Down-regulation of protein kinase C in Swiss 3T3 fibroblasts is independent of its phosphorylating activity

Lindner, Dieter; Gschwendt, Michael; Marks, Friedrich

doi:10.1016/0006-291x(91)90416-5

Cited by 23 publications

(7 citation statements)

References 22 publications

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“…The observed lack of effect of STAU on TPA-induced PKC downregulation is compatible with reports suggesting that PKC downregulation is independent of its phosphorylating activity (Freisewinkel et aZ., 1991;Pears and Parker, 1991;Lindner et al, 1991). In the presence of STAU, more immunodetectable PKC remained attached to the particulate fraction after TPA-induced enzyme downregulation than in its absence.…”

Section: Discussionsupporting

confidence: 89%

Modulation by staurosporine of phorbol‐ester‐induced effects on growth and protein kinase C localization in a549 human lung‐carcinoma cells

Bradshaw

Gescher

Pettit

1992

Intl Journal of Cancer

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12-O-tetradecanoylphorbol-13-acetate (TPA) and bryostatin 1 are activators of protein kinase C (PKC). TPA is a potent inhibitor of the growth of A549 cells, while bryostatin 1 exerts a weak antiproliferative effect upon this cell line. We tested the hypothesis that the PKC inhibitor staurosporine (STAU) can interfere with the effects of TPA or bryostatin 1 on A549 cells. STAU alone arrested A549 cell growth effectively with an IC50 of 0.65 nM as determined by cell counting after incubation for 96 hr. It also caused the release of lactate dehydrogenase from cells with an IC50 of 18.4 nM. On incubation with cells for up to 8 hr, STAU (100 nM) alone did not reduce thymidine incorporation into cells. However, it partially abrogated the inhibition of DNA synthesis caused by TPA or bryostatin 1 (10 nM). The IC50 for inhibition by STAU of the activity of PKC purified from A549 cells was 6.1 nM. Localization and levels of PKC were studied by Western blot and phorbol ester receptor binding analyses. STAU (100 nM) did not prevent the TPA-induced rapid redistribution of PKC to the cell membrane, but instead increased it by 25%. The PKC downregulation caused by TPA was not reduced in the presence of STAU. The results suggest that (i) PKC activation is involved in growth inhibition caused by TPA or bryostatin 1 in A549 cells, and (ii) subcellular localization or levels of PKC can be pharmacologically manipulated even under conditions of inhibited kinase function.

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Section: Discussionsupporting

confidence: 89%

Modulation by staurosporine of phorbol‐ester‐induced effects on growth and protein kinase C localization in a549 human lung‐carcinoma cells

Bradshaw

Gescher

Pettit

1992

Intl Journal of Cancer

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“…In this case in rat cortex synaptosomal membranes, B‐50 phosphorylation was increased by acute application of PDB, however acute PDB had no effect on synaptosomes from cortex slices previously incubated with PDB for 20 h. As a further index of PKC down‐regulation we also measured PKCα immunoreactivity and it was reduced following PDB treatment. These effects on B‐50 are in agreement with other studies where prolonged incubation with phorbol esters results in a loss of detectable PKC enzyme protein and kinase activity ( Ballester & Rosen, 1985 ; Adams & Gullick, 1989 ; Matthies et al ., 1987 ; Lindner et al ., 1991 ) indicating down‐regulation.…”

Section: Discussionmentioning

confidence: 99%

“…Chronic activation of PKC with the tumour promoting phorbol ester, phorbol 12‐myristate 13‐acetate (PMA), can effectively deplete PKC from intact cells (e.g. Blackshear et al ., 1985 ; Adams & Gullick, 1989 ; Lindner et al ., 1991 ). The corresponding loss of PKC protein is due to a net increase in the proteolysis of activated PKC by protease(s) at a susceptible linker region between the regulatory and catalytic domain ( Kishimoto et al ., 1983 , 1989 ).…”

Section: Introductionmentioning

confidence: 99%

Differential abilities of phorbol esters in inducing protein kinase C (PKC) down‐regulation in noradrenergic neurones

Kotsonis

Funk

Prountzos

et al. 2001

British J Pharmacology

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1 The ability of several phorbol ester protein kinase C (PKC) activators (phorbol 12, 13-dibutyrate, PDB; phorbol 12, 13-diacetate, PDA; and 12-deoxyphorbol 13-acetate, dPA) to downregulate PKC was studied by assessing their e ects on electrical stimulation-induced (S-I) noradrenaline release from rat brain cortical slices and phosphorylation of the PKC neural substrate B-50 in rat cortical synaptosomal membranes. 2 In cortical slices which were incubated for 20 h with vehicle, acute application of PDB, PDA and dPA (0.1 ± 3.0 mM) enhanced the S-I noradrenaline release in a concentration-dependent manner to between 200 ± 250% of control in each case. In slices incubated with PDB (1 mM for 20 h), subsequent acute application of PDB (0.1 ± 3.0 mM) failed to enhance S-I release, indicating PKC down-regulation. However, in tissues incubated with PDA or dPA (3 mM) for 20 h, there was no reduction in the facilitatory e ect of their respective phorbol esters or PDB (0.1 ± 3.0 mM) when acutely applied, indicating that PKC was not down-regulated. This was con®rmed using Western blot analysis which showed that PDB (1 mM for 20 h) but not PDA (3 mM for 20 h) caused a signi®cant reduction in PKCa. 3 Incubation with PDB for 20 h, followed by acute application of PDB (3 mM) failed to increase phosphorylation of B-50 in synaptosomal membranes, indicating down-regulation. In contrast, tissues incubated with PDA or dPA for 20 h, acute application of their respective phorbol ester (10 mM) or PDB (3 mM) induced a signi®cant increase in B-50 phosphorylation. 4 Acutely all three phorbol esters elevate noradrenaline release to about the same extent, yet PDA and dPA have lower a nities for PKC compared to PDB, suggesting unique neural e ects for these agents. This inability to cause functional down-regulation of PKC extends their unusual neural properties. Their neural potency and lack of down-regulation may be related to their decreased lipophilicity compared to other phorbol esters. 5 We suggest that PKC down-regulation appears to be related to binding a nity, where agents with high a nity, irreversibly insert PKC into arti®cial membrane lipid and generate Ca 2+ -independent kinase activity which degrades and deplete PKC. We suggest that this mechanism may also underlie the ability of PDB to down-regulate PKC in nerve terminals, in contrast to PDA and dPA.

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“…Differential down-regulation of various PKC isozymes may be responsible for this apparent paradox; however, the disparity between PKC activity and substrate phosphorylation has been recorded by other workers (Rozengurt et al, 1983;Parrow et al, 1992). Down-regulation of PKC may be independent of its phosphorylation activity (Lindner et al, 1991). The participation of other kinases may also explain the MARCKS hyperphosphorylation observed (Schönwasser et al, 1996).…”

Section: Discussionmentioning

confidence: 96%

PMA-induced reduction in invasiveness is associated with hyperphosphorylation of MARCKS and talin in invasive bladder cancer cells

Yokoyama¹,

Ito²,

Hanson³

et al. 1998

Int. J. Cancer

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Protein kinase C (PKC) plays a critical role in signal transduction for a variety of cell activation processes. Enhanced PKC activity is often found in cancer cells that show marked invasive and/or metastatic potential. Thus, a specific PKC inhibitor may serve as a tool to reduce invasive or metastatic potential of cancer cells. We show here that phorbol 12‐myristate 13‐acetate (PMA), a PKC activator, also reduces invasiveness of EJ invasive transitional carcinoma cells. PMA‐induced reduction in invasiveness was parallel with inhibition of cell motility. PMA neither induced E‐cadherin expression nor augmented cell‐matrix adhesion of EJ cells. PMA caused retraction of microspikes from the rim of the cells and consequently rounding of the cellular rim, and the disappearance of microfilaments from the cytoplasm. PMA at 10−7 M, at which concentration the motility of EJ cells was completely inhibited, down‐regulated PKC activity over 5 hr after transient translocation of PKC activity to the membrane fraction. At the same time, PMA induced hyperphosphorylation of MARCKS and talin. During the process of cell movement, actin‐binding proteins are in a cycle of phosphorylation and dephosphorylation. Once this cycle is interrupted, cells can no longer maintain the dynamics of cytoskeletal structure. We suggest that retention of the hyperphosphorylated state of MARCKS and talin is responsible for the mechanism(s) by which PMA produces inhibitory activity against invasiveness of EJ cells. Int. J. Cancer 75:774–779, 1998.© 1998 Wiley‐Liss, Inc.

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Down-regulation of protein kinase C in Swiss 3T3 fibroblasts is independent of its phosphorylating activity

Cited by 23 publications

References 22 publications

Modulation by staurosporine of phorbol‐ester‐induced effects on growth and protein kinase C localization in a549 human lung‐carcinoma cells

Modulation by staurosporine of phorbol‐ester‐induced effects on growth and protein kinase C localization in a549 human lung‐carcinoma cells

Differential abilities of phorbol esters in inducing protein kinase C (PKC) down‐regulation in noradrenergic neurones

PMA-induced reduction in invasiveness is associated with hyperphosphorylation of MARCKS and talin in invasive bladder cancer cells

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