BMC Seminar Thursday 8 October at 12:00 in Árnagarður in room 301
Title: Unravelling mechanisms for impaired Cubilin trafficking in a Drosophila model for Dent's disease type 1
Speaker: Salomon Christer, PhD student, Institute of Human Genetics, University Hospital Heidelberg
Abstract: Dent’s disease type 1 is a rare inherited X-linked renal disorder characterized by loss of endocytic receptors cubilin and megalin from the proximal tubular epithelia leading to low molecular weight (LMW) proteinuria. This is accompanied by a myriad of complications that ultimately leads to progressive renal failure for which the only existing treatment is dialysis and transplantation. This devastating disease is caused by mutations in CLCN5 which encodes the Cl-/H+ antiporter: ClC-5, but the disease mechanism remains elusive. Through knockdown (KD) of ClC-c, the orthologue of CLCN5 in Drosophila melanogaster, a new model for Dent's disease was established using garland nephrocytes, which share many functional similarities to renal podocytes and proximal tubules. In this model, Cubilin was markedly lost from the plasma membrane which lead to a strong loss of endocytic uptake of albumin. Moreover, the endolysosomal pathway was substantially perturbed with strong cortical buildup of early and recycling endosomes, while autophagic aggregates emerged the perinuclear area. Cubilin additionally accumulated in the endoplasmic reticulum (ER) of ClC-c KD nephrocytes, while its transmembrane binding parter; Amnionless, was lost. Loss of ClC-c lead to ER fragmentation and accumulation of Golgi-stacks suggesting secretory pathway impairment. Knockdown of Vacuolar type H+-ATPase (V-ATPase) in nephrocytes lead to similar phenotypes, suggesting that impaired trafficking of Cubilin might be linked to defects in acidification and glycosylation in the Golgi apparatus. Loss of Amnionless and ER retention of cubilin was additionally confirmed in Clcn5 KO mice, highlighting the clinical relevance of the mechanism.
