In the rat, mouse and gerbil cortex and hippocampus, subcellular fractionation reveals a significant enrichment of Kal7 at the PSD [3,17,18]. We prepared PSDs from mouse striatum to examine the distribution of the different Kalirin isoforms in this brain region (Figure 6). The distributions of BiP, an ER resident chaperone, and the NR2B subunit of the NMDA receptor, were used to verify the success of the fractionation scheme. As expected, BiP was enriched in the P3 fraction, which contains ER, Golgi and other intracellular membranous compartments, and NR2B was enriched in the PSD fraction. Cytosol was enriched in Kal12 and Kal9 and was devoid of Kal7. Kal7 was enriched in the PSD fraction, which also contained detectable amounts of Kal12 and Kal9, but no detectable ΔKal7.
