Disruption of APOL1-miR193a Axis Induces Disorganization of Podocyte Actin Cytoskeleton

Vinod Kumar,Moin A Saleem,Alok Jha,Karl Skorecki,Pravin C Singhal,Sheetal Chowdhary,Nitpriya Paliwal,Himanshu Vashistha,Nirupama Chandel,Kamesh Ayasolla,Ashwani Malhotra,Praveen N Chander

doi:10.1038/s41598-019-39376-y

Abstract

APOL1-miR193a axis participates in the preservation of molecular phenotype of differentiated podocytes (DPDs). We examined the hypothesis that APOL1 (G0) preserves, but APOL1 risk alleles (G1 and G2) disrupt APOL1-miR193a axis in DPDs. DPDG0s displayed down-regulation of miR193a, but upregulation of nephrin expression. DPDG1s/G2s exhibited an increase in miR193a and down-regulation of the expression of adherens complex’s constituents (CD2AP, nephrin, and dendrin). DPDG0s showed decreased Cathepsin L, enhanced dynamin expressions, and the intact actin cytoskeleton. On the contrary, DPDG1s/G2s displayed an increase in Cathepsin L, but down-regulation of dynamin expressions and disorganization of the actin cytoskeleton. APOL1 silencing enhanced miR193a and Cathepsin L, but down-regulated dynamin expressions. DPDG1s/G2s displayed nuclear import of dendrin, indicating an occurrence of destabilization of adherens complexes in APOL1 risk milieu. These findings suggest that DPDG1s and DPDG2s developed disorganized actin cytoskeleton as a consequence of disrupted APOL1-miR193a axis. Interestingly, docking and co-labeling studies suggested an interaction between APOL1 and CD2AP. APOL1G1/G1 and APOL1G1/G2 transgenic mice displayed nuclear import of dendrin indicating destabilization of adherens complexes in podocytes; moreover, these mice showed a four-fold increase in urinary albumin to creatinine ratio and development of focal segmental glomerular lesions.

Highlights

Optimal expression of the adherens complexes (ACs) proteins is considered to be an integral part of podocyte health[20,21]
DPDs silenced for either Apolipoprotein 1 (APOL1) or nephrin displayed attenuated expression of CD2AP (Fig. 1A and D) but enhanced expression of CTSL (Fig. 1A and E). These findings suggest that both nephrin and APOL1 are required to maintain the stability of the ACs in human DPDs
Enhanced expression of CTSL and down-regulation of dynamin expression suggested the destabilization of the ACs in DPDG1s and DPDG2s

Summary

Introduction

Optimal expression of the AC proteins is considered to be an integral part of podocyte health[20,21]. In Danio rerio (Zebrafish), silencing of its endogenous APOL1 contributed to altered expression of nephrin in nephrocytes as well as in the development of a dysfunctional glomerular filtration barrier[25]. These investigators suggested a role of Zebrafish APOL1. We have examined the role of APOL1– miR193a axis in the maintenance of stability of the ACs and the integrity of actin cytoskeleton in human differentiated podocytes. We have evaluated the effects of disruption of APOL1-mIR193a axis on the stability of the ACs and the organization of actin filaments in podocytes expressing APOL1 risk alleles. We used interventions which resolved the defective signaling in adverse milieus and podocytes expressing APOL1 risk alleles

Methods

Results

Conclusion