Rollason Ruth, Wherlock Matthew, Heath Jenny A, Heesom Kate J, Saleem Moin A, Welsh Gavin I
Academic Renal Unit, School of Clinical Sciences, University of Bristol, Dorothy Hodgkin Building, Whitson Street, Bristol BS1 3NY, U.K.
Biosci Rep. 2016 Jan 13;36(1):e00302. doi: 10.1042/BSR20150252.
Focal segmental glomerulosclerosis (FSGS) is a devastating form of nephrotic syndrome which ultimately leads to end stage renal failure (ESRF). Mutations in inverted formin 2 (INF2), a member of the formin family of actin-regulating proteins, have recently been associated with a familial cause of nephrotic syndrome characterized by FSGS. INF2 is a unique formin that can both polymerize and depolymerize actin filaments. How mutations in INF2 lead to disease is unknown. In the present study, we show that three mutations associated with FSGS, E184K, S186P and R218Q, reduce INF2 auto-inhibition and increase association with monomeric actin. Furthermore using a combination of GFP-INF2 expression in human podocytes and GFP-Trap purification coupled with MS we demonstrate that INF2 interacts with profilin 2 and the F-actin capping protein, CapZ α-1. These interactions are increased by the presence of the disease causing mutations. Since both these proteins are involved in the dynamic turnover and restructuring of the actin cytoskeleton these changes strengthen the evidence that aberrant regulation of actin dynamics underlies the pathogenesis of disease.
局灶节段性肾小球硬化（FSGS）是一种严重的肾病综合征形式，最终会导致终末期肾衰竭（ESRF）。肌动蛋白调节蛋白formin家族成员倒转formin 2（INF2）的突变，最近被认为是导致以FSGS为特征的家族性肾病综合征的原因。INF2是一种独特的formin，既能使肌动蛋白丝聚合，也能使其解聚。INF2的突变如何导致疾病尚不清楚。在本研究中，我们发现与FSGS相关的三个突变E184K、S186P和R218Q，会降低INF2的自我抑制作用，并增加其与单体肌动蛋白的结合。此外，我们通过在人足细胞中表达绿色荧光蛋白（GFP）-INF2，并结合GFP-Trap纯化和质谱分析，证明INF2与原肌球蛋白2和F-肌动蛋白封端蛋白CapZα-1相互作用。致病突变的存在会增加这些相互作用。由于这两种蛋白都参与肌动蛋白细胞骨架的动态周转和重组，这些变化进一步证明了肌动蛋白动力学的异常调节是疾病发病机制的基础。
