Hierarchical Phosphorylation of Tyrosine Hydroxylase is Dependent on the Activation Sequence of Signaling Pathways. Protein phosphorylation is a fundamental process in biology. It controls protein expression and function in all cells. Hierarchical phosphorylation is defined as the phosphorylation of a protein at one site leading to an altered phosphorylation at another site on the same protein and an altered biological outcome. We have discovered that the enzyme tyrosine hydroxylase undergoes a ....Hierarchical Phosphorylation of Tyrosine Hydroxylase is Dependent on the Activation Sequence of Signaling Pathways. Protein phosphorylation is a fundamental process in biology. It controls protein expression and function in all cells. Hierarchical phosphorylation is defined as the phosphorylation of a protein at one site leading to an altered phosphorylation at another site on the same protein and an altered biological outcome. We have discovered that the enzyme tyrosine hydroxylase undergoes a form of hierarchical phosphorylation not previously reported. Here we examine hierarchical phosphorylation in rat and human tyrosine hydroxylase and its functional consequence in intact cells. The approaches and methods developed will also be applicable to investigation of hierarchical phosphorylation in other proteins.Read moreRead less