Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Erythropoietin stimulation of erythroid cells induces a rapid increase in c-myc and decrease in c-myb mRNA levels. The signal pathway to c-myc requires activation of protein kinase C. We now report that erythropoietin down-regulates expression of c-myb via a discrete, serine/threonine-specific phosphatase-dependent pathway. The protein kinase C-blocker H7 completely prevents the c-myc response to erythropoietin, but has no effect on the c-myb response. In contrast, the phosphatase blocker okadaic acid prevents the c-myb response but not the c-myc response. This effect of okadaic acid on the c-myb response is concentration-dependent. Both the protein kinase C-dependent signal to c-myc and the phosphatase-dependent signal to c-myb regulate gene expression by a transcriptional arrest mechanism operative within the first intron of the respective protooncogenes. In contrast, the chemical inducer of differentiation, dimethyl sulfoxide, regulates expression of c-myc and c-myb without activation of these phosphatase- and kinase-dependent pathways.
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PMID:Activation of two discrete signaling pathways by erythropoietin. 132 29

Treatment of murine erythroleukemia cells (MELC) attached to fibronectin-coated dishes with dimethyl sulfoxide causes the cells to become committed to the erythroid differentiation pathway. These cells mature extensively and acquire the characteristics of erythroid cells. The cells lose their cell-surface fibronectin receptors and accumulate red cell-specific membrane proteins, such as band 3, in amounts comparable to those in erythrocytes. Previous studies of MELC have shown that the presence of protein kinase C (PKC) is required for commitment to differentiation, but that the level of PKC activity declines progressively during maturation. In this study, we have established a role for PKC in the maturation of MELC committed to differentiation. Our results show that down-regulation of PKC by addition of phorbol 12-myristate 13-acetate (PMA) to committed MELC blocks subsequent maturation of the cells. Treatment of MELC with the PKC inhibitors H7 and sphingosine had similar effects. Down-regulation of PKC was assayed by measuring cytosolic PKC activity as well as by Western blotting using PKC antibodies. MELC maturation was monitored by loss of the cell-surface fibronectin receptor, release of cells from fibronectin plates, and accumulation of the band 3 anion transport protein. Immunoprecipitation of surface-labeled proteins by an anti-fibronectin receptor (integrin) antibody showed that PMA-treated cultures had more fibronectin receptor protein than untreated cultures 6 days post-induction. As a result, cultures of committed MELC treated with PMA remained attached to fibronectin-coated plates, whereas non-PMA-treated cells were released into the culture medium. Furthermore, PKC-depleted cells accumulated much smaller amounts of band 3 protein and band 3 mRNA than did non-PKC-depleted controls. Our results show that although PKC activity declines progressively during post-commitment maturation of MELC, its continued presence is critical for the process of cellular maturation.
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PMID:Maturation of murine erythroleukemia cells committed to differentiation requires protein kinase C. 138 58

Activin A/erythroid differentiation factor (EDF), a dimeric polypeptide hormone composed of two beta A subunits, regulates growth and erythroid differentiation of human hematopoietic progenitor and erythroleukemia cells. We have identified activated human peripheral blood monocytes as a natural source of activin A/EDF. In these cells, lipopolysaccharide (LPS) induced rapidly the expression of the beta A subunit mRNAs through protein kinase C-dependent transcriptional regulation. The beta A subunit mRNA expression was also increased by 1,25-dihydroxyvitamin D3, an inducer of macrophage maturation of monocytes. Western analysis with an anti-beta A antibody and an erythroid differentiation bioassay confirmed that the conditioned media of LPS-activated monocytes contained the activin A/EDF protein. We suggest that monocyte/macrophage-derived activin A/EDF may not only modulate hematopoiesis but may also act as a mediator molecule in the diverse physiologic and pathogenetic events in which these cells are involved.
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PMID:Activin A/erythroid differentiation factor is induced during human monocyte activation. 140 87

We have previously reported (J. P. Durkin et al., Blood, 79: 1161-1171, 1992) the isolation of a human differentiation-inhibiting protein (DIP) which selectively inhibits and blocks the differentiation of erythroid burst-forming unit progenitor cells in bone marrow colony assay, and the dimethyl sulfoxide (DMSO)-induced differentiation of cultured murine erythroleukemia (MEL) cells. DIP blocks MEL cell differentiation directly, without affecting the ability of the cells to proliferate. In the present study, DIP (at < 1 ng/ml) inhibited MEL cell differentiation only when added to the culture medium within 1 h after DMSO induction, indicating that it blocked an early, critical step in erythroleukemia cell differentiation. The protein kinase C (PKC) inhibitor H-7 also maximally inhibited the differentiation of MEL cells during this same period following induction, suggesting that DIP may have blocked an early PKC-dependent process. Indeed, DIP was found to abolish a transient increase in membrane PKC activity which was triggered in MEL cells within 10-30 min after DMSO addition. This increase in membrane PKC activity resulted from the activation of an inactive pool of PKC residing on membranes, and not from the translocation of cytosolic PKC to membranes. DMSO also stimulated membrane PKC activity and differentiation in human erythroleukemia cells and HL-60 myeloid leukemia cells. As was the case with MEL cells, DIP prevented the early activation of PKC and the differentiation of human erythroleukemia cells. However, it did not inhibit the early increase in PKC activity in HL-60 cells or the subsequent differentiation of these cells. These results suggest that DIP blocks erythroleukemia cell differentiation by inhibiting an early and critical activation of inactive membrane PKC.
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PMID:Evidence that a novel human differentiation-inhibiting protein blocks the dimethyl sulfoxide-induced differentiation of erythroleukemia cells by inhibiting the activation of membrane protein kinase C. 142 78

We searched for a possible role for protein kinase C in the growth of human erythroid progenitor cells, using pharmacologic approaches. Two protein kinase C inhibitors, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7) and staurosporine, dose-dependently inhibited the growth of immature erythroid progenitor cells (BFU-E) induced by interleukin 3 (IL-3) plus erythropoietin (Ep) or granulocyte macrophage colony-stimulating factor (GM-CSF) plus Ep whereas a weaker analog of H-7, N-(2-guanidinoethyl)-5-isoquinoline sulfonamide (HA-1004), had no effect on the number of BFU-E. These three compounds had no effect on the growth of mature erythroid progenitor cells (CFU-E) stimulated by Ep. The culture of accessory cell-depleted bone marrow demonstrated that the effects of these compounds on colony formation do not appear to be mediated by accessory cells. The potential of these compounds to inhibit the GM-CSF-dependent growth of KG-1 cells correlated well with the extent of their inhibitor of protein kinase C activities from KG-1 cells. Thus, the protein kinase C system is apparently involved in the growth of BFU-E, supported by IL-3 or GM-CSF. The growth signal for CFU-E transduced by Ep may be achieved through other systems.
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PMID:A role for protein kinase C in the growth of human erythroid progenitor cells. 154 67

Although it is well known that protein kinase C (PKC) is an important signaling molecule in Friend erythroleukemia cells it is not clear what role PKC may play in either regulated or unregulated erythroid cell proliferation and differentiation. The purpose of this study was to test the hypothesis that a decrease in nuclear PKC activity is associated with the induction of differentiation in Friend erythroleukemia cells. The effects of staurosporine, a selective inhibitor of PKC, and the tumor promoter, 12-O-tetradecanoyl phorbol-13-acetate, an activator of PKC, on Friend cell proliferation and differentiation were examined. Neither the inhibitor nor the activator of PKC affected proliferation at 96 h as measured by [3H]thymidine incorporation, but both compounds inhibited cell differentiation. In addition, nuclear PKC activity was highest in untreated and in tumor promoter-treated cells that were not differentiated, and it was lowest in cells induced to differentiate with hexamethylene bisacetamide or dimethylsulfoxide. It is concluded that nuclear PKC activity is essential for Friend erythroleukemia cell proliferation, and that a decrease in enzyme activity within the nucleus is associated with differentiation.
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PMID:Nuclear protein kinase C activity is decreased in Friend erythroleukemia cells induced to differentiate. 156 47

A cell line (TI-1) has been established from the peripheral blood of a patient with acute myeloid leukemia (M2). A typical TI-1 cell displayed many abnormalities of its chromosomes, but not the Philadelphia (Ph1) chromosome. Light and electron microscopic examination and histochemical analysis indicated that the TI-1 cells were undifferentiated blast cells, but immunologic marker studies suggested that these cells had myeloid characteristics. The proliferation of TI-1 cells was dependent on the concentration of fetal bovine serum (FBS). Their doubling time was 13.8 hours when they were cultured in a medium containing 10% FBS. Phorbol-12 myristate 13-acetate (PMA) induced the TI-1 cells to differentiate into monocyte-like cells, as judged by their morphologic similarity to monocytes, their adhesion to the culture dish, and their increase of both nitroblue tetrazolium (NBT)-reducing ability and nonspecific esterase (NSE)-activity. PMA significantly inhibited the proliferation and DNA synthesis of TI-1 cells in a dose-dependent manner. The PMA-induced differentiation was significantly inhibited by the protein kinase C inhibitors (H-7, staurosporine). Hemin induced the TI-1 cells to differentiate into erythroid cells. The number of hemoglobin-producing cells and hemoglobin production was increased by hemin treatment. Hemin also inhibited the proliferation of the TI-1 cells. Thus, the TI-1 cell represents a bipotent, granulo-monocytoid, and erythroid cell line. The TI-1 cell line will be a useful model for monocytoid and erythroid differentiation.
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PMID:Characterization, growth, and differentiation of a human myeloid leukemia cell line, TI-1 cell. 161 Oct 97

We have previously shown that HL-60 cells treated with 1 alpha, 25-(OH)2D3 in magnesium-deficient medium are committed to differentiate but do not express differentiation-related phenotypes. In the present study, we demonstrated that Mg2+ deprivation blocked the process of differentiation before the induction of lysozyme mRNA and that the process of HL-60 cell differentiation could be divided into two steps, i.e., a commitment step and a phenotypic expression step. We studied the effects of protein kinase A (PKA) and calcium/phospholipid-dependent protein kinase (PKC) modulators at each step. The results indicated that agonists of PKA enhanced both steps but that N-(2-[methylamino]ethyl-5-isoquinolinesulfonamide inhibited them. On the other hand, 1-oleyl-2-acetylglycerol and 12-O-tetradecanoylphorbol-13-acetate enhanced the commitment step but inhibited that of phenotypic expression. Staurosporine and 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine inhibited the commitment step and enhanced that of phenotypic expression. These results indicate that PKA acts as a positive regulatory signal and that PKC has a dual role in the process of HL-60 cell differentiation, i.e., as a positive regulatory signal in the commitment step and as a negative one in the phenotypic expression step. Recently, we have also shown that in K-562 cell differentiation into erythroid lineage, PKA may serve as a negative regulatory signal in both steps; however, PKC may act dually, namely as a negative regulatory signal in the commitment step and as a positive one in the phenotypic expression step.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of protein kinase A and calcium/phospholipid-dependent kinase modulators in the process of HL-60 cell differentiation: their opposite effects between HL-60 cell and K-562 cell differentiation. 166 Nov 33

The proto-oncogene c-myc has been identified as an early response gene for erythropoietin (Epo) in transformed murine erythroleukemia cells. Epo activation of c-myc in these cells requires protein kinase C. We now show the fidelity of this signaling pathway in normal erythroid cells isolated from the spleens of phenylhydrazine-treated mice. Mouse spleen cells rich in erythroid progenitors were washed free of endogenous Epo and then incubated in the absence of Epo. Subsequent addition of Epo for 1 hour led to a dramatic elevation of c-myc transcript. Addition of the protein synthesis inhibitor cycloheximide did not prevent the c-myc response, thus identifying c-myc as an Epo early response gene in normal cells. We used this c-myc response as a reporter for signals initiated by the Epo receptor. Using a series of inhibitors with known specificities and established rank-orders of potency for different kinases, we determined that the c-myc response to Epo was blocked with the following rank order: staurosporine much greater than H7 greater than sangivamycin greater than H8. This sequence is identical to that obtained using transformed cells and is diagnostic of a protein kinase C-dependent signal. Because direct activation of protein kinase by phorbol esters does not induce terminal differentiation of normal cells, the pathway to c-myc established by these studies must represent one part of a signal transduction mechanism.
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PMID:c-myc is an erythropoietin early response gene in normal erythroid cells: evidence for a protein kinase C-mediated signal. 172 20

Erythropoietin, the prime regulator of red blood cell growth and differentiation, causes rapid changes in the phosphorylation of several integral plasma membrane proteins (Choi, H-S., Wojchowski, D. M., and Sytkowski, A. J. (1987) J. Biol. Chem. 262, 2933-2936; Choi, H-S., Bailey, S. C., Donahue, K. A., Vanasse, G. J., and Sytkowski, A. J. (1990) J. Biol. Chem. 265, 4143-4148). In the present study we have demonstrated that erythropoietin's signal is transduced rapidly to the cytosol resulting in specific phosphorylation/dephosphorylation events. Erythropoietin treatment of Rauscher murine erythroleukemia cells previously labeled with [32P]orthophosphate results in a rapid increase in phosphorylation of two cytosolic proteins, designated pp96 and pp80, and a decrease in phosphorylation of another protein, designated pp90. The relative molecular mass and pI of pp80 are virtually identical to those reported for the protein kinase C substrate p80, or "MARCKS protein." Treatment of the cells with 12-O-tetradecanoylphorbol-13-acetate also increases pp80 but not pp96 phosphorylation, suggesting that erythropoietin triggers a protein kinase C-dependent pathway to pp80 and a protein kinase C-independent pathway to pp96. The effect of erythropoietin on pp96 phosphorylation was also shown in nontransformed erythroid cells isolated from the spleens of phenylhydrazine-treated mice. In contrast, almost no 32P labeling of pp80 or pp90 was detected, and pp80 and pp90 protein were nearly absent from these normal cells. These differences in expression and phosphorylation of erythropoietin-sensitive phosphoproteins may be related to the growth factor independence or dependence of the erythroid cells.
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PMID:Erythropoietin induces cytosolic protein phosphorylation and dephosphorylation in erythroid cells. 174 84


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