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粘附分子。许多细胞间信号分子作为膜锚定蛋白产生，并且它们经受蛋白水解加工以释放它们的细胞外结构域（胞外域脱落）。本研究主要围绕ADAM（A Disintegrin And Metalloprotease，解整合素和金属蛋白酶）家族蛋白在细胞间相互作用和胞外域脱落中的调控作用，阐明Meltrin beta（ADAM 19/ a disintegrin and metalloprotease 19）在外周神经系统（PNS）发育和再生中的作用和功能。在Meltrin β缺陷小鼠中，神经肌肉接头形成和坐骨神经再生受到影响。在坐骨神经再生的情况下，轴突的再髓鞘形成延迟，因为雪旺细胞的终末分化，包括Krox-20的活化，在Meltrin β不存在的情况下受到影响。离体神经的膜制备 ...更多信息 与野生型小鼠相比，在β缺陷小鼠中，显示施万细胞中Akt途径的活化降低。这些结果表明Meltrin beta参与了PNS中神经支配雪旺细胞发育的ADAMs信号传导的调节。另一方面，我们通过监测活体斑马鱼胚胎的细胞行为来评估ADAMs的作用和功能。通过监测荧光蛋白标记的斑马鱼血液前体和血管，我们发现了一种新的血液循环启动机制，其中涉及调节血管接触的蛋白水解。实时成像显示第一次血液循环同步发生。这种同步是通过红细胞前体在从主动脉下区域一个接一个地内渗后保留在血管腔上，然后通过这些前体几乎同时释放到血浆流中来实现的。在心脏和脉管系统形成后，将金属蛋白酶抑制剂注射到循环中，扰乱了血液循环的同步开始，这表明脉管系统内腔中的金属蛋白酶活性是血细胞同时释放到流动中的先决条件。其中一种金属蛋白酶ADAM 8参与了这一过程。在ADAM 8耗尽的胚胎中观察到血液停滞。细胞生物学分析和在加塔-1启动子下的ADAM 8的失活蛋白酶的表达表明，在原始血液中表达的ADAM 8自主地消除了它们对脉管系统细胞的粘附。基于这些发现，我们提出，第一血液需要流量依赖的被动和蛋白水解依赖的主动过程进入循环。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