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Abstract: TH-PO317

FOXI1 Promotes Expression of V-ATPase and Gpr116 in M1 Cells

Session Information

Category: Fluid‚ Electrolyte‚ and Acid-Base Disorders

  • 1001 Fluid‚ Electrolyte‚ and Acid-Base Disorders: Basic


  • Kui, Mackenzie, Johns Hopkins Medicine, Baltimore, Maryland, United States
  • Pluznick, Jennifer L., Johns Hopkins Medicine, Baltimore, Maryland, United States
  • Zaidman, Nathan, Johns Hopkins Medicine, Baltimore, Maryland, United States

G protein-coupled receptors (GPCRs) are a diverse family of integral membrane proteins. We previously reported that GPR116 (ADGRF5), an adhesion-class GPCR, is a critical regulator of vacuolar-type H+-ATPase (V-ATPase) surface expression in A-type intercalated cells (AICs) in mouse kidney cortical collecting ducts. The V-ATPase is a multi-subunit proton pump that localizes to the plasma membrane in specialized acid-secreting epithelial cells. FOXI1 is a transcription factor that regulates V-ATPase expression in ICs and other mitochondria-rich cells. Recently, FOXI1 was identified as a key regulator of CFTR-rich pulmonary ionocytes which express both V-ATPase and GPR116. We hypothesized that GPR116 is transcriptionally regulated by FOXI1 in ICs.


We cloned FOXI1 from whole mouse kidney into an expression vector (pFOXI1), transfected it into the immortalized M1 mouse collecting duct cell line, and assessed changes. We localized FOXI by RNAScope in situ hybridization.


Transfection with pFOXI1 increased expression (qRT-PCR) of GPR116 in M1 cells (N=3, CT±SD: pFOXI1=33.1±1.3, mock=38.4±1.4), but not HEK293 cells. GPR116 transcripts co-localize in pFOXI1 transfected M1 cells, as well as mouse collecting ducts, as determined by RNAscope. Furthermore, pFOXI1 upregulates transcripts of several V-ATPase subunits in M1 cells, including ATP6V1B1 (N=3, CT±SD: pFOXI1=32.9±1.5, mock=undetected), ATP6V1G3 (pFOXI1=30.2±0.6, mock=undetected), and ATP6V0D2 (pFOXI1=31.6±0.3, mock=37.7±2.0). Surprisingly, ATP6V0A4 was not sensitive to transfection with pFOXI1 (pFOXI1=34.3±0.7, mock=34.7±1.1). Immunofluorescence microscopy revealed cytoplasmic localization of V-ATPase (β1/2 antibody) in FOXI1-expressing M1 cells. No V-ATPase protein is detected by microscopy in mock transfected M1 cells. Additionally, transfection with pFOXI1 caused an increase in SLC4A9 (pFOXI1=33.5±1.1, mock=undetected), SLC26A4 (pFOXI1=33.2±1.0, mock=36.0±0.6) and GPR110 (pFOXI1=36.9±2.7, mock=undetected). AQP6, CAR2, and CLCN5 transcripts are not sensitive to pFOXI1 in M1 cells, and SLC4A1 is not detected.


FOXI1 upregulates GPR116 and V-ATPase in M1 cells, generating IC-like cells in vitro. FOXI1 is also a transcriptional regulator of GPR110 (ADGRF1), an adhesion GPCR similar to GPR116. Finally, GPR116 may be a universal and genetically coded regulator of V-ATPase surface expression in FOXI1-positive cells.


  • NIDDK Support