Author:
Chahdi Ahmed,Yousefi Keyvan,Capcha Jose Manuel Condor,Irion Camila Iansen,Lambert Guerline,Shehadeh Serene A.,Dunkley Julian C.,Lee Yee-Shuan,Khan Aisha,Ramic Melina,Andrade Nadja S.,Zeier Zane,Dykxhoorn Derek M.,Katsoufis Chryso Pefkaros,Freundlich Michael,Hare Joshua M.,Nabity Mary,Rivera Carolina,Lymperopoulos Anastasios,Shehadeh Lina A.
Abstract
ABSTRACTAlport syndrome (AS) is a rare disease of the glomerular basement membrane type IV collagen causing progressive renal failure. We reported increased accumulation of low-density lipoprotein (LDL) receptor (LDLR) and subsequent LDL cholesterol (LDL-C) uptake in renal tubular epithelial cells (TEC) in Alport mice, but the mechanisms regulating LDLR stability and function remain unknown. Here, we show that a selective β2-Adrenoceptor (β2AR) agonist, salbutamol, decreased LDLR levels and LDL-C uptake in Alport kidneys accompanied with reduced albuminuria and improved cardiac systolic and diastolic function. Similarly, salbutamol decreased LDL-C uptake in HK2 and HEK293 human renal epithelial cell lines, in smooth muscle cells from an X-linked hereditary nephropathy dog model (a large animal model of AS), and in TECs differentiated from AS patient-derived iPSCs. We show that the Rac1/Cdc42 guanine nucleotide exchange factor β1Pix blocked β2AR-induced LDLR degradation and, hence, increased LDL-C uptake. β1Pix also abrogated ubiquitination and degradation of LDLR induced by the inducible degrader of the LDLR (IDOL), an E3 ubiquitin ligase that promotes lysosomal LDLR ubiquitination and degradation. We identify a multimolecular complex comprised of βPix, IDOL, and LDLR and demonstrate that βPix counteracts β2AR-mediated LDLR degradation by sequestering IDOL. Our findings show βPix acts as a significant post-transcriptional regulator of IDOL-mediated LDLR degradation and identify β2AR activation as a potential treatment for Alport pathology.
Publisher
Cold Spring Harbor Laboratory