Biomedical subjects

L M Ballas

Publications and source records attributed to L M Ballas.

At least 19 recordsLinked to original sources

PubMed1999

Estrogen receptor (ER) modulators each induce distinct conformational changes in ER alpha and ER beta.

Estrogen receptor (ER) modulators produce distinct tissue-specific biological effects, but within the confines of the established models of ER action it is difficult to understand why. Previous studies have suggested that there might be a relationship between ER structure and activity. Different ER modulators may induce conformational changes in the receptor that result in a specific biological activity. To investigate the possibility of modulator-specific conformational changes, we have applied affinity selection of peptides to identify binding surfaces that are exposed on the apo-ERs alpha and beta and on each receptor complexed with estradiol or 4-OH tamoxifen. These peptides are sensitive probes of receptor conformation. We show here that ER ligands, known to produce distinct biological effects, induce distinct conformational changes in the receptors, providing a strong correlation between ER conformation and biological activity. Furthermore, the ability of some of the peptides to discriminate between different ER alpha and ER beta ligand complexes suggests that the biological effects of ER agonists and antagonists acting through these receptors are likely to be different.

Amino Acid Sequence↗

PubMed1997

Synthesis and protein kinase C inhibitory activities of balanol analogs with replacement of the perhydroazepine moiety.

Balanol is a potent protein kinase C (PKC) inhibitor that is structurally composed of a benzophenone diacid, a 4-hydroxybenzamide, and a perhydroazepine ring. A number of balanol analogs in which the perhydroazepine moiety is replaced have been synthesized and their biological activities evaluated against both PKC and cAMP-dependent kinase (PKA). The results suggested that the activity and the isozyme/kinase selectivity of these compounds are largely related to the conformation about this nonaromatic structural element of the molecules.

Azepines↗

PubMed1997

Synthesis and protein kinase C inhibitory activities of balanol analogues with modification of 4-hydroxybenzamido moiety.

A series of racemic balanol analogues with modification of the benzamido moiety of balanol have been synthesized and evaluated for their inhibitory activities against human protein kinase C isozymes (PKC-alpha, -beta I, -beta II, -gamma, -delta, -epsilon, and -eta). The structural modification includes replacement of the 4-hydroxyphenyl group with variously substituted phenyl rings, substitution of the amide linkage with a sulfonamide or an ester, and replacement of the 4-hydroxyphenyl substructure with a hydroxyl substituted indole or a hydroxybenzyl group. in general, these analogues were found to be less potent than balanol, but a number of analogues were identified with improved isozyme selectivity. The structure-activity relationship studies of these analogues also indicated that (1) the optimal general PKC inhibition requires a free 4-hydroxyl group in the benzamido portion of the molecule, (2) the amide linkage of the benzamido moiety is important for PKC inhibition, and (3) the conformation associated with the benzamido moiety seems to have a profound effect on PKC inhibition. The requirement of a free 4-hydroxyl group in conjunction with an appropriate conformation of the benzamido moiety for optimal PKC inhibition suggests that the 4-hydroxyphenyl group may be involved in a specific inhibitor-enzyme interaction important for PKC inhibition.

Animals↗

PubMed1996

Effects of sphingosine stereoisomers on P-glycoprotein phosphorylation and vinblastine accumulation in multidrug-resistant MCF-7 cells.

To investigate the role of protein kinase C (PKC) in the regulation of multidrug resistance and P-glycoprotein (P-gp) phosphorylation, the natural isomer of sphingosine (SPH), D-erythro sphingosine (De SPH), and its three unnatural stereoisomers were synthesized. The SPH isomers showed similar potencies as inhibitors of in vitro PKC activity and phorbol binding, with IC50 values of approximately 50 microM in both assays. Treatment of multidrug-resistant MCF-7ADR cells with SPH stereoisomers increased vinblastine (VLB) accumulation up to 6-fold at 50 microM but did not alter VLB accumulation in drug-sensitive MCF-7 wild-type (WT) cells or accumulation of 5-fluorouracil in either cell line. Phorbol dibutyrate treatment of MCF-7ADR cells increased phosphorylation of P-gp, and this increase was inhibited by prior treatment with SPH stereoisomers. Treatment of MCF-7ADR cells with SPH stereoisomers decreased basal phosphorylation of the P-gp, suggesting inhibition of PKC-mediated phosphorylation of P-gp. Most drugs that are known to reverse multidrug resistance, including several PKC inhibitors, have been shown to directly interact with P-gp and inhibit drug binding. SPH stereoisomers did not inhibit specific binding of [3H] VLB to MCF-7ADR cell membranes or [3H]azidopine photoaffinity labeling of P-gp or alter P-gp ATPase activity. These results suggest that SPH isomers are not substrates of P-gp and suggest that modulation of VLB accumulation by SPH stereoisomers is associated with inhibition of PKC-mediated phosphorylation of P-gp.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1996

(S)-13-[(dimethylamino)methyl]-10,11,14,15-tetrahydro-4,9:16, 21-dimetheno-1H, 13H-dibenzo[e,k]pyrrolo[3,4-h][1,4,13]oxadiazacyclohexadecene-1,3(2H)-d ione (LY333531) and related analogues: isozyme selective inhibitors of protein kinase C beta.

Protein kinase C (PKC) is a family of closely related serine and threonine kinases. Overactivation of some PKC isozymes has been postulated to occur in several diseases states, including diabetic complications. Selective inhibition of overactivated PKC isozymes may offer a unique therapeutic approach to disease states such as diabetic retinopathy. A novel series of 14-membered macrocycles containing a N-N'-bridged bisindolylmaleimide moiety is described. A panel of eight cloned human PKC isozymes (alpha, beta I, beta II, gamma, delta, epsilon, sigma, eta) was used to identify the series and optimize the structure and associated activity relationship. The dimethylamine analogue LY333531 (1), (S)-13-[(dimethylamino)methyl]-10,11,14,15-tetrahydro-4,9:16, 21-dimetheno-1H, 13H-dibenzo[e,k]pyrrolo[3,4-h][1,4,13]oxadiazacyclohexadecene++ +-1,3(2H)-dione, inhibits the PKC beta I (IC50 = 4.7 nM) and PKC beta II (IC50 = 5.9 nM) isozymes and was 76- and 61-fold selective for inhibition of PKC beta I and PKC beta II in comparison to PKC alpha, respectively. The additional analogues described in the series are also selective inhibitors of PKC beta. LY333531 (1) exhibits ATP dependent competitive inhibition of PKC beta I and is selective for PKC in comparison to other ATP dependent kinases (protein kinase A, calcium calmodulin, caesin kinase, src tyrosine kinase). The cellular activity of the series was assessed using bovine retinal capillary endothelial cells. Retinal endothelial cell dysfunction has been implicated in the development of diabetic retinopathy. Plasminogen activator activity stimulated by a phorbol ester (4 beta-phorbol 12,13-dibutyrate) in endothelial cells was inhibited by the compounds in the series with ED50 values ranging from 7.5 to 0.21 microM. A comparison of the PKC isozyme and related ATP dependent kinase inhibition profiles is provided for the series and compared to the profile for staurosporine, a nonselective PKC inhibitor. The cellular activity of the series is compared with that of the kinase inhibitor staurosporine.

Amino Acid Sequence↗

PubMed1996

Amelioration of vascular dysfunctions in diabetic rats by an oral PKC beta inhibitor.

The vascular complications of diabetes mellitus have been correlated with enhanced activation of protein kinase C (PKC). LY333531, a specific inhibitor of the beta isoform of PKC, was synthesized and was shown to be a competitive reversible inhibitor of PKC beta 1 and beta 2, with a half-maximal inhibitory constant of approximately 5 nM; this value was one-fiftieth of that for other PKC isoenzymes and one-thousandth of that for non-PKC kinases. When administered orally, LY333531 ameliorated the glomerular filtration rate, albumin excretion rate, and retinal circulation in diabetic rats in a dose-responsive manner, in parallel with its inhibition of PKC activities.

Administration, Oral↗

PubMed1995

Naturally occurring protein kinase C inhibitors; II. Isolation of oligomeric stilbenes from Caragana sinica.

The oligomeric stilbenes (+)-alpha-viniferin (1), miyabenol C (2), and kobophenol A (3) have been isolated from Caragana sinica (Buchoz) Rehd (Leguminosae). (+)-alpha-Viniferin (1) and miyabenol C (2) exhibited protein kinase C inhibitory activity at low micromolar concentrations. (+)-alpha-Viniferin inhibited keratinocyte proliferation (0.4 microM) and free radical release in whole blood (47 microM), in vitro, and may be useful in treating hyperproliferative or inflammatory skin diseases.

Cells, Cultured↗

PubMed1995

Vitamin E prevents diabetes-induced abnormal retinal blood flow via the diacylglycerol-protein kinase C pathway.

We have characterized effects of d-alpha-tocopherol (vitamin E) on activation of protein kinase C (PKC) and diacylglycerol (DAG) levels in retinal tissues of diabetic rats and correlated its effects to diabetes-induced changes in retinal hemodynamics. Membrane PKC specific activities were increased by 71% in streptozocin-induced diabetic rats compared with controls (P < 0.05). Western blot analysis showed that membrane PKC-beta II was increased by 133 +/- 5% (P < 0.05). Injection of d-alpha-tocopherol (40 mg/kg ip) every other day prevented the increases in membrane PKC specific activity and PKC-beta II protein by immunoblots. Diabetes-induced increases in DAG levels were also normalized by d-alpha-tocopherol treatment of 2 wk duration. Physiologically, angiographic abnormalities of retinal hemodynamics based on computerized video-based fluorescein angiography and associated with increases of DAG and membranous PKC levels were also prevented by d-alpha-tocopherol treatment in diabetic rats. The effect of d-alpha-tocopherol on retinal vascular cells was also studied. Exposure of retinal endothelial cells to 22 mM glucose for 3 days increased total DAG and [3H]palmitate-labeled DAG levels by 35 +/- 8 and 50 +/- 8% (P < 0.05), respectively, compared with exposure to 5.5 mM glucose. The presence of d-alpha-tocopherol (50 micrograms/ml) prevented the increases in total DAG and [3H]palmitate-labeled DAG levels in cells exposed to 22 mM glucose. These findings suggested that treatment with d-alpha-tocopherol can prevent diabetes-induced abnormalities in rat retinal blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Activation of protein kinase C family members by the novel polyphosphoinositides PtdIns-3,4-P2 and PtdIns-3,4,5-P3.

The effect of phosphoinositides on the activity of protein kinase C (PKC) isotypes was investigated. PKC alpha, beta I, beta II, gamma, delta, epsilon, eta, and zeta were expressed in baculovirus-infected insect cells and purified by column chromatography. The calcium-activated PKC isotypes alpha, beta I, beta II, and gamma were not significantly activated by any of the phosphoinositides investigated (phosphatidylinositol-4-phosphate (PtdIns-4-P), PtdIns-3-P, PtdIns-4,5-P2, PtdIns-3,4-P2, and PtdIns-3,4,5-P3) when added in the presence of concentrations of phosphatidylserine that give maximal stimulation. The calcium-insensitive PKC isotypes delta, epsilon, and theta also showed little response to PtdIns-3-P, PtdIns-4-P, or PtdIns-4,5-P2 when these lipids were added in the presence of phosphatidylserine. In contrast, PtdIns-3,4-P2 and PtdIns-3,4,5-P3 caused a 5-15-fold stimulation of these enzymes compared with phosphatidylserine alone. 50% maximal stimulation of PKC epsilon by PtdIns-3,4,5-P3 occurred when this lipid was present at about 1% of the carrier PtdIns-4,5-P2 (about 100 nM). These lipids had little effect on baculovirus-expressed PKC zeta, which was constitutively active. A short chain version of PtdIns-3,4,5-P3, dioctanoyl-PtdIns-3,4,5-P3, activated PKC delta, epsilon, and eta in the absence of other lipids, whereas a short chain version of PtdIns-4,5-P2, dihexanoyl-PtdIns-4,5-P2, did not. Since PtdIns-3,4-P2 and PtdIns-3,4,5-P3 are nominally absent in unstimulated cells and appear within seconds to minutes of stimulation by various cell activators, these lipids could act as second messengers to activate PKC delta, epsilon, or eta in vivo.

Animals↗

PubMed1994

Staurosporine aglycone (K252-c) and arcyriaflavin A from the marine ascidian, Eudistoma sp.

Staurosporine aglycone (K252-c) (compound 1) and arcyriaflavin A (2) were isolated from a specimen of the marine ascidian, Eudistoma sp., collected off the coast of West Africa. In addition to expressing micromolar and submicromolar inhibition of enzyme activity against seven protein kinase C isoenzymes and inhibition of proliferation of the human lung cancer A549 and P388 murine leukemia cell lines, 1 also inhibited cell adhesion of the EL-4.IL-2 cell line and expressed activity in the K562 bleb and neutrophil assays.

Africa, Western↗

PubMed1994

New hexahydroxybiphenyl derivatives as inhibitors of protein kinase C.

We have previously shown that some ellagitannins are potent inhibitors of protein kinase C (PKC). On the basis of this finding, several series of hexahydroxybiphenyl derivatives of ellagic acid were synthesized as simple analogs of these ellagitannins and were evaluated for their inhibitory effect against PKC. Compounds 23 and 26 were found to be potent inhibitors of PKC, while hexakis-(benzyloxy)biphenyl derivatives exhibited weak anti-PKC activity.

Biphenyl Compounds↗

PubMed1994

Antiproliferative actions of 7-substituted 1,3-dihydroxyacridones; possible involvement of DNA topoisomerase II and protein kinase C as biochemical targets.

7-Chloro-1,3-dihydroxyacridone (1) reversibly inhibited growth of KB and vero cell lines with IC50's of 35 and 40 microM, respectively, and a topoisomerase II-mediated multidrug resistant KB sub-clone was found to be about three-fold more susceptible to 1. In contrast, two cell lines of lymphoid origin were killed following treatments with 60 microM and at higher concentrations of 1. KB cell growth inhibition correlated with a rapid, reversible suppression of thymidine incorporation. Uridine but not leucine incorporation was also rapidly suppressed. The in vitro activities of DNA topoisomerase II and novel protein kinase C-subtype delta were inhibited at effective concentrations in tissue-culture, but 1 did not stimulate intracellular protein-associated DNA breaks nor interfere initially with topoisomerase II-mediated DNA cleavage in KB cells. In addition to antiproliferative effects against cells, the compound was weakly virustatic for herpes simplex virus type I with an IC50 of 8 microM. Limited studies comparing three 1-congeners and citpressine-I, an acridone alkaloid with reported antiherpes activity, demonstrated that 7-substituted 1,3-dihydroxyacridones are novel antiproliferative agents which share similar biological and biochemical properties.

Acridines↗

PubMed1994

Anti-AIDS agents, 11. Betulinic acid and platanic acid as anti-HIV principles from Syzigium claviflorum, and the anti-HIV activity of structurally related triterpenoids.

Betulinic acid [1] and platanic acid [2], isolated from the leaves of Syzigium claviforum, were found to be inhibitors of HIV replication in H9 lymphocyte cells. Evaluation of anti-HIV activity with eight derivatives of 1 revealed that dihydrobetulinic acid [3] was also a potent inhibitor of HIV replication. The C-3 hydroxy group and C-17 carboxylic acid group, as well as the C-19 substituents, contribute to enhanced anti-HIV activity. The inhibitory activity of these compounds against protein kinase C (PKC) was also examined, since a correlation between anti-HIV and anti-PKC activities has been suggested. However, there was no apparent correlation between anti-HIV activity and the inhibition of PKC among these compounds.

Antiviral Agents↗

PubMed1994

New cytotoxic peroxylactones from the marine sponge, Plakinastrella onkodes.

Three new peroxylactones, plakortolides B [6], C [7], and D [8], and a new peroxy ester, epiplakinic acid E methyl ester [9], were isolated and characterized from a previously unstudied marine sponge, Plakinastrella onkodes. A mixture of steroidal peroxides was also found in this organism. Plakortolides B [6] and D [8], and epiplakinic acid E methyl ester [9], were evaluated for biological activity and found to show cytotoxicity against the A549 human lung carcinoma and P388 murine leukemia cell lines, and to effect adhesion in an assay employing the EL-4.IL-2 cell line, which correlates with signal transduction activity.

Animals↗

PubMed1994

Translocation and downregulation of protein kinase C isoenzymes-alpha and -epsilon by phorbol ester and bryostatin-1 in human keratinocytes and fibroblasts.

Protein kinase C isoenzymes can be subdivided into two classes, based on their requirement for calcium. Protein kinase C-alpha, beta I, -beta II, and -gamma are calcium dependent, whereas protein kinase C-gamma, -epsilon, -zeta, -eta, and -theta are calcium independent. We have examined the expression, translocation, downregulation, and activation of calcium-dependent and -independent protein kinase C isoenzymes in human skin keratinocytes and fibroblasts. Human keratinocytes and fibroblasts expressed protein kinase C-alpha, -delta, -epsilon, and -zeta mRNA and protein, whereas protein kinase C-eta (L) was detected only in keratinocytes. Protein kinase C-beta I, -beta II, -gamma, and -theta were not detected in either cell type. The protein kinase C activators 12-0-tetradecanoylphorbol 13-acetate and bryostatin-1 (50 nM, for 5 min) induced translocation of protein kinase C-alpha and -epsilon cytosol to membrane in both keratinocytes and fibroblasts. 12-0-tetradecanoylphorbol 13-acetate and bryostatin-1, for 18 h, induced complete downregulation (i.e., loss) of protein kinase C-alpha and -epsilon in keratinocytes, but only partial downregulation was observed in fibroblasts. The subcellular distribution of protein kinase C-delta, -zeta or protein kinase C-eta, in keratinocytes or fibroblasts, did not change in response to 12-0-tetradecanoylphorbol 13-acetate or bryostatin-1. These data indicate differential expression, subcellular distribution, and regulation of protein kinase C isoenzymes in human skin cells.

Base Sequence↗

PubMed1993

Molecular and biochemical characterization of a recombinant human PKC-delta family member.

Two cDNA clones coding for the human protein kinase C-delta (PKC-delta) were fortuitously isolated during the process of screening a human library for a cDNA clone of an unrelated protein, the nucleolar protein fibrillarin. The two human homologues have about 88% nucleotide sequence identity to the rat and mouse PKC-delta cDNA clones. A comparison of the predicted amino acid sequences of the two human PKC-delta clones with the rat and mouse homologues indicated a greater degree of sequence divergence (89-90% homology) compared to the high degree of sequence conservation observed with other human PKC family members and their mammalian counterparts. Expression of the clones in the baculovirus insect-cell expression system indicated that both proteins exhibited phorbol ester binding activity, and were dependent upon phosphatidylserine and diacylglycerol for maximal activation. Further characterization of the properties of the human PKC-delta revealed substrate and lipid dependencies distinct from other members of the protein kinase C family; including PKC-deltas isolated from other species. The dissimilarities in the predicted amino acid sequences between the human and other mammalian species could account in part for some of these observed biochemical differences.

Amino Acid Sequence↗

PubMed1992

Novel non-cross resistant diaminoanthraquinones as potential chemotherapeutic agents.

A novel series of diaminoanthraquinones was discovered initially as protein kinase C inhibitors with IC50s in the 50-100 microM range. They exhibited potent tumor cell growth inhibitory activity in vitro without cross resistance to adriamycin. Further evaluation of two of the most active compounds NSC 639365 (3) and NSC 639366 (4) in human tumor cloning assay showed potent cytocidal activity. The results suggest therapeutical potentials against human tumors.

Anthraquinones↗

PubMed1992

Sequence and expression of human protein kinase C-epsilon.

Two human homologues of protein kinase C-epsilon (E1 and E2) were isolated from two distinct cDNA libraries. Sequence comparisons to PKC-epsilon cDNAs from several species indicated that each of these human epsilon clones contained cloning artifacts. Thus, a composite PKC-epsilon (E3) clone was derived from clones E1 and E2. Human PKC-epsilon (E3) has an overall sequence identity of 90-92% at the nucleotide level compared to the previously characterized mouse, rat and rabbit clones. At the amino acid level, the deduced human epsilon sequence shows a 98-99% identity with the mouse, rat and rabbit sequences. Expression of the human PKC-epsilon clone in Sf9 cells confirmed that the recombinant protein displayed protein kinase C activity and phorbol ester binding activity. The recombinant protein was also recognized by two distinct epsilon-specific polyclonal antibodies.

Amino Acid Sequence↗