SRGAP1 Controls Small Rho GTPases To Regulate Podocyte Foot Process Maintenance

Area of Science:

• Nephrology
• Cell Biology
• Molecular Biology

Background:

• Small Rho GTPases regulate the actin cytoskeleton and are implicated in podocyte foot process effacement in glomerular diseases like FSGS.
• A comprehensive understanding of Rho GTPase regulatory networks in podocytes is currently lacking.

Purpose of the Study:

• To elucidate the regulatory network of small Rho GTPases in podocytes.
• To investigate the role of SRGAP1 in podocyte structure and function.
• To explore SRGAP1 as a potential therapeutic target for glomerular diseases.

Main Methods:

• Analysis of podocyte transcriptome and proteome datasets for Rho GTPases.
• Mapping of in vivo, podocyte-specific Rho GTPase affinity networks.
• Generation and analysis of Srgap1 conditional knockout mice and SRGAP1 knockout podocytes.
• Evaluation of podocyte foot-process morphology using super-resolution and electron microscopy.
• In situ proximity ligation assays and quantitative interaction proteomics.

Main Results:

• SRGAP1 localizes to podocyte foot processes and limits protrusive actin networks.
• Srgap1 knockout mice exhibit an FSGS-like phenotype and increased susceptibility to nephropathy.
• SRGAP1 deletion leads to podocyte foot process effacement and excessive protrusion formation.
• SRGAP1 interacts with actin networks and its redistribution is observed in human FSGS.

Conclusions:

• SRGAP1, a podocyte-specific RhoGAP, is crucial for maintaining podocyte foot-process architecture.
• SRGAP1 limits the activity of protrusive, branched actin networks, thereby controlling foot-process effacement.
• Understanding the SRGAP1 regulatory network offers potential for precise interventions in glomerular diseases.