Contact inhibition is a key cellular phenomenon that prevents cells from hyper-proliferating upon reaching confluence. Although not fully characterized, a critical driver of this process is the Hippo signaling pathway, whose downstream effector yes-associated protein plays pivotal roles in cell growth and differentiation. Here, we provide evidence that the E3 ligase WWP1 (WW-domain containing protein 1) mono-ubiquitinates AMOTL2 (angiomotin-like 2) at K347 and K408. Mono-ubiquitinated AMOTL2, in turn, interacts with the kinase LATS2, which facilitates recruitment of the upstream Hippo pathway component SAV1 and ultimately promotes yes-associated protein phosphorylation and subsequent cytoplasmic sequestration and/or degradation. Furthermore, contact inhibition induced by high cell density promoted the localization and stabilization of WWP1 at cell junctions, where it interacted with Crumbs polarity proteins. Notably, the Crumbs complex was functionally important for AMOTL2 mono-ubiquitination and LATS activation under high cell density conditions. These findings delineate a functionally important molecular mechanism in which AMOTL2 mono-ubiquitination by WWP1 at cell junctions and LATS activation are tightly coupled to upstream cell density cues.

中文翻译：

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WWP1 的 AMOTL2 单泛素化通过促进 LATS 激活来促进接触抑制。

接触抑制是一种关键的细胞现象，可防止细胞在达到汇合时过度增殖。虽然没有完全表征，但这一过程的关键驱动因素是 Hippo 信号通路，其下游效应物是相关蛋白在细胞生长和分化中起关键作用。在这里，我们提供的证据表明 E3 连接酶 WWP1（含有蛋白质 1 的 WW 结构域）在 K347 和 K408 处单泛素化 AMOTL2（血管动蛋白样 2）。反过来，单泛素化的 AMOTL2 与激酶 LATS2 相互作用，从而促进上游 Hippo 途径组分 SAV1 的募集，并最终促进与相关蛋白磷酸化和随后的细胞质隔离和/或降解。此外，由高细胞密度引起的接触抑制促进了 WWP1 在细胞连接处的定位和稳定，它与 Crumbs 极性蛋白相互作用。值得注意的是，Crumbs 复合物在高细胞密度条件下对 AMOTL2 单泛素化和 LATS 激活具有重要的功能。这些发现描绘了一种功能上重要的分子机制，其中 WWP1 在细胞连接处的 AMOTL2 单泛素化和 LATS 激活与上游细胞密度线索紧密耦合。