Differential regulation of the calpain-calpastatin complex by the L-domain of calpastatin
Differential regulation of the calpain-calpastatin complex by the L-domain of calpastatin
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DOI：
10.1016/j.bbamcr.2014.07.002
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发表时间：
2014-11-01
影响因子：
5.1
通讯作者：
Melloni, Edon
中科院分区：
文献类型：
--
作者：
De Tullio, Roberta;Averna, Monica;Melloni, Edon
在这里，我们证明了l结构域在calpastatin中的存在诱导了与calpain的双相相互作用。竞争实验表明，l结构域参与定位第一个抑制单元在封闭和开放构象中接近和正确接近钙蛋白酶活性位点间隙。在高浓度的calpastatin下，calpain结构域IV和VI中的多个EF-hand结构可以结合calpastatin，维持活性位点对底物的可达性。基于这些观察，我们假设可能出现两种不同的钙蛋白酶和钙pastatin复合物，其中钙蛋白酶可以完全抑制(I)或完全活跃（II）。在络合物II中，可达的钙蛋白酶活性位点可被一个额外的钙蛋白酶分子占据，现在是一个可切割的底物。随后的蛋白水解促进了无钙蛋白酶抑制单位的积累，这些单位能够提高细胞抑制钙蛋白酶的能力。这一过程在[Ca2+]长期改变的条件下进行，例如在家族性肌萎缩性侧索硬化症（FALS）中，calpastatin水平升高。我们的研究结果表明，钙pastatin的l结构域在决定与钙蛋白酶复合物形成的过程中起着至关重要的作用，其中钙蛋白酶可以被抑制或仍然具有活性。此外，天然全长钙蛋白酶分子中多个抑制结构域的存在提供了一个潜在抑制单元库，用于对抗异常的钙蛋白酶活性。(C) 2014 Elsevier B.V.版权所有
Here we demonstrate that the presence of the L-domain in calpastatins induces biphasic interaction with calpain. Competition experiments revealed that the L-domain is involved in positioning the first inhibitory unit in close and correct proximity to the calpain active site cleft, both in the closed and in the open conformation. At high concentrations of calpastatin, the multiple EF-hand structures in domains IV and VI of calpain can bind calpastatin, maintaining the active site accessible to substrate. Based on these observations, we hypothesize that two distinct calpain calpastatin complexes may occur in which calpain can be either fully inhibited (I) or fully active (II). In complex II the accessible calpain active site can be occupied by an additional calpastatin molecule, now a cleavable substrate. The consequent proteolysis promotes the accumulation of calpastatin free inhibitory units which are able of improving the capacity of the cell to inhibit calpain. This process operates under conditions of prolonged [Ca2+] alteration, as seen for instance in Familial Amyotrophic Lateral Sclerosis (FALS) in which calpastatin levels are increased. Our findings show that the L-domain of calpastatin plays a crucial role in determining the formation of complexes with calpain in which calpain can be either inhibited or still active. Moreover, the presence of multiple inhibitory domains in native full-length calpastatin molecules provides a reservoir of potential inhibitory units to be used to counteract aberrant calpain activity. (C) 2014 Elsevier B.V. All rights reserved.