Proteomic analysis of rat hippocampal plasma membrane: characterization of potential neuronal-specific plasma membrane proteins.

The hippocampus is a distinct brain structure that is crucial in memory storage and retrieval. To identify comprehensively proteins of hippocampal plasma membrane (PM) and detect the neuronal-specific PM proteins, we performed a proteomic analysis of rat hippocampus PM using the following three technical strategies. First, proteins of the PM were purified by differential and density-gradient centrifugation from hippocampal tissue and separated by one-dimensional electophoresis, digested with trypsin and analyzed by electrospray ionization (ESI) quadrupole time-of-flight (Q-TOF) tandem mass spectrometry (MS/MS). Second, the tryptic peptide mixture from PMs purified from hippocampal tissue using the centrifugation method was analyzed by liquid chromatography ion-trap ESI-MS/MS. Finally, the PM proteins from primary hippocampal neurons purified by a biotin-directed affinity technique were separated by one-dimensional electrophoresis, digested with trypsin and analyzed by ESI-Q-TOF-MS/MS. A total of 345, 452 and 336 non-redundant proteins were identified by each technical procedure respectively. There was a total of 867 non-redundant protein entries, of which 64.9% are integral membrane or membrane-associated proteins. One hundred and eighty-one proteins were detected only in the primary neurons and could be regarded as neuronal PM marker candidates. We also found some hypothetical proteins with no functional annotations that were first found in the hippocampal PM. This work will pave the way for further elucidation of the mechanisms of hippocampal function.