# A previously unrecognized β/γ-secretases complex as a therapeutic target for AD

> **NIH NIH R03** · BRIGHAM AND WOMEN'S HOSPITAL · 2020 · $179,000

## Abstract

The production of Aβ peptides occurs throughout life in mammals, and their progressive accumulation in
human brain is an invariant and necessary feature in all cases of Alzheimer’s disease. The production of Aβ
requires proteolysis by β-secretase followed by γ-secretase, and understanding the process underlying these
sequential cleavages is fundamental to cell biology. In particular, identifying the mechanism by which holo-APP
is cleaved sequentially to Aβ peptides is critical for designing safe and effective inhibitors and modulators of
this process in order to treat and ultimately prevent a major portion of age-related cognitive decline. Using
biochemical and cell biological approaches, we recently discovered that APP processing by α- and γ-
secretases can occur in a large, multi-protease fraction that allows for efficient sequential cleavages of
substrates within a high molecular weight (HMW) complex stabilized by members of the tetraspanin web(1).
This unexpected finding about coordinated α/γ processing raised the question of whether a similar mechanism
exists for the β- and γ-secretase cleavages which generates Aβ from APP and could create analogous protein
fragments from many other β/γ substrates. In the last few years, there has been substantial progress in
deciphering the 20-TMD structure of the PS/γ-secretase complex(2). However, we still know very little about
the cell biological mechanism of the two-step processing that defines RIP. It has been assumed that the post-
sheddase CTFs are trafficked to a membrane site where γ-secretase is active(3), but how such presumptive
movement within the membrane occurs so that the CTFs correctly finds and enters the docking and active
sites of γ-secretase remains a mystery. It is this obligatory, 2-step feature of RIP that we probe in this R03
application by an early stage investigator. To address these mechanisms and also test the feasibility of
targeting the β/γ complex, we propose the following two Specific Aims. First, we will confirm and characterize
a novel, catalytically active β/γ-secretase complex we recently discovered and isolated from cultured cells,
mouse brain and human brain by using 1) protein-protein-interaction approaches including co-IP, native PAGE,
FPLC, PLA, NanoBiT (reversible with kinetics) and BiFC (irreversible), and 2) a novel experimental paradigm
the PI invented to perform functional enzymatic characterization of β/γ-secretases through a collection of new
homemade Aβ ELISA assays. Second, we will search for regulatory components associated with this β/γ-
secretase complex through 1) protein identification and quantitative proteomics analysis of β/γ-secretases
complexes isolated from cultured cells and human brain; 2) genetic manipulation of potential hits from
proteomic screening to explore complex assembly and stabilization; and 3) test and design small compounds
based on the β/γ-mechanism we’ve discovered. The completion of the proposed study will provide mechanistic
i...

## Key facts

- **NIH application ID:** 9902298
- **Project number:** 5R03AG063046-02
- **Recipient organization:** BRIGHAM AND WOMEN'S HOSPITAL
- **Principal Investigator:** Lei Liu
- **Activity code:** R03 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $179,000
- **Award type:** 5
- **Project period:** 2019-04-01 → 2021-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9902298

## Citation

> US National Institutes of Health, RePORTER application 9902298, A previously unrecognized β/γ-secretases complex as a therapeutic target for AD (5R03AG063046-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9902298. Licensed CC0.

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