title: Rho activation of mDia formins is modulated by an interaction with inverted formin 2 (INF2).
abstract: Inverted formin 2 (INF2) encodes a member of the diaphanous subfamily of formin proteins. Mutations in INF2 cause human kidney disease characterized by focal and segmental glomerulosclerosis. Disease-causing mutations occur only in the diaphanous inhibitory domain (DID), suggesting specific roles for this domain in the pathogenesis of disease. In a yeast two-hybrid screen, we identified the diaphanous autoregulatory domains (DADs) of the mammalian diaphanous-related formins (mDias) mDia1, mDia2, and mDia 3 as INF2_DID-interacting partners. The mDias are Rho family effectors that regulate actin dynamics. We confirmed in vitro INF2_DID/mDia_DAD binding by biochemical assays, confirmed the in vivo interaction of these protein domains by coimmunoprecipitation, and observed colocalization of INF2 and mDias in glomerular podocytes. We investigated the influence of this INF2_DID/mDia_DAD interaction on mDia mediated actin polymerization and on serum response factor (SRF) activation. We find that the interaction of INF2_DID with mDia_DAD inhibited mDia-mediated, Rho-activated actin polymerization, as well as SRF-responsive gene transcriptional changes. Similar assays using the disease-causing E184K and R218Q mutations in INF2_DID showed a decreased effect on SRF activation and gene transcription. The binding of INF2_DID to mDia_DAD may serve as a negative regulatory mechanism for mDias' function in actin-dependent cell processes. The effects of disease-causing INF2 mutations suggest an important role for this protein and its interaction with other formins in modulating glomerular podocyte phenotype and function.
authors.affiliation: Nephrology Division, Department of Medicine, Shanghai Children's Medical Center, Shanghai Jiaotong University School of Medicine, Shanghai 200127, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Sun
authors.forename: Johannes S
authors.initials: JS
authors.lastname: Schlondorff
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Brown
authors.forename: Henry N
authors.initials: HN
authors.lastname: Higgs
authors.forename: Martin R
authors.initials: MR
authors.lastname: Pollak
mesh_terms: D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D000080865:Formins; D005923:Glomerulosclerosis, Focal Segmental / Q000235:genetics; D057809:HEK293 Cells; D006801:Humans; D047468:Immunoprecipitation; D008156:Luciferases; D051379:Mice; D008840:Microfilament Proteins / Q000235:genetics* / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D041681:NIH 3T3 Cells; D050199:Podocytes / Q000378:metabolism; D058105:Polymerization; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013050:Spectrometry, Fluorescence; D020798:Two-Hybrid System Techniques
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; C112200:CDC40 protein, human; D018797:Cell Cycle Proteins; C108962:DIAPH1 protein, human; D017931:DNA Primers; D000080865:Formins; C546959:INF2 protein, human; D008840:Microfilament Proteins; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins; D008156:Luciferases