The Cl-/H+ antiporter ClC-7 is the primary chloride permeation pathway in lysosomes
The Cl-/H+ antiporter ClC-7 is the primary chloride permeation pathway in lysosomes
复制标题
DOI：
10.1038/nature06907
复制
发表时间：
2008-06-05
期刊：
影响因子：
64.8
通讯作者：
Mindell, Joseph A.
中科院分区：
文献类型：
--
作者：
Graves, Austin R.;Curran, Patricia K.;Mindell, Joseph A.
溶酶体是内吞途径上细胞末端细胞器的胃，内化的大分子在这里被降解。溶酶体含有广泛的水解酶，依赖于维持酸性的管腔pH值来实现有效的功能。虽然酸化是由V型质子ATPase介导的，但平行的阴离子途径对于允许大量质子运输是必不可少的(1，2)。这种阴离子转运蛋白的分子特性尚不清楚。最近的基因敲除实验结果提出，ClC-7是CLC阴离子通道和转运体家族的成员，可能是破骨细胞溶酶体样间隔中这一途径的贡献者，CLC-7功能的丧失导致骨化症[3]。CLC家族中的几个哺乳动物成员已被详细描述，其中一些(包括CLC-0、CLC-1和CLC-2)作为氯(-)传导离子通道(4)，而另一些(包括CLC-4和CLC-5)作为氯(-)/H(+)逆向转运体(5，6)。然而，以前异源表达ClC-7的尝试都没有得到功能蛋白的证据，因此尚不清楚ClC-7在溶酶体生物学中是否具有重要的功能，也不清楚该蛋白是作为氯(-)通道、氯(-)/氢(+)逆向转运体还是其他完全的功能。在这里，我们直接展示了溶酶体内的阴离子转运途径，该途径具有ClC Cl(-)/H(+)逆向转运蛋白的明确特征，并表明该转运蛋白是Cl(-)通过溶酶体膜的主要途径。此外，通过短干扰RNA抑制ClC-7的表达，可以基本消除溶酶体的Cl(-)/H(+)逆向转运活性，并能显著降低溶酶体体内酸化的能力，这表明ClC-7是一种Cl(-)/H(+)逆向转运体，它构成了溶酶体的主要Cl(-)通透性，在溶酶体酸化中起着重要的作用。
Lysosomes are the stomachs of the cell - terminal organelles on the endocytic pathway where internalized macromolecules are degraded. Containing a wide range of hydrolytic enzymes, lysosomes depend on maintaining acidic luminal pH values for efficient function. Although acidification is mediated by a V- type proton ATPase, a parallel anion pathway is essential to allow bulk proton transport(1,2). The molecular identity of this anion transporter remains unknown. Recent results of knockout experiments raise the possibility that ClC- 7, a member of the CLC family of anion channels and transporters, is a contributor to this pathway in an osteoclast lysosome- like compartment, with loss of ClC- 7 function causing osteopetrosis(3). Several mammalian members of the CLC family have been characterized in detail; some ( including ClC- 0, ClC- 1 and ClC- 2) function as Cl(-) -conducting ion channels(4), whereas others act as Cl(-)/H(+) antiporters ( ClC- 4 and ClC-5) (5,6). However, previous attempts at heterologous expression of ClC- 7 have failed to yield evidence of functional protein, so it is unclear whether ClC- 7 has an important function in lysosomal biology, and also whether this protein functions as a Cl(-) channel, a Cl(-)/H(+) antiporter, or as something else entirely. Here we directly demonstrate an anion transport pathway in lysosomes that has the defining characteristics of a CLC Cl(-)/H(+) antiporter and show that this transporter is the predominant route for Cl(-) through the lysosomal membrane. Furthermore, knockdown of ClC- 7 expression by short interfering RNA can essentially ablate this lysosomal Cl(-)/H(+) antiport activity and can strongly diminish the ability of lysosomes to acidify in vivo, demonstrating that ClC- 7 is a Cl(-)/H(+) antiporter, that it constitutes the major Cl(-) permeability of lysosomes, and that it is important in lysosomal acidification.