■淋巴瓣膜是收集淋巴管的特殊结构,对于防止逆行淋巴流动至关重要。瓣膜形成基因的突变在临床上与先天性淋巴水肿的病理学有关。当来自通过PI3K/AKT途径的淋巴流信号的振荡剪切应力促进触发淋巴瓣膜的生长和维持的瓣膜形成基因的转录时,淋巴瓣膜形成。传统上,在许多细胞类型中,AKT在Ser473处被mTORC2(哺乳动物雷帕霉素靶标复合物2)磷酸化。然而,mTORC2尚未参与淋巴瓣的形成。
■使用体内和体外技术来研究Rictor的作用,mTORC2的重要组成部分,在淋巴内皮。
■这里,我们发现Rictor的胚胎和出生后淋巴缺失,mTORC2的关键组成部分,导致淋巴瓣膜的显着减少,并阻止了收集淋巴管的成熟。RICTOR在人真皮淋巴管内皮细胞中的敲除不仅在无流动条件下降低了激活的AKT水平和瓣膜形成基因的表达,而且消除了响应振荡剪切应力的AKT活性和瓣膜形成基因的上调。我们进一步表明,AKT目标,FOXO1(叉头盒蛋白O1),淋巴瓣膜形成的抑制因子,体内Rictor敲除肠系膜淋巴管内皮细胞的核活性增加。在Rictor敲除小鼠中Foxo1的缺失使瓣膜的数量恢复到耳朵和肠系膜淋巴管中的对照水平。
■我们的工作确定了RICTOR在机械转导信号通路中的新作用,其中它激活AKT并防止瓣膜抑制物的核积累,FOXO1,最终能够形成和维持淋巴瓣膜。
UNASSIGNED: Lymphatic valves are specialized structures in collecting lymphatic vessels and are crucial for preventing retrograde lymph flow. Mutations in valve-forming genes have been clinically implicated in the pathology of congenital lymphedema. Lymphatic valves form when oscillatory shear stress from lymph flow signals through the PI3K/AKT pathway to promote the transcription of valve-forming genes that trigger the growth and maintenance of lymphatic valves. Conventionally, in many cell types, AKT is phosphorylated at Ser473 by the mTORC2 (mammalian target of rapamycin complex 2). However, mTORC2 has not yet been implicated in lymphatic valve formation.
UNASSIGNED: In vivo and in vitro techniques were used to investigate the role of Rictor, a critical component of mTORC2, in lymphatic endothelium.
UNASSIGNED: Here, we showed that embryonic and postnatal lymphatic deletion of Rictor, a critical component of mTORC2, led to a significant decrease in lymphatic valves and prevented the maturation of collecting lymphatic vessels. RICTOR knockdown in human dermal lymphatic endothelial cells not only reduced the level of activated AKT and the expression of valve-forming genes under no-flow conditions but also abolished the upregulation of AKT activity and valve-forming genes in response to oscillatory shear stress. We further showed that the AKT target, FOXO1 (forkhead box protein O1), a repressor of lymphatic valve formation, had increased nuclear activity in Rictor knockout mesenteric lymphatic endothelial cells in vivo. Deletion of Foxo1 in Rictor knockout mice restored the number of valves to control levels in lymphatic vessels of the ear and mesentery.
UNASSIGNED: Our work identifies a novel role for RICTOR in the mechanotransduction signaling pathway, wherein it activates AKT and prevents the nuclear accumulation of the valve repressor, FOXO1, which ultimately enables the formation and maintenance of lymphatic valves.