nArgBP2 together with GKAP and SHANK3 forms a dynamic layered structure.

Area of Science:

• Neuroscience
• Cell Biology
• Biochemistry

Background:

• nArgBP2 protein disruption is linked to intellectual disability.
• nArgBP2 is concentrated in excitatory spine synapses and regulates spine structure via a triad with GKAP and SHANK.
• Understanding the precise localization and interaction of these proteins is crucial for synaptic function.

Purpose of the Study:

• To investigate the self-assembly and localization dynamics of nArgBP2, GKAP, and SHANK3 within biomolecular condensates.
• To determine the role of CaMKIIα activation in the structural organization and dispersal of these protein condensates.
• To explore the contribution of protein phase separation to the layered organization of dendritic spines.

Main Methods:

• Co-expression of nArgBP2, GKAP, SHANK3, and CaMKIIα in living fibroblasts.
• Confocal microscopy to visualize protein localization and condensate formation.
• Analysis of protein distribution and segregation within phase-separated condensates under various conditions, including CaMKIIα activation.

Main Results:

• nArgBP2, GKAP, and SHANK3 form distinct layered biomolecular condensates with specific phase preferences (nArgBP2 inner, SHANK3 outer, GKAP in both).
• CaMKIIα localized centrally with peripheral SHANK3 and GKAP, a structure maintained by nArgBP2.
• CaMKIIα activation led to the dispersal of most condensates, resulting in an even protein distribution.

Conclusions:

• Protein segregation through liquid-liquid phase separation contributes to the layered organization observed in dendritic spines.
• The dynamic assembly and disassembly of these condensates, modulated by CaMKIIα, play a role in synaptic structural plasticity.
• These findings provide insights into the molecular mechanisms underlying synaptic organization and potential links to neurological disorders.