New Paradigm for Cytoskeletal Organization in Podocytes: Proteolytic Fragments of INF2 Formin Function Independently of INF2 Actin Regulatory Activity
| Autor: | Mira Krendel, David Pruyne |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Glomerulosclerosis
Focal Segmental Podocytes Microfilament Proteins Cytoskeletal Organization Formins Foot process effacement General Medicine Biology Actins Cell biology Podocyte INF2 medicine.anatomical_structure Basic Research Nephrology Mutation biology.protein medicine Humans Actin Function (biology) |
| Zdroj: | J Am Soc Nephrol |
| ISSN: | 1533-3450 |
| 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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