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Reactive oxygen species regulate heat-shock protein 70 via the JAK/STAT pathway
N R Madamanchi1, S Li, C Patterson
1Program in Molecular Cardiology, University of North Carolina, Chapel Hill, USA. mrunge@med.unc.edu
Abstract:
Reactive oxygen species (ROS) such as hydrogen peroxide (H(2)O(2)) activate intracellular signal transduction pathways implicated in the pathogenesis of cardiovascular disease. H(2)O(2) is a mitogen for rat vascular smooth muscle cells (VSMCs), and protein tyrosine phosphorylation is a critical event in VSMC mitogenesis. Therefore, we investigated whether the mitogenic effects of H(2)O(2), such as stimulation of extracellular signal-regulated kinase (ERK)2, are mediated via activation of cytoplasmic Janus tyrosine kinases (JAKs). JAK2 was activated rapidly in VSMCs treated with H(2)O(2), and signal transducers and activators of transcription (STAT) STAT1 and STAT3 were tyrosine-phosphorylated and translocated to the nucleus in a JAK2-dependent manner. Inhibition of JAK2 activity with AG-490 partially inhibited H(2)O(2)-induced ERK2 activity, suggesting that JAK2 is upstream of the Ras/Raf/mitogen-activated protein kinase-ERK/ERK mitogenic pathway. Because heat-shock proteins (HSPs) can protect cells from ROS, we investigated the effect of H(2)O(2) on HSP expression. H(2)O(2) stimulated HSP70 expression in a time-dependent manner, and AG-490 abolished H(2)O(2)-induced HSP70 expression. H(2)O(2) activated the HSP70 promoter via enhanced binding of STATs to cognate binding sites in the promoter. Regulation of chaperones such as HSP70 via activation of the JAK/STAT pathway suggests that in addition to its growth-promoting effects, this pathway may help VSMCs adapt to oxidative stress.
Insights
Hydrogen peroxide (H2O2) activates Janus tyrosine kinases (JAKs), specifically JAK2, which promotes vascular smooth muscle cell growth and heat-shock protein 70 (HSP70) expression, aiding adaptation to oxidative stress.
Area of Science:
- Cellular signaling
- Cardiovascular research
- Oxidative stress biology
Background:
- Reactive oxygen species (ROS), like hydrogen peroxide (H2O2), are involved in cardiovascular disease pathogenesis.
- H2O2 acts as a mitogen for vascular smooth muscle cells (VSMCs), with protein tyrosine phosphorylation being crucial for this process.
Purpose of the Study:
- To investigate if H2O2-induced mitogenic effects in VSMCs are mediated by Janus tyrosine kinases (JAKs).
- To explore the role of JAK2 in the activation of extracellular signal-regulated kinase (ERK) and heat-shock protein (HSP) expression.
Main Methods:
- VSMCs were treated with H2O2, and JAK2 activation was assessed.
- Signal transducers and activators of transcription (STAT) phosphorylation and nuclear translocation were analyzed.
- The effect of JAK2 inhibition (using AG-490) on ERK2 activity and HSP70 expression was evaluated.
- HSP70 promoter activity was examined in relation to STAT binding.
Main Results:
- H2O2 rapidly activated JAK2 in VSMCs.
- STAT1 and STAT3 were tyrosine-phosphorylated and translocated to the nucleus in a JAK2-dependent manner.
- JAK2 inhibition partially blocked H2O2-induced ERK2 activity and HSP70 expression.
- H2O2 stimulated HSP70 expression, which was dependent on JAK2 and STAT activation of the HSP70 promoter.
Conclusions:
- JAK2 is upstream of the Ras/Raf/MAPK-ERK pathway, mediating H2O2's mitogenic effects on VSMCs.
- The JAK/STAT pathway regulates HSP70 expression, suggesting a role in VSMC adaptation to oxidative stress.
- This pathway has implications for both cell growth and cellular defense mechanisms against ROS in cardiovascular contexts.