ACE2 on epithelial cells is the SARS-CoV-2 entry receptor. Single-cell RNA-sequencing data derived from two COVID-19 cohorts revealed that MAP4K3/GLK-positive epithelial cells were increased in patients. SARS-CoV-2-induced GLK overexpression in epithelial cells was correlated with COVID-19 severity and vesicle secretion. GLK overexpression induced the epithelial cell-derived exosomes containing ACE2; the GLK-induced exosomes transported ACE2 proteins to recipient cells, facilitating pseudovirus infection. Consistently, ACE2 proteins were increased in the serum exosomes from another COVID-19 cohort. Remarkably, SARS-CoV-2 spike protein-stimulated GLK, and GLK stabilized ACE2 in epithelial cells. Mechanistically, GLK phosphorylated ACE2 at two serine residues (Ser776, Ser783), leading to the dissociation of ACE2 from its E3 ligase UBR4. Reduction in UBR4-induced Lys48-linked ubiquitination at three lysine residues (Lys26, Lys112, Lys114) of ACE2 prevented its degradation. Furthermore, SARS-CoV-2 pseudovirus or live virus infection in humanized ACE2 mice induced GLK and ACE2 protein levels, and ACE2-containing exosomes. Collectively, ACE2 stabilization by SARS-CoV-2-induced MAP4K3/GLK may contribute to the pathogenesis of COVID-19.

中文翻译：

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SARS-CoV-2 刺突蛋白增强 MAP4K3/GLK 诱导的 COVID-19 中 ACE2 的稳定性

上皮细胞上的 ACE2 是 SARS-CoV-2 进入受体。来自两个 COVID-19 队列的单细胞 RNA 测序数据显示，患者的 MAP4K3/GLK 阳性上皮细胞增加。SARS-CoV-2 诱导的上皮细胞中 GLK 过表达与 COVID-19 的严重程度和囊泡分泌相关。GLK过表达诱导上皮细胞衍生的含有ACE2的外泌体；GLK诱导的外泌体将ACE2蛋白转运到受体细胞，促进假病毒感染。一致地，来自另一个 COVID-19 队列的血清外泌体中的 ACE2 蛋白增加。值得注意的是，SARS-CoV-2 刺突蛋白刺激了 GLK，而 GLK 稳定了上皮细胞中的 ACE2。从机制上讲，GLK 在两个丝氨酸残基（Ser776、Ser783）处磷酸化 ACE2，导致 ACE2 从其 E3 连接酶 UBR4 上解离。在 ACE2 的三个赖氨酸残基（Lys26、Lys112、Lys114）上，UBR4 诱导的 Lys48 连接泛素化的减少阻止了其降解。此外，人源化 ACE2 小鼠中的 SARS-CoV-2 假病毒或活病毒感染可诱导 GLK 和 ACE2 蛋白水平以及含有 ACE2 的外泌体。总的来说，SARS-CoV-2 诱导的 MAP4K3/GLK 稳定 ACE2 可能有助于 COVID-19 的发病机制。