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C A Pasternak

Publications and source records attributed to C A Pasternak.

At least 37 records · Page 2Linked to original sources
PubMed1990

Cellular stress induces a redistribution of the glucose transporter.

The mechanism by which cells increase their rate of glucose uptake in response to stress is unclear. Using an immunofluorescence technique to localize the glucose transporter protein in BHK cells, we found that hyperthermia, treatment with arsenite, infection with vesicular stomatitis virus or Semliki Forest virus, and treatment with insulin cause the transporter to move from an intracellular site in the perinuclear region to the plasma membrane; the degree of translocation correlates approximately with the increase in glucose uptake. We conclude that stress induces an insulin-like distribution of certain membrane proteins.

Animals↗
PubMed1990

Heat shock proteins induce pores in membranes.

Human heat shock protein (hsp) 70 and bacterial protein groEL promote leakage of calcein from liposomes induced by human serum albumin signal peptide, by S. aureus alpha toxin or by diphtheria toxin. Hsp 70 and groEL, as well as two mycobacterial homologues hsp 71 and hsp 65, induce ion conducting pores across planar lipid bilayers at low or neutral pH. It is concluded that hsp induce pores in membranes and that this may contribute to their action within cells.

Amino Acid Sequence↗
PubMed1990

Action of diphtheria toxin does not depend on the induction of large, stable pores across biological membranes.

Vero cells exposed to diphtheria toxin at pH 4.5 leak monovalent cations but not amino acids or phosphorylated metabolites; affected cells do not take up trypan blue. Monovalent cation leakage is inhibited by 1 mM Cd2+, but not by 1 mM Zn2+ or Ca2+. Cd2+ blocks calcein leakage from liposomes and closes diphtheria toxin-induced channels in lipid bilayers. It is concluded that translocation of the A fragment of diphtheria toxin across biological membranes does not depend on the formation of large stable pores, but that small Cd2(+)-sensitive pores may play a role.

Animals↗
PubMed1990

Pore-forming toxins: experiments with S. aureus alpha-toxin, C. perfringens theta-toxin and E. coli haemolysin in lipid bilayers, liposomes and intact cells.

Three quite different bacterial toxins (S. aureus alpha-toxin, C. perfringens theta-toxin and E. coli haemolysin) induce the leakage of phosphorylated metabolites from Lettre cells and of calcein from liposomes; in each case leakage is inhibited by Zn2+ greater than Ca2+ greater than Mg2+. Inhibition is not due to displacement of toxin from the membrane, since divalent cations inhibit leakage through pre-formed pores. Electrical conductivity across phospholipid bilayers is induced by each of the three toxins; in each case the probability of channels being in the open state is reduced by divalent cations. Although the pores induced in phospholipid bilayers and liposomes vary greatly in size (theta-toxin much greater than haemolysin greater than alpha-toxin), in Lettre cells the lesions appear more uniform, suggestive of a limiting effect in cells.

Animals↗
PubMed1990

Transmembrane communication and disease.

Many disease affect cell behaviour by an effect at the cell surface, often leading to altered communication across the plasma membrane. Two examples of this from our own work are presented. The first concerns the induction of pores, leading to a breach of insulating properties of the cell membrane, by agents as diverse as certain viruses, bacterial and animal toxins, or immune molecules. In each case, membrane damage can be prevented by divalent cations such as Ca2+ or Zn2+. The second example concerns the effect of stress stimuli on the ability of cells to take up glucose. Different stresses, such as hyperthermia, toxic chemicals or infection by certain viruses, cause cells to increase glucose uptake. As with insulin-stimulated glucose uptake, the mechanism is by translocation of the glucose transporter protein from an intracellular (inactive) site to the plasma membrane.

Animals↗
PubMed1989

Protection of cells against membrane damage by haemolytic agents: divalent cations and protons act at the extracellular side of the plasma membrane.

The protective effect of Ca2+, Zn2+ and H+ against membrane damage induced by different haemolytic agents has been studied by measuring monovalent cation leakage and haemolysis of erythrocytes, and phosphoryl[3H]choline and adenine nucleotide leakage from Lettre cells prelabelled with [3H]choline. The protective effect of Ca2+ and Zn2+ on erythrocytes damaged by Staphylococcus aureus alpha-toxin, Sendai virus or melittin is unaffected by the addition of A23187, even though this ionophore greatly increases the uptake of 45Ca2+ or 65Zn2+. The same result has been found for the protective effect of Zn2+ on Lettre cells damaged by S. aureus alpha-toxin, Sendai virus, melittin or Triton X-100. Leakage of phosphoryl[3H]choline from prelabelled Lettre cells is inhibited if extracellular pH is lowered; lowering the intracellular pH without affecting the extracellular pH, affords little protection. It is concluded that Ca2+, Zn2+ and H+ protect cells against membrane damage induced by haemolytic agents by an action at the extracellular side of the plasma membrane.

Animals↗
PubMed1989

Bradykinin enhances excitability in cultured rat sensory neurones by a GTP-dependent mechanism.

The excitatory action of bradykinin (Bk; 0.1-1.0 microM) on cultured rat dorsal root ganglion neurones (DRGs) was studied using the whole cell clamp technique. In a subpopulation of DRGs, a 1 s depolarising voltage pulse from -70 to +20 mV evoked more than one inward current. In these neurones, local application of Bk increased the inward current frequency from 7.0 +/- 0.7 s-1 to 14.9 +/- 1.0 s-1 (mean +/- S.E.M., n = 53). Intracellular application of the GTP analogue, guanosine 5'O-3-thiotriphosphate (GTP gamma S) mimicked this excitatory action of Bk: the frequency of inward currents increased from 5.0 +/- 0.8 s-1, 30 s after the start of recording to 6.9 +/- 1.1 s-1 at 5 min to a maximum of 18.5 +/- 2.2 s-1 at 15 min (n = 16). In control cells, the frequency decreased from 4.6 +/- 0.8 s-1 to 2.5 +/- 0.5 s-1 at 5 min (n = 12). Bk also increased excitability in 4/11 Herpes Simplex Virus I (HSV-I)-infected DRGs. Thus, we demonstrate an excitatory action of Bk in DRGs, which may involve G-protein activation.

Action Potentials↗
PubMed1989

Common pathway for the induction of hexose transport by insulin and stress.

The effect of stress (heat shock, arsenite, or Semliki Forest virus [SFV] infection) on the induction of increased hexose transport has been compared with that of insulin. All four treatments increase the Vmax for transport by BHK cells three- to five-fold, with little effect (less than 40% decrease) on Km. Hydrogen peroxide and phenylarsine oxide (PAO) prevent the increase in hexose transport induced by stress treatments as effectively as they do that induced by insulin. Pinocytosis is not affected by any of the four treatments. On the other hand, the induction by insulin is sensitive to amiloride, whereas that by arsenite is not. Rat embryo fibroblasts, which respond poorly to insulin, respond well to arsenite, heat shock, or SFV infection. It is concluded that the stress response is mediated by certain compounds that may be common to those required for the action of insulin, but that those compounds act at a stage subsequent to the function of the insulin receptor.

Amiloride↗
PubMed1989

Mechanisms of attack and defence at the cell surface: the use of phospholipid bilayers as models for cell membrane.

Electrical conductivity across phospholipid bilayers induced by various cytotoxic proteins has been used to analyse the damaging action of such proteins on cells; the protective effect of divalent cations and protons against such attack has also been investigated. The predominant effect of divalent cations and protons is to promote the closed state of membrane pores, i.e. to "gate" protein-induced lesions.

Bacterial Outer Membrane Proteins↗
PubMed1989

Plasma membrane potential of lymphocytes from ataxia telangiectasia patients.

The plasma membrane potential of lymphocytes prepared from ataxia telangiectasia (AT) patients and normal subjects was assessed using the optical indicator bis-(3-phenyl-5-oxoisoxazol-4-yl) pentamethineoxonol (oxonol-V). AT lymphocytes had a potential of -46 +/- 9 mV and normal lymphocytes had a potential of -63 +/- 4 mV. The intracellular cation content (Na+ and K+) of AT and normal lymphocytes was similar. AT and normal lymphocytes were both depolarized by extracellular K+ and to a similar extent. This study indicates that one feature characterizing ataxia telangiectasia is a modification of the ability of the lymphocyte cell membrane to sustain a normal membrane potential.

Adolescent↗
PubMed1988

Cell damage by cytolysin. Spontaneous recovery and reversible inhibition by divalent cations.

Cytolysin-induced membrane damage (which requires low Ca2+) has been studied 1) in E by assay of hemolysis, 2) in Lettre cells by measurement of transmembrane potential, intracellular content of K+ and Na+, leakage of phosphoryl[3H]choline or 51Cr from [3H]choline-labeled or 51CrO4(2-)-labeled cells and leakage of lactate dehydrogenase, and 3) in phospholipid bilayers by measurement of electrical conductivity changes. In Lettre cells, damage is restricted and reversible: little lactate dehydrogenase leaks from cells that leak substantial amounts of Na+, K+, and phosphoryl[3H]choline; at low amounts of cytolysin, membrane potential and intracellular content of Na+ and K+ recover within minutes. In E and Lettre cells, membrane damage is inhibited by Zn2+, by high Ca2+, or by low pH. Inhibition is reversible: addition of EGTA to Zn2+-protected E or Lettre cells (incubated in the presence of cytolysin, low Ca2+ and Zn2+) initiates leakage; removal of Zn2+ (and cytolysin and Ca2+) by washing also initiates leakage; such leakage is again sensitive to Zn2+, high Ca2+, or H+. In phospholipid bilayers, channels induced by cytolysin (at low Ca2+) are partially closed by negative voltage; Ca2+, Zn2+, or H+ promote channel closure. Channels are re-opened (only partially in the case of Zn2+) by positive voltage. From all these results it is concluded that the action of cytolysin on membranes is similar to that of other pore-forming agents: damage does not necessarily lead to lysis of nucleated cells, and can be prevented by Ca2+, Zn2+, or H+.

Animals↗
PubMed1988

Ion modulation of membrane permeability: effect of cations on intact cells and on cells and phospholipid bilayers treated with pore-forming agents.

Leakage of ions (Na+, K+) and phosphorylated metabolites (phosphorylcholine, 2-deoxyglucose 6-phosphate) through membrane lesions in intact cells or in cells modified by 'pore-forming' agent has been studied. Leakage from intact cells is induced by protons and by divalent cations such as Cu2+, Cd2+ or Zn2+. Leakage from agent-modified cells--or across phospholipid bilayers modified by agent--is prevented by low concentrations of the same cations and by higher concentrations of Ca2+, Mn2+ or Ba2+; Mg2+, dimethonium, spermine, or spermidine are virtually ineffective. The relative efficacy of a particular cation (e.g. Ca2+) depends more on cell type than on the nature of the pore-forming agent. The predominant effect is on binding of cation to specific sites, not on surface charge. Surface charge, on the other hand, does affect leakage from agent-modified cells in that suspension in nonionic media reduces leakage, which can be restored by increasing the ionic strength: univalent (Na+, K+, Rb+, NH4+) and divalent (Mg2+, dimethonium) cations are equally effective; addition of protons or divalent cations such as Zn2+ to this system inhibits leakage. From this and other evidence here presented it is concluded that leakage across membranes is modulated by the presence of endogenous anionic components: when these are in the ionized state, leakage is favored; when unionized (as a result of protonation) or chelated (by binding to divalent cation), leakage is prevented. It is suggested that such groups are exposed at the extracellular face of the plasma membrane.

Animals↗
PubMed1988

Stress-induced increase of hexose transport as a novel index of cytopathic effects in virus-infected cells: role of the L protein in the action of vesicular stomatitis virus.

The VSV-specific increase in hexose transport by BHK cells has been measured by assay of the [3H]dGlc/[14C]AIB uptake ratio. The effect was abolished by uv-irradiation of the virus, indicating that viral gene expression is required. Cells infected with the T1026 R1 mutant of VSV, which causes only slight cytopathic changes, exhibited only a slight increase in hexose uptake. Cells infected with temperature-sensitive (ts) mutants of VSV that are defective in the function of the viral N, NS, G, or M proteins at the restrictive temperature (39.5 degrees) exhibited increased [3H]dGLC/[14C]AIB uptake ratios typical of wild-type virus at either restrictive (39.5 degrees) or permissive temperature (34 degrees). Cells infected with a mutant defective in the function of the viral L protein exhibited an increased [3H]dGlc/[14C]AIB uptake ratio at permissive temperature (34 degrees) only; at restrictive temperature (39.5 degrees) the uptake ratio was essentially the same as that of mock-infected cells. Temperature-shift experiments indicated that the effect on hexose transport persisted for at least 6 hr in cells which no longer expressed function L protein, and that when expression of L was restricted to the first 2 hr of infection, an almost complete stimulation of hexose transport was observed 4 hr later. These results indicate that expression of the L gene is a necessary factor for inducing an increased hexose uptake in VSV-infected BHK cells. They also suggest that the action of the L protein on hexose transport is indirect, and is presumably mediated by other cellular constituents. The studies support the concept that an increased dGlc uptake may be a useful index of the cytopathic consequences of virus infection.

Animals↗
PubMed1988

Protection against complement-mediated cell damage by Ca2+ and Zn2+.

Ca2+ and Zn2+ prevent antibody-dependent complement-induced permeability changes in tonsil lymphocytes and Lettre cells. Lactate dehydrogenase leaks out from Lettre cells at high complement:cell ratios, under which conditions higher concentrations of Ca2+ and Zn2+ are required for protection. Ca2+ and Zn2+ do not inhibit complement activation or C9 binding to Lettre cells, and prevent leakage through preformed lesions. It is concluded that the extent of complement-induced membrane damage depends on the concentration of extracellular Ca2+, and may be modulated by changes in extracellular Ca2+ or Zn2+.

Animals↗
PubMed1987

A novel form of host defence: membrane protection by Ca2+ and Zn2+.

This review focusses on two questions: (1) How can the intracellular toxicity of ions such as Ca2+ or Zn2+ be reconciled with their extracellular benefit? (2) Why is the dietary requirement for Zn2+ so high when its documented biological role is that of a tightly-bound prosthetic group of certain enzymes? An answer to both questions is provided by the observation that extracellular cations such as Ca2+ and Zn2+ protect the plasma membrane of cells against non-specific leakage, including an influx of Ca2+ or Zn2+. It is suggested that such protection, against leakage induced by microbial and other toxins, may contribute to the high dietary requirement for zinc. These arguments lead to the proposal that a previously unrecognized form of host defence is one of protection of the cell plasma membrane by divalent cations against damage induced by cytotoxic agents of environmental origin.

Animals↗