FSGS-Causing INF2 Mutation Impairs Cleaved INF2 N-Fragment Functions in Podocytes
| Autor: | Balajikarthick Subramanian, Henry N. Higgs, Seth L. Alper, Chandra Perez-Gill, Justin Chun, Johannes Schlondorff, Martin R. Pollak, Isaac E. Stillman, Paul Yan |
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| Rok vydání: | 2020 |
| Předmět: |
0301 basic medicine
Gene isoform 030232 urology & nephrology Formins Podocyte foot Cleavage (embryo) Podocyte Mice 03 medical and health sciences 0302 clinical medicine Up Front Matters medicine Animals Humans Protein Isoforms Cells Cultured Actin biology Glomerulosclerosis Focal Segmental Podocytes Chemistry General Medicine Cathepsins Peptide Fragments Cell biology Mice Inbred C57BL INF2 HEK293 Cells 030104 developmental biology medicine.anatomical_structure Nephrology Mutation biology.protein MDia1 |
| Zdroj: | J Am Soc Nephrol |
| ISSN: | 1533-3450 1046-6673 |
| DOI: | 10.1681/asn.2019050443 |
| Popis: | Background Mutations in the gene encoding inverted formin-2 (INF2), a member of the formin family of actin regulatory proteins, are among the most common causes of autosomal dominant FSGS. INF2 is regulated by interaction between its N-terminal diaphanous inhibitory domain (DID) and its C-terminal diaphanous autoregulatory domain (DAD). INF2 also modulates activity of other formins, such as the mDIA subfamily, and promotes stable microtubule assembly. Why the disease-causing mutations are restricted to the N terminus and how they cause human disease has been unclear. Methods We examined INF2 isoforms present in podocytes and evaluated INF2 cleavage as an explanation for immunoblot findings. We evaluated the expression of INF2 N- and C-terminal fragments in human kidney disease conditions. We also investigated the localization and functions of the DID-containing N-terminal fragment in podocytes and assessed whether the FSGS-associated R218Q mutation impairs INF2 cleavage or the function of the N-fragment. Results The INF2-CAAX isoform is the predominant isoform in podocytes. INF2 is proteolytically cleaved, a process mediated by cathepsin proteases, liberating the N-terminal DID to function independently. Although the N-terminal region normally localizes to podocyte foot processes, it does not do so in the presence of FSGS-associated INF2 mutations. The C-terminal fragment localizes to the cell body irrespective of INF2 mutations. In podocytes, the N-fragment localizes to the plasma membrane, binds mDIA1, and promotes cell spreading in a cleavage-dependent way. The disease-associated R218Q mutation impairs these N-fragment functions but not INF2 cleavage. Conclusions INF2 is cleaved into an N-terminal DID-containing fragment and a C-terminal DAD-containing fragment. Cleavage allows the N-terminal fragment to function independently and helps explain the clustering of FSGS-associated mutations. |
| Databáze: | OpenAIRE |
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