Identification of activity-regulated proteins in the postsynaptic density fraction.

The postsynaptic density (PSD) at synapses is a specialized submembranous structure where neurotransmitter receptors are linked to cytoskeleton and signalling molecules. Activity-dependent dynamic change in the components of the PSD is a mechanism of synaptic plasticity. Identification of the PSD proteins and examination of their modulations dependent on synaptic activity will be valuable for an understanding of the molecular basis of learning and memory. We attempted here to identify proteins in the PSD fraction by two-dimensional (2D) gel electrophoresis and mass spectrometry. About 1.7 x 103 protein spots were detected on 2D gels. A total of 90 spots were identified, containing 47 different protein species. In addition to previously identified PSD proteins such as PSD-95/SAP90, several new proteins were identified in the PSD fraction. They included stomatin-like protein 2 and NIPSNAP1. We also examined activity-dependent modulations of PSD proteins by 2D gel electrophoresis. The spot concentration of G protein beta subunit 5 and NIPSNAP1 increased 2 h after kainate treatment that caused generalized seizures. These results indicate that the combination of 2D gel electrophoresis and mass spectrometry is an excellent tool for the identification of activity-regulated PSD proteins.