https://www.selleckchem.com/products/fasoracetam-ns-105.html However, further extension of CTEP treatment for 36 weeks was found ineffective in reversing memory deficit, neurogliosis, or Aβ-related pathology. We found that this loss in CTEP efficacy in 15 month old APPswe/PS1ΔE9 mice was due to the abolished contribution of ZBTB16 and mTOR-mediated signaling to AD neuropathology at this advanced disease stage. Our findings indicate that the contribution of pathological mGluR5-signaling to AD may shift as the disease progresses. Thus, we provide the first evidence that the underlying pathophysiological mechanism(s) of AD may unfold along the course of the disease and treatment strategies should be modified accordingly to ensure maximal therapeutic outcomes. Copyright © 2020 American Chemical Society.The histamine H4 receptor (H4R) activates Gαi-mediated signaling and recruits β-arrestin2 upon stimulation with histamine. β-Arrestins play a regulatory role in G protein-coupled receptor (GPCR) signaling by interacting with phosphorylated serine and threonine residues in the GPCR C-terminal tail and intracellular loop 3, resulting in receptor desensitization and internalization. Using bioluminescence resonance energy transfer (BRET)-based biosensors, we show that G protein-coupled receptor kinases (GRK) 2 and 3 are more quickly recruited to the H4R than β-arrestin1 and 2 upon agonist stimulation, whereas receptor internalization dynamics toward early endosomes was slower. Alanine-substitution revealed that a serine cluster at the distal end of the H4R C-terminal tail is essential for the recruitment of β-arrestin1/2, and consequently, receptor internalization and desensitization of G protein-driven extracellular-signal-regulated kinase (ERK)1/2 phosphorylation and label-free cellular impedance. In contrast, alanine substitution of serines and threonines in the intracellular loop 3 of the H4R did not affect β-arrestin2 recruitment and receptor desensitization, but reduced