Progesterone receptor phosphorylation complexities in defining a functional role.
All steroid receptors are phosphoproteins and several, including progesterone receptors (PRs), become hyperphosphorylated upon binding of ligand. PR phosphorylation is complex, occurring in different cellular compartments and perhaps requiring multiple serine kinases. A model that is emerging proposes that PR phosphorylation is progressive, occurring in at least a three-stage cascade. However, the functional significance of this phosphorylation cascade remains unclear.
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Glenn S. Takimoto and Kathryn B. Horiwitz are at the Division of Endocrinology, University of Colorado Health Sciences Center, Denver, CO 80262, USA.
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