Herein, we report that Shroom3 knockdown, via Fyn inhibition, induced albuminuria with foot process effacement (FPE) without focal segmental glomerulosclerosis (FSGS) or podocytopenia. Interestingly, knockdown mice had reduced podocyte volumes. Human minimal change disease (MCD), where podocyte Fyn inactivation was reported, also showed lower glomerular volumes than FSGS. We hypothesized that lower glomerular volume prevented the progression to podocytopenia. To test this hypothesis, we utilized unilateral and 5/6th nephrectomy models in Shroom3-KD mice. Knockdown mice exhibited less glomerular and podocyte hypertrophy after nephrectomy. FYN-knockdown podocytes had similar reductions in podocyte volume, implying that Fyn was downstream of Shroom3. Using SHROOM3 or FYN knockdown, we confirmed reduced podocyte protein content, along with significantly increased phosphorylated AMPK, a negative regulator of anabolism. AMPK activation resulted from increased cytoplasmic redistribution of LKB1 in podocytes. Inhibition of AMPK abolished the reduction in glomerular volume and induced podocytopenia in mice with FPE, suggesting a protective role for AMPK activation. In agreement with this, treatment of glomerular injury models with AMPK activators restricted glomerular volume, podocytopenia, and progression to FSGS. Glomerular transcriptomes from MCD biopsies also showed significant enrichment of Fyn inactivation and Ampk activation versus FSGS glomeruli. In summary, we demonstrated the important role of AMPK in glomerular volume regulation and podocyte survival. Our data suggest that AMPK activation adaptively regulates glomerular volume to prevent podocytopenia in the context of podocyte injury.
Bibliographical noteFunding Information:
We acknowledge David Carling, University College London, London, United Kingdom, and Michael Caplan, Lloyd Cantley, and Shuta Ishibe of Yale University School of Medicine for critical discussions regarding data. We also acknowledge Peter Heeger of Mount Sinai for feedback on data, Gail Celio at the University of Minnesota Imaging Center, and Ronald Gordon at the electron microscopy core of Icahn School of Medicine at Mount Sinai. We would like to acknowledge Barbara Murphy for her strong support, encouragement, and mentorship, which were essential to the completion of this study. MCM wishes to acknowledge funding from the NIH (R01-DK122164), American Heart Association (AHASDG25870018), and philanthropy from Nina and Homer Eaton.NEPTUNE, U54-DK-083912, is a part of the NIH Rare Disease Clinical Research Network, supported through a collaboration between the Office of Rare Diseases Research, National Center for Advancing Translational Sciences, and the National Institute of Diabetes and Digestive and Kidney Diseases. Additional funding and/or programmatic support for this project has been provided by the University of Michigan, NephCure Kidney International, and the Halpin Foundation.
Copyright: © 2021, Banu et al.
PubMed: MeSH publication types
- Journal Article
- Research Support, Non-U.S. Gov't
- Research Support, N.I.H., Extramural