Figure 7. Schematic representation of the proposed 5-HT_4d receptor-stimulated signaling pathway leading to increased sAPPα production.

The proteins involved in 5-HT_4d receptor-mediated non-amyloidogenic APP shedding are shown with green circles while orange circles and red characters indicate proteins or second messengers that were tested but were ineffective in modulating 5-HT_4d receptor-stimulated sAPPα release. The dotted lines with the question marks indicate remaining areas of investigation for further elucidation of the molecular mechanism of α-secretase activation. cAMP-dependent pathway of α-secretase induction was previously reported and is depicted as a plausible way for 5-HT_4d receptor-mediated sAPPα release [15].