# Mechanisms of Gamma-Secretase

> **NIH NIH R01** · UNIVERSITY OF KANSAS LAWRENCE · 2020 · $291,638

## Abstract

Project Summary
 γ-Secretase is a membrane-embedded protease complex with presenilin as its catalytic component. This
complex cleaves the transmembrane domains (TMDs) of a wide variety of type I integral membrane proteins
after their ectodomain release by sheddases. Among these substrates are Notch and the amyloid β-protein
precursor (APP). TMD cleavage of Notch receptors is part of cell signaling mechanisms essential to metazoan
biology and dysregulated in cancer, and TMD cleavage of APP to amyloid β-protein (Aβ) is essential to the
pathogenesis of Alzheimer's disease (AD). The overarching goal of this proposal is to elucidate how
intramembrane proteolysis is accomplished by γ-secretase. Toward this end, we will address three central
open questions regarding the mechanism of this complex enzyme that is so critical in biology and medicine.
(1) How does γ-secretase recognize substrates? As the enzyme cleaves the TMD of substrate, we seek to
understand the role of helicity in substrate recognition. In addition, we have used a recent high-resolution
structure of the protease complex to design experiments to identify the gate on presenilin that allows access of
substrate TMD into the active site. (2) How does γ-secretase carry out processive proteolysis? γ-Secretase
initially cleaves substrates within their TMDs close to the cytosolic interface, followed by processive
carboxypeptidase trimming resulting in secreted peptides. We will address whether the longer Aβ peptide
intermediates have higher affinity for the enzyme, allowing more time for trimming, than shorter Aβ peptides.
We will also address whether peptide product intermediates remain bound or dissociate from the enzyme prior
to further trimming. (3) How does γ-secretase unwind helical TMD substrates for proteolysis? We have
designed a series of hybrid helical peptide/transition-state analog inhibitors to mimic the TMD substrate bound
to the enzyme in the transition state. In collaboration with a leading structural biology lab, structure elucidation
of the most potent hybrid inhibitor bound to active γ-secretase will be determined to understand the structural
basis of the γ-secretase mechanism of action.

## Key facts

- **NIH application ID:** 10004095
- **Project number:** 5R01GM122894-04
- **Recipient organization:** UNIVERSITY OF KANSAS LAWRENCE
- **Principal Investigator:** Michael S Wolfe
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $291,638
- **Award type:** 5
- **Project period:** 2017-09-20 → 2022-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10004095

## Citation

> US National Institutes of Health, RePORTER application 10004095, Mechanisms of Gamma-Secretase (5R01GM122894-04). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10004095. Licensed CC0.

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