In these slices, we conducted additional recordings in which we analyzed the possibility that acid ceramidase inhibition might interfere with the postsynaptic components of synaptic transmission in CA1 pyramidal cells of the hippocampus.
We concluded, from these electrophysiological experiments, that the influence of acid ceramidase inhibition on synaptic transmission was postsynaptic in origin and specific to the NMDA subtype of glutamate receptors (see Figure 1(d)).
Lysosomal acid ceramidase inhibition, in obvious contrast with 68 kDa Tau isoforms, produced no reliable changes in phosphorylation for the other two isoforms detected and estimated, with the help of molecular weight standards, to be around 62 and 56 kDa (Figure 3(a)).
These data are consistent with the notion that inhibition of acid ceramidase may induce Tau hyperphosphorylation by activating GluN2B-containing NMDA receptors.
Interestingly, however, we noticed that regulation of Tau phosphorylation during lysosomal acid ceramidase inhibition was totally abrogated in slices pretreated with the CaMKII inhibitor KN62(10 [micro]M).
Our data suggest that ceramide accumulation, resulting from lysosomal acid ceramidase inhibition, can enhance NMDA receptor activity via a mechanism involving initially GluN2B receptor phosphorylation.