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Stimulation of multiple MAPK pathways by mechanical overload in the perfused amphibian heart
I K Aggeli1, C Gaitanaki, A Lazou
1Department of Animal and Human Physiology, School of Biology, Faculty of Sciences, University of Athens, Panepistimioupolis, Athens 157 84, Greece.
Abstract:
The mitogen-activated protein kinase (MAPK) signal transduction pathway activated by mechanical stress was investigated in the isolated perfused amphibian (Rana ridibunda) heart. High perfusion pressure induced the rapid (30 s) and prolonged (30 min) phosphorylation of a p43-extracellular regulated kinase, a response almost completely inhibited by 25 microM PD-98059. c-Jun NH2-terminal kinase (JNK) was also phosphorylated with maximal values attained at 15 min and remained elevated over 30 min. In-gel kinase assays verified that phosphorylated JNKs are active, phosphorylating the transcription factor c-Jun. Furthermore, pressure overload rapidly stimulated the p38-MAPK phosphorylation (30 s), a transient process (5 min) abolished by 1 microM SB-203580. In-gel kinase assays revealed that with phosphorylation, active p38-MAPKs phosphorylate their substrate MAP kinase-activated protein kinase 2. Biochemical analysis along with immunohistochemical studies showed that with activation, the three MAPK subfamily members examined are localized not only in the cytoplasm but in the nucleus as well. Present results therefore demonstrate for the first time in an amphibian species the involvement of multiple MAPK pathways in the mechanical overload-induced adaptive responses of the heart as well as their possible physiological roles.
Insights
Mechanical stress activates multiple mitogen-activated protein kinase (MAPK) pathways in amphibian hearts. These pathways, including extracellular regulated kinase, c-Jun NH2-terminal kinase, and p38-MAPK, are crucial for the heart
Area of Science:
- Cardiovascular Physiology
- Molecular Biology
- Signal Transduction
Background:
- Mechanical stress is a significant factor influencing cardiac function.
- Mitogen-activated protein kinase (MAPK) pathways are involved in cellular responses to stress.
- Understanding these pathways in non-mammalian vertebrates provides comparative insights into cardiac adaptation.
Purpose of the Study:
- To investigate the role of MAPK signal transduction pathways in response to mechanical stress in the amphibian heart.
- To identify specific MAPK members activated by pressure overload.
- To determine the subcellular localization and physiological relevance of activated MAPKs.
Main Methods:
- Isolated perfused amphibian (Rana ridibunda) heart model.
- High perfusion pressure applied to induce mechanical stress.
- Western blotting and in-gel kinase assays to detect MAPK phosphorylation and activity.
- Biochemical analysis and immunohistochemistry for subcellular localization.
Main Results:
- High perfusion pressure rapidly induced phosphorylation of extracellular regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK), and p38-MAPK.
- In-gel kinase assays confirmed the activation of JNK and p38-MAPK pathways.
- Activated MAPKs (ERK, JNK, p38) were found in both the cytoplasm and nucleus.
- Specific inhibitors (PD-98059 for ERK, SB-203580 for p38) demonstrated pathway specificity.
Conclusions:
- Multiple MAPK pathways (ERK, JNK, p38) are activated by mechanical stress in the amphibian heart.
- These activated MAPKs translocate to the nucleus, suggesting roles in transcriptional regulation.
- The findings highlight the conserved nature of MAPK signaling in cardiac mechanical adaptation across species.