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A L Kuo

Publications and source records attributed to A L Kuo.

5 recordsLinked to original sources
PubMed1982

Phorbol ester induction of leukemic cell differentiation is a membrane-mediated process.

Phorbol esters are potent inducers of macrophage-like differentiation in the HL-60 promyelocytic leukemia cell line. The sequence of events by which they bring about this transition is poorly understood. However, it is known that phorbol esters bind to the surface membrane of HL-60 cells and to various other cells as well. Our studies were directed toward determining the biologic importance of this membrane association. [3H]Phorbol dibutyrate (PBu2) was specifically bound by HL-60 cells with a Kd of 23 nM and with 1.9 X 10(5) binding sites for [3H]PBu2 per cell. There was no internalization of bound [3H]PBu2. Specific binding was fully reversible upon washing in fresh medium, and [3H]PBu2 added thereafter bound normally to its receptor. Within 10 min of binding, PBu2 stimulated [14C]choline incorporation into phosphatidylcholine, with a rapid return to normal upon removal of the PBu2. Membrane-bound PBu2 progressively inhibited DNA synthesis, with 70% inhibition by 8 hr. This process was interrupted if the PBu2 was removed, and little recovery of DNA synthesis occurred in previously inhibited cells. Between 8 and 16 hr, PBu2 induced adherence of cells to plastic, but only in those cells in which phosphatidylcholine synthesis was stimulated, and this process was also interrupted if PBu2 was removed prior to 16 hr. Similarly, nonspecific esterase, which develops after 72 hr of incubation, was induced in cells exposed to PBu2 for the initial 16 hr but not in cells exposed for 5 hr. These studies demonstrate that phorbol esters exert their effects while retained at the cell surface. Inhibition of cell growth and the acquisition of surface and enzymatic properties that characterize macrophages are separable events, each of which proceeds through a receptor-mediated, transmembrane process. The stimulation of phosphatidylcholine synthesis appears to be a part of that process.

Carboxylesterase↗
PubMed1982

Decreased synthesis of high-molecular-weight glycopeptides in human promyelocytic leukemic cells (HL-60) during phorbol ester-induced macrophage differentiation.

The human promyelocytic leukemia ell line, HL-60, synthesized a class of high-molecular-weight (M.W. 5000 to 7000), N-linked glycopeptides as the major class of protein-bound carbohydrates. Small glycopeptides (M.W. 2500 to 3500), typical of most mammalian cells except erythrocytes, represented a minor component in these cells. The large glycopeptides were labeled efficiently with fucose, glucosamine, and galactose but only poorly with mannose. They were found not to be glycolipids, glycosaminoglycans, or mucin-type glycopeptides and were not susceptible to exoglycosidases, but they were partially degraded by endo-beta-galactosidases. These characteristics are similar to those of the large glycopeptides synthesized by erythrocytes, by another human myeloid leukemia cell line (K562), and by human and murine teratocarcinoma cells. High-molecular-weight glycopeptides predominated on another human myeloid leukemia cell line KG1, but they were expressed at low levels on both a human monocytic leukemia cel line (THP-1) and a human T-lymphoblastoid cell line (Jurkat). When HL-60 cells were induced to differentiate into macrophage-like cells with phorbol esters, the proportion of large glycopeptides decreased, and the production of small glycopeptides predominated. This shift was observed within the first several hr after exposure to phorbol esters and was temporally related to the acquisition of adherent properties by the induced cells. In contrast, when HL-60 cells were induced to differentiate into granulocytes by dimethyl sulfoxide, hypoxanthine, or retinoic acid, they continued to synthesize glycopeptides similar to uninduced cells. Human peripheral blood granulocytes synthesized primarily large glycopeptides, whereas monocytes and lymphocytes synthesized mostly small glycopeptides. These results indicate that the synthesis of high-molecular-weight glycopeptides is a property of human myeloid leukemia cell lines and that it persists throughout myeloid differentiation. A proportionate decrease in the synthesis of these large glycopeptidase is a part of the differentiation program for monocytes and macrophages.

Cell Adhesion↗
PubMed1981

Inhibition of sterol and phospholipid synthesis in HL-60 promyelocytic leukemia cells by inducers of myeloid differentiation.

Myeloid differentiation is induced in HL-60 promyelocytic leukemia cells by dimethyl sulfoxide, retinoic acid, hypoxanthine, and a number of other chemical agents. We questioned whether the induction process was associated with changes in lipid synthesis. With [14C]acetate, a precursor for all cell lipids, a decrease in sterol and phospholipid synthesis (but not triglyceride synthesis) was observed within the first 5 hr after exposure to inducer, a time prior to inhibition of DNA synthesis or cessation of cell growth. Similarly, the membrane fraction of HL-60 cells exhibited decreased incorporation of newly synthesized lipid. Synthesis of phosphatidylcholine from choline as well as from the transmethylation of membrane phosphatidylethanolamine was also inhibited by myeloid inducers. In contrast, neither sterol nor phospholipid degradation was stimulated under these conditions. Both cholesterol and lanosterol were synthesized by growing HL-60 cells, but cholesterol esters were not. Synthesis of sterols was subject to feedback inhibition by cholesterol in the medium, but such feedback inhibition did not affect differentiation in the presence of myeloid inducers and did not alter the effect of myeloid inducers on phospholipid synthesis. Removal of dimethyl sulfoxide at 16 hr permitted a return to normal lipid synthesis and prevented differentiation, whereas removal of dimethyl sulfoxide at 40 hr was followed by continued inhibition of lipid synthesis and progressive differentiation. These studies demonstrate that the induction of myeloid differentiation is associated with an early inhibition of the synthesis of those lipids which are normally a part of cell membranes.

Acetates↗
PubMed1975

Immunochemical studies on factor V.

Native bovine factor V exhibits a molecular weight of 300000 as determined by gel filtration of untreated plasma. Highly purified factor V exhibits multiple molecular weight forms which range from small active fragments to aggregates of several million which are generated during the purification on cellulose phosphate. Isoelectric focusing on a single high-molecular-weight species produced a single protein and activity peak at pH 4.65. Factor V activity is associated with each protein band observed following polyacrylamide gel electrophoresis. Antisera to factor V prepared in rabbits produces a time-dependent and concentration-dependent inhibition of factor V activity in plasma and purified factor V. The multiple molecular weight forms of factor V appear equivalent upon immunodiffusion and on immunoelectrophoresis migrate as an alpha globulin between albumin and fibrinogen. Immunoprecipitation arcs are equivalent in plasma and serum. Factor V consists of two major types of subunits, a light chain (73000), aggregates of which form the high-molecular-weight species, and a heavy chain (125 000). Using preparations containing one or both chains isolated by disc gel electrophoresis, antiserum was shown to contain two families of antibodies, one against each subunit. Cross reactivity with both light and heavy chain antigens is observed in sheep and goat but not monkey or human plasma. The antisera also neutralized goat and sheep factor V activity.

Animals↗