Abstract
Anisomycin or osmotic stress induced by sorbitol activated c-Jun N-terminal protein kinases (JNKs) in ventricular myocytes cultured from neonatal rat hearts. After 15-30 min, JNK was activated by 10-20-fold. Activation by anisomycin was transient, but that by sorbitol was sustained for at least 4 h. In-gel JNK assays confirmed activation of two renaturable JNKs of 46 and 55 kDa (JNK-46 and JNK-55, respectively). An antibody against human JNK1 immunoprecipitated JNK-46 activity. Endothelin-1, an activator of extracellular signal-regulated protein kinases (ERKs), also transiently activated JNKs by 2-5-fold after 30 min. Phorbol 12-myristate 13-acetate did not activate the JNKs although it activated ERK1 and ERK2, which phosphorylated the c-Jun transactivation domain in vitro. ATP depletion and repletion achieved by incubation in cyanide+deoxyglucose and its subsequent removal from the medium activated the ERKs but failed to activate the JNKs. Sorbitol (but not anisomycin) also stimulated the ERKs. Sorbitol-stimulated JNK activity could be resolved into three peaks by fast protein liquid chromatography on a Mono Q column. The two major peaks contained JNK-46 or JNK-55. These results demonstrate that cellular stresses differentially activate the JNKs and ERKs and that there may be "cross-talk" between these MAPK pathways.
Highlights
The mammalian ventricular myocyte is a terminally differentiated cell that responds to neurohumoral or mechanical stimuli by adaptational growth in the absence of cell division [1]
Regulation via the serum response element involves the phosphorylation of the ternary complex factor p62TCF by the extracellular signal-regulated protein kinase (ERK) subfamily of mitogen-activated protein kinases (MAPKs)2 [4], whereas the sisinducible element is involved in receptor protein tyrosine kinase signaling [3]
Lated protein kinases additional to ERKs, we have examined the activation of isoforms of Jun N-terminal protein kinases (JNKs) and ERKs in cultured neonatal rat ventricular myocytes exposed to cellular stresses or hypertrophic neurohumoral stimuli
Summary
The mammalian ventricular myocyte is a terminally differentiated cell that responds to neurohumoral or mechanical stimuli by adaptational growth in the absence of cell division (hypertrophy) [1]. We used a solid-phase kinase assay [10] to identify protein kinases that bind to and phosphorylate the N-terminal domain of c-Jun. Exposure of ventricular myocytes to 0.5 M sorbitol or 50 ng/ml anisomycin produced 2–5-fold changes in JNK activity after 5 min, and this increased to 10 –20-fold changes after 15–30 min (Fig. 1A). PMA does not activate JNK in solid-phase kinase assays (Fig. 1A).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
