ASN's Mission

ASN leads the fight to prevent, treat, and cure kidney diseases throughout the world by educating health professionals and scientists, advancing research and innovation, communicating new knowledge, and advocating for the highest quality care for patients.

learn more

Contact ASN

1401 H St, NW, Ste 900, Washington, DC 20005

email@asn-online.org

202-640-4660

The Latest on Twitter

Kidney Week

Abstract: FR-PO929

Shroom3-Fyn Interaction Regulates Podometrics via Activation of AMP-Kinase (AMPK)

Session Information

Category: Glomerular Diseases

  • 1204 Podocyte Biology

Authors

  • Banu, Khadija, Icahn School of Medicine at Mount Sinai, New York, New York, United States
  • Basgen, John M., Charles Drew University , Minnetonka, Minnesota, United States
  • Garzon, Felipe, Icahn School of Medicine at Mount Sinai, New York, New York, United States
  • Wei, Chengguo, Icahn School of Medicine at Mount Sinai, New York, New York, United States
  • Planoutene, Marina, Icahn School of Medicine at Mount Sinai, New York, New York, United States
  • He, John Cijiang, Icahn School of Medicine at Mount Sinai, New York, New York, United States
  • Murphy, Barbara T., Icahn School of Medicine at Mount Sinai, New York, New York, United States
  • Menon, Madhav C., Icahn School of Medicine at Mount Sinai, New York, New York, United States
Background

We recently showed that Shroom3 interacts with Fyn, an Src kinase in podocytes, regulating Fyn activation. Intriguingly Shroom3 knockdown reduced podocyte and glomerular volume (Vglom).

Methods

To investigate mechanism of this phenotype, we examined Shroom3- (S3KD) & Fyn-knockdown (FynKD) human podocytes, and inducible Shroom3 knockdown mice (s3kd).

Results

FynKD podocytes also had reduced cell volume vs controls, suggesting that Fyn mediated the effect of S3KD on podocyte morphology. To investigate whether glomerular Shroom3 regulated Vglom hypertrophy, we performed unilateral nephrectomy in control and s3kd mice and examined Vglom in remnant kidneys. At day 7, s3kd mice showed restricted Vglom hypertrophy vs controls, (n=5; 8% vs 19%; P<0.05) and reduced expansion of podocyte fraction of Vglom. To investigate whether reductions of cell size were due to reduced protein content we measured protein:DNA ratio. S3KD & FynKD podocytes had reduced Protein:DNA ratios (n=5; P<0.01). Since MTOR is a key pathway regulating protein biosynthesis, we examined MTOR signaling. Phospho AMPK, a negative regulator of MTORC1 was significantly increased with S3KD/FynKD cells as well as in glomeruli of s3kd (Fig 1- immunofluoresence). Ribosomal biogenesis (18S RNA), downstream of MTORC1, was inhibited by qPCR in S3KD/FynKD cells (n=3) and s3kd kidney lysates. Since Fyn activation causes nuclear retention of LKB1, an AMPK-kinase, we examined ratio of cytoplasmic:nuclear LKB1, which was increased in S3KD and FynKD cells explaining AMPK activation.

Conclusion

In summary we show regulation of Vglom and podometrics by Shroom3-Fyn interaction that regulates protective AMPK-signaling. These findings have implications to loss of nephron mass and minimal change disease where podocyte Fyn-inactivation has been specifically observed.

s3kd mice have activation of glomerular p-AMPK

Funding

  • NIDDK Support