Basement membranes (BMs) are critical but frequently ignored components of the vascular system. Using high-resolution confocal imaging of whole-mount-stained mesenteric arteries, we identify integrins, vinculin, focal adhesion kinase (FAK) and several BM proteins including laminins as novel components of myoendothelial junctions (MEJs), anatomical microdomains that are emerging as regulators of cross-talk between endothelium and smooth muscle cells (SMCs). Electron microscopy revealed multiple layers of the endothelial BM that surround endothelial projections into the smooth muscle layer as structural characteristics of MEJs. The shear-responsive calcium channel TRPV4 is broadly distributed in endothelial cells and occurs in a proportion of MEJs where it localizes to the tips of the endothelial projections that are in contact with the underlying SMCs. In mice lacking the major endothelial laminin isoform, laminin 411 (Lama4^−/−), which we have previously shown over-dilate in response to shear and exhibit a compensatory laminin 511 upregulation, localization of TRPV4 at the endothelial-SMC interface in MEJs was increased. Endothelial laminins do not affect TRPV4 expression, rather in vitro electrophysiology studies using human umbilical cord arterial endothelial cells revealed enhanced TRPV4 signalling upon culturing on an RGD-motif containing domain of laminin 511. Hence, integrin-mediated interactions with laminin 511 in MEJ structures unique to resistance arteries modulate TRPV4 localization at the endothelial-smooth muscle interface in MEJs and signalling over this shear-response molecule.

基底膜 (BM) 是血管系统的重要组成部分，但经常被忽视。利用全染色肠系膜动脉的高分辨率共聚焦成像，我们鉴定了整合素、纽蛋白、粘着斑激酶（FAK）和几种BM蛋白，包括作为肌内皮连接（MEJ）的新成分的层粘连蛋白，以及作为调节剂出现的解剖微结构域内皮细胞和平滑肌细胞（SMC）之间的串扰。电子显微镜显示内皮 BM 的多层围绕内皮投射进入平滑肌层，这是 MEJ 的结构特征。剪切响应钙通道 TRPV4 广泛分布在内皮细胞中，并出现在部分 MEJ 中，它定位于与下面的 SMC 接触的内皮突起的尖端。在缺乏主要内皮层粘连蛋白亚型层粘连蛋白 411 ( Lama4 ^−/− ) 的小鼠中，我们之前已经证明层粘连蛋白 411 在剪切反应中过度扩张并表现出代偿性层粘连蛋白 511 上调，TRPV4 在 MEJ 中内皮-SMC 界面的定位是增加。内皮层粘连蛋白不影响 TRPV4 表达，而是使用人脐带动脉内皮细胞进行的体外电生理学研究表明，在含有 RGD 基序的层粘连蛋白 511 结构域上培养后，TRPV4 信号传导增强。因此，整合素介导的与层粘连蛋白 511 在 MEJ 结构中的相互作用是独特的动脉阻力调节 TRPV4 在 MEJ 内皮-平滑肌界面的定位，并通过该剪切响应分子发出信号。