Posttranslational modifications of signaling proteins such as phosphorylation/dephosphorylation and oxidation/reduction cycles are critical events in the action of membrane receptors, modulating their function. In general, the intercommunication between different types of membrane receptors involve protein phosphorylation of receptors and downstream activation of many protein kinases (second messenger-dependent kinases: PKC, PKA; phosphoinositide 3-kinase: PI3K, phosphoinositide-dependent kinases: PDK1. Protein phosphatases have a key role in this regulation mechanism that amplified the extracellular stimuli; many protein phosphatases have a constitutive activity that maintain proteins in the non-phosphorylated state.
Activation of membrane receptors induces the production of reactive oxygen species that by modulating the activity of kinases and/or phosphatases alter the phosphorylation state of key regulatory proteins in signal transduction pathways. These processes (phosphorylation/dephosphorylation and oxidation/reduction) allow integration of multiples signals in the cell.
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