Gelsolin activates DNase I in vitro and in cystic fibrosis sputum
Gelsolin activates DNase I in vitro and in cystic fibrosis sputum
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DOI：
10.1021/bi9711487
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发表时间：
1997-08-12
期刊：
影响因子：
2.9
通讯作者：
Bubb, MR
中科院分区：
文献类型：
--
作者：
Davoodian, K;Ritchings, BW;Bubb, MR
由于肌动蛋白可以在体外形成含有凝溶胶蛋白和DNA酶I的复合物，因此凝溶胶蛋白和DNA酶I被认为独立地与肌动蛋白结合。虽然这一假设是一致的凝溶胶蛋白与一个肌动蛋白和肌动蛋白与DNA酶I，这表明，凝溶胶蛋白和DNA酶I的肌动蛋白上的结合位点是不同的和单独的已知的晶体结构，我们建议，第二个肌动蛋白结合位点的凝溶胶蛋白竞争与DNA酶I的肌动蛋白。由于肌动蛋白是DNA酶I的抑制剂，在第二个结合位点的竞争导致DNA酶I被凝溶胶蛋白激活。共价交联实验证实，DNA酶I阻止肌动蛋白被凝溶胶蛋白二聚化，这与DNA酶I从凝溶胶蛋白中置换一个肌动蛋白一致。凝溶胶蛋白激活DNA酶I是一种细胞骨架蛋白的新功能，可能对生物学有广泛的影响，例如在启动细胞凋亡中的作用。这些结果也可以解释为什么凝溶胶蛋白和DNA酶I降低囊性纤维化（CF）痰液粘度。虽然DNA酶I的活性最初归因于DNA的片段化，但随后的数据表明凝溶胶蛋白和DNA酶I都可能通过解聚丝状肌动蛋白来影响粘度。目前的结果也表明，CF痰液中凝溶胶蛋白对肌动蛋白-DNA酶I复合物的解离导致组成型DNA酶I的核酸酶活性活化。因此，单独的DNA酶I的核酸酶活性足以解释凝溶胶蛋白和DNA酶I对CF痰液的影响。
Because actin can form a complex in vitro containing both gelsolin and DNase I, gelsolin and DNase I have been assumed to bind independently to actin. Although this assumption is consistent with the known crystalline structures of gelsolin with one actin and of actin with DNase I, which suggest that the binding sites on actin for both gelsolin and DNase I are distinct and separate, we propose that a second actin binding site on gelsolin competes with DNase I for actin. Since actin is an inhibitor of DNase I, competition at the second binding site results in activation of DNase I by gelsolin. Covalent cross-linking experiments confirm that DNase I prevents dimerization of actin by gelsolin, consistent with displacement of one actin from, gelsolin by DNase I. Activation of DNase I by gelsolin is a novel function for a cytoskeletal protein and could have broad implications for biology, such as a role in initiating apoptosis. These results also may explain why both gelsolin and DNase I decrease sputum viscosity in cystic fibrosis (CF). While the activity of DNase I had originally been attributed to fragmentation of DNA, subsequent data suggested that both gelsolin and DNase I may affect viscosity by depolymerizing filamentous actin. The current results alternatively suggest that dissociation of the actin-DNase I complex by gelsolin in CF sputum results in activation of the nuclease activity of constitutive DNase I. The nuclease activity of DNase I alone is therefore sufficient to explain the effects of both gelsolin and DNase I on CF sputum.