Regulatory roles of Meltrins, membrane-anchored ADAMs, in cell-cell interactions

发育和再生需要各种细胞间信号和黏附分子。许多细胞间信号分子是以膜锚定蛋白的形式产生的，它们经过蛋白降解处理以释放其胞外结构域(胞外结构域脱落)。本研究主要针对ADAM家族蛋白在细胞间相互作用和胞外结构域脱落过程中的调控作用进行了研究，阐明了Meltrin beta(ADAM19/a DisIntegrin and Metals Protease 19)在周围神经系统(PNS)发育和再生中的作用。在Meltrinβ基因缺陷小鼠中，神经肌肉接头的形成和坐骨神经再生受到影响。在坐骨神经再生的情况下，轴突的重新髓鞘形成延迟，因为雪旺细胞的终末分化，包括KROX-20的激活，在没有Meltrin beta的情况下受到影响。…神经分离膜的制备与野生型小鼠相比，β基因缺陷小鼠雪旺细胞中Akt通路的激活程度更低。这些结果表明，Meltrin beta参与了PNS中神经调控雪旺细胞发育的旁分泌信号的调节。另一方面，我们通过监测活的斑马鱼胚胎的细胞行为来评估ADAMS的作用和功能。通过监测斑马鱼中荧光蛋白标记的血液前体和血管，我们展示了一种启动血液循环的新机制，其中包括调节血管接触的蛋白质分解。现场成像显示，第一次血液循环是同步发生的。这种同步性是通过血管内注射后红系前体一个接一个地从主动脉下区域保留在血管管腔上，然后几乎同时将这些前体释放到血浆流中而实现的。在心脏和血管系统形成后，将金属蛋白酶抑制剂注入循环中，扰乱了血液循环的同步启动，这表明血管系统管腔中的金属蛋白酶活性是血细胞同时释放到血流中的先决条件。斑马鱼ADAM(去整合素和金属蛋白水解酶家族)中的ADAM8被鉴定为参与该过程的金属蛋白水解酶。在ADAM8耗竭的胚胎中观察到血液停滞。细胞生物学分析和在GATA-1启动子下ADAM8失活的蛋白酶的表达表明，在原始血液中表达的ADAM8自主地取消了它们与血管细胞的黏附。基于这些发现，我们认为，第一批血液需要依赖于流动的被动过程和依赖于蛋白质分解的主动过程才能进入循环。较少

Development and regeneration require various kinds of intercellular signaling and adhesion molecules. Many intercellular signaling molecules are generated as membrane-anchored proteins, and they are subjected to proteolytic processing to liberate their extracellular domains (ectodomain shedding). Our research has been focused on regulatory roles of ADAM (A Disintegrin And Metalloprotease) family proteins in such cell-cell interactions and the ectodomain shedding.We clarified roles and functions of Meltrin beta (ADAM19 / a disintegrin and metalloprotease 19) in development and regeneration of peripheral nervous system (PNS). In Meltrin beta-deficient mice, neuromuscular junction formation and sciatic nerve regeneration was affected. In the case of sciatic nerve regeneration, re-myelination of axons delayed because terminal differentiation of Schwann cells, including activation of Krox-20, was affected in the absence of Meltrin beta. The membrane preparation of nerves isolated from meltr … More in beta deficient mice showed decreased activation of Akt pathway in Schwann cells compared to that from wild type mice. These results suggest that Meltrin beta is involved in the regulation of juxtacrine signaling by which nerves in the PNS governs Schwann cell development.On the other hand, we evaluated roles and functions of ADAMs by monitoring cellular behaviors in living zebrafish embryos. By monitoring fluorescent protein-labeled blood precursors and blood vessels in zebrafish, we showed a novel mechanism for the onset of blood circulation, which involves proteolysis that regulates blood-vessel contacts. The live imaging reveals that the first blood circulation occurs synchronously. This synchrony is achieved by retention of erythroid precursors on the lumen of blood vessels after intravasation one after another from the sub-aortic region, and then, by almost simultaneous release of these precursors into the plasma flow. Injection of metalloprotease inhibitors into the circulation after formation of the heart and vasculature disturbed the synchronous onset of blood circulation, suggesting that metalloprotease activity in the lumen of the vasculature is prerequisite for the simultaneous release of blood cells into the flow. One of zebrafish ADAM (a disintegrin and metalloprotease family), ADAM8, was identified as a metalloprotease participating in that process. Blood stagnation was observed in ADAM8-depleted embryos. Cell biological analyses and expression of an inactive protease of ADAM8 under a gata-1 promoter suggest that ADAM8 expressed in the primitive blood abrogates their adhesion to the vasculature cell autonomously. Based on these findings, we propose that the first blood requires both flow-dependent passive and proteolysis-dependent active processes to enter into circulation. Less