# Role of GRP170 in ENaC Biogenesis and Renal Physiology

> **NIH NIH R01** · UNIVERSITY OF PITTSBURGH AT PITTSBURGH · 2021 · $337,020

## Abstract

Project Summary
The focus of this proposal is to investigate the mechanism by which the conserved molecular chaperone,
GRP170/Lhs1, regulates the degradation, assembly, and trafficking of the epithelial sodium channel, ENaC.
ENaC is responsible for salt reabsorption across epithelia of the kidney and lung, and controls both blood
pressure and ion and fluid homeostasis. Gain- and loss-of-function mutations in ENaC lead to disease, and
ENaC activity is also associated with other diseases associated with epithelial malfunction. ENaC is a
heterotrimeric channel composed of an α, β, and γ subunit. Each subunit contains two transmembrane domains,
a large extracellular loop, and short cytosolic N- and C-termini. Soon after synthesis, ENaC is subject to
Endoplasmic Reticulum Associated Degradation (ERAD), which targets misfolded proteins and orphaned
subunits of multimeric complexes for destruction by the cytosolic 26S proteasome. Not surprisingly, ENaC
subunits individually are targeted for ERAD, but a significant percent of ENaC is degraded even when all three
ENaC subunits are present. How sufficient subunit assembly occurs in order to escape ERAD is mysterious.
However, data from this team of investigators uncovered a new role for the Lhs1 chaperone (GRP170 in
mammalian cells) during ENaC biogenesis. Specifically, Lhs1 facilitated the degradation of the α subunit but had
no effect on β or γ subunit degradation, yet when all three ENaC subunits were expressed, intersubunit
interactions between the transmembrane domains blocked Lhs1-dependent ERAD. Consistent with these data,
GRP170 also targeted the α subunit for ERAD in mammalian cells but promoted trafficking of the assembled
heterotrimeric channel. Three model systems will be used to further understand these events: 1) An established,
genetically facile yeast system will be used to define the structural elements required to differentiate between an
orphaned ENaC subunit and the assembled heterotrimeric channel; 2) A Fischer rat thyroid (FRT) cell system
will be used to confirm results from the yeast system and define amino acid motifs required for GRP170-mediated
channel assembly and trafficking; 3) A conditional GRP170 knock out mouse, which lacks GRP170 in kidney
tubules, will be used to determine how ENaC regulation by the GRP170 chaperone affects renal physiology.
Overall, this proposal will use a multi-system approach to define how a single molecular chaperone regulates
ENaC and—for the first time—indicate how chaperones can select an orphaned subunit for degradation as well
as facilitate assembly of an oligomeric protein. Together, understanding the mechanism of action of GRP170 will
provide novel insights into ENaC function and associated disease states. More generally, this work will help
decipher how membrane assembly of a multimeric protein in the ER results in stabilization and trafficking, which
is vital for the function of numerous other ion transporters in the kidney. The experiments ...

## Key facts

- **NIH application ID:** 10133059
- **Project number:** 5R01DK117126-03
- **Recipient organization:** UNIVERSITY OF PITTSBURGH AT PITTSBURGH
- **Principal Investigator:** Teresa M Buck
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $337,020
- **Award type:** 5
- **Project period:** 2019-04-01 → 2024-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10133059

## Citation

> US National Institutes of Health, RePORTER application 10133059, Role of GRP170 in ENaC Biogenesis and Renal Physiology (5R01DK117126-03). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10133059. Licensed CC0.

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