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Kidney Week

Abstract: PO2007

The Role for FNBP1L in Podocytes

Session Information

  • Podocyte Biology
    October 22, 2020 | Location: On-Demand
    Abstract Time: 10:00 AM - 12:00 PM

Category: Glomerular Diseases

  • 1204 Podocyte Biology

Authors

  • Tang, Qiaoli, Jinling Hospital National Clinical Research Center of Kidney Diseases, Nanjing General Hospital of Nanjing Military Command Research Institute of Nephrology, Nanjing, Jiangsu, China
  • Ren, Lu, Jinling Hospital National Clinical Research Center of Kidney Diseases, Nanjing General Hospital of Nanjing Military Command Research Institute of Nephrology, Nanjing, Jiangsu, China
  • Song, Hui, Jinling Hospital National Clinical Research Center of Kidney Diseases, Nanjing General Hospital of Nanjing Military Command Research Institute of Nephrology, Nanjing, Jiangsu, China
  • Sipan, Zhang, Jinling Hospital National Clinical Research Center of Kidney Diseases, Nanjing General Hospital of Nanjing Military Command Research Institute of Nephrology, Nanjing, Jiangsu, China
  • Tang, Zheng, Jinling Hospital National Clinical Research Center of Kidney Diseases, Nanjing General Hospital of Nanjing Military Command Research Institute of Nephrology, Nanjing, Jiangsu, China
  • Shi, Shaolin, Jinling Hospital National Clinical Research Center of Kidney Diseases, Nanjing General Hospital of Nanjing Military Command Research Institute of Nephrology, Nanjing, Jiangsu, China
Background

Podocytes exhibit a complex cellular morphology characterized by the formation of foot processes. The normal structure of podocytes depends on their unique cytoskeleton, of which actin microfilaments are one component. Nucleation of actin monomers is the rate limiting step in actin polymerization. There are two distinct nucleators for actin nucleation in podocytes, Arp2/3 complex and formins, which mediate branch and linear actin filament formations, respectively. Our previous study identified hundreds of genes expressed in every single podocyte, which were potential podocyte essential genes. Of them, FNBP1L is known to be involved in Arp2/3 complex and formins activity in nucleation, supporting FNBP1L’s essentiality for podocytes. Here, we test this hypothesis.

Methods

Cultured podocytes were used for this study. FNBP1L was knocked down by siRNA, and immumostaining, immunoblotting, qPCR, wound healing assay, co-immunoprecipitation were performed to test FNBP1L essentiality and mechanism.

Results

FNBP1L was specifically expressed in podocytes in glomeruli, and its expression was decreased in purimycin aminonucleasides-treated in podocytes. When FNBP1L was knocked down, we found that the expression of WT1, SYNPO and CD2AP was decreased; that the migratory capability was impaired; that F-actin stress fibers were reduced and disorganized; and that focal adhesion number was decreased while their size increased as shown by p-FAK staining.Mechanistically, FNBP1L regulated Arp2/3 complex and INF2 (a formin) actin nucleation activities. Co-IP and IF showed that FNBP1L colocalized and interacted with CDC42 and N-WASP to facilitate interaction of N-WASP with Arp2/3 complex, thereby increasing the activity of Arp2/3 complex in actin nucleation. FNBP1L also interacted with INF2 and affected its localization in cytoplasm and its actin nucleation. Consistently, the reduction of FNBP1L impaired the interaction between N-WASP and Arp2/3 complex and mis-localized INF2 in the cytoplasm.

Conclusion

FNBP1L may regulate branched and linear actin filament polymerization by regulating Arp2/3 complex and INF2 actin nucleation activities in podocytes, thereby maintaining podocyte normal structure and function. Reduction of FNBP1L expression is involved in podocyte injury and targeting FNBP1L may represent a novel therapeutic approach for podocytopathies.

Funding

  • Government Support - Non-U.S.