# Assaying and controlling the kidney cell function using a genetically encoded pH-sensor

> **NIH NIH R21** · MAYO CLINIC ROCHESTER · 2022 · $238,500

## Abstract

Abstract: Assaying and controlling the proximal tubule using the nbce1A promoter and ion-sensors
Bicarbonate absorption of filtered blood by the kidney is critical to not just blood pH homeostasis but also for
life. The proximal tubule (PT) absorbs isotonic NaHCO3. Basal metabolism generates 70 mM H+, making it
crucial to buffer this acid (CO2/HCO3-) or removed (low pH urine with titratable acids). Proximal tubule
HCO3- absorption is mediated by basolateral NBCe1A (SLC4A4-A), the electrogenic Na+ bicarbonate
cotransporter. The final phase of kidney acid excretion is accomplished through apical H+ extrusion by the
α-intercalated cells (αIC).
 In the past several years, we have focused cellular and Drosophila experiments using genetically encoded
ion-sensors (pH, Cl-, Ca2+). We developed a new but bright, red fluorescent protein (pHire), a pH-sensor that
we have used in cells and to make transgenic flies. Here, we will test the lox-stop-lox-pHire (LSL-pHire) mouse
we have made (Rosa26 targeted) as a tool for general kidney pH-regulation experiments. We will direct pHire
to the PT using the SGLT2-Cre and to the αIC using KitcreERT2/+. From our mouse crosses, we will microdissect
PT and collecting ducts (for αIC) and test intracellular pH-regulation. We will further test PT functional
differences by SGLT2:pHire ± NBCe1A- knockout (Nbce1A-KO mouse).
 After tissue specific-validation, we will monitor mice to make sure that marker proteins as well as basic
renal function and morphology are unchanged from wild-type and the LSL-pHire parent strain. We will follow
nephron-segment specific antibodies morphology (cryosections) for comparison. Prior to sacrifice, we will
longitudinally track animals: GFR measurements; total kidney volume (TKV) and cardiac function by
ultrasound.
 The red-fluorescent pHire will allow us and others in the kidney and KUH community to quickly focus on
specific-cell types for either pH experiments ± other gene knockdowns or sort cells for high enrichment of this
cell population for RNAseq or protein analysis. Thus, pursuing these Aims creates a new set of acid/base-
specific assessment tools for the entire KUH community.

## Key facts

- **NIH application ID:** 10527146
- **Project number:** 1R21DK129897-01A1
- **Recipient organization:** MAYO CLINIC ROCHESTER
- **Principal Investigator:** MICHAEL F. ROMERO
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $238,500
- **Award type:** 1
- **Project period:** 2022-08-15 → 2024-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10527146

## Citation

> US National Institutes of Health, RePORTER application 10527146, Assaying and controlling the kidney cell function using a genetically encoded pH-sensor (1R21DK129897-01A1). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10527146. Licensed CC0.

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