Site-specific phosphorylation of PSD-95 dynamically regulates the postsynaptic density as observed by phase...

Area of Science:

• Neuroscience
• Molecular Biology
• Cell Biology

Background:

• Postsynaptic density protein 95 (PSD-95) is a crucial scaffolding protein in excitatory glutamatergic neurons.
• PSD-95 organizes signaling complexes via its PSD/Dlg/ZO domains, but its regulation by phosphorylation is poorly understood due to technical challenges.

Purpose of the Study:

• To investigate the molecular details of PSD-95 regulation by phosphorylation.
• To examine how site-specific phosphorylations impact PSD-95 binding interactions and phase separation.

Main Methods:

• Genetically engineered 11 phosphorylated variants of PSD-95, introducing site-specific phosphorylations.
• Assessed the effects of these variants on binding to known interaction partners, including GluN2B and stargazin.
• Analyzed the impact of phosphorylation on the phase separation of PSD-95 complexes.

Main Results:

• Identified two novel phosphorylation sites on PSD-95 with opposing effects on complex formation.
• Phosphorylation at Ser78 inhibited phase separation with GluN2B and stargazin.
• Phosphorylation at Ser116 promoted phase separation specifically with stargazin.

Conclusions:

• Site-specific phosphorylation dynamically regulates PSD-95 interactions and phase separation.
• These findings provide new insights into the molecular mechanisms governing PSD-95 function in the postsynaptic density.
• Understanding PSD-95 phosphorylation is key to deciphering the dynamics of excitatory synapses.