Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cell lines stably overexpressing protein kinase C (PKC)-alpha were previously described by us. These cell lines were generated by the introduction of the full length cDNA coding for PKC-alpha into Swiss/3T3 cells. Here we show that activation of PKC-alpha by phorbol-esters induced in these cells specific phosphorylation of two cellular proteins p90 and p52. Phosphorylation of p80 (MARCKS protein), previously identified as a substrate for PKC, was also enhanced. Phosphorylated p90 and p52 proteins were associated with particulate membrane-enriched fractions and were extractable with the use of nonionic detergents. Time course analysis of phorbol-ester induced phosphorylation of p90 and p52 revealed maximal stimulation of phosphorylation after 15-30 min. Phosphamino acid analysis showed that phosphorylation of p90 and p52 occurred mainly on serine residues. Phosphorylation of p52 was also on threonine residues. Whereas, phorbol ester activation induced phosphorylation of both p90 and p52, the mitogens platelet-derived growth factor (PDGF) and fibroblast growth factor (FGF) enhanced phosphorylation of p90, but not p52. Thus, our studies showed the involvement of PKC-alpha in the regulation of p90 and p52 phosphorylation and provided direct evidence for the role of PKC-alpha in cellular signaling by PDGF and FGF. Moreover, the fact that phosphorylation of p52 was specific to phorbol ester activation may suggest its involvement in tumor promotion. Characterization of p90 and p52 will enable us to reveal the phosphorylation cascade activated downstream to PKC-alpha and to determine their role in mitogenic signaling and tumor promotion.
Mol Biol Cell 1992 Sep
PMID:Phosphorylation of p90 and p52 in response to phorbol-esters in Swiss/3T3 cells overexpressing protein kinase C-alpha. 142 77

The present study examined the concentration-dependent effects of phorbol 12-myristate 13-acetate (PMA), a PKC-activating phorbol ester, on contractile force and [Ca2+]i in guinea-pig hearts and isolated cardiac myocytes, respectively. Contractile force was measured using isolated Langendorff-perfused hearts while [Ca2+]i was measured independently in isolated cardiac myocytes loaded with fura2-AM. Phorbol 12-myristate 13-acetate, as well as another PKC-activating phorbol, phorbol dibutyrate (PDBu), and two non-PKC-activating phorbols, alpha-phorbol didecanoate (alpha PDD) and 4 alpha-phorbol, exerted time- and concentration-dependent effects on contractility. A significant positive inotropic response was observed with either PMA (10(-12) M; 5-15 min of perfusion) or PDBu (10(-12) M; 5 min of perfusion). In contrast, 10(-10) M PMA caused a significant negative inotropic effect following 30 min of perfusion while 10(-8) M PMA produced a significant negative inotropic effect which occurred earlier (10 min) and was sustained throughout the 30 min perfusion period. A similar negative inotropic effect was seen with 10(-8) M of either PDBu or alpha PDD. In addition, 4 alpha-phorbol (10(-8) M) exerted a modest, but significant negative inotropic effect following 25 and 30 min of perfusion. Both concentration-dependent increases and decreases of +dF/dt and -dF/dt were observed in the presence of PMA. In addition, both PMA and PDBu caused a concentration-dependent increase in coronary perfusion pressure. The positive inotropic responses and coronary perfusion pressure effects elicited by PMA and PDBu were largely prevented by the addition of the PKC inhibitors H7 (6 nM) or HAG (10 nM); however, these drugs were without effect on the negative inotropic response to higher concentrations of both PKC-activating (PMA, PDBu) and non-PKC-activating (alpha PDD, 4 alpha-phorbol) phorbol compounds. The lowest concentration of either PMA or PDBu (10(-12) M) increased the 340/380 fluorescence ratio of isolated cardiac myocytes loaded with fura2-AM on a time scale similar to that at which the positive inotropic response was seen in the whole heart. However, in contrast to results in the isolated heart, PDBu elicited a greater and sustained increase in the fluorescence ratio measured in isolated cardiac myocytes. The higher concentration of either PMA or PDBu (10(-8) M), resulted in a decrease in the 340/380 ratio.(ABSTRACT TRUNCATED AT 400 WORDS)
J Mol Cell Cardiol 1992 Sep
PMID:Positive and negative inotropic effects of phorbol 12-myristate 13-acetate: relationship to PKC-dependence and changes in [Ca2+]i. 143 22

We compared the ability of estradiol and progesterone to modulate gonadotropin-releasing hormone (GnRH) and protein kinase C (PKC)-mediated luteinizing hormone (LH) secretion. Long-term (48 h) treatment of rat pituitary cells with 1 nM estradiol enhanced GnRH and phorbol ester (TPA)-stimulated LH secretion. This positive effect was facilitated by additional short-term (4 h) treatment with progesterone (100 nM). However, long-term progesterone treatment, which inhibited GnRH-stimulated LH secretion, did not influence TPA-stimulated gonadotropin release. These steroid actions occurred without an effect on the total amount of LH in the cell cultures (total LH = LH secreted + LH remaining in the cell) and neither the secretagogues nor the steroids altered total LH. Since GnRH or TPA-induced LH secretion depends on Ca2+ influx into the gonadotroph, we also analyzed the effects of estradiol and progesterone under physiological extracellular Ca2+ concentrations and in the absence of extracellular Ca2+. The steroids were able to influence GnRH or TPA-induced LH secretion under both conditions. However, when TPA was used as stimulus in Ca(2+)-deficient medium the relative changes induced by estradiol and progesterone were more pronounced, possibly indicating that the extracellular Ca(2+)-independent component of PKC-mediated LH secretion is more important for the regulation of the steroid effects. It is concluded that estradiol and progesterone might mediate their modulatory actions on GnRH-stimulated LH secretion via an influence on PKC. This effect can occur independently from de novo synthesis of LH and Ca2+ influx into gonadotrophs.
J Steroid Biochem Mol Biol 1992 Dec
PMID:Modulatory actions of estradiol and progesterone on phorbol ester-stimulated LH secretion from cultured rat pituitary cells. 147 53

A human non-small-cell lung carcinoma cell line, Calu-6 (from an anaplastic carcinoma), was transfected with the Ki-ras-related anti-oncogene Krev-1. Several transfectant lines were obtained that showed a reduced tumorigenicity in nude mice with respect to the parental and control transfected cell lines. This decrease was approximately 50% in tumor incidence at 4 wk after subcutaneous inoculation of the transfected cells. In addition, the volume of the Calu-6 revertant-derived tumors was three to 10 times smaller than that of the equivalent tumors produced by inoculation of the control cell line transfected with the neomycin-resistance gene. Krev-1--transfected cells that exhibited reduced tumorigenicity expressed Krev-1 mRNA and had variable numbers of copies of the Krev-1 gene. Moreover, Krev-1--transfected cells exhibited a more differentiated squamous epithelial morphology than the parental and control cell lines did. Moderately elevated levels of protein kinase C activity were detected in some revertant clones. Such activity correlated with the level of expression of Krev-1 mRNA in most cases. In summary, Krev-1 induced important morphological and biological changes in transfected Calu-6 cells that we interpreted as partial reversion of the malignant phenotype.
Mol Carcinog 1992
PMID:Partial suppression of tumorigenicity in a human lung cancer cell line transfected with Krev-1. 148 16

The effect of hypoxia on the incorporation of [14C]serine into serine glycerophospholipids was investigated in rat brain cortex. Brain slices were incubated, in the presence of the labeled precursor, in Krebs-Henseleit Ringer bicarbonate or Krebs Ringer phosphate, and hypoxia was induced by bubbling nitrogen in the medium. The lowering of oxygen caused an increase of the incorporation of the base into phosphatidylserine in slices incubated in both media, although the effect was greater in Krebs Ringer phosphate. Such an effect was also observed in the homogenate subjected to N2-treatment, with an increase in the incorporation similar to that obtained in slices incubated in Krebs-Henseleit Ringer bicarbonate. Phosphatidylserine is synthesized in mammalian tissues by a "base-exchange" enzyme, strictly Ca2+ dependent, and, moreover, is necessary for protein kinase C activity. We postulate that the increased synthesis of phosphatidylserine might affect signal transduction mechanisms and participate in the modification of lipid metabolism observed in hypoxia and/or ischemia.
Mol Chem Neuropathol 1992 Dec
PMID:Serine incorporation into phosphatidylserine in hypoxic rat brain cortex. 149 81

Our object was to obtain information about the regulatory mechanism which modulates the effect of basic fibroblast growth factor (bFGF) on commitment to growth in human umbilical vein endothelial (HUVE) cells. Firstly, phorbol ester PMA, a known activator of protein kinase C (PKC), was found to be able to act synergistically with bFGF to stimulate 3H thymidine incorporation in HUVE cells. Secondly, bFGF and PMA induced a stimulated phospholipase A2 (PLA2)-catalyzed release of 14C arachidonate. Thirdly, inhibitors of PLA2, PKC and HETE, but not an inhibitor of cyclooxygenase metabolites, inhibited FGF/PMA-stimulated DNA synthesis. Fourth, the stable cyclooxygenase metabolite of prostacyclin was not found to be changed when cells were treated with bFGF plus PMA. The present data suggest that PKC is able of acting synergistically with bFGF in order to stimulate DNA-primary initiation activity in HUVE cells via the PLA2-dependent generation of lipoxygenase metabolites such as HETE.
Cell Mol Biol 1992 Jul
PMID:Possible involvement of arachidonic acid metabolites in the synergistic action of endothelial mitogenesis by basic fibroblast growth factor and phorbol ester. 149 42

A number of studies have demonstrated the activation of phospholipase C-mediated hydrolysis of phosphatidylcholine (PC-PLC) both by growth factors and by the product of the ras oncogene, p21ras. Evidence has been presented indicating that the stimulation of this phospholipid degradative pathway is sufficient to activate mitogenesis in fibroblasts as well as that it is sufficient and necessary for induction of maturation in Xenopus laevis oocytes. However, the mechanism whereby PC-PLC transduces mitogenic signals triggered by growth factors or oncogenes remains to be elucidated. In this study, data are presented that show the involvement of protein kinase C zeta subspecies in the channelling of the mitogenic signal activated by insulin-p21ras-PC-PLC in Xenopus oocytes as well as the lack of a critical role of protein kinase C isotypes alpha, beta, gamma, delta, and epsilon in these pathways.
Mol Cell Biol 1992 Sep
PMID:Evidence for a role of protein kinase C zeta subspecies in maturation of Xenopus laevis oocytes. 150 83

A new protein kinase C (PKC)-related cDNA with unique tissue distribution has been isolated and characterized. This cDNA encodes a protein, nPKC theta, which consists of 707 amino acid residues and showed the highest sequence similarity to nPKC delta (67.0% in total). nPKC theta has a zinc-finger-like cysteine-rich sequence (C1 region) and a protein kinase domain sequence (C3 region), both of which are common in all PKC family members. However, nPKC theta lacks a putative Ca2+ binding region (C2 region) that is seen only in the conventional PKC subfamily (cPKC alpha, -beta I, -beta II, and -gamma) but not in the novel PKC subfamily (nPKC delta, -epsilon, -zeta, and -eta). Northern (RNA) blot analyses revealed that the mRNA for nPKC theta is expressed predominantly in skeletal muscle. Furthermore, nPKC theta mRNA is the most abundantly expressed PKC isoform in skeletal muscle among the nine PKC family members. nPKC theta expressed in COS1 cells serves as a phorbol ester receptor. By the use of an antipeptide antibody specific to the D2-D3 region of the nPKC theta sequence, nPKC theta was recognized as a 79-kDa protein upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis in mouse skeletal muscle extract and also in an extract from COS1 cells transfected with an nPKC theta cDNA expression plasmid. Autophosphorylation of immunoprecipitated nPKC theta was observed; it was enhanced by phosphatidylserine and 12-O-tetradecanoylphorbol-13-acetate but attenuated by the addition of Ca2+. These results clearly demonstrate that nPKC theta should be considered a member of the PKC family of proteins that play crucial roles in the signal transduction pathway.
Mol Cell Biol 1992 Sep
PMID:A new member of the protein kinase C family, nPKC theta, predominantly expressed in skeletal muscle. 150 94

In GH4C1 rat pituitary cells, cell swelling stimulates prolactin (PRL) secretion by increasing Ca2+ influx through nifedipine-sensitive Ca2+ channels; however, the mechanism by which cell swelling opens Ca2+ channels is still unclear. To evaluate the role of protein kinase C (PKC) in this phenomenon, we studied the effect of down-regulating PKC by 12-h pretreatment with phorbol ester or by treatment with H-7, a protein kinase C inhibitor. Cell swelling induced by either 27% medium hyposmolarity or 80 mM isotonic urea caused a prompt rise in both [Ca2+]i and PRL secretion in otherwise untreated control GH4C1 cells. Removal of medium Ca2+ enhanced the osmotically induced cell swelling but prevented the increase in [Ca2+]i and PRL secretion. Both PKC down-regulation and H-7 suppressed the cell swelling-induced increases in [Ca2+]i concentration and PRL secretion, although they enhanced the induced cell volume expansion. Our data indicate that in GH4C1 cells PKC plays an important positive modulating role in the osmotic opening of plasmalemma Ca2+ channels, a critical component of the early transduction chain by which cell swelling causes PRL secretion in tumor-derived clonal pituitary cells.
Mol Cell Endocrinol 1992 Aug
PMID:Protein kinase C modulates cell swelling-induced Ca2+ influx and prolactin secretion in GH4C1 cells. 151 83

Intracellular calcium ([Ca2+]i) was measured in single immortalized gonadotroph alpha T3-1 cells using dual wavelength fluorescence microscopy combined with dynamic video imaging. Gonadotrophin-releasing hormone (GnRH, 10(-8) M) produced a biphasic rise in [Ca2+]i which could be abolished by a GnRH antagonist. The initial calcium transient was complete within seconds while the smaller secondary plateau phase lasted several minutes. The calcium spike was reduced by nifedipine (10(-6) M), a calcium channel blocker, and thapsigargin (10(-6) M) which inhibits inositol 1,4,5-trisphosphate (IP3) mediated release of [Ca2+]i but abolished by the intracellular calcium antagonist TMB-8 (10(-6) M). The secondary phase was reduced following pretreatment with either nifedipine or the protein kinase C (PKC) antagonist, H-7 (10(-6) M). The PKC agonist PMA (phorbol 12-myristate 13-acetate, 10(-6) M) produced a small rise in basal [Ca2+]i and abolished the GnRH calcium response. The initial calcium response to GnRH therefore involves both an IP3-mediated rise in cytosolic calcium due to the release from intracellular stores and an influx of extracellular calcium through second messenger-operated calcium channels. In contrast the secondary calcium response mainly involves the influx of extracellular calcium through PKC-activated calcium channels.
Mol Cell Endocrinol 1992 Aug
PMID:Characterization of the gonadotrophin-releasing hormone calcium response in single alpha T3-1 pituitary gonadotroph cells. 151 86


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