Involvement of Protein Kinase C and Rho GTPase in the Nuclear Signalling Pathway by Transforming Growth Factor-β1 in Rat-2 Fibroblast Cells

Bombesin induces the down-regulation of protein kinase C-Δ (PKC-Δ) and PKC-ϵ in Swiss 3T3 cells. Simultaneous addition of transforming growth factor β1 (TGFβ1) selectively blocks PKC-Δ down-regulation at mid-S-phase, whereas PKC-ϵ levels continue to decline. Northern blot analysis shows that PKC-ϵ levels could be controlled in part at the level of transcription; PKC-Δ mRNA levels remained constant at these later times. Bombesin induces a sustained elevation of some species of diacylglycerol (DAG), consistent with the observed loss of PKC-Δ and PKC-ϵ. Interestingly, the combination of bombesin and TGF-β1 produces an even greater DAG response. Flow cytometric analysis demonstrates that bombesin induces only 15% of the cells to enter the cell cycle, in contrast to the combination of TGFβ1 plus bombesin which induces 75–80% of the cells to progress through the cycle. The protection of PKC-Δ from down-regulation under conditions of sustained DAG elevation correlates with the mitogenic response and implies that the down-regulation process itself is regulated. Consistent with this, it is demonstrated that bombesin plus TGFβ1 protects PKC-Δ from phorbol ester-induced down-regulation.

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Stimulus-dependent Subcellular Localization of Activated Protein Kinase C; a Study with Acidic Fibroblast Growth Factor and Transforming Growth Factor-β1 in Cardiac Myocytes

Journal of Molecular and Cellular Cardiology ◽

10.1006/jmcc.1995.0235 ◽

1995 ◽

Vol 27 (11) ◽

pp. 2473-2481 ◽

Cited By ~ 29

Author(s):

M Disatnik

Keyword(s):

Protein Kinase C ◽

Growth Factor ◽

Protein Kinase ◽

Fibroblast Growth Factor ◽

Cardiac Myocytes ◽

Transforming Growth Factor ◽

Transforming Growth Factor Β1 ◽

Fibroblast Growth ◽

Acidic Fibroblast Growth Factor ◽

Kinase C

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Stimulation of hyaluronan biosynthesis by platelet-derived growth factor-BB and transforming growth factor-β1 involves activation of protein kinase C

Biochemical Journal ◽

10.1042/bj3070817 ◽

1995 ◽

Vol 307 (3) ◽

pp. 817-821 ◽

Cited By ~ 95

Author(s):

M Suzuki ◽

T Asplund ◽

H Yamashita ◽

C H Heldin ◽

P Heldin

Keyword(s):

Protein Kinase C ◽

Growth Factors ◽

Growth Factor ◽

Protein Kinase ◽

Transforming Growth Factor ◽

Human Fibroblasts ◽

Transforming Growth Factor Β1 ◽

Platelet Derived Growth Factor ◽

Tgf Beta ◽

Kinase C

The intracellular signal transduction pathways that mediate the stimulatory effects of platelet-derived growth factor (PDGF)-BB and transforming growth factor (TGF)-beta on hyaluronan biosynthesis in human fibroblasts were investigated. The stimulatory effects of both PDGF-BB and TGF-beta 1 were dependent on protein kinase C (PKC), since the PKC inhibitor calphostin C inhibited the stimulation by the growth factors. Direct activation of PKC by phorbol 12-myristate 13-acetate (PMA) also stimulated hyaluronan production, and the combination of either PDGF-BB or TGF-beta 1 and PMA gave an increased effect. One possible mechanism for activation of PKC is via induction of phospholipase C (PLC) activity; U-17322, an inhibitor of PLC-gamma, was found to inhibit partially PDGF-BB-stimulated hyaluronan synthesis. PDGF-BB is known to activate PLC-gamma through tyrosine phosphorylation; however, a PDGF beta-receptor mutant unable to interact with and activate PLC-gamma was still able to mediate induction of hyaluronan biosynthesis, indicating that PDGF-mediated stimulation is not entirely dependent on PLC-gamma. The stimulations by PDGF-BB and TGF-beta 1 were partly dependent on protein synthesis, since parts of the effects were inhibited by cycloheximide; in contrast, the effects mediated by PMA were not. Our results indicate that PKC is involved in the transduction of the effects of growth factors on hyaluronan biosynthesis, and that the effects involve direct or indirect activation of existing hyaluronan synthetase molecules, as well as induction of new enzyme molecules.

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