Involvement of individual hippocampal signaling protein levels in spatial memory formation is strain-dependent

Although a series of signaling cascades involved in spatial memory have been identified, their link to spatial memory and strain-dependent expression has not been reported so far. Hippocampal levels of the abovementioned signaling proteins were determined in laboratory inbred strain C57BL/6J, the wild-derived inbred strain PWD/PhJ and the wild caught mouse Apodemus sylvaticus (AS) by immunoblotting. The resulting hippocampal protein levels were correlated with results from MWM. Hippocampal signaling protein (hSP) levels were tested also in yoked controls. Within-strain comparison between trained and yoked controls revealed significant differences between levels of Phospho-CaMKII (alpha), Phospho-CREB, Egr-1, c-Src, Phospho-ERK5, Phospho-MEK5 and NOS1 in all of the three strains tested. In addition, the three strains revealed different involvement of individual hSP levels clearly indicating that individual mouse strains were linked to individual hSPs in spatial memory. Phospho-ERK5 levels were not detectable in hippocampi of yoked controls of each strain. We learn from this study that a series of hSPs are associated with spatial memory and that different hSPs are linked to spatial memory in different strains that show different outcome in the MWM. Even correlational patterns in the individual hSPs differed between mouse strains. This is of importance for the interpretation of previous studies on the abovementioned signaling cascades as well as for the design of future studies on these hippocampal proteins. It is intriguing that individual mouse strains, laboratory or wild caught, may use different signaling pathways for spatial memory in the Morris water maze.     

Mass spectrometrical characterisation of mouse and rat synapsin isoforms 2a and 2b

Synapsin 2 proteins are key elements of the synaptic machinery and still hold the centre stage in neuroscience research. Although fully sequenced at the nucleic acid level in mouse and rat, structural information on amino acid sequences and post-translational modifications (PTMs) is limited. Knowledge on protein sequences and PTMs, however, is mandatory for several purposes including conformational studies and the generation of antibodies. Hippocampal proteins from rat and mouse were extracted, run on two-dimensional gel electrophoresis and multi-enzyme digestion was carried out to generate peptides for mass spectrometrical analysis [nano-LC-ESI-(CID/ETD)-MS/MS]. As much as 12 synapsin 2 proteins (6 alpha and 6 beta isoforms) in the mouse and 13 synapsin 2 proteins (6 alpha and 7 beta isoforms) were observed in the rat. Protein sequences were highly identical to nucleic acid sequences, and only few amino acid exchanges probably representing polymorphisms or sequence conflicts were detected. Mouse and rat synapsins 2a differed in three amino acids, while rat and mouse synapsins 2b differed in two amino acids. As much as 13 phosphorylation sites were determined by MS/MS data in rat and mouse hippocampus and 5 were verified by phosphatase treatment. These findings are important for interpretation of previous results and design of future studies on synapsins.