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Chembiochem : a European Journal of... Apr 2018To investigate the cellular distribution of tumor-promoting vs. non-tumor-promoting bryostatin analogues, we synthesized fluorescently labeled variants of two bryostatin...
To investigate the cellular distribution of tumor-promoting vs. non-tumor-promoting bryostatin analogues, we synthesized fluorescently labeled variants of two bryostatin derivatives that have previously shown either phorbol ester-like or bryostatin-like biological activity in U937 leukemia cells. These new fluorescent analogues both displayed high affinity for protein kinase C (PKC) binding and retained the basic properties of the parent unlabeled compounds in U937 assays. The fluorescent compounds showed similar patterns of intracellular distribution in cells, however; this argues against an existing hypothesis that various patterns of intracellular distribution are responsible for differences in biological activity. Upon further characterization, the fluorescent compounds revealed a slow rate of cellular uptake; correspondingly, they showed reduced activity for cellular responses that were only transient upon treatment with phorbol ester or bryostatin 1.
Topics: Bryostatins; Fluorescent Dyes; Humans; Phorbol Esters; Protein Binding; Protein Kinase C; U937 Cells
PubMed: 29424951
DOI: 10.1002/cbic.201700655 -
Free Radical Research Dec 2019Matrix metalloproteinases (MMPs), zinc-containing proteinases, play a critical role in tumour progression by degrading extracellular matrix components. MMP2 and MMP9 are...
Matrix metalloproteinases (MMPs), zinc-containing proteinases, play a critical role in tumour progression by degrading extracellular matrix components. MMP2 and MMP9 are secreted from tumour-associated macrophages as well as tumour cells and have been implicated in the formation of the tumour microenvironment. Therefore, the inhibition of these MMPs may suppress tumour progression and metastasis. 4-Hydroperoxy-2-decenoic acid ethyl ester (HPO-DAEE) is known to cause apoptosis in the human lung cancer cell line A549 by inducing endoplasmic reticulum (ER) stress. However, the effects of HPO-DAEE on tumour progression remain unclear. HPO-DAEE pre-treatment significantly suppressed phorbol 12-myristate 13-acetate (TPA)-triggered MMP activation in human monocytic THP-1 cells. It also enhanced the expression of haem oxygenase-1, an antioxidant enzyme, and suppressed the TPA-triggered intracellular accumulation of reactive oxygen species (ROS). Furthermore, HPO-DAEE suppressed transforming growth factor-β1-triggered human prostate cancer PC3 cell migration and this was accompanied by the inhibition of MMP expression and activities. The present results indicate that HPO-DAEE may exert inhibitory effects on tumour progression by suppressing MMP expression and activities.
Topics: Antineoplastic Agents; Cell Movement; Cell Proliferation; Cells, Cultured; Dose-Response Relationship, Drug; Drug Screening Assays, Antitumor; Esters; Fatty Acids; Fatty Acids, Monounsaturated; Humans; Male; Matrix Metalloproteinases; Phorbol Esters; Prostatic Neoplasms; Reactive Oxygen Species; Structure-Activity Relationship; Transforming Growth Factor beta1
PubMed: 31575304
DOI: 10.1080/10715762.2019.1675874 -
PloS One 2015The lysophosphatidic acid receptors LPA1, LPA2, and LPA3 were individually expressed in C9 cells and their signaling and regulation were studied. Agonist-activation...
RESULTS
The lysophosphatidic acid receptors LPA1, LPA2, and LPA3 were individually expressed in C9 cells and their signaling and regulation were studied. Agonist-activation increases intracellular calcium concentration in a concentration-dependent fashion. Phorbol myristate acetate markedly inhibited LPA1- and LPA3-mediated effect, whereas that mediated by LPA2 was only partially diminished; the actions of the phorbol ester were inhibited by bisindolylmaleimide I and by overnight incubation with the protein kinase C activator, which leads to down regulation of this protein kinase. Homologous desensitization was also observed for the three LPA receptors studied, with that of LPA2 receptors being consistently of lesser magnitude; neither inhibition nor down-regulation of protein kinase C exerted any effect on homologous desensitization. Activation of LPA1-3 receptors induced ERK 1/2 phosphorylation; this effect was markedly attenuated by inhibition of epidermal growth factor receptor tyrosine kinase activity, suggesting growth factor receptor transactivation in this effect. Lysophosphatidic acid and phorbol myristate acetate were able to induce LPA1-3 phosphorylation, in time- and concentration-dependent fashions. It was also clearly observed that agonists and protein kinase C activation induced internalization of these receptors. Phosphorylation of the LPA2 subtype required larger concentrations of these agents and its internalization was less intense than that of the other subtypes.
CONCLUSION
Our data show that these three LPA receptors are phosphoproteins whose phosphorylation state is modulated by agonist-stimulation and protein kinase C-activation and that differences in regulation and cellular localization exist, among the subtypes.
Topics: Animals; Cell Line; ErbB Receptors; Humans; Lysophospholipids; Phosphorylation; Protein Kinase C; Protein Transport; Rats; Receptors, Lysophosphatidic Acid; Tetradecanoylphorbol Acetate
PubMed: 26473723
DOI: 10.1371/journal.pone.0140583 -
Journal of Agricultural and Food... May 2015Although flavonoids have been reported for their benefits and nutraceutical potential use, the importance of their structure on their beneficial effects, especially on...
Number of Hydroxyl Groups on the B-Ring of Flavonoids Affects Their Antioxidant Activity and Interaction with Phorbol Ester Binding Site of PKCδ C1B Domain: In Vitro and in Silico Studies.
Although flavonoids have been reported for their benefits and nutraceutical potential use, the importance of their structure on their beneficial effects, especially on signal transduction mechanisms, has not been well clarified. In this study, three flavonoids, pinocembrin, naringenin, and eriodictyol, were chosen to determine the effect of hydroxyl groups on the B-ring of flavonoid structure on their antioxidant activity. In vitro assays, including DPPH scavenging activity, ROS quantification by flow cytometer, and proteins immunoblotting, and in silico analysis by molecular docking between the flavonoids and C1B domain of PKCδ phorbol ester binding site were both used to complete this study. Eriodictyol (10 μM), containing two hydroxyl groups on the B-ring, exhibited significantly higher (p < 0.05) antioxidant activity than pinocembrin and naringenin. The IC50 values of eriodictyol, naringenin, and pinocembrin were 17.4 ± 0.40, 30.2 ± 0.61, and 44.9 ± 0.57 μM, respectively. In addition, eriodictyol at 10 μM remarkably inhibited the phosphorylation of PKCδ at 63.4% compared with PMA-activated RAW264.7, whereas pinocembrin and naringenin performed inhibition activity at 76.8 and 72.6%, respectively. According to the molecular docking analysis, pinocembrin, naringenin, and eriodictyol showed -CDOCKER_energy values of 15.22, 16.95, and 21.49, respectively, reflecting that eriodictyol could bind with the binding site better than the other two flavonoids. Interestingly, eriodictyol had a remarkably different pose to bind with the kinase as a result of the two hydroxyl groups on its B-ring, which consequently contributed to greater antioxidant activity over pinocembrin and naringenin.
Topics: Animals; Antioxidants; Binding Sites; Cell Line; Cell Survival; Computer Simulation; Flavonoids; Mice; Molecular Docking Simulation; Molecular Structure; Oxidative Stress; Phorbol Esters; Phosphorylation; Protein Binding; Protein Kinase C-delta; Protein Structure, Tertiary
PubMed: 25907027
DOI: 10.1021/acs.jafc.5b00312 -
Journal of Biomolecular Structure &... Jul 2016Protein kinase C (PKC) isozymes are important regulatory enzymes that have been implicated in many diseases, including cancer, Alzheimer's disease, and in the...
Protein kinase C (PKC) isozymes are important regulatory enzymes that have been implicated in many diseases, including cancer, Alzheimer's disease, and in the eradication of HIV/AIDS. Given their potential clinical ramifications, PKC modulators, e.g. phorbol esters and bryostatin, are also of great interest in the drug development. However, structural details on the binding between PKC and its modulators, especially bryostatin - the highly potent and non-tumor promoting activator for PKCs, are still lacking. Here, we report the first comparative molecular dynamics study aimed at gaining structural insight into the mechanisms by which the PKC delta cys2 activator domain is used in its binding to phorbol ester and bryostatin-1. As anticipated in the phorbol ester binding, hydrogen bonds are formed through the backbone atoms of Thr242, Leu251, and Gly253 of PKC. However, the opposition of H-bond formation between Thr242 and Gly253 may cause the phorbol ester complex to become less stable when compared with the bryostatin binding. For the PKC delta-bryostatin complex, hydrogen bonds are formed between the Gly253 backbone carbonyl and the C30 carbomethoxy substituent of the ligand. Additionally, the indole Nε1 of the highly homologous Trp252 also forms an H-bond to the C20 ester group on bryostatin. Backbone fluctuations also suggest that this latter H-bond formation may abrogate the transient interaction between Trp252 and His269, thus dampening the fluctuations observed on the nearby Zn(2+)-coordinating residues. This new dynamic fluctuation dampening model can potentially benefit future design of new PKC modulators.
Topics: Binding Sites; Bryostatins; Hydrogen Bonding; Hydrophobic and Hydrophilic Interactions; Ligands; Models, Molecular; Molecular Conformation; Molecular Docking Simulation; Molecular Dynamics Simulation; Phorbol Esters; Protein Binding; Protein Interaction Domains and Motifs; Protein Kinase C
PubMed: 26292580
DOI: 10.1080/07391102.2015.1084479 -
Anti-cancer Agents in Medicinal... 2021Medicinal plants serve as sources of compounds used to treat other types of cancers. The root of the plant Lophira alata (Ochnaceae) has been used as a component of...
BACKGROUND
Medicinal plants serve as sources of compounds used to treat other types of cancers. The root of the plant Lophira alata (Ochnaceae) has been used as a component of traditional herbal decoctions administered to cancer patients in southwestern Nigeria. However, the mechanism of the cytotoxic effects of Lophira alata alone or in the presence of phorbol ester has not been investigated in brain tumor cells.
OBJECTIVE
This study aimed to examine the cytotoxic potential of the methanolic fraction of Lophira alata root on malignant glioma invasive cellular growth and survival.
METHODS
The methanolic fraction of Lophira alata (LAM) was subjected to high-performance liquid chromatography to determine the fingerprints of the active molecules. The antiproliferative effects of Lophira alata were assessed using the MTT and LDH assays. Protein immunoblots were carried out to test the effects of Lophira alata, alone or in the presence of phorbol ester, on survival signaling pathways, such as Akt, mTOR, and apoptotic markers such as PARP and caspases.
RESULTS
The methanolic fraction of Lophira alata (LAM) induced a concentration-dependent and time-dependent decrease in glioma cell proliferation. In addition, LAM attenuated phorbol ester-mediated signaling of downstream targets such as Akt/mTOR. Gene silencing using siRNA targeting PKC-alpha attenuated LAM-mediated downregulation of Akt. In addition, LAM induced both PARP and caspase cleavages. The HPLC fingerprint of the fraction indicates the presence of flavonoids.
CONCLUSION
LAM decreases cell proliferation and induces apoptosis in glioma cell lines and thus could serve as a therapeutic molecule in the management of gliomas.
Topics: Antineoplastic Agents, Phytogenic; Cell Proliferation; Drug Screening Assays, Antitumor; Glioblastoma; Humans; Ochnaceae; Phorbol Esters; Plant Extracts; Protein Kinase C-alpha; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Tumor Cells, Cultured
PubMed: 33622229
DOI: 10.2174/1871520621666210223094235 -
Biomolecules & Therapeutics Jan 2016Fisetin, a natural flavonoid found in a variety of vegetables and fruits, has been shown to possess many biological functions. The present study was undertaken to...
Fisetin, a natural flavonoid found in a variety of vegetables and fruits, has been shown to possess many biological functions. The present study was undertaken to investigate the influence of fisetin on vascular smooth muscle contractility and to determine the mechanism involved. Denuded aortic rings from male rats were used and isometric contractions were recorded and combined with molecular experiments. Fisetin significantly relaxed fluoride-, thromboxane A2- or phorbol ester-induced vascular contraction suggesting as a possible anti-hypertensive on the agonist-induced vascular contraction regardless of endothelial nitric oxide synthesis. Furthermore, fisetin significantly inhibited fluoride-induced increases in pMYPT1 levels and phorbol ester-induced increases in pERK1/2 levels suggesting the mechanism involving the inhibition of Rho-kinase activity and the subsequent phosphorylation of MYPT1 and MEK activity and the subsequent phosphorylation of ERK1/2. This study provides evidence regarding the mechanism underlying the relaxation effect of fisetin on agonist-induced vascular contraction regardless of endothelial function.
PubMed: 26759702
DOI: 10.4062/biomolther.2015.104 -
Pflugers Archiv : European Journal of... Jan 2024Particularly expressed in the kidney, αKlotho is a transmembrane protein that acts together with bone hormone fibroblast growth factor 23 (FGF23) to regulate renal...
Particularly expressed in the kidney, αKlotho is a transmembrane protein that acts together with bone hormone fibroblast growth factor 23 (FGF23) to regulate renal phosphate and vitamin D homeostasis. Soluble Klotho (sKL) is released from the transmembrane form and controls various cellular functions as a paracrine and endocrine factor. αKlotho deficiency accelerates aging, whereas its overexpression favors longevity. Higher αKlotho abundance confers a better prognosis in cardiovascular and renal disease owing to anti-inflammatory, antifibrotic, or antioxidant effects and tumor suppression. Serine/threonine protein kinase C (PKC) is ubiquitously expressed, affects several cellular responses, and is also implicated in heart or kidney disease as well as cancer. We explored whether PKC is a regulator of αKlotho. Experiments were performed in renal MDCK or NRK-52E cells and PKC isoform and αKlotho expression determined by qRT-PCR and Western Blotting. In both cell lines, PKC activation with phorbol ester phorbol-12-myristate-13-acetate (PMA) downregulated, while PKC inhibitor staurosporine enhanced αKlotho mRNA abundance. Further experiments with PKC inhibitor Gö6976 and RNA interference suggested that PKCγ is the major isoform for the regulation of αKlotho gene expression in the two cell lines. In conclusion, PKC is a negative regulator of αKlotho gene expression, an effect which may be relevant for the unfavorable effect of PKC on heart or kidney disease and tumorigenesis.
Topics: Humans; Protein Kinase C; Glucuronidase; Fibroblast Growth Factors; Protein Isoforms; Gene Expression; Kidney Diseases
PubMed: 37773536
DOI: 10.1007/s00424-023-02863-3 -
Cell Cycle (Georgetown, Tex.) Mar 2022Exocytosis of large dense core vesicles is responsible for hormone secretion in neuroendocrine cells. The population of primed vesicles ready to release upon cell...
Exocytosis of large dense core vesicles is responsible for hormone secretion in neuroendocrine cells. The population of primed vesicles ready to release upon cell excitation demonstrates large heterogeneity. However, there are currently no models that clearly reflect such heterogeneity. Here, we develop a novel model based on single vesicle release events from amperometry recordings of PC12 cells using carbon fiber microelectrode. In this model, releasable vesicles can be grouped into two subpopulations, namely, SP1 and SP2. SP1 vesicles replenish quickly, with kinetics of ~0.0368 s, but likely undergo slow fusion pore expansion (amperometric signals rise at ~2.5 pA/ms), while SP2 vesicles demonstrate slow replenishment (kinetics of ~0.0048 s) but prefer fast dilation of fusion pore, with an amperometric signal rising rate of ~9.1 pA/ms. Phorbol ester enlarges the size of SP2 partially via activation of protein kinase C and conveys SP1 vesicles into SP2. Inhibition of Rho GTPase-dependent actin rearrangement almost completely depletes SP2. We also propose that the phorbol ester-sensitive vesicle subpopulation (SP2) is analogous to the subset of superprimed synaptic vesicles in neurons. This model provides a meticulous description of the architecture of the readily releasable vesicle pool and elucidates the heterogeneity of the vesicle priming mechanism.
Topics: Animals; Dense Core Vesicles; Exocytosis; PC12 Cells; Phorbol Esters; Rats; Synaptic Vesicles
PubMed: 35067177
DOI: 10.1080/15384101.2022.2026576 -
Journal of Cell Science Feb 2021KRIT1 is a scaffolding protein that regulates multiple molecular mechanisms, including cell-cell and cell-matrix adhesion, and redox homeostasis and signaling. However,...
KRIT1 is a scaffolding protein that regulates multiple molecular mechanisms, including cell-cell and cell-matrix adhesion, and redox homeostasis and signaling. However, rather little is known about how KRIT1 is itself regulated. KRIT1 is found in both the cytoplasm and the nucleus, yet the upstream signaling proteins and mechanisms that regulate KRIT1 nucleocytoplasmic shuttling are not well understood. Here, we identify a key role for protein kinase C (PKC) in this process. In particular, we found that PKC activation promotes the redox-dependent cytoplasmic localization of KRIT1, whereas inhibition of PKC or treatment with the antioxidant N-acetylcysteine leads to KRIT1 nuclear accumulation. Moreover, we demonstrated that the N-terminal region of KRIT1 is crucial for the ability of PKC to regulate KRIT1 nucleocytoplasmic shuttling, and may be a target for PKC-dependent regulatory phosphorylation events. Finally, we found that silencing of PKCα, but not PKCδ, inhibits phorbol 12-myristate 13-acetate (PMA)-induced cytoplasmic enrichment of KRIT1, suggesting a major role for PKCα in regulating KRIT1 nucleocytoplasmic shuttling. Overall, our findings identify PKCα as a novel regulator of KRIT1 subcellular compartmentalization, thus shedding new light on the physiopathological functions of this protein.
Topics: Active Transport, Cell Nucleus; HeLa Cells; Humans; KRIT1 Protein; Phosphorylation; Protein Kinase C-alpha; Tetradecanoylphorbol Acetate
PubMed: 33443102
DOI: 10.1242/jcs.250217