Kidney Week

Abstract: SA-PO561

ATP-Binding Cassette A–13 (ABCA13) Is a Candidate Gene for Familial FSGS

Session Information

• Noncystic Mendelian Diseases
  November 04, 2017 | Location: Hall H, Morial Convention Center
  Abstract Time: 10:00 AM - 10:00 AM

Category: Genetic Diseases of the Kidney

• 802 Non-Cystic Mendelian Diseases

Authors

• Hall, Gentzon, Duke University Medical Center, Durham, North Carolina, United States

Gentzon Hall,

• Chryst-ladd, Megan, Duke Molecular Physiology Institute, Durham, North Carolina, United States

Megan Chryst-ladd,

• Wang, Liming, Duke University Medical Center, Durham, North Carolina, United States

Liming Wang,

• Kovalik, Gina E., Duke University, Durham, North Carolina, United States

Gina E. Kovalik,

• Wu, Guanghong, Duke university, Durham, North Carolina, United States

Guanghong Wu,

• Lane, Brandon M., Duke University, Durham, North Carolina, United States

Brandon M. Lane,

• Kovalik, Eugene C., Duke University Medical Center, Durham, North Carolina, United States

Eugene C. Kovalik,

• Spurney, Robert F., Duke University Medical Center, Durham, North Carolina, United States

Robert F. Spurney,

• Gbadegesin, Rasheed A., Duke University Medical Center, Durham, North Carolina, United States

Rasheed A. Gbadegesin,

Background

FSGS is a major cause of ESKD that is characterized by steroid-resistant nephrotic syndrome, rapid progression to ESKD, focal scarring of the glomerular capillary tuft and effacement of podocyte foot processes. Characteristic features of FSGS-associated podocytopathy include 1.) dysregulation of actin cytoskeletal dynamics and dysmotility, 2.) inappropriate cell cycle re-entry and hyperproliferation, and 3.) apoptosis. We carried out whole exome sequencing (WES) on a family with FSGS. Three variants segregated with disease in the family. Of the three variants, only the change in ABCA13 (p.2330fsX2354) is a novel, loss-of-function (truncating) variant. ABCA13 is the largest member of a family of 13 transport proteins involved in cellular drug and lipid efflux. Given the established role of ABCA1 deficiency in cholesterol-induced podocyte injury in diabetic nephropathy, we hypothesized that ABCA13 knockdown (KD) in immortalized human podocytes may induce dysfunction via a mechanism that involves impaired cholesterol efflux. Futher, given the known role of cholesterol as an activator of Rac1 signaling, we postulated that ABCA13 KD may induce inappropriate activation of Rac1 and promote podocyte dysmotility through the Rac1-mediated upregulation of JNK/paxillin signaling.

Methods

Whole-exome sequencing, direct sequencing, lentivirus-mediated siRNA gene silencing, scratch wound healing assays, and immunoblotting.

Results

ABCA13 KD induced an upregulation of JNK activation (p < 0.01) and an increase in Rac1 membrane recruitment in podocytes. Additionally, cell migration in ABCA13 KD podocytes was significantly increased (p <0.01) relative to scramble siRNA controls. This enhanced podocyte motility was significantly attenuated by the cholesterol extracting agent methyl-b-cyclodextrin (p = 0.03) and the JNK inhibitor tanzasertib (p < 0.01). Additionally, ABCA13 KD enhanced paxillin phosphorylation at the JNK target site Ser178 in podocytes.

Conclusion

ABCA13 KD enhances podocyte motility possibly through the dysregulation of Rac1/JNK/Paxillin signaling axis. These data suggest that: 1. Rac1/JNK/Paxillin signaling may play an important role in the pathogenesis of FSGS, and that 2. targeting this signaling pathway may be a novel therapeutic approach for the treatment of FSGS.

Funding

• NIDDK Support