Galpha13 induces preproET-1 gene expression via JNK

Area of Science:

• Molecular Biology
• Cell Signaling
• Renal Physiology

Background:

• The endothelin B receptor (ETBR) mediates endothelin-1 (ET-1) autoinduction.
• ETBR is known to interact with Galpha13, a G protein subunit.
• The precise mechanism of ET-1 autoinduction by ETBR and Galpha13 requires further elucidation.

Purpose of the Study:

• To investigate whether Galpha13 induces preproET-1 (ppET-1) gene transcription.
• To determine the role of Galpha13 in ET-1 autoinduction in renal epithelial cells.
• To elucidate the signaling pathways involved in Galpha13-mediated ppET-1 gene expression.

Main Methods:

• Generation of a reporter gene construct driven by the ppET-1 promoter.
• Transient expression of ETBR, Galpha13 (constitutively active forms), and dominant-negative signaling molecules (JNK, MEKK) in COS-7 cells.
• Measurement of ppET-1 promoter activity using the reporter gene assay.

Main Results:

• ETBR expression increased ppET-1 promoter activity upon ET-1 treatment.
• Constitutively active Galpha13 and Galpha9 activated the ppET-1 promoter.
• ETBR-stimulated and Galpha13-induced promoter activity were partially inhibited by dominant-negative JNK and MEKK.
• JNK inhibition specifically blocked Galpha13-induced ppET-1 promoter activation.

Conclusions:

• Galpha13 induces ppET-1 gene expression through a c-Jun N-terminal kinase (JNK)-dependent pathway.
• This Galpha13-coupled signaling pathway is implicated in sustained ET-1 autoinduction.
• The findings suggest a potential role in pathophysiological conditions involving ET-1 dysregulation.