# Structure-function studies of DELE1-mediated activation of the integrated stress response

> **NIH NIH R01** · SCRIPPS RESEARCH INSTITUTE, THE · 2024 · $632,667

## Abstract

ABSTRACT
Protein homeostasis (proteostasis) is tightly regulated by an intricate network of finely tuned cellular pathways.
Among the pathways required for responding to internal or external cellular insults is the Integrated Stress
Response, which halts general protein production while specifically increasing production of a select subset of
“pro-survival” proteins. As we age, our cells decline in their ability to maintain proteostasis, serving as a hallmark
for a range of age-related diseases such as Alzheimer’s, Parkinson’s, Huntington’s, and amyotrophic lateral
sclerosis. This pathological loss of proteostasis correlates with increases in ISR activity, establishing the
importance of gaining a detailed understanding of the mechanisms involved in ISR activation. Four kinases serve
as upstream triggers of the ISR. Each kinase is activated by distinct forms of cellular stress, but all convergently
phosphorylate the eIF2α translation complex to activate the ISR pathway. One of these kinases, Heme-
Regulated Inhibitor (HRI), was recently shown to signal mitochondrial stress to the ISR via a protein called
DELE1. The HRI kinase is the principal mediator of ISR activation in neurons with perturbed proteostasis, and
is thus of particular relevance to age-related brain diseases. However, the detailed mechanism through which
DELE1 activates this kinase to relay mitochondrial stress to the ISR is unknown. Recent structural and cellular
studies on the DELE1 protein from our group have shown that that ISR activation is dependent on oligomerization
of DELE1 in the cytosol. Our high-resolution single particle cryo-EM structure of DELE1, combined with
biochemical and cellular studies, indicate that the higher-order assembly likely serves as a structural scaffold for
HRI binding and activation. We plan to elucidate how interactions between DELE1, HRI, and eIF2α transduce
mitochondrial stress to ISR activity using single-particle cryo-EM, crystallographic, and functional studies.
Atomic-level descriptions of the interacting elements of this pathway could enable us to precisely counter human
mitochondrial pathologies without impacting the capacity of cells to respond to other stresses, such as ER stress
or viral infections. We will use a range of complementary methodologies to probe the mechanistic underpinnings
of the DELE1-HRI-eIF2α pathway to gain much-needed insights into this branch of ISR activation. We will
combine biophysical, biochemical, structural, and cellular studies in three Aims that: 1) tests our hypothesis that
DELE1 oligomerization leads to auto- or trans-phosphorylation of bound HRI kinases; 2) defines the role of
cleavage in DELE1 oligomerization and ISR activation; and 3) examine the structural details of eIF2α recruitment
to HRI and the mechanism of its activation. These studies will provide a comprehensive, mechanistic description
of the key interactions that relay mitochondrial stress to the ISR, and will provide novel avenues to specific...

## Key facts

- **NIH application ID:** 10973140
- **Project number:** 1R01AG088908-01
- **Recipient organization:** SCRIPPS RESEARCH INSTITUTE, THE
- **Principal Investigator:** Gabriel C Lander
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $632,667
- **Award type:** 1
- **Project period:** 2024-08-15 → 2029-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10973140

## Citation

> US National Institutes of Health, RePORTER application 10973140, Structure-function studies of DELE1-mediated activation of the integrated stress response (1R01AG088908-01). Retrieved via AI Analytics 2026-06-12 from https://api.ai-analytics.org/grant/nih/10973140. Licensed CC0.

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