The Role of Palladin in Podocytes

• Published in: Journal of the American Society of Nephrology 2018-06, Vol.29 (6), p.1662-1678
• Main Authors: Artelt, Nadine, Ludwig, Tim A, Rogge, Henrik, Kavvadas, Panagiotis, Siegerist, Florian, Blumenthal, Antje, van den Brandt, Jens, Otey, Carol A, Bang, Marie-Louise, Amann, Kerstin, Chadjichristos, Christos E, Chatziantoniou, Christos, Endlich, Karlhans, Endlich, Nicole
• Format: Article
• Language: English
• Subjects: Actins - metabolism; Animals; Basic Research; Cytoskeletal Proteins - genetics; Cytoskeletal Proteins - metabolism; Cytoskeleton; Female; Focal Adhesions; Gene Expression; Gene Silencing; Human health and pathology; Humans; Kidney Glomerulus - pathology; Life Sciences; Male; Mice, Knockout; Microfilament Proteins - metabolism; Morpholinos - pharmacology; Phosphoproteins - genetics; Phosphoproteins - metabolism; Podocytes - metabolism; Podocytes - pathology; RNA, Messenger - metabolism; Vinculin - genetics; Vinculin - metabolism; Zebrafish; Zebrafish Proteins - genetics; Zebrafish Proteins - metabolism
• ISSN: 1046-6673; 1533-3450
• DOI: 10.1681/ASN.2017091039

Podocyte loss and effacement of interdigitating podocyte foot processes are the major cause of a leaky filtration barrier and ESRD. Because the complex three-dimensional morphology of podocytes depends on the actin cytoskeleton, we studied the role in podocytes of the actin bundling protein palladin, which is highly expressed therein. We knocked down palladin in cultured podocytes by siRNA transfection or in zebrafish embryos by morpholino injection and studied the effects by immunofluorescence and live imaging. We also investigated kidneys of mice with podocyte-specific knockout of palladin (PodoPalld-/- mice) by immunofluorescence and ultrastructural analysis and kidney biopsy specimens from patients by immunostaining for palladin. Compared with control-treated podocytes, palladin-knockdown podocytes had reduced actin filament staining, smaller focal adhesions, and downregulation of the podocyte-specific proteins synaptopodin and -actinin-4. Furthermore, palladin-knockdown podocytes were more susceptible to disruption of the actin cytoskeleton with cytochalasin D, latrunculin A, or jasplakinolide and showed altered migration dynamics. In zebrafish embryos, palladin knockdown compromised the morphology and dynamics of epithelial cells at an early developmental stage. Compared with PodoPalld+/+ controls, PodoPalld-/- mice developed glomeruli with a disturbed morphology, an enlarged subpodocyte space, mild effacement, and significantly reduced expression of nephrin and vinculin. Furthermore, nephrotoxic serum injection led to significantly higher levels of proteinuria in PodoPalld-/- mice than in controls. Kidney biopsy specimens from patients with diabetic nephropathy and FSGS showed downregulation of palladin in podocytes as well. Palladin has an important role in podocyte function and .