Hydrogen peroxide activates p70(S6k) signaling pathway

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• p70S6k is crucial for cell cycle progression from G0/G1 to S phase.
• p70S6k regulates protein synthesis by up-regulating specific mRNA transcripts.
• The role of reactive oxygen species (ROS) in p70S6k activation was unclear.

Purpose of the Study:

• To investigate the role of ROS in the activation of p70S6k.
• To elucidate the signaling pathway involved in ROS-mediated p70S6k activation.
• To determine if ROS act as messengers in growth factor-induced p70S6k signaling.

Main Methods:

• Treatment of JB6 mouse epidermal cells with hydrogen peroxide (H2O2).
• Analysis of p70S6k, p90Rsk, and MAPK phosphorylation.
• Use of specific inhibitors (rapamycin, wortmannin, Ro-31-8220) and Ca2+ chelation.
• Assessment of ROS generation by growth factors (PDGF, EGF) and catalase treatment.

Main Results:

• H2O2 treatment induced dose-dependent and transient activation of p70S6k, p90Rsk, and MAPK.
• ROS-induced p70S6k activation was upstream of phosphatidylinositol 3-kinase and FRAP/RAFT.
• Ca2+ chelation inhibited ROS-induced p70S6k activation, indicating Ca2+ as a mediator.
• PKC activation was not required for ROS-induced p70S6k activation.
• Growth factors rapidly increased H2O2, leading to p70S6k activation, which was blocked by catalase.

Conclusions:

• ROS play a significant role in p70S6k activation.
• ROS act as intracellular messengers in growth factor-induced p70S6k signaling pathways.
• The findings provide insight into cell cycle regulation and signaling mechanisms.