important for the maximal activity of cTnC. The N-terminal helix may function in a relatively non-specific manner to prevent unfavorable interactions between domains in cTnC or between cTnC and other troponin subunits.

Nickel-induced transformation of human cells causes loss of the phosphorylation of the retinoblastoma protein

The retinoblastoma (Rb) protein (pRb) has been studied in various crystalline NiS-transformed cell clones derived from the human osteoblast cell line, HOS TE-85. The parental HOS cells were not able to proliferate in soft agar medium, but they acquired this property following treatment with crystalline NiS. The pRb was found only in the hypophosphorylated form in 8 of 9 nickel-transformed clones examined, whereas in the parental cells the pRb appeared in both phosphorylated and unphosphorylated forms. Neither Rb gene expression nor its phosphorylation was affected by acute nickel treatments of HOS cells. The nickel-transformed HOS clones expressed the major regulators of Rb phosphorylation, cyclin E and cdk-2, at levels similar to those of the parental cells. In coimmunoprecipitation assays with cell lysates from the transformed clones that exhibited the hypophosphorylated form of pRb, the Rb protein failed to form a complex with simian virus 40 large T-antigen, indicating a lack of functional activity. When a plasmid containing the normal Rb gene was transfected into these nickel-transformed cells, it restored the Rb phosphorylation pattern observed in parental cells and the cells acquired a normal phenotype (i.e., they were no longer able to grow in soft agar). This suggested that a mutation was induced in nickel-transformed cells that affected the ability of the Rb protein to be phosphorylated and function normally, and this mutation allowed the human nickel-transformed cells to acquire anchorage-independent growth.

NMDA receptor activation in differentiating cerebellar cell cultures regulates the expression of a new POU gene, Cns-1

POU/homeobox genes encode transcription regulatory proteins that are important in defining cellular phenotypes. Expression of these genes may be critical for to the regulation of CNS cellular differentiation. We have identified a cDNA corresponding to a new member of the POU/homeobox gene family. Expression of RNA encoded by this new gene occurs predominantly in the CNS. Thus, this new gene was designated Cns-1. Cns-1 transcripts are expressed in differentiating cells cultured from the early postnatal cerebellum. Treatment of these cultured cells with NMDA results in an increase in the level of Cns-1 RNA. This increase is blocked by simultaneous treatment with the specific NMDA receptor antagonist amino-5-phosphonovaleric acid. Continued activation of the NMDA receptor allows maintenance of this new steady state level of Cns-1 mRNA for at least 5 d in these cultured cells. A transcription runoff assay suggests that this increase in the level of RNA is due, at least in part, to an increase in transcription from the Cns-1 gene. The NMDA-induced increase in Cns-1 mRNA was reduced by pretreatment with calcium chelators EGTA or 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) tetrakis(acetoxymethyl). These studies suggest that specific activation of the NMDA receptor in cultures of differentiating cerebellar cells increases Cns-1 gene expression and that calcium entry through the NMDA channel may be required for this response. This change in Cns-1 expression may modify phenotypic characteristics of these cultured cells.

Differences in the metabolism of 18:2n-6 and 18:3n-6 by the liver and kidney may explain the anti-hypertensive effect of 18:3n-6

The present study examined the in vitro and in vivo metabolism of 18:2n-6 and 18:3n-6 by kidney and liver in the male adult spontaneously hypertensive (SHR) and normotensive (WKY) rats. In liver and kidney slices incubated for 1 h with either [1-14C]18:2n-6 or [1-14C]18:3n-6 (60 microM), substantial amounts of radioactivity were incorporated into triacylglycerol and phospholipid fractions. Approximately 15% of the radiolabeled 18:2n-6 was converted into 18:3n-6 in liver slices but no conversion was found in kidney slices. When incubated with radiolabeled 18:3n-6, over 40% of the radioactivity was metabolized mainly to 20:4n-6 in liver slices, but evenly to 20:3n-6 and 20:4n-6 in kidney slices. There were no differences between the results from SHR and those from WKY. In WKY rats given an oral bolus of radiolabeled 18:3n-6, most of the radioactivity was recovered in the liver and significantly less in the kidney. In both tissues, the radioactivity was associated initially only with 18:3n-6 and later with its elongation product, 20:3n-6. These findings indicated that the kidney, although unable to metabolize 18:2n-6, could metabolize 18:3n-6 taken up from the circulation. The effectiveness of 18:3n-6, compared to 18:2n-6, as an anti-hypertensive agent may result from the provision of a post-delta 6-desaturation metabolite which can be directly converted to blood pressure-regulating eicosanoids in the kidney.

[Hepatic ultrasonographic imaging and serum amino acid levels in cured schistosomiasis cases]

Ultrasonography (B mode) of liver and serum amino-acid levels were studied in 15 cases of schistosomiasis japonica who had been cured for more than 5-15 years. Typical B-ultrasonic images of hepatic fibrosis due to schistosomiasis were found in all patients which could be classified into three types, namely, the spotty type (I), the tortoise-shell type (II) and the net-patchy type (III) according to the patterns of echogenic bands. Moderate to marked echogenic thickening of portal vein wall, and dilation of portal and splenic veins were revealed in patients with type II and III images. Free amino acids in sera were determined by using HPLC-AAAS. The result revealed that the concentration of 8 nonessential and 3 essential amino acids (threonine, valine, tryptophan) were significantly decreased in the 15 patients. The ratio of aromatic to aliphatic amino acid was markedly elevated in 3 patients of type III. The serum amino acid imbalance was attributed to the severe hepatic damage and impaired liver function.

Emulsification and fatty acid chain length affect the kinetics of [14C]-medium-chain triacylglycerol utilization by neonatal piglets

In vivo oxidation kinetics of medium-chain triglycerides (MCT) composed of [1-14C]hexanoate (tri-6:0) or [1-14C]octanoate (tri-8:0) were compared after being fed to day-old piglets (1.4 kg; n = 4/treatment). Animals were fitted with arterial and oro-gastric catheters and placed into respiration chambers held at 35 degrees C. The radiolabeled MCT were fed in equimolar amounts (6.5 mmol/kg0.75), in either nonemulsified form or as 30% (v/v) emulsions, using polyoxyethylene sorbitan monooleate as an emulsifier. Expired CO2 was quantified and specific radioactivity (Bq/mumol) determined at 20-min intervals over 24 h, and serial blood samples were drawn for measurement of plasma hexanoate and octanoate by HPLC. The rate [mumol/(h.kg0.75)] and extent (mmol/kg0.75) of MCT oxidative utilization (i.e., composite of digestion, absorption and oxidation) were calculated from the kinetics of 14CO2 expiration. Emulsification increased both the rate and extent of MCT oxidative utilization by > 20% regardless of fatty acid chain length (P < 0.05). Maximal MCT oxidation rates occurred at 3.5 h after feeding and were sufficient to meet up to 48% of the piglets' energy expenditure. The maximal rate of tri-6:0 oxidative utilization exceeded that of tri-8:0 by 37% (P < 0.05), but the extent of utilization was not affected by fatty acid chain length. Plasma medium-chain fatty acid concentrations were in agreement with these observations, being higher in pigs fed emulsified MCT than in pigs fed nonemulsified MCT (P < 0.05) and being higher in pigs fed tri-6:0 than in animals fed tri-8:0 (P < 0.05). Collectively, these data demonstrate that newborn piglets can effectively digest, absorb and oxidize MCT, that utilization is improved with emulsification, and that tri-6:0 is utilized more rapidly than tri-8:0.

Use of k0-NAA in the life sciences

The applicability and usefulness of k0-based reactor neutron activation analysis (NAA) in the life sciences is evaluated from the following examples: 1. Instrumental NAA of NIST SRM 1633a coal fly ash, as a quality assessment; 2. Radiochemical NAA of Versieck's reference human serum, and--herewith associated--the development of practical correction procedures for neutron-induced reaction interferences and of improved methods to evaluate the detection efficiency and the correction for true coincidence; and 3. Determination of the lanthanides in plant leaves and lichens near a Portuguese coal-fired power station, which led to the introduction of the Westcott formalism and to the use of a low-energy photon detector. As concluded, k0-based NAA is at present capable of tackling a large variety of analytical problems when it comes to the multielement determination in environmental and biological matrices.

An epidemiological model for HIV/AIDS with proportional recruitment

A model for HIV transmission is formulated for a homosexual population of varying size, with recruitment into the susceptible class proportional to the active population size and with stages of progression to AIDS. Analysis of this model includes identifying the threshold that determines whether the disease dies out or proportions remain endemic and establishing criteria that determine whether the population size decays asymptotically exponentially to zero or grows asymptotically exponentially to infinity. In an analogous heterosexual model, the conservation of heterosexual contacts is shown to imply that this two-sex model reduces to the one-sex model.

[Clinical analysis of 160 cases with the magnetic foreign bodies in the posterior segment of the eye]

One hundred and sixty cases of magnetic foreign bodies in the posterior segment of the eye are reported. Most of the foreign bodies are small (61.2% are less than 2mm) and near the wall of the eye (73.7% are less than 2mm). 110 cases were successfully operated in conventional way and just 20 cases needed to have vitrectomy. The result of the operation depends on the damage of the eye, location of the foreign body and the complication of the operation. In 77.6% of the cases, the wound was on the cornea or limbus. That is one of the important factors to affect the patients' postoperation vision.

Effects of maternal dietary n-3 and n-6 fatty acids (pre- and post-delta 6 desaturation) on tissue glycerophospholipid fatty acid compositions in dams and suckling mice

The present study examined the effects of supplementation of either 18:3n-3 or a mixture of its post-delta 6-desaturation metabolites, 20:5n-3/22:6n-3, in combination with either 18:2n-6 or its immediate delta 6-desaturation product, 18:3n-6, in the maternal diet (n-3 to n-6 ratio at 0.25) on brain, liver, heart, and kidney glycerophospholipid fatty acid composition in dams (B6D2F1 mice) and their 12-day-old suckling pups. As expected, n-3 and n-6 fatty acids competed for incorporation into tissue glycerophospholipids in both dams and their suckling pups. Feeding a 20:5n-3/22:6n-3 as compared with an 18:3n-3 rich diet increased the tissue levels of 20:5n-3 and 22:5n-3, whereas it decreased those of 20:3n-6 and 20:4n-6. Replacing 18:2n-6 with 18:3n-6 in the maternal diet increased significantly the levels of 18:3n-6, 20:3n-6, and 20:4n-6, whereas it reduced those of 20:5n-3. However, the effects of maternal dietary fats on tissue fatty acid compositions in pups were qualitatively similar to but quantitatively smaller than those in dams. The discrepancy might be due to differences in the composition of fatty acids taken up and synthesized by the dams and that transferred to the pups.

Voltage-dependent block by neomycin of the ATP-induced whole cell current of guinea-pig outer hair cells

1. The effects of externally applied ATP and neomycin on whole cell currents of isolated guinea pig cochlear outer hair cells (OHCs) were studied using the whole cell voltage-clamp technique. In OCHs held at -70 mV, ATP activated a large inward current. In the presence of neomycin, the ATP-induced whole cell current activated along a relatively unaltered time course, but the current then decreased to a reduced steady level. The neomycin inhibition of the ATP-induced current was dose dependent. The half-inhibitory concentration (IC50) of neomycin measured at steady state was estimated to be 90 microM. 2. Neomycin inhibition of the ATP response could not be reversed by increasing the concentration of ATP, indicating that the effect was noncompetitive. The inhibition was voltage dependent and was greatly reduced when OHCs were held at positive potentials. 3. Cells treated with 100 microM ATP gave maximal current responses. Addition of neomycin substantially increased membrane current noise of the 100 microM ATP responses. When neomycin concentration was varied from 10 to 500 microM, the current noise level peaked between 50 and 100 microM. The noise increase was observed at negative holding potentials but not at positive potentials. 4. The neomycin-induced whole cell current noise was used to estimate the size of the underlying elementary current. The ATP-induced single channel current of OHCs at -70 mV was estimated to be approximately 0.3 pA. The number of ATP-activated channels in a single OHC was estimated to be in the range of a few thousand. 5. The characteristics of the neomycin inhibition of ATP-induced currents were consistent with an open channel blocking mechanism. Analysis of the voltage dependence of the steady state neomycin inhibition suggested a neomycin binding site at an electrical distance of 0.3 from the extracellular side.

Recombinant canditropsin, an extracellular aspartic protease from yeast Candida tropicalis. Escherichia coli expression, purification, zymogen activation, and enzymic properties

A cDNA fragment which encodes the zymogen of canditropsin, the extracellular aspartic protease from the yeast Candida tropicalis (Togni,G., Sanglard, D., Falchetto, R., and Monod, M. (1991) FEBS Lett. 286, 181-185) was cloned into a T7 expression vector for the synthesis of the recombinant zymogen in Escherichia coli. Recombinant canditropsinogen (Ctg), which was expressed as inclusion bodies in the cytosol of E. coli, was refolded by dialysis from an 8 M urea solution and purified to homogeneity using chromatographies on Sephacryl S-300 and on MonoQ columns. The purified Ctg was converted into canditropsin by either acid activation or trypsin conversion. The specificity of the resulting recombinant canditropsin toward polypeptide substrates is significantly different from other aspartic proteases. Canditropsin hydrolyzes oxidized insulin B chain between Ala-Leu and many other minor cleavage sites. Canditropsin also hydrolyzes keratin and collagen, which are components of connective tissues known to be hydrolyzed by canditropsin during Candida infections. Canditropsin was strongly inhibited by the universal aspartic protease inhibitor pepstatin (Ki = 1.75 x 10(-8) M) and inactivated by two aspartic protease inactivators, DAN and EPNP. Canditropsin is weakly inhibited by leupeptin and antipain, with an apparent Ki of 1.74 x 10(-4)M and 1.5 x 10(-5) M, respectively.

[A study on P21(ras) in human lung cancer and body fluid of cancer patients]

The McAb of anti-P21(ras) has been used to screen 9 cases of human lung cancer tissues, 18 cases of samples and 2 cases of hydrothorax samples of lung cancer patients by means of PAGE-immunoblots. The expression of ras gene was found in 8 cases of human lung cancer among which the expression of 4 cases was higher than that of normal control. P21(ras) has not been detected in serum and hydrothorax samples of cancer patients. The present study indicated that there was P21(ras) in human lung cancer and normal control and the expression level of ras gene in lung cancer was related to the differentiation of cancer.

Conformational instability of the N- and C-terminal lobes of porcine pepsin in neutral and alkaline solutions

Pepsin contains, in a single chain, two conformationally homologous lobes that are thought to have been evolutionarily derived by gene duplication and fusion. We have demonstrated that the individual recombinant lobes are capable of independent folding and reconstitution into a two-chain pepsin or a two-chain pepsinogen (Lin, X., et al., 1992, J. Biol. Chem. 267, 17257-17263). Pepsin spontaneously inactivates in neutral or alkaline solutions. We have shown in this study that the enzymic activity of the alkaline-inactivated pepsin was regenerated by the addition of the recombinant N-terminal lobe but not by the C-terminal lobe. These results indicate that alkaline inactivation of pepsin is due to a selective denaturation of its N-terminal lobe. A complex between recombinant N-terminal lobe of pepsinogen and alkaline-denatured pepsin has been isolated. This complex is structurally similar to a two-chain pepsinogen, but it contains an extension of a denatured pepsin N-terminal lobe. Acidification of the complex is accompanied by a cleavage in the pro region and proteolysis of the denatured N-terminal lobe. The structural components that are responsible for the alkaline instability of the N-terminal lobe are likely to be carboxyl groups with abnormally high pKa values. The electrostatic potentials of 23 net carboxyl groups in the N-terminal domain (as compared to 19 in the C-terminal domain) of pepsin were calculated based on the energetics of interacting charges in the tertiary structure of the domain. The groups most probably causing the alkaline denaturation are Asp11, Asp159, Glu4, Glu13, and Asp118.(ABSTRACT TRUNCATED AT 250 WORDS)

Intracellular diversion of glycoprotein GP160 of human immunodeficiency virus to lysosomes as a strategy of AIDS gene therapy

A potential gene therapy strategy against human immunodeficiency virus (HIV-1) is to disrupt the intracellular transport of viral proteins. We report here the binding and transporting of HIV-1 glycoprotein gp160 to lysosomes as a result of the expression of fusion genes consisting of soluble CD4 and lysosome targeting domains. The effective lysosome targeting domain tested includes a lysosomal protease zymogen, procathepsin D, and the COOH-terminal domains of three lysosome membrane proteins: lamp-1, lamp-2, and lysosomal acid phosphatase. We demonstrated that cell fusion (syncytium), caused by the transport of gp160 to the surface of HeLa-CD4+ cells, was completely abolished by the expression of these fusion genes. The lysosomal localization of gp160 in HeLa cells coexpressing CD4-fusion genes was also established. From pulse-chase experiments, we observed that gp160 and the fusion proteins were degraded, as expected of lysosomal activities. Additionally, T lymphoblastoid cells transiently and permanently expressing these fusion genes strongly retarded the propagation of human immunodeficiency virus type 1. Thus, these fusion genes can deprive HIV of newly synthesized envelope protein gp160 for the assembly of new virions and are potentially useful in gene therapy against AIDS.