High resolution

Module 2: Figure plasma membrane ROS formation

Receptor-dependent reactive oxygen species (ROS) formation at the plasma membrane.

The formation of reactive oxygen species (ROS) occurs in response to many external signals such as cytokines, growth factors and hormones. In many cases, these signals activate receptors coupled to PtdIns 3-kinase (PI 3-K) which produces PtdIns3,4,5P3 (PIP3) that then acts through Rac to stimulate NADPH oxidase at the plasma membrane. An electron is removed from NADPH and transferred to oxygen to form superoxide radical (O2−•). This O2−• is then transformed by the addition of further electrons by superoxide dismutase (SOD) to form hydrogen peroxide (H2O2). There is a positive-feedback loop that will amplify the redox signalling pathway because one of the actions of H2O2 is to inhibit the enzyme phosphatase and tensin homologue deleted on chromosome 10 (PTEN) that hydrolyses PIP3.