# Dialing down caspase-7 through allosteric control: An integrated approach

> **NIH NIH R01** · UNIVERSITY OF IOWA · 2020 · $309,000

## Abstract

Our goal is to provide a physical and chemical rationale for how human caspase-7 (C7) is allosterically
controlled, particularly by small molecules. Caspase dysregulation, both catalytic and autocatalytic,
has been implicated in numerous neurodegenerative, inflammatory diseases and cancers. Due to a
highly charged active site, with low druggability and selectivity problems, development of active site
inhibitors has been problematic. However, there has been enormous interest in targeting an allosteric
pocket of C7, which is located more than 17 Å from the active site. The current proposal includes data
that represents a breakthrough advance in our understanding of how small drug-like molecules may
be used to allosterically “dial down” the activity of C7. This initial groundwork has been made possible
by advances in Fragment Based Drug Discovery (FBDD), which includes a confluence of chemical
informatics, biophysical methods such as Surface Plasmon Resonance, X-ray crystallography and
molecular dynamics. The work described in this proposal centers on our discovery of a series of
reversible allosteric inhibitors that bind in this allosteric pocket, which are the first drug-like compounds
to show such activity in caspases. The allosteric effectors obtained from our FBDD campaign were
used to elucidate several high resolution crystal structures of the inhibited complex, which revealed a
way forward for specific allosteric control for this enzyme. The use of FBDD, as illustrated by our two
inhibited high resolution crystal structures, PDB-ID 5V6U and 5V6Z, provide us with the first rational
basis for structure-activity relationships for reversible allosteric inhibitors for the executioner caspase
class of drug targets. These two structures clearly show that binding of the allosteric inhibitor to the
remote allosteric pocket of C7, yields structures with C7’s catalytic thiolate (Cys186) oriented in a non-
productive conformation (pointing into the P1 pocket instead of into the active site). Another important
feature of these allosterically inhibited complexes is a large increase in crystallographic B-factors
(relative to crystal structures of uninhibited C7) of a number of important loop regions. This proposal
will focus on obtaining high resolution structures of the many other distinct allosteric effectors resulting
from our FBDD campaign, which have not been co-crystallized with C7, including 13 confirmed
inhibitors, 5 binders that do not inhibit, and one activator; completion of this work will provide a
structural Rosetta Stone (an ability to directly compare inhibitor, non-inhibitor and activator) for
understanding how C7’s catalytic power is affected by remote ligation at the allosteric pocket. Upon
successful completion, not only will we learn what chemical space occupancy in the C7 allosteric
pocket results in inhibition, but more importantly, we will know how these remotely bound species are
achieving their dampening of C7’s catalytic power.

## Key facts

- **NIH application ID:** 10027338
- **Project number:** 1R01GM138471-01
- **Recipient organization:** UNIVERSITY OF IOWA
- **Principal Investigator:** Michael Ashley Spies
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $309,000
- **Award type:** 1
- **Project period:** 2020-09-15 → 2024-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10027338

## Citation

> US National Institutes of Health, RePORTER application 10027338, Dialing down caspase-7 through allosteric control: An integrated approach (1R01GM138471-01). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10027338. Licensed CC0.

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