Regulation of Cyclic Adenosine 3′,5′-Monophosphate-Dependent Protein Kinase Activity and Regulatory Subunit RIIβ Content by Basic Fibroblast Growth Factor (bFGF) during Granulosa Cell Differentiation: Possible Implication of Protein Kinase C in bFGF Action1

Abstract

We have previously shown that basic fibroblast growth factor (bFGF) inhibits the FSH-induced differentiation of cultured rat granulosa cells, as manifested by prominent reduction of the LH receptor expression. We now investigate the possible sites and mechanism of action of bFGF. Whereas bFGF decreased the cAMP formation induced by FSH, it enhanced the cAMP production caused by cholera toxin and forskolin, suggesting that bFGF exerted its inhibitory action on cell differentiation at a step to cAMP production. Photoaffinity labeling with 8-azido-[32P]cAMP revealed that bFGF markedly reduced the FSH-induced increase in the level of regulatory subunit RII beta of the cAMP-dependent protein kinase (PKA) type II. In contrast to its striking effect on RII beta expression (70-80% inhibition), bFGF decreased PKA enzymatic activity by only 30%. On the other hand, transforming growth factor-beta (TGF beta) slightly amplified the stimulatory action of FSH and antagonized the bFGF inhibitory effect on both LH receptor expression and RII beta synthesis. We report that the protein kinase C (PKC) activator 12-O-tetradecanoylphorbol-13-acetate (TPA), which impaired granulosa cell differentiation, also abolished the RII beta synthesis induced by FSH. The activation of PKC by bFGF in granulosa cells was supported by the following findings: (i) bFGF markedly enhanced the production of diacylglycerol (2.3-fold stimulation at 5 min), the intracellular activator of PKC; (ii) bFGF promoted tight association of PKC to cellular membranes, a process that is believed to correlate with the enzyme activation; (iii) bFGF induced the phosphorylation of an endogenous M(r) 78,000/pI 4.7 protein that appears as a specific PKC substrate; (iv) bFGF mimicked the TPA-induced transmodulation of the epidermal growth factor (EGF) receptor, reducing by 36% the 125I-EGF binding on granulosa cells. We conclude that bFGF may exert its repressive action on RII beta synthesis, PKA activity, and granulosa cell differentiation by primarily targeting PKC activation.

Tyrosine Hydroxylase Induction by Basic Fibroblast Growth Factor and Cyclic AMP Analogs in Striatal Neural Stem Cells: Role of ERK1/ERK2 Mitogen-activated Protein Kinase and Protein Kinase C

“…Results from the present study strongly suggest the participation of PKC in TH expression: (a) the accumulation of inositol monophosphate on bFGF-treated cultures and results from other authors (Oury et al 1992;Cross et al 2002) indicate that bFGF can activate the PLC␥-PKC pathway through the stimulation of FGFRs; (b) staurosporin partially blocks changes in the morphology of the astrocytes promoted by bFGFϩdbcAMP treatment that, as mentioned above, might be necessary for TH induction; and (c) the addition of staurosporin to the cultures inhibits the effects of bFGFϩdbcAMP on TH protein expression in a dose-dependent manner. Although staurosporin might inhibit other protein kinases differently than PKC, the fact that PKC downregulation also reduces the ability of bFGFϩdbcAMP to generate TH-positive cells strongly supports our hypothesis about the participation of PKC in TH induction.…”

Aging-related premature luteinization of granulosa cells is avoided by early oocyte retrieval

“…Therefore, it is possible that hCG administration changes cell sensitivity of the FSH response. This hypothesis is supported by evidence from non-luteinizing GCs, where FSH activates the protein kinase A (PKA) pathway and then induces LHCGR transcription (Oury et al 1992). But luteinization increases the stability of PKA subunit, which inhibited PKA activation by FSH (Gonzalez-Robayna et al 1999).…”

Neuroprotection by Peptide Growth Factors against Anoxia and Nitric Oxide Toxicity Requires Modulation of Protein Kinase C

“…For example, both PKA and cGMP dependent protein kinase have been implicated in the pathogenesis of NO toxicity (Maiese et aI., 1993b). Basic FGF can regulate cAMP levels (Oury et al, 1992) and requires cAMP for mitogenic ac tivity (Chen et aI., 1991;Logan and Logan, 1991). In addition, EGF can modulate both cAMP and cGMP levels in some cell systems (Miyazaki et aI., 1992;Nair et aI., 1993).…”

“…PKC mediates the migratory (Joyce and Meklir, 1992) and trophic re sponses (Abe et al, 1992) of EGF. In addition, bFGF has been shown to activate PKC (Oury et al, 1992) and be dependent on PKC activity (Presta et al, 1991) for cell proliferation. Therefore, we examined whether the protective effects of the trophic factors bFGF and EGF were linked to the regulation of PKC activity.…”