S1P phosphatase activity increases in temporal GM of AD brains. Total S1P phosphatase activity in hippocampus (A) and temporal GM (B) extracts of control (n = 9), Braak stage I/II (n = 8), Braak III/IV (n = 7), and Braak V/VI (n = 10) brains. Overall association between S1P phosphatase activity activity and Braak stage was significant (P < 0.0001 by one-way ANOVA) for temporal GM but not hippocampus (P = 0.063). Sgpp1 (C) and Sgpp2 (D) protein levels in the temporal GM tissue extracts were determined by western blotting and normalised to housekeeping gene β-actin. (E) Example western blots for Sgpp1 and Sgpp2 protein. Braak stage is indicated for each sample.