Amyloid-β Protein Precursor Regulates Depolarization-Induced Calcium-Mediated Synaptic Signaling in Brain Slices

Abstract

Background: Coordinated calcium influx upon neuronal depolarization activates pathways that phosphorylate CaMKII, ERKs, and the transcription factor CREB and, therefore, expression of pro-survival and neuroprotective genes. Recent evidence indicates that amyloid-␤ protein precursor (A␤PP) is trafficked to synapses and promotes their formation. At the synapse, A␤PP interacts with synaptic proteins involved in vesicle exocytosis and affects calcium channel function. Objective: Herein, we examined the role of A␤PP in depolarization-induced calcium-mediated signaling using acute cerebral slices from wild-type C57bl/6 mice and A␤PP-/-C57bl/6 mice. Methods: Depolarization of acute cerebral slices from wild-type C57bl/6 and A␤PP-/-C57bl/6 mice was used to induce synaptic signaling. Protein levels were examined by western blot and calcium dynamics were assessed using primary neuronal cultures. Results: In the absence of A␤PP, decreased pCaMKII and pERKs levels were observed. This decrease was sensitive to the inhibition of N-and P/Q-type Voltage Gated Calcium Channels (N-and P/Q-VGCCs) by ω-conotoxin GVIA and ω-conotoxin MVIIC, respectively, but not to inhibition of L-type VGCCs by nifedipine. However, the absence of A␤PP did not result in a statistically significant decrease of pCREB, which is a known substrate of pERKs. Finally, using calcium imaging, we found that down regulation of A␤PP in cortical neurons results in a decreased response to depolarization and altered kinetics of calcium response. Conclusion: A␤PP regulates synaptic activity-mediated neuronal signaling by affecting N-and P/Q-VGCCs.

Cav3 T-Type Voltage-Gated Ca2+ Channels and the Amyloidogenic Environment: Pathophysiology and Implications on Pharmacotherapy and Pharmacovigilance

“…In addition, APP was shown to regulate depolarization-induced Ca 2+ -mediated synaptic signaling in brain slices via modification of trafficking to synapses and promotion of their formation [ 211 ]. On the synaptic level, APP interacts with synaptic proteins engaged in vesicle exocytosis and modulates Ca 2+ channel function.…”

“…This decrement was susceptible to the inhibition of Ca v 2.1 P/Q- and Ca v 2.2 N-type VGCCs by ω-conotoxin GVIA and ω-conotoxin MVIIC, respectively. However, it turned out to be insensitive to inhibition of L-type VGCCs by the DHP nifedipine [ 211 ]. These findings illustrate that APP also regulates synaptic-activity-mediated neuronal signaling by affecting P/Q- and N-type VGCCs.…”