Abstract: TH-PO386

Regulation of Actin Cytoskeletal Remodeling in Glomerular Podocytes by Testis Specific Protein Kinase 1 (TESK1)

Session Information

Category: Cell Biology

  • 201 Cell Signaling, Oxidative Stress

Authors

  • Wang, Liming, Duke University Medical Center, Durham, North Carolina, United States
  • Buckley, Anne, Duke University, Durham, North Carolina, United States
  • Spurney, Robert F., Duke University Medical Center, Durham, North Carolina, United States
Background

In published studies, we found that expression of a constitutively active Rho A construct (V14Rho) in glomerular podocytes in vivo induced albuminuria and foot process (FP) effacement (Kidney Int 81:1075, 2012). We postulated that these effects might be mediated by the Rho A effector Rho kinase (ROK).

Methods

V14Rho mice were treated with the ROK inhibitor Y27632. We then examined the effects of ROK inhibition on albuminuria and FP effacement. These in vivo studies were supplemented with cell culture experiments using an immortalized mouse podocyte cell line.

Results

Treatment with the ROK inhibitor Y27632 failed to attenuate albuminuria or FP effacement in V14Rho mice. An important target phosphorylated and inhibited by ROK is the actin depolymerizing factor cofilin 1 (CFL1). Sustained phosphorylation of CFL1 is implicated in human nephrotic diseases. In V14Rho mice, Y27632 did not inhibit phosphorylation of CFL1 despite effective ROK inhibition in vivo. CFL1 is also phosphorylated by testis-specific kinase 1 (TESK1) on the same serine residue. While the cell type specific expression of TESK1 is restricted, TESK1 was expressed in podocytes. Integrins activate TESK1, and plating podocytes on fibronectin to activate integrins increased CFL1 phosphorylation. Fibronectin induced CFL1 phosphorylation was not blocked by Y27632 but was inhibited by the β1-integrin agonist pyrintegrin. To examine the role of TESK1 in podocytes, we created TESK1 knockout (KO) cells. In contrast to podocytes expressing TESK1, Y27632 inhibited phosphorylation of CFL1 in KO cells. TESK1 KO did not affect actin polymerization under basal conditions, but reduced actin polymerization in the presence of Y27632. ROK inhibition also promoted podocyte motility, which was blocked by either TESK1 KO or pyrintegrin.

Conclusion

TESK1 plays a key role in regulating podocyte cytoskeletal dynamics. Because glomerular filtration barrier integrity requires an intact podocyte cytoskeleton, TESK1 may be a novel target for the treatment of glomerular diseases.

Funding

  • NIDDK Support