Site-Specific Phosphorylation of PSD-95 PDZ Domains Reveals Fine-Tuned Regulation of Protein-Protein Interactions.

Søren W Pedersen, Louise Albertsen, Griffin E Moran, Brié Levesque, Stine B Pedersen, Lina Bartels, Hannah Wapenaar, Fei Ye, Mingjie Zhang, Mark E Bowen, Kristian Strømgaard

ACS chemical biology 2017 Sep 15

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The postsynaptic density protein of 95 kDa (PSD-95) is a key scaffolding protein that controls signaling at synapses in the brain through interactions of its PDZ domains with the C-termini of receptors, ion channels, and enzymes. PSD-95 is highly regulated by phosphorylation. To explore the effect of phosphorylation on PSD-95, we used semisynthetic strategies to introduce phosphorylated amino acids at four positions within the PDZ domains and examined the effects on interactions with a large set of binding partners. We observed complex effects on affinity. Most notably, phosphorylation at Y397 induced a significant increase in affinity for stargazin, as confirmed by NMR and single molecule FRET. Additionally, we compared the effects of phosphorylation to phosphomimetic mutations, which revealed that phosphomimetics are ineffective substitutes for tyrosine phosphorylation. Our strategy to generate site-specifically phosphorylated PDZ domains provides a detailed understanding of the role of phosphorylation in the regulation of PSD-95 interactions.

Citation

Søren W Pedersen, Louise Albertsen, Griffin E Moran, Brié Levesque, Stine B Pedersen, Lina Bartels, Hannah Wapenaar, Fei Ye, Mingjie Zhang, Mark E Bowen, Kristian Strømgaard. Site-Specific Phosphorylation of PSD-95 PDZ Domains Reveals Fine-Tuned Regulation of Protein-Protein Interactions. ACS chemical biology. 2017 Sep 15;12(9):2313-2323