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Vöing K, Michgehl U, Mertens ND, Picciotto C, Maywald ML, Goretzko J, Waimann S, Gilhaus K, Rogg M, Schell C, Klingauf J, Tsytsyura Y, Hansen U, van Marck V, Edinger AL, Vollenbröker B, Rescher U, Braun DA, George B, Weide T, Pavenstädt H. Disruption of the Rab7-Dependent Final Common Pathway of Endosomal and Autophagic Processing Results in a Severe Podocytopathy. J Am Soc Nephrol 2023; 34:1191-1206. [PMID: 37022133 PMCID: PMC10356157 DOI: 10.1681/asn.0000000000000126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 03/03/2023] [Indexed: 04/07/2023] Open
Abstract
SIGNIFICANCE STATEMENT Endocytosis, recycling, and degradation of proteins are essential functions of mammalian cells, especially for terminally differentiated cells with limited regeneration rates and complex morphology, such as podocytes. To improve our understanding on how disturbances of these trafficking pathways are linked to podocyte depletion and slit diaphragm (SD) injury, the authors explored the role of the small GTPase Rab7, which is linked to endosomal, lysosomal, and autophagic pathways, using as model systems mice and Drosophila with podocyte-specific or nephrocyte-specific loss of Rab7, and a human podocyte cell line depleted for Rab7. Their findings point to maturation and fusion events during endolysosomal and autophagic maturation as key processes for podocyte homeostasis and function and identify altered lysosomal pH values as a putative novel mechanism for podocytopathies. BACKGROUND Endocytosis, recycling, and degradation of proteins are essential functions of mammalian cells, especially for terminally differentiated cells with limited regeneration rates, such as podocytes. How disturbances within these trafficking pathways may act as factors in proteinuric glomerular diseases is poorly understood. METHODS To explore how disturbances in trafficking pathways may act as factors in proteinuric glomerular diseases, we focused on Rab7, a highly conserved GTPase that controls the homeostasis of late endolysosomal and autophagic processes. We generated mouse and Drosophila in vivo models lacking Rab7 exclusively in podocytes or nephrocytes, and performed histologic and ultrastructural analyses. To further investigate Rab7 function on lysosomal and autophagic structures, we used immortalized human cell lines depleted for Rab7. RESULTS Depletion of Rab7 in mice, Drosophila , and immortalized human cell lines resulted in an accumulation of diverse vesicular structures resembling multivesicular bodies, autophagosomes, and autoendolysosomes. Mice lacking Rab7 developed a severe and lethal renal phenotype with early-onset proteinuria and global or focal segmental glomerulosclerosis, accompanied by an altered distribution of slit diaphragm proteins. Remarkably, structures resembling multivesicular bodies began forming within 2 weeks after birth, prior to the glomerular injuries. In Drosophila nephrocytes, Rab7 knockdown resulted in the accumulation of vesicles and reduced slit diaphragms. In vitro , Rab7 knockout led to similar enlarged vesicles and altered lysosomal pH values, accompanied by an accumulation of lysosomal marker proteins. CONCLUSIONS Disruption within the final common pathway of endocytic and autophagic processes may be a novel and insufficiently understood mechanism regulating podocyte health and disease.
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Affiliation(s)
- Kristin Vöing
- Department of Internal Medicine and Nephrology, University Hospital of Münster, Medical Clinic D, Munster, Germany
| | - Ulf Michgehl
- Department of Internal Medicine and Nephrology, University Hospital of Münster, Medical Clinic D, Munster, Germany
| | - Nils David Mertens
- Department of Internal Medicine and Nephrology, University Hospital of Münster, Medical Clinic D, Munster, Germany
| | - Cara Picciotto
- Department of Internal Medicine and Nephrology, University Hospital of Münster, Medical Clinic D, Munster, Germany
| | - Mee-Ling Maywald
- Department of Internal Medicine and Nephrology, University Hospital of Münster, Medical Clinic D, Munster, Germany
| | - Jonas Goretzko
- Research Group Regulatory Mechanisms of Inflammation, Institute of Medical Biochemistry, Centre for Molecular Biology of Inflammation, University of Muenster, Muenster, Germany
| | - Sofie Waimann
- Department of Internal Medicine and Nephrology, University Hospital of Münster, Medical Clinic D, Munster, Germany
| | - Kevin Gilhaus
- Department of Internal Medicine and Nephrology, University Hospital of Münster, Medical Clinic D, Munster, Germany
| | - Manuel Rogg
- Institute of Surgical Pathology, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany
- Freiburg Institute for Advanced Studies (FRIAS), University of Freiburg, Freiburg, Germany
| | - Christoph Schell
- Institute of Surgical Pathology, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany
- Freiburg Institute for Advanced Studies (FRIAS), University of Freiburg, Freiburg, Germany
| | - Jürgen Klingauf
- Institute of Medical Physics and Biophysics, University of Muenster, Muenster, Germany
| | - Yaroslav Tsytsyura
- Institute of Medical Physics and Biophysics, University of Muenster, Muenster, Germany
| | - Uwe Hansen
- Institute for Musculoskeletal Medicine (IMM), University of Muenster, Muenster, Germany
| | - Veerle van Marck
- Department of Pathology, University Hospital Muenster Muenster, Germany
| | - Aimee L. Edinger
- Department of Developmental & Cell Biology, University of California, Irvine, California
| | - Beate Vollenbröker
- Department of Internal Medicine and Nephrology, University Hospital of Münster, Medical Clinic D, Munster, Germany
| | - Ursula Rescher
- Research Group Regulatory Mechanisms of Inflammation, Institute of Medical Biochemistry, Centre for Molecular Biology of Inflammation, University of Muenster, Muenster, Germany
| | - Daniela Anne Braun
- Department of Internal Medicine and Nephrology, University Hospital of Münster, Medical Clinic D, Munster, Germany
| | - Britta George
- Department of Internal Medicine and Nephrology, University Hospital of Münster, Medical Clinic D, Munster, Germany
| | - Thomas Weide
- Department of Internal Medicine and Nephrology, University Hospital of Münster, Medical Clinic D, Munster, Germany
| | - Hermann Pavenstädt
- Department of Internal Medicine and Nephrology, University Hospital of Münster, Medical Clinic D, Munster, Germany
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