ABC transporters couple ATP hydrolysis to the transport of substrates across cellular membranes. This protein superfamily has diverse activities resulting from differences in their cargo and subcellular localization. Our work investigates the role of the ABCG family member WHT-2 in the biogenesis of gut granules, a Caenorhabditis elegans lysosome-related organelle. In addition to being required for the accumulation of birefringent material within gut granules, WHT-2 is necessary for the localization of gut granule proteins when trafficking pathways to this organelle are partially disrupted. The role of WHT-2 in gut granule protein targeting is likely linked to its function in Rab GTPase localization. We show that WHT-2 promotes the gut granule association of the Rab32 family member GLO-1 and the endolysosomal RAB-7, identifying a novel function for an ABC transporter. WHT-2 localizes to gut granules where it could play a direct role in controlling Rab localization. Loss of CCZ-1 and GLO-3, which likely function as a guanine nucleotide exchange factor (GEF) for GLO-1, lead to similar disruption of GLO-1 localization. We show that CCZ-1, like GLO-3, is localized to gut granules. WHT-2 does not direct the gut granule association of the GLO-1 GEF and our results point to WHT-2 functioning differently than GLO-3 and CCZ-1 Point mutations in WHT-2 that inhibit its transport activity, but not its subcellular localization, lead to the loss of GLO-1 from gut granules, while other WHT-2 activities are not completely disrupted, suggesting that WHT-2 functions in organelle biogenesis through transport-dependent and transport-independent activities.

中文翻译：

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ABCG 转运蛋白在秀丽隐杆线虫 Rab 定位和溶酶体相关细胞器生物发生中发挥作用。

ABC 转运蛋白将 ATP 水解与底物跨细胞膜的转运结合起来。该蛋白质超家族由于其货物和亚细胞定位的差异而具有多种活性。我们的工作研究了 ABCG 家族成员 WHT-2 在肠道颗粒（一种与秀丽隐杆线虫溶酶体相关的细胞器）生物发生中的作用。除了肠道颗粒内双折射材料积累所必需的之外，当通往该细胞器的运输途径部分中断时，WHT-2 对于肠道颗粒蛋白的定位也是必需的。WHT-2 在肠道颗粒蛋白靶向中的作用可能与其在 Rab GTP 酶定位中的功能有关。我们发现 WHT-2 促进 Rab32 家族成员 GLO-1 和内溶酶体 RAB-7 的肠道颗粒关联，从而确定了 ABC 转运蛋白的新功能。WHT-2 定位于肠道颗粒，可以在控制 Rab 定位中发挥直接作用。CCZ-1 和 GLO-3（可能作为 GLO-1 的鸟嘌呤核苷酸交换因子 (GEF)）的缺失，会导致 GLO-1 定位的类似破坏。我们发现 CCZ-1 与 GLO-3 一样，定位于肠道颗粒。WHT-2 不指导 GLO-1 GEF 的肠道颗粒关联，我们的结果表明 WHT-2 的功能与 GLO-3 和 CCZ-1 不同 WHT-2 中的点突变抑制其转运活性，但不抑制其亚细胞活性定位，导致 GLO-1 从肠道颗粒中丢失，而其他 WHT-2 活性并未完全破坏，表明 WHT-2 通过转运依赖性和转运非依赖性活性在细胞器生物发生中发挥作用。