A helix-breaking mutation in TRPML3 leads to constitutive activity underlying deafness in the varitint-waddler mouse
A helix-breaking mutation in TRPML3 leads to constitutive activity underlying deafness in the varitint-waddler mouse
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DOI：
10.1073/pnas.0709846104
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发表时间：
2007-12-04
影响因子：
11.1
通讯作者：
Heller, Stefan
中科院分区：
文献类型：
--
作者：
Grimm, Christian;Cuajungco, Math P.;Heller, Stefan
表达TRPML3（粘脂蛋白3）突变异构体（A419P）的纯合子变异构体-蹒跚（Va）小鼠严重失聋，表现出前庭和色素沉着缺陷、不育和围产期死亡率。在这里，我们发现携带A419P突变的TRPML3变体-waddler异构体代表了一个组成活跃的阳离子通道，该阳离子通道也可以在天然变体-waddler毛细胞中被识别为一个独特的内整流电流。我们假设TRPML3的组成性激活是由于跨膜结构域5 （TM5）中的螺旋断裂脯氨酸取代而发生的。脯氨酸替代扫描表明，TRPML3的TM5的内三分之一对脯氨酸基结非常敏感。在TRPML1、TRPML2、TRPV5和TRPV6的TRP通道TM5中进行脯氨酸替换，发现TRPML1、TRPML2、TRPV5和TRPV6在相似位置表现出相似的易感性，而其他TRP通道不受影响。我们得出结论，变步鼠耳聋的分子基础是由组成型TRPML3活性引起的毛细胞死亡的结果。据我们所知，我们的研究首次提供了TRP离子通道突变与哺乳动物听力损失之间的直接机制联系。
Homozygote varitint-waddler (Va) mice, expressing a mutant isoform (A419P) of TRPML3 (mucolipin 3), are profoundly deaf and display vestibular and pigmentation deficiencies, sterility, and perinatal lethality. Here we show that the varitint-waddler isoform of TRPML3 carrying an A419P mutation represents a constitutively active cation channel that can also be identified in native varitint-waddler hair cells as a distinct inwardly rectifying current. We hypothesize that the constitutive activation of TRPML3 occurs as a result of a helix-breaking proline substitution in transmembrane-spanning domain 5 (TM5). A proline substitution scan demonstrated that the inner third of TRPML3's TM5 is highly susceptible to proline-based kinks. Proline substitutions in TM5 of other TRIP channels revealed that TRPML1, TRPML2, TRPV5, and TRPV6 display a similar susceptibility at comparable positions, whereas other TRP channels were not affected. We conclude that the molecular basis for deafness in the varitint-waddler mouse is the result of hair cell death caused by constitutive TRPML3 activity. To our knowledge, our study provides the first direct mechanistic link of a mutation in a TRP ion channel with mammalian hearing loss.