title: Dysregulated autophagy contributes to podocyte damage in Fabry's disease.
abstract: Fabry's disease results from an inborn error of glycosphingolipid metabolism that is due to deficiency of the lysosomal hydrolase α-galactosidase A. This X-linked defect results in the accumulation of enzyme substrates with terminally α-glycosidically bound galactose, mainly the neutral glycosphingolipid Globotriaosylceramide (Gb3) in various tissues, including the kidneys. Although end-stage renal disease is one of the most common causes of death in hemizygous males with Fabry's disease, the pathophysiology leading to proteinuria, hematuria, hypertension, and kidney failure is not well understood. Histological studies suggest that the accumulation of Gb3 in podocytes plays an important role in the pathogenesis of glomerular damage. However, due to the lack of appropriate animal or cellular models, podocyte damage in Fabry's disease could not be directly studied yet. As murine models are insufficient, a human model is needed. Here, we developed a human podocyte model of Fabry's disease by combining RNA interference technology with lentiviral transduction of human podocytes. Knockdown of α-galactosidase A expression resulted in diminished enzymatic activity and slowly progressive accumulation of intracellular Gb3. Interestingly, these changes were accompanied by an increase in autophagosomes as indicated by an increased abundance of LC3-II and a loss of mTOR kinase activity, a negative regulator of the autophagic machinery. These data suggest that dysregulated autophagy in α-galactosidase A-deficient podocytes may be the result of deficient mTOR kinase activity. This finding links the lysosomal enzymatic defect in Fabry's disease to deregulated autophagy pathways and provides a promising new direction for further studies on the pathomechanism of glomerular injury in Fabry patients.
authors.affiliation: Department 2 of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany.
authors.forename: Max C
authors.initials: MC
authors.lastname: Liebau
authors.forename: Fabian
authors.initials: F
authors.lastname: Braun
authors.forename: Katja
authors.initials: K
authors.lastname: Höpker
authors.forename: Claudia
authors.initials: C
authors.lastname: Weitbrecht
authors.forename: Valerie
authors.initials: V
authors.lastname: Bartels
authors.forename: Roman-Ulrich
authors.initials: RU
authors.lastname: Müller
authors.forename: Susanne
authors.initials: S
authors.lastname: Brodesser
authors.forename: Moin A
authors.initials: MA
authors.lastname: Saleem
authors.forename: Thomas
authors.initials: T
authors.lastname: Benzing
authors.forename: Bernhard
authors.initials: B
authors.lastname: Schermer
authors.forename: Markus
authors.initials: M
authors.lastname: Cybulla
authors.forename: Christine E
authors.initials: CE
authors.lastname: Kurschat
mesh_terms: D001343:Autophagy / Q000502:physiology*; D017931:DNA Primers / Q000235:genetics; D000795:Fabry Disease / Q000503:physiopathology*; D005455:Fluorescent Antibody Technique; D055785:Gene Knockdown Techniques; D057809:HEK293 Cells; D006801:Humans; D020287:In Situ Nick-End Labeling; D008156:Luciferases; D018942:Macrolides; D008297:Male; D008954:Models, Biological; D050199:Podocytes / Q000378:metabolism / Q000473:pathology*; D034622:RNA Interference; D060888:Real-Time Polymerase Chain Reaction; D020123:Sirolimus; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D014281:Trihexosylceramides / Q000378:metabolism*; D000519:alpha-Galactosidase / Q000235:genetics
chemical_list: D017931:DNA Primers; D018942:Macrolides; D014281:Trihexosylceramides; C057620:bafilomycin A; C018549:globotriaosylceramide; D008156:Luciferases; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D000519:alpha-Galactosidase; D020123:Sirolimus