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The peroxisome proliferator-activated receptor (PPAR) family plays central roles in brown adipose tissue (BAT) adipogenesis and contributes to body temperature maintenance. The transcriptional activity of PPAR family has been shown to be tightly controlled by cellular signal networks. β-arrestins function as major secondary messengers of G protein-coupled receptors (GPCR) signaling by functional interactions with diverse proteins. Here, we report that β-arrestin-1 knock-out mice show enhanced cold tolerance. We found that β-arrestin-1 directly interacts with PPARα and PPARγ through a LXXXLXXXL motif, while D371 in PPARα and L311/N312/D380 in PPARγ are required for their interactions with β-arrestin-1. Further mechanistic studies showed that β-arrestin-1 promotes PPARα- but represses PPARγ-mediated transcriptional activities, providing potential regulatory pathway for BAT function.

Alzheimer's disease (AD) is a progressive and complex neurodegenerative disease in which the γ-secretase-mediated amyloid-β (Aβ) pathology plays an important role. We found that a multifunctional protein, β-arrestin1, facilitated the formation of NCT/APH-1 (anterior pharynx-defective phenotype 1) precomplex and mature γ-secretase complex through its functional interaction with APH-1. Deficiency of β-arrestin1 or inhibition of binding of β-arrestin1 with APH-1 by small peptides reduced Aβ production without affecting Notch processing. Genetic ablation of β-arrestin1 diminished Aβ pathology and behavioral deficits in transgenic AD mice. Moreover, in brains of sporadic AD patients and transgenic AD mice, the expression of β-arrestin1 was upregulated and correlated well with neuropathological severity and senile Aβ plaques. Thus, our study identifies a regulatory mechanism underlying both γ-secretase assembly and AD pathogenesis, and indicates that specific reduction of Aβ pathology can be achieved by regulation of the γ-secretase assembly.

Elucidation of γ-secretase structure and dynamic conformational changes is of importance to drug discovery targeting this enzyme. Electron microscopy analyses provided important structural information, but the dynamic changes of γ-secretase in cells need to be explored further. We found that PS1 internal fluorescence resonance energy transfer (FRET) probes can incorporate into γ-secretase complex and possess secretase activity. Our results from fluorescence lifetime image microscopy (FLIM) and acceptor photobleaching FRET show different PS1 internal FRET when PS1 fluorescent probes expressed alone or with other secretase subunits Aph1aL, Nicastrin, and Pen2, indicating that PS1 internal FRET could be applied for probing conformational change of γ-secretase complex. Further, we accessed whether γ-secretase activity interfering compounds induced different conformational changes of PS1. Our results show that both γ-secretase modulators and inhibitors affect PS1 internal FRET but in different manners. These results demonstrate that FLIM and acceptor photobleaching FRET could be applied to monitor different PS1 conformational changes in γ-secretase.