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Abstract: FR-PO713

Synaptopodin Enables Podocyte Focal Adhesions to Resist Perpendicular Force

Session Information

Category: Glomerular Diseases

  • 1304 Glomerular Diseases: Podocyte Biology

Authors

  • Qu, Chengqing, Washington University in St Louis, St Louis, Missouri, United States
  • Jiang, Shumeng, Washington University in St Louis, St Louis, Missouri, United States
  • Genin, Guy M., Washington University in St Louis, St Louis, Missouri, United States
  • Suleiman, Hani, Washington University in St Louis, St Louis, Missouri, United States
  • Miner, Jeffrey H., Washington University in St Louis, St Louis, Missouri, United States
Background

Focal adhesions resist shear forces in nearly all cell types. Kidney podocytes are unusual in that they must resist stresses perpendicular to their basement membrane. We hypothesized that synaptopodin, a unique actin-associated protein that is highly expressed in podocytes, serves as a linker to enable focal adhesions to resist such perpendicular forces.

Methods

We developed an in vitro system to study the effect of perpendicular forces on cells cultured on hydrogels of defined stiffness, coated with defined extracellular matrix (ECM) proteins. By varying these factors, culture conditions, and the centrifugal forces applied, this setup allowed us to simulate the perpendicular forces that podocytes experience in their native glomerular microenvironment. We used primary podocytes taken from control (WT) mice as well as mice lacking synaptopodin (Synpo KO). We compared these cells to 3T3 cells as well as immortalized mouse podocytes cultured in both undifferentiated and differentiated conditions. We assessed the cellular responses to the centrifugal forces using morphological analysis as well immunostaining for integrins, synaptopodin, a-actinin-4, myosin II and actin.

Results

Whereas perpendicular forces caused 3T3 cells to detach or become spindle-like, they caused WT primary podocytes to spread and form a continuous skirt of integrins at their periphery. Synpo KO primary podocytes and podocyte cell lines did not show this continuous integrin b1 pattern at the cell periphery but rather showed a diffuse pattern and were model likely to detach.

Conclusion

We uncover a mechanical role for synaptopodin in podocytes. When centrifugal force is applied, WT primary podocytes were able to resist these perpendicular forces through a major rearrangement of the focal adhesions. Lack of synaptopodin weakened podocyte responses to these forces and was associated with more podocyte detachment. This function of synaptopodin could be important for podocyte adhesion to the basement membrane during their responses to elevated stresses and injury.

Funding

  • NIDDK Support