Department of Ophthalmology, Margaret Dyson Vision Research Institute, Weill Cornell Medical College, New York, NY 10065, USA.
Proc Natl Acad Sci U S A. 2012 Mar 6;109(10):3820-5. doi: 10.1073/pnas.1117949109. Epub 2012 Feb 16.
The coxsackie and adenovirus receptor (CAR) plays key roles in epithelial barrier function at the tight junction, a localization guided in part by a tyrosine-based basolateral sorting signal, (318)YNQV(321). Sorting motifs of this type are known to route surface receptors into clathrin-mediated endocytosis through interaction with the medium subunit (μ2) of the clathrin adaptor AP-2, but how they guide new and recycling membrane proteins basolaterally is unknown. Here, we show that YNQV functions as a canonical YxxΦ motif, with both Y318 and V321 required for the correct basolateral localization and biosynthetic sorting of CAR, and for interaction with a highly conserved pocket in the medium subunits (μ1A and μ1B) of the clathrin adaptors AP-1A and AP-1B. Knock-down experiments demonstrate that AP-1A plays a role in the biosynthetic sorting of CAR, complementary to the role of AP-1B in basolateral recycling of this receptor. Our study illustrates how two clathrin adaptors direct basolateral trafficking of a plasma membrane protein through interaction with a canonical YxxΦ motif.
柯萨奇病毒和腺病毒受体 (CAR) 在紧密连接处的上皮屏障功能中发挥关键作用，这种定位部分由基于酪氨酸的基底外侧分拣信号 (318)YNQV(321)指导。这种类型的分拣基序已知可通过与网格蛋白衔接蛋白 AP-2 的中型亚基 (μ2) 相互作用将表面受体引导至网格蛋白介导的内吞作用，但它们如何引导新的和再循环的膜蛋白基底外侧尚不清楚。在这里，我们表明 YNQV 作为一个典型的 YxxΦ 基序发挥作用，Y318 和 V321 对于 CAR 的正确基底外侧定位和生物合成分拣以及与网格蛋白衔接蛋白 AP-1A 和 AP-1B 的中型亚基 (μ1A 和 μ1B) 中高度保守的口袋相互作用都是必需的。敲低实验表明，AP-1A 在 CAR 的生物合成分拣中发挥作用，与 AP-1B 在该受体基底外侧再循环中的作用互补。我们的研究说明了两个网格蛋白衔接蛋白如何通过与典型的 YxxΦ 基序相互作用来指导质膜蛋白的基底外侧运输。
