Synaptic activity bidirectionally regulates a novel sequence-specific S-Q phosphoproteome in neurons

Area of Science:

• Neuroscience
• Molecular Biology
• Cell Biology

Background:

• Protein phosphorylation is vital for neuronal functions like transcription, translation, cell viability, and synaptic plasticity.
• Specific enzymes and substrates link neuronal activity to these functions, but many remain uncharacterized.

Purpose of the Study:

• To identify and characterize a novel, synaptically regulated neuronal phosphoproteome.
• To investigate the role of specific kinases and motifs in neuronal signaling.

Main Methods:

• Phosphoproteomics was used to identify SQ-containing substrates.
• Bicuculline and NMDA applications were used to study the activation and inactivation of the phosphoproteome.
• Immunohistochemistry and pharmacology were employed to determine kinase localization and function.

Main Results:

• A novel SQ (serine/threonine-glutamine) phosphoproteome was identified, predominantly localized to dendrites and synapses.
• Bicuculline application induced SQ phosphoproteome activation via calcium influx, while NMDA application inactivated it.
• The SQ motif kinase Ataxia-telangiectasia mutated (ATM) localizes to dendrites and is activated by bicuculline.
• ATM and ATR kinase activity up-regulate neuronal SQ substrates.
• Over 150 SQ-containing substrates were identified, with phosphorylation bidirectionally regulated by synaptic activity.

Conclusions:

• Synaptic activity bidirectionally regulates a novel SQ phosphoproteome in neurons.
• Calcium influx and specific kinases like ATM play key roles in modulating this phosphoproteome.
• This discovery provides new targets for understanding neuronal function and plasticity.