Mdm muscular dystrophy:: interactions with calpain 3 and a novel functional role for titin's N2A domain
Mdm muscular dystrophy:: interactions with calpain 3 and a novel functional role for titin's N2A domain
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DOI：
10.1093/hmg/ddi313
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发表时间：
2005-10-01
影响因子：
3.5
通讯作者：
Cox, GA
中科院分区：
文献类型：
--
作者：
Huebsch, KA;Kudryashova, E;Cox, GA
人类胫骨肌营养不良症和四肢带状肌营养不良症2J是由肌肉特异性蛋白钙蛋白酶3(CAPN3)结合位点附近的巨大肌节蛋白Titin(TTN)突变引起的。肌营养不良伴肌炎(MDM)是一种隐性突变，由肌蛋白(TTN-N2A(Delta 83))的N2A域缺失引起的严重进行性肌肉变性，破坏了CAPN3的一个假定结合部位。为了确定突变的MDM小鼠的肌营养不良是否是由于CAPN3活性调节不当引起的，我们建立了CAPN3过表达转基因(C3Tg)和CAPN3基因敲除(C3KO)小鼠的遗传杂交。在这里，我们报告CAPN3的过度表达会加剧MDM疾病，导致更短的寿命和更严重的肌营养不良。然而，在CAPN3‘S作为MDM病理介质的直接遗传测试中，C3KO；MDM双突变小鼠在疾病的进展或严重程度方面没有改变，表明CAPN3的异常活性不是该病的主要机制。为了确定我们是否可以在非疾病状态下检测到肌动蛋白的功能缺陷，我们检测了杂合+/MDM小鼠的跑步机运动，并检测到伴随着站立时间的增加，步态时间显著增加。有趣的是，在转基因C3Tg；+/MDM小鼠中，CAPN3的过度表达完全纠正了这些改变的步态参数，支持TTN的N2A域在肌肉收缩动力学中的CAPN3依赖作用。
Human tibial muscular dystrophy and limb-girdle muscular dystrophy 2J are caused by mutations in the giant sarcomeric protein titin (TTN) adjacent to a binding site for the muscle-specific protease calpain 3 (CAPN3). Muscular dystrophy with myositis (mdm) is a recessive mouse mutation with severe and progressive muscular degeneration caused by a deletion in the N2A domain of titin (TTN-N2A(Delta 83)), disrupting a putative binding site for CAPN3. To determine whether the muscular dystrophy in mutant mdm mice is caused by misregulation of CAPN3 activity, genetic crosses with CAPN3 overexpressing transgenic (C3Tg) and CAPN3 knockout (C3KO) mice were generated. Here, we report that overexpression of CAPN3 exacerbates the mdm disease, leading to a shorter life span and more severe muscular dystrophy. However, in a direct genetic test of CAPN3's role as a mediator of mdm pathology, C3KO;mdm double mutant mice showed no change in the progression or severity of disease indicating that aberrant CAPN3 activity is not a primary mechanism in this disease. To determine whether we could detect a functional deficit in titin in a non-disease state, we examined the treadmill locomotion of heterozygous +/mdm mice and detected a significant increase in stride time with a concomitant increase in stance time. Interestingly, these altered gait parameters were completely corrected by CAPN3 overexpression in transgenic C3Tg;+/mdm mice, supporting a CAPN3-dependent role for the N2A domain of TTN in the dynamics of muscle contraction.