# Targeting a Membrane Protease that Controls NK Cell Maturation

> **NIH NIH R21** · JOHNS HOPKINS UNIVERSITY · 2022 · $245,625

## Abstract

PROJECT SUMMARY/ABSTRACT
A variety of important biological pathways in health and disease are regulated by intramembrane proteolysis, the
process that achieves the targeted cleavage of protein substrates within or proximal to the lipid bilayer. Four
classes of intramembrane proteases have been described, including the site 2 protease (S2P) metalloprotease
family, the rhomboid serine protease family, the Rce1 glutamyl protease family, and the aspartyl protease family
that includes presenilins and the related Signal Peptide Peptidase (SPP)-like (SPPL) subfamily. The aspartyl
proteases of the SPPL subfamily, including SPP, SPPL2a, SPPL2b, SPPL2c, and SPPL3, are perhaps the least
understood subset of intramembrane proteases. Only recently have the biological roles of some of these
proteases emerged, and only a handful of relevant biological substrates have been identified. How these
intramembrane proteases specifically recognize and cleave their substrates remains mysterious. We discovered
a critical role for SPPL3 in NK cell maturation and cytotoxicity. SPPL3 is required in a cell-autonomous manner
for the maturation of NK cells from the immature CD27+CD11b- stage to the CD27+CD11b+ and CD27-CD22b+
stages, and for normal NK cell cytotoxicity toward tumor cell targets. Mice engineered to express only SPPL3
D271A in the NK lineage revealed that the proteolytic function of SPPL3 is required in NK cell maturation and
function. Like other aspartyl intramembrane proteases of the SPPL subfamily, very little is known about how
SPPL3 recognizes and cleaves its substrates. All SPPL proteases possess YD and GXGD motifs that contain
the catalytic aspartates, but other regions in the protein that are required for substrate recognition and cleavage
have not been identified. Furthermore, although some SPPL3 substrates have been identified, the relevant
substrate that must be cleaved by SPPL3 during NK cell maturation is currently unknown. To expand our basic
understanding of SPPL3 and related aspartyl intramembrane proteases, and to advance understanding of the
key checkpoint in NK cell maturation controlled by SPPL3, we will use newly developed substrate binding and
cleavage assays to define SPPL3 determinants required for substrate selection and to identify SPPL3 substrates
in NK cells. Our results will expand understanding of intramembrane aspartyl proteases and illuminate molecular
events that control NK cell development and function.

## Key facts

- **NIH application ID:** 10506509
- **Project number:** 1R21AI171001-01
- **Recipient organization:** JOHNS HOPKINS UNIVERSITY
- **Principal Investigator:** Joel L Pomerantz
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $245,625
- **Award type:** 1
- **Project period:** 2022-06-01 → 2024-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10506509

## Citation

> US National Institutes of Health, RePORTER application 10506509, Targeting a Membrane Protease that Controls NK Cell Maturation (1R21AI171001-01). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10506509. Licensed CC0.

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