Synaptopodin protects against proteinuria by disrupting Cdc42: IRSp53:Mena signaling complexes in kidney podocytes

Etsuko Yanagida-Asanuma, Katsuhiko Asanuma, Kwanghee Kim, Mary Donnelly, Young Choi Hoon, Hyung Chang Jae, Shiro Suetsugu, Yasuhiko Tomino, Tadaomi Takenawa, Christian H Faul, Peter Mundel

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108 Scopus citations

Abstract

The actin-based foot processes of kidney podocytes and the interposed slit diaphragm form the final barrier to proteinuria. Mutations affecting several podocyte proteins cause disruption of the filtration barrier and rearrangement of the highly dynamic podocyte actin cytoskeleton. Proteins regulating the plasticity of the podocyte actin cytoskeleton are therefore of critical importance for sustained kidney barrier function. Synaptopodin is an actin-associated protein essential for the integrity of the podocyte actin cytoskeleton because synaptopodin-deflcient mice display impaired recovery from protamine sulfate-induced foot process effacement and lipopohysaccharide-induced nephrotic syndrome. Moreover, bigenic heterozygosity for synaptopodin and CD2AP is sufficient to induce spontaneous proteinuria and focal segmental glomerulosclerosis-like glomerular damage in mice. Mechanistically, synaptopodin induces stress fibers by blocking the proteasomal degradation of RhoA. Here we show that synaptopodin directly binds to ERSp53 and suppresses Cdc42:IRSp53:Mena-initiated filopodia formation by blocking the binding of Cdc42 and Mena to IRSp53. The Mena inhibitor FP4-Mito suppresses aberrant filopodia formation in synaptopodin knockdown podocytes, and when delivered into mice protects against lipopoh/saccharide-induced proteinuria. The identification of synaptopodin as an inhibitor of Cdc42:IRSp53:Mena signaling defines a novel antiproteinuric signaling pathway and offers new targets for the development of antiproteinuric therapeutic modalities.

Original languageEnglish
Pages (from-to)415-427
Number of pages13
JournalAmerican Journal of Pathology
Volume171
Issue number2
DOIs
StatePublished - Aug 1 2007
Externally publishedYes

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ASJC Scopus subject areas

  • Pathology and Forensic Medicine

Cite this

Yanagida-Asanuma, E., Asanuma, K., Kim, K., Donnelly, M., Hoon, Y. C., Jae, H. C., Suetsugu, S., Tomino, Y., Takenawa, T., Faul, C. H., & Mundel, P. (2007). Synaptopodin protects against proteinuria by disrupting Cdc42: IRSp53:Mena signaling complexes in kidney podocytes. American Journal of Pathology, 171(2), 415-427. https://doi.org/10.2353/ajpath.2007.070075