Endothelial nitric-oxide synthase antisense (NOS3AS) gene encodes an autophagy-related protein (APG9-like2) highly expressed in trophoblast
Endothelial nitric-oxide synthase antisense (NOS3AS) gene encodes an autophagy-related protein (APG9-like2) highly expressed in trophoblast
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DOI：
10.1074/jbc.m413957200
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发表时间：
2005-05-06
影响因子：
4.8
通讯作者：
Scherer, SW
中科院分区：
文献类型：
--
作者：
Yamada, T;Carson, AR;Scherer, SW
自噬是一种细胞内降解蛋白质和一些细胞器的系统，在所有真核生物中都是保守的。自噬在哺乳动物发育中的确切作用以及在疾病中的潜在参与仍有待观察。酵母Atg9p是第一个完整的膜蛋白，被证明是必不可少的细胞质空泡靶向（CVT）途径和自噬，而其哺乳动物功能的直向同源物尚未确定。我们已经鉴定了两个与酵母Atg9p同源的人类基因，并将其命名为APG9L1和APG9L2。我们以前已经确定APG9L2作为NOS3AS，它通过其反义重叠参与7号染色体上的内皮一氧化氮合酶（NOS3）基因的转录后调节。在成人组织中，APG9L1广泛表达，而APG9L2在胎盘（滋养层细胞）和垂体中高度表达。在瞬时转染试验中，我们发现这两种蛋白质主要定位于核周区域，也分散在整个细胞溶质中作为点，其中一个子集与饥饿条件下的自噬体特异性标记LC 3共定位。最后，通过小干扰RNA介导的HeLa细胞中APG9L1的敲低，我们证明了APG9L1是饥饿诱导的自噬体形成所必需的。此外，APG9L2在此过程中可与APG9L1功能互补。这些结果，加上系统发育和序列分析的结果，表明APG 9L1和APG 9L2在自噬体形成中与yATG 9在功能上直系同源。此外，APG9L2是一个脊椎动物特异性基因，可能通过快速进化在哺乳动物特异性发育事件（如胎盘形成）中发挥关键作用。
Macroautophagy is an intracellular degradation system for the majority of proteins and some organelles that is conserved in all eukaryotic species. The precise role of autophagy in mammalian development and potential involvement in disease remain to be discerned. Yeast Atg9p is the first integral membrane protein shown to be essential for the cytoplasm to vacuole targeting (Cvt) pathway and autophagy, whereas its mammalian functional orthologue has yet to be identified. We have identified two human genes homologous to yeast Atg9p and designated these as APG9L1 and APG9L2. We have previously identified APG9L2 as NOS3AS, which participates in the post-transcriptional regulation of the endothelial nitric-oxide synthase (NOS3) gene on chromosome 7 through its antisense overlap. In human adult tissues, APG9L1 was ubiquitously expressed, whereas APG9L2 was highly expressed in placenta (trophoblast cells) and pituitary gland. In transient transfection assays we found that both proteins were primarily localized to the perinuclear region and also scattered throughout the cytosol as dots, a subset of which colocalized with an autophagosome-specific marker LC3 under starvation conditions. Finally, by the small interfering RNA-mediated knockdown of APG9L1 in HeLa cells, we demonstrated that APG9L1 is essential for starvation-induced autophagosome formation. In addition, APG9L2 can functionally complement APG9L1 in this process. These results, taken together with those of phylogenetic and sequence analyses, suggest that both APG9L1 and APG9L2 are functionally orthologous to the yATG9 in autophagosome formation. Moreover, APG9L2 is a vertebrate-specific gene that may have gained critical roles in mammalian-specific developmental events, such as placentation, through rapid evolution.