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Modulation of amyloid precursor protein cleavage by γ-secretase activating protein through phase separation.

ABSTRACT: Aberrant cleavage of amyloid precursor protein (APP) by γ-secretase is closely associated with Alzheimer’s disease (AD). γ-secretase activating protein (GSAP) specifically promotes γ-secretase–mediated cleavage of APP. However, the underlying mechanism remains enigmatic. Here, we demonstrate that the 16-kDa C-terminal fragment of GSAP (GSAP-16K) undergoes phase separation in vitro and forms puncta-like condensates in cells. GSAP-16K exerts dual modulation on γ-secretase cleavage; GSAP-16K in dilute phase increases APP–C-terminal 99-residue fragment (C99) cleavage toward preferred production of β-amyloid peptide 42 (Aβ42), but GSAP-16K condensates reduce APP-C99 cleavage through substrate sequestration. Notably, the Aβ42/Aβ40 ratio is markedly elevated with increasing concentrations of GSAP-16K. GSAP-16K stably associates with APP-C99 through specific sequence elements. These findings mechanistically explain GSAP-mediated modulation of γ-secretase activity that may have ramifications on the development of potential therapeutics.

SUBMITTER: Jin C

PROVIDER: S-EPMC8944281 | biostudies-literature | 2022 Mar

REPOSITORIES: biostudies-literature

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Modulation of amyloid precursor protein cleavage by γ-secretase activating protein through phase separation.

Jin Chen C Wang Jiaoni J Wang Yumeng Y Jia Bojun B Guo Xuefei X Yang Guanghui G Xu Peng P Greengard Paul P Zhou Rui R Shi Yigong Y

Proceedings of the National Academy of Sciences of the United States of America 20220317 12

Aberrant cleavage of amyloid precursor protein (APP) by γ-secretase is closely associated with Alzheimer’s disease (AD). γ-secretase activating protein (GSAP) specifically promotes γ-secretase–mediated cleavage of APP. However, the underlying mechanism remains enigmatic. Here, we demonstrate that the 16-kDa C-terminal fragment of GSAP (GSAP-16K) undergoes phase separation in vitro and forms puncta-like condensates in cells. GSAP-16K exerts dual modulation on γ-secretase cleavage; GSAP-16K in dil ...[more]

PMID: 35298330

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Project description:INTRODUCTION: Inhibition of gamma-secretase presents a direct target for lowering A? production in the brain as a therapy for Alzheimer's disease (AD). However, gamma-secretase is known to process multiple substrates in addition to amyloid precursor protein (APP), most notably Notch, which has limited clinical development of inhibitors targeting this enzyme. It has been postulated that APP substrate selective inhibitors of gamma-secretase would be preferable to non-selective inhibitors from a safety perspective for AD therapy. METHODS: In vitro assays monitoring inhibitor potencies at APP ?-site cleavage (equivalent to A?40), and Notch ?-site cleavage, in conjunction with a single cell assay to simultaneously monitor selectivity for inhibition of A? production vs. Notch signaling were developed to discover APP selective gamma-secretase inhibitors. In vivo efficacy for acute reduction of brain A? was determined in the PDAPP transgene model of AD, as well as in wild-type FVB strain mice. In vivo selectivity was determined following seven days x twice per day (b.i.d.) treatment with 15 mg/kg/dose to 1,000 mg/kg/dose ELN475516, and monitoring brain A? reduction vs. Notch signaling endpoints in periphery. RESULTS: The APP selective gamma-secretase inhibitors ELN318463 and ELN475516 reported here behave as classic gamma-secretase inhibitors, demonstrate 75- to 120-fold selectivity for inhibiting A? production compared with Notch signaling in cells, and displace an active site directed inhibitor at very high concentrations only in the presence of substrate. ELN318463 demonstrated discordant efficacy for reduction of brain A? in the PDAPP compared with wild-type FVB, not observed with ELN475516. Improved in vivo safety of ELN475516 was demonstrated in the 7d repeat dose study in wild-type mice, where a 33% reduction of brain A? was observed in mice terminated three hours post last dose at the lowest dose of inhibitor tested. No overt in-life or post-mortem indications of systemic toxicity, nor RNA and histological end-points indicative of toxicity attributable to inhibition of Notch signaling were observed at any dose tested. CONCLUSIONS: The discordant in vivo activity of ELN318463 suggests that the potency of gamma-secretase inhibitors in AD transgenic mice should be corroborated in wild-type mice. The discovery of ELN475516 demonstrates that it is possible to develop APP selective gamma-secretase inhibitors with potential for treatment for AD.

Dataset Information

Modulation of amyloid precursor protein cleavage by γ-secretase activating protein through phase separation.

Publications

Modulation of amyloid precursor protein cleavage by γ-secretase activating protein through phase separation.

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