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W S May

Publications and source records attributed to W S May.

At least 73 records · Page 4Linked to original sources
PubMed1987

Phosphorylation of the surface transferrin receptor stimulates receptor internalization in HL60 leukemic cells.

The transferrin receptor is a target protein for phosphorylation by activated intracellular protein kinase C (May, W. S., Sahyoun, N., Jacobs, S., Wolf, M., and Cuatrecasas, P. (1985) J. Biol. Chem. 260, 9419-9426). Recently we reported that the potent tumor-promoting agent phorbol diester or a synthetic diacylglycerol could mediate rapid down-regulation of the surface transferrin receptor in association with receptor phosphorylation in HL60 leukemic cells and suggested that this phosphorylation may provide a signal for receptor internalization. In this communication we have tested experimentally the predictions generated by the hypothesis that receptor phosphorylation may play such a role in the intracellular cycling of the transferrin receptor. Results indicate that phorbol diester-stimulated phosphorylation occurs stoichiometrically only on the surface-oriented receptor and precedes internalization. Using a specific inhibitor of protein kinase C, it was found that both phorbol diester-mediated receptor phosphorylation and down-regulation could be antagonized. While the mechanism of internalization of the phosphorylated receptor is not clear, phorbol diester treatment significantly increases the rate constant for endocytosis from 0.183 to 0.462 min-1, while inhibiting only slightly the rate constant for exocytosis of the internalized receptor from 0.113 to 0.079 min-1. Thus, we conclude that phorbol diester treatment affects intracellular cycling of receptors and establishes a new steady state distribution of surface and intracellular receptors. These data support a role for receptor phosphorylation as a trigger for internalization primarily by stimulating the process of transferrin receptor endocytosis while affecting the subsequent exocytosis of the receptor cycling only slightly.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1987

Antineoplastic bryostatins are multipotential stimulators of human hematopoietic progenitor cells.

The bryostatins are macrocyclic lactones, extracted from the marine bryozoan Bugula neritina, and have been reported to be potent antineoplastic agents. Results described here demonstrate that the bryostatins may also be useful as stimulators of normal human hematopoietic cells since they can (i) directly stimulate bone marrow progenitor cells to form colonies in vitro and (ii) functionally activate neutrophils. Structure-activity studies with bryostatin congeners indicate that these stimulatory properties may be dependent on the chain length and the unsaturated nature of the acylated group at carbons 20 and 7 of the bryostatin molecule. These stimulatory properties demonstrate that the naturally occurring bryostatins can mimic many of the biological effects of multipotential granulocyte-macrophage colony-stimulating factor. Thus, the coupling of antineoplastic activity with stimulatory growth properties for normal hematopoietic cells makes this agent an excellent probe to dissect the mechanism(s) of normal hematopoiesis. In addition, bryostatin may represent a clinically attractive agent useful for treating bone marrow failure states.

Antineoplastic Agents↗
PubMed1987

Bryostatin induces changes in protein kinase C location and activity without altering c-myc gene expression in human promyelocytic leukemia cells (HL-60).

When human promyelocytic leukemia cells (HL-60) are induced by phorbol esters to differentiate to macrophages, the process is accompanied by immediate activation of protein kinase C (PK-C) in the cytoplasm and later changes in DNA and RNA synthesis. Although these events are temporarily related, it remains unclear how activation of this protein kinase leads to changes in nuclear transcription. In this study, we find that bryostatin, a macrocyclic lactone which does not induce differentiation of HL-60 cells but activates PK-C, mimics the effects of phorbol esters on protein phosphorylation and PK-C location. Treatment of HL-60 cells with bryostatin stimulates phosphorylation of the surface transferrin receptor and in the cytoplasm of five proteins having the molecular weights of 17-43 kDa over the same time course as that stimulated by phorbol esters. Similarly, prolonged treatment with bryostatin, like that with phorbol esters, causes the loss of all cellular PK-C activity. Unlike the phosphorylation studies, bryostatin treatment, over a 1-100 nM concentration range and for varying lengths of time, did not affect HL-60 c-myc RNA levels, while phorbol ester treatment rapidly decreased c-myc RNA levels. These data suggest that neither the activation of PK-C and the phosphorylation of specific substrates nor the loss of total cellular PK-C activity from HL-60 cells is sufficient to induce marked decreases in c-myc levels and differentiation of HL-60 cells.

Bryostatins↗
PubMed1986

Affinity isolation of the interleukin-3 surface receptor.

Interleukin-3 (IL-3) is a pluripotent hematopoietic growth factor which can stimulate both proliferation and differentiation of progenitor cells. Using the factor dependent NSF-60 and FDC-P1 cells, which possess specific, high affinity binding sites for 125I-IL-3 (i.e. KD 9.5 and 10.7 X 10(-11)M, respectively) the IL-3 surface receptor has been isolated. Using two separate affinity techniques the IL-3 receptor identified from both cell types was invariant. The IL-3 receptor is a protein of molecular weight 65-70,000 daltons.

Affinity Labels↗
PubMed1986

Intracellular activation of protein kinase C and regulation of the surface transferrin receptor by diacylglycerol is a spontaneously reversible process that is associated with rapid formation of phosphatidic acid.

The effect of the synthetic diacylglycerol, sn-1,2-dioctanoylglycerol (diC8), on the expression of the surface transferrin receptor reveals that exogenous diC8 can act as an intracellular activator of protein kinase C and stimulate both down-regulation and increased receptor phosphorylation in a manner similar to that induced by the active tumor promotor, 4 beta-phorbol 12,13-dibutyrate. Unlike the spontaneously irreversible effect noted when 4 beta-phorbol 12, 13-dibutyrate is added, this same effect mediated by diC8 is brief, lasting only minutes, and is spontaneously reversible. The rate of reversibility is dependent on the concentration of diC8 added, and it is associated with rapid formation of a newly detected intracellular phospholipid that corresponds to sn-1,2-dioctanoyl phosphatidic acid. These data, in conjunction with findings that demonstrate that exogenous diacylglycerols (including diC8) when added to cells do not stimulate cellular phospholipase A2 or C, argue that protein kinase C is activated only briefly in this system since exogenous diC8 is subject to rapid intracellular metabolism to phosphatidic acid.

Calcimycin↗
PubMed1986

Respiratory monitoring.

Scientific advances over the last 20 years have enabled us to monitor the respiratory status of our patients beyond the age-old methods taught in physical diagnosis. It is now possible to measure almost every parameter of ventilation, oxygen transport, and CO2 transport, thus enhancing patient safety and patient care.

Carbon Dioxide↗
PubMed1985

Mechanism of phorbol diester-induced regulation of surface transferrin receptor involves the action of activated protein kinase C and an intact cytoskeleton.

Phorbol diesters are tumor-promoting agents that cause differentiation of HL60 human leukemic cells and concomitantly regulate surface transferrin receptors. Regulation of transferrin receptors by phorbol diesters involves receptor internalization in association with increased receptor phosphorylation (hyperphosphorylation). The intracellular mechanism of action of phorbol diester involves binding to and activation of the Ca2+-phospholipid-dependent protein kinase (protein kinase C). Present studies comparing results obtained with whole cells and those from a cell-free system reconstituted from purified protein kinase C and transferrin receptor components have revealed that the transferrin receptor is phosphorylated by protein kinase C activated by phorbol esters. Following tryptic digestion and two-dimensional separation of phosphopeptides of phosphorylated transferrin receptors, two major and several minor phosphoserine-containing fragments are resolved. These fragments are identical whether transferrin receptor is phosphorylated in whole cells incubated with phorbol diesters or following phosphorylation of affinity immobilized transferrin receptor in the in vitro reconstitution system. Phosphoamino acid analysis of these fragments indicates that serine is the only amino acid phosphorylated in whole cells or in the cell-free system. In addition, colchicine is shown to inhibit in a dose-dependent manner phorbol diester-induced internalization but not hyperphosphorylation of the surface transferrin receptor in whole cells. This inhibition is specific for colchicine since inactive beta- and gamma-Lumicolchicine have no such effect, while taxol reverses the inhibition. These results indicate that the phorbol diester-mediated process of down-regulation of the surface transferrin receptor is associated with phosphorylation of the receptor by activated protein kinase C and requires an intact cytoskeleton to affect receptor internalization.

Cell Line↗
PubMed1985

Amiloride inhibits phorbol ester-stimulated Na+/H+ exchange and protein kinase C. An amiloride analog selectively inhibits Na+/H+ exchange.

The human leukemic cell line, HL-60, differentiates in response to tumor-promoting phorbol esters. Recently, we have reported that one of the first events evoked by phorbol esters in HL-60 cells is the stimulation of Na+-dependent H+ efflux. In efforts to determine whether stimulation of Na+/H+ exchange by phorbol esters is coupled to induction of cellular differentiation, we found that 1) amiloride, a frequently used inhibitor of Na+/H+ exchange, rapidly inhibits phorbol ester-stimulated protein phosphorylation in vivo and protein kinase C-mediated phosphorylation in vitro, both with potency similar to that with which amiloride inhibits Na+/H+ exchange; 2) an amiloride analog, dimethylamiloride, is a far more potent inhibitor of Na+/H+ exchange than is amiloride, while being no more potent than amiloride in inhibiting phorbol ester/protein kinase C-mediated phosphorylation; and 3) at concentrations sufficient to completely inhibit Na+/H+ exchange, amiloride blocked phorbol ester-induced adhesion of HL-60 cells (adhesion being a property indicative of the differentiated state), but dimethylamiloride (as well as ethylisopropylamiloride, another very potent amiloride analog) did not. Thus, dimethylamiloride represents a potential tool for distinguishing protein kinase C-coupled from Na+/H+ exchange-coupled events in phorbol ester-stimulated cells.

Amiloride↗
PubMed1984

Association of phorbol ester-induced hyperphosphorylation and reversible regulation of transferrin membrane receptors in HL60 cells.

Phorbol diesters are tumor-promoting agents that cause differentiation of HL60 human leukemic cells and concomitantly alter surface transferrin-receptor expression [Rovera, G., Ferreo, D., Pagliardi, G. L., Vartikar, J., Pessano, S., Bottero, L., Abraham, S. & Lebman, D. (1982) Ann. N.Y. Acad. Sci. 397, 211-220]. Transferrin-receptor regulation is shown here to result from a rapid and reversible internalization process that is temporally associated with reversible increased phosphorylation (hyperphosphorylation) of the transferrin receptor. Such a reversible mechanism involving regulation of these surface proteins could result in the rapid generation of an early signal for HL60 cellular differentiation.

Carcinogens↗
PubMed1981

Familial association of giant cell arteritis. A case report and brief review.

The initial report of a father-daughter pair with giant cell arteritis (GCA) is made. To our knowledge, it represents only the 12th known familial aggregation of polymyalgia rheumatica (PMR) and/or GCA. This provides evidence for direct transmission of GCA during the two generations and helps to establish a genetic mode of inheritance for this disease. Clinically, the familial and nonfamilial forms of PMR and/or GCA are indistinguishable.

Aged↗
PubMed1978

Glutamate-induced uptake of proline by Streptomyces antibioticus.

Streptomyces antibioticus possesses an energy-dependent, carrier mediated transport system for the uptake of L-glutamate and L-proline. Amino acid transport was found to have a temperature optimum of 35 degrees C and a pH optimum from 7.0 to 8.0 for glutamate and 6.5 to 7.5 for proline uptake. Uptake did not depend upon Mg2+, Ca2+, Zn2+, Na+, or Fe2+ ions. Reversible p-hydroxymercuribenzoate inhibition of uptake indicated the involvement of an active sulfhydryl group. L-Glutamate uptake was mediated by a glutamate-inducible, nonspecific transport system, which was extremely stable and was not subject to substrate inhibition by L-proline. On the other hand, L-proline transport was mediated by at least two systems. The L-glutamate-inducible nonspecific system can account for uptake of proline by the mycelium grown in glutamate. In addition, a proline-specific, constitutive transport system was found to be present in the mycelium grown in organic and inorganic nitrogen sources other than L-glutamate. Shift experiments revealed that proline transport is not as stable as glutamate transport when the glutamate-inducible nonspecific system is utilized.

Bacterial Proteins↗
PubMed1978

Glucose-induced hyperkalemia with normal aldosterone levels. Studies in a patient with diabetes mellitus.

A diabetic patient exhibited glucose-induced hyperkalemia despite normal plasma and urinary aldosterone levels. The patient received no diuretics, was not acidotic, and had a creatinine clearance of 39 ml/min. Insulin or pharmacologic doses of desoxycorticosterone acetate eliminated the glucose-induced hyperkalemia. Normal aldosterone levels may be insufficient to protect certain diabetic patients from glucose-induced hyperkalemia.

Aged↗
PubMed1974

Effect of pipecolic acid isomers on the biogenesis of actinomycins.

Streptomyces antibioticus produces a family of actinomycin components which differ solely at the "imino acid" site of the molecule; however, new congeners of actinomycin are synthesized when cultures are supplemented with pipecolic acid (PA). The quantitative and qualitative nature of the actinomycins produced differed when cultures were incubated in the presence of either l-, d-, or racemic PA. In the presence of d-PA, the quantitative and qualitative nature of those actinomycins produced were similar to those produced in the absence of supplementation. By contrast, in the presence of l-PA or dl-PA new actinomycin components containing PA were synthesized at the expense of normally produced components. Also, the total amount of antibiotic produced decreased in response to increasing concentrations of exogenously supplied l-PA. This effect occurred whether or not d-PA was also added to cultures. Concentrations of l-PA greater than 125 mug/ml of medium resulted in no additional decrease in the amount of antibiotic produced. Although PA-containing actinomycins were formed as early as 6 h after the addition of 250 mug of l-PA per ml, it was not until 24 h postaddition that the relative percentages of actinomycin components produced approached a constant value. Evidence presented here indicated that the l-isomer of PA replaces l-proline in the pentapeptide of actinomycin.

Amino Acids↗
PubMedDate not supplied

Bryostatins trigger human polymorphonuclear neutrophil and monocyte oxidative metabolism: association with in vitro antineoplastic activity.

Bryostatin-1-but not bryostatin-13-a macrocyclic lactone isolated from the marine bryozoan Bugula neritina, triggered human polymorphonuclear neutrophil (PMN) and monocyte release of reactive oxygen radicals, as measured by the generation of lucigenin chemiluminescence and by the ferricytochrome c reduction assay. The release of oxygen radicals by bryostatins was sensitive to inhibitors of protein kinases, but resistant to the inhibition of phospholipase A2 activity and arachidonic acid metabolism (prior treatment with mepacrine or indomethacin). Comparison of the effect of protein kinase (PK) inhibitors H-8, H-7 and staurosporine on bryostatin-1-induced neutrophil oxygen radical release further suggested a requirement for activation of phospholipid-dependent PKC, but not for cGMP- or cAMP-dependent PK. In cytostatic assays, PMNs treated with bryostatin-1 inhibited the growth of the erythroleukaemic cell line K562 in a concentration-dependent manner. These findings suggest that the reported antineoplastic effect of bryostatins may result at least in part from activation of PMNs and monocytes.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMedDate not supplied

A model for intracellular translocation of protein kinase C involving synergism between Ca2+ and phorbol esters.

The activation of protein kinase C by diacylglycerol and by tumour promoters has implicated this enzyme in transmembrane signalling and in the regulation of the cell cycle. In vitro studies revealed that catalytic activity requires the presence of calcium and phospholipids with a preference for phosphatidylserine. Diacylglycerol and tumour promoters such as phorbol esters bind to the enzyme, leading to its activation while sharply increasing its affinity for Ca2+ and phospholipid. Addition of diacylglycerol analogues or phorbol esters to intact cells results in the phosphorylation of specific polypeptides. Several cellular processes, including hormone and neurotransmitter release and receptor down-regulation, are modulated by the activation of protein kinase C, while phorbol ester-induced stimulation of the enzyme in whole cells has been associated with its translocation from the cytoplasm to the plasma membrane. Moreover, the use of Ca2+ ionophores has revealed an apparent synergism between Ca2+ mobilization and protein kinase C activation. This synergism has recently also been found to apply to receptor down-regulation (ref. 23 and accompanying paper). Here we describe a reconstitution system in which intracellular translocation of protein kinase C and the synergism between Ca2+ and enzyme activators can be studied. The results suggest a rationale for concomitant Ca2+ mobilization and diacylglycerol formation in response to some hormones, neurotransmitters and growth factors.

Calcium↗