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The kinase inhibitor iso-H7 stimulates rat satellite cell differentiation through a non-protein kinase C pathway by
C Lagord1, M P Leibovitch, G Carpentier
1Laboratoire CRRET, Université Paris, Créteil, France.
Abstract:
We analysed the signaling pathways involved in myogenic differentiation of primary cultures of rat satellite cells using substances targeting the protein kinase C (PKC) and the cAMP protein kinase (PKA) pathways. We have previously shown that iso-H7, which putatively inhibits both PKC and PKA, strongly stimulates satellite cell differentiation, as well as the PKA inhibitor HA1004. In the study reported here, the effects of iso-H7 on satellite cell differentiation were compared to those observed in the presence of agents which reduce PKC activity. It was shown that treatments with the highly specific PKC inhibitor GF109203X or with 12-O-tetradecanoylphorbol 13-acetate (TPA) which induced a partial PKC downregulation, did not significantly alter myogenic differentiation. Northern blot analyses showed that iso-H7 activated the expression of myogenin but not that of MyoD mRNA. Concurrently, iso-H7 increased myosin light-chain mRNA expression. In contrast, TPA had no effect on these syntheses. Taken together, these results showed that iso-H7 did not act intracellularly as a PKC inhibitor but rather as a PKA inhibitor as previously suggested. Our results are compatible with the hypothesis that a reduction in PKA activity controls satellite cell myogenesis through an increased myogenin mRNA expression.
Insights
Iso-H7 stimulates rat satellite cell differentiation by inhibiting cAMP protein kinase (PKA), not protein kinase C (PKC). Reduced PKA activity enhances myogenin mRNA expression, controlling satellite cell myogenesis.
Area of Science:
- Muscle biology
- Cell signaling
- Biochemistry
Background:
- Satellite cells are crucial for muscle regeneration and differentiation.
- Protein kinase C (PKC) and cAMP protein kinase (PKA) pathways play roles in myogenic differentiation.
- Previous studies suggested iso-H7 stimulates differentiation and inhibits both PKC and PKA.
Purpose of the Study:
- To investigate the specific roles of PKC and PKA in rat satellite cell differentiation.
- To determine whether iso-H7 acts as a PKC or PKA inhibitor in this context.
- To elucidate the signaling mechanisms controlling satellite cell myogenesis.
Main Methods:
- Primary cultures of rat satellite cells were treated with iso-H7, HA1004, GF109203X, and 12-O-tetradecanoylphorbol 13-acetate (TPA).
- Myogenic differentiation was assessed.
- Northern blot analyses were performed to measure mRNA expression of myogenin, MyoD, and myosin light-chain.
Main Results:
- Iso-H7 and HA1004 (PKA inhibitor) strongly stimulated satellite cell differentiation.
- Specific PKC inhibitors (GF109203X) and PKC downregulators (TPA) did not significantly alter differentiation.
- Iso-H7 increased myogenin and myosin light-chain mRNA expression, but not MyoD mRNA, while TPA had no effect on these mRNAs.
Conclusions:
- Iso-H7 functions as a PKA inhibitor, not a PKC inhibitor, in rat satellite cells.
- Reduced PKA activity is a key regulator of satellite cell myogenesis.
- Increased myogenin mRNA expression is a downstream effect of PKA inhibition in this process.