Laminar flow downregulates Notch activity to promote lymphatic sprouting
Laminar flow downregulates Notch activity to promote lymphatic sprouting
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DOI：
10.1172/jci87442
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发表时间：
2017-04-03
影响因子：
15.9
通讯作者：
Hong, Young-Kwon
中科院分区：
文献类型：
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作者：
Choi, Dongwon;Park, Eunkyung;Hong, Young-Kwon
淋巴系统的主要功能是从组织中排出间质液体。功能性引流导致液体流量增加，从而触发淋巴管扩张，这在概念上类似于低氧触发的血管生成。在这里，我们已经确定了一条机械转导途径，将层流诱导的剪应力转化为淋巴萌发的激活。虽然低速率层流通常在血液内皮细胞和淋巴管内皮细胞(LECs)中诱导经典的剪应力反应，但只有LECs表现出Notch活性降低和发芽能力增加。作为对FLOW的响应，质膜钙通道ORAI1介导晶状体上皮细胞钙内流，并激活钙调蛋白以促进剪切反应的主要调节因子Kruppel-like factor2(KLF2)和淋巴发育的主要调节因子PROX1之间的物理相互作用。PROX1/KLF2复合体上调DTX1和DTX3L的表达。DTX1和DTX3L作为异二聚体Notch E3连接酶，协同下调NOTCH1活性，促进淋巴管萌发。值得注意的是，钙报告基因GCaMP3的过度表达出人意料地抑制了淋巴管的萌发，可能是通过干扰钙信号。内皮特异的Orai1和KLF2基因敲除也显著地损害了淋巴管的萌发。此外，Dtx3l功能缺失导致淋巴发芽缺陷，而Dtx3l功能增强挽救了Orai1KO胚胎发芽障碍。总之，这些数据揭示了层流诱导淋巴管萌发的分子机制。
The major function of the lymphatic system is to drain interstitial fluid from tissue. Functional drainage causes increased fluid flow that triggers lymphatic expansion, which is conceptually similar to hypoxia-triggered angiogenesis. Here, we have identified a mechanotransduction pathway that translates laminar flow-induced shear stress to activation of lymphatic sprouting. While low-rate laminar flow commonly induces the classic shear stress responses in blood endothelial cells and lymphatic endothelial cells (LECs), only LECs display reduced Notch activity and increased sprouting capacity. In response to flow, the plasma membrane calcium channel ORAI1 mediates calcium influx in LECs and activates calmodulin to facilitate a physical interaction between Kruppel-like factor 2 (KLF2), the major regulator of shear responses, and PROX1, the master regulator of lymphatic development. The PROX1/KLF2 complex upregulates the expression of DTX1 and DTX3L. DTX1 and DTX3L, functioning as a heterodimeric Notch E3 ligase, concertedly downregulate NOTCH1 activity and enhance lymphatic sprouting. Notably, overexpression of the calcium reporter GCaMP3 unexpectedly inhibited lymphatic sprouting, presumably by disturbing calcium signaling. Endothelial-specific knockouts of Orai1 and Klf2 also markedly impaired lymphatic sprouting. Moreover, Dtx3l loss of function led to defective lymphatic sprouting, while Dtx3l gain of function rescued impaired sprouting in Orai1 KO embryos. Together, the data reveal a molecular mechanism underlying laminar flow-induced lymphatic sprouting.