The guanine nucleotide exchange factor Arf-like protein 13b is essential for assembly of the mouse photoreceptor transition zone and outer segment
The guanine nucleotide exchange factor Arf-like protein 13b is essential for assembly of the mouse photoreceptor transition zone and outer segment
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DOI：
10.1074/jbc.ra117.000141
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发表时间：
2017-12-29
影响因子：
4.8
通讯作者：
Baehr, Wolfgang
中科院分区：
文献类型：
--
作者：
Hanke-Gogokhia, Christin;Wu, Zhijian;Baehr, Wolfgang
Arf样蛋白13 b（ARL 13 b）是一种小的GT3，作为ARL 3-GDP的鸟苷酸交换因子（GEF）发挥作用。ARL 13 b仅位于光感受器外节（OS），推测通过棕榈酰化锚定到盘，而ARL 3是内节细胞质蛋白。影响ARL 13 b G-结构域的亚型突变可导致人类Joubert综合征（JS）。然而，ARL 13 b突变诱导的Joubert综合征的分子机制，特别是初级纤毛的功能，仍然没有完全了解。因为小鼠中的Arl 13 b种系敲除是致命的，我们产生了ARL 13 b的视网膜特异性缺失，其中ARL 3-GTP形成受损。在出生后第6天（P6）及更大的小鼠（ret）Arl 13 b（-/-）中央视网膜中，外节缺失，从而阻止了外节蛋白向其目的地的运输。出生后第10天（P10）的中央（ret）Arl 13 b（-/-）光感受器的超微结构显示对接的基体细胞膜，但成熟的过渡区和光盘结构缺席。通过他莫昔芬诱导的Cre/loxP重组在成年小鼠中缺失ARL 13 b表明轴丝逐渐缩短，外节逐渐退化。IFT 88，必需的顺行鞭毛内运输（IFT），显着减少（tam）Arl 13 b（-/-）基体，表明鞭毛内运输的损害。AAV 2/8载体介导的（ret）Arl 13 b（-/-）视网膜中的ARL 13 b表达拯救了纤毛发生。
Arf-like protein 13b (ARL13b) is a small GTPase that functions as a guanosine nucleotide exchange factor (GEF) for ARL3-GDP. ARL13b is located exclusively in photoreceptor outer segments (OS) presumably anchored to discs by palmitoylation, whereas ARL3 is an inner segment cytoplasmic protein. Hypomorphic mutations affecting the ARL13b G-domain inactivate GEF activity and lead to Joubert syndrome (JS) in humans. However, the molecular mechanisms in ARL13b mutation-induced Joubert syndrome, particularly the function of primary cilia, are still incompletely understood. Because Arl13b germline knockouts in mouse are lethal, we generated retina-specific deletions of ARL13b in which ARL3-GTP formation is impaired. In mouse (ret)Arl13b(-/-) central retina at postnatal day 6 (P6) and older, outer segments were absent, thereby preventing trafficking of outer segment proteins to their destination. Ultrastructure of postnatal day 10 (P10) central (ret)Arl13b(-/-) photoreceptors revealed docking of basal bodies to cell membranes, but mature transition zones and disc structures were absent. Deletion of ARL13b in adult mice via tamoxifen-induced Cre/loxP recombination indicated that axonemes gradually shorten and outer segments progressively degenerate. IFT88, essential for anterograde intraflagellar transport (IFT), was significantly reduced at (tam)Arl13b(-/-) basal bodies, suggesting impairment of intraflagellar transport. AAV2/8 vector-mediated ARL13b expression in the (ret)Arl13b(-/-) retina rescued ciliogenesis.