Podocyte-associated talin1 is critical for glomerular filtration barrier maintenance
Xuefei Tian, … , Jochen Reiser, Shuta Ishibe
Xuefei Tian, … , Jochen Reiser, Shuta Ishibe
Published February 17, 2014
Citation Information: J Clin Invest. 2014;124(3):1098-1113. https://doi.org/10.1172/JCI69778.
View: Text | PDF | Corrigendum
Research Article

Podocyte-associated talin1 is critical for glomerular filtration barrier maintenance

Abstract

Podocytes are specialized actin-rich epithelial cells that line the kidney glomerular filtration barrier. The interface between the podocyte and the glomerular basement membrane requires integrins, and defects in either α3 or β1 integrin, or the α3β1 ligand laminin result in nephrotic syndrome in murine models. The large cytoskeletal protein talin1 is not only pivotal for integrin activation, but also directly links integrins to the actin cytoskeleton. Here, we found that mice lacking talin1 specifically in podocytes display severe proteinuria, foot process effacement, and kidney failure. Loss of talin1 in podocytes caused only a modest reduction in β1 integrin activation, podocyte cell adhesion, and cell spreading; however, the actin cytoskeleton of podocytes was profoundly altered by the loss of talin1. Evaluation of murine models of glomerular injury and patients with nephrotic syndrome revealed that calpain-induced talin1 cleavage in podocytes might promote pathogenesis of nephrotic syndrome. Furthermore, pharmacologic inhibition of calpain activity following glomerular injury substantially reduced talin1 cleavage, albuminuria, and foot process effacement. Collectively, these findings indicate that podocyte talin1 is critical for maintaining the integrity of the glomerular filtration barrier and provide insight into the pathogenesis of nephrotic syndrome.

Authors

Xuefei Tian, Jin Ju Kim, Susan M. Monkley, Nanami Gotoh, Ramiro Nandez, Keita Soda, Kazunori Inoue, Daniel M. Balkin, Hossam Hassan, Sung Hyun Son, Yashang Lee, Gilbert Moeckel, David A. Calderwood, Lawrence B. Holzman, David R. Critchley, Roy Zent, Jochen Reiser, Shuta Ishibe

×

Figure 5

Lack of talin1 in podocytes results in reduced integrin activation, adhesion, and cell spreading.

Options: View larger image (or click on image) Download as PowerPoint
Lack of talin1 in podocytes results in reduced integrin activation, adhe...
(A) Representative images of kidney sections from control and Pod-Tln1–KO mouse kidneys stained with WT1, a podocyte-specific transcription factor, at 2 weeks of age. Scale bar: 10 μm. (B) Quantification of WT1 staining per glomerulus in A. n = 6 experiments. (C) TUNEL staining of kidney sections from control and Pod-Tln1–KO mice at 2 weeks of age. G, glomerulus. Scale bar: 20 μm. (D) Primary podocytes isolated from control and Pod-Tln1–KO kidneys immunoblotted for β1 integrin, α3 integrin, and GAPDH. (E) Cell-surface expression of integrins on freshly isolated primary podocytes from control and Pod-Tln1–KO mice analyzed by FACS by staining with Abs against total β1 integrin and 9EG7 epitope of active β1 integrin. Pod-Tln1–KO podocytes are denoted in green, and control podocytes are denoted in red histograms. (F) Quantification of E expressed as percentage of β1 integrin activation per total β1 integrin. n = 4 experiments. (G) Primary podocytes isolated from control and Pod-Tln1–KO mice demonstrate a small but significant decrease in adhesion to laminin (LN) and not to fibronectin (FN) or collagen type I (Col I). n = 4 experiments. (H) Representative image of control and Pod-Tln1–KO podocytes plated on laminin and monitored by live cell imaging for 120 minutes. (I) Quantification of cell area was performed on 50 random cells in each experiment. n = 3 experiments. Scare bar: 20 μm. *P < 0.01.