Paris Cardiovascular Research Center, Paris, France.
FASEB J. 2013 Aug;27(8):3008-16. doi: 10.1096/fj.12-222299. Epub 2013 Apr 12.
Mechanical factors such as strain, pressure, and shear stress are key regulators of cell function, but the molecular mechanisms underlying the detection and responses to such stimuli are poorly understood. Whether the angiotensin II (AngII) AT1 receptor (AT1R) transduces shear stress in endothelial cells (ECs) is unknown. We exposed human umbilical cord endothelial cells (HUVECs) to a shear stress of 0 (control) or 15 dyn/cm(2) for 5 or 10 min. The colocalization of AT1R with caveolin-1 (Cav1), endosomal markers Rab5, EEA1, and Rab7, and lysosomal marker Lamp-1 increased in shear stimulated cells, detected by immunocytochemistry. Shear stress reduced labeling of wild-type mouse ECs (18±3% of unsheared control, P<0.01) but not Cav1(-/-) ECs (90±10%) with fluorescent AngII, confirming that internalization of AT1R requires Cav1. Shear stress activated ERK1/2 2-fold (P<0.01), which was prevented by the AT1R blocker losartan. NADPH oxidase inhibition with apocynin prevented both the colocalization of AT1R with Cav1 and the induction of ERK1/2 by shear stress. Moreover, shear-dependent ERK1/2 activation was minimal in CHO cells expressing an AT1Ra mutant that does not internalize, compared with cells expressing wild-type AT1Ra (P<0.05). Hence, AT1R may be an important transducer of shear stress-dependent activation of ERK1/2.
机械因素，如应变、压力和切应力，是细胞功能的关键调节因子，但对于细胞如何感知和响应这些刺激的分子机制还知之甚少。血管紧张素 II（AngII）AT1 受体（AT1R）是否在血管内皮细胞（ECs）中传递切应力尚不清楚。我们将人脐静脉内皮细胞（HUVEC）暴露于 0（对照）或 15 dyn/cm(2)的切应力下 5 或 10 min。免疫细胞化学检测到，AT1R 与 caveolin-1（Cav1）、内体标记物 Rab5、EEA1 和 Rab7 以及溶酶体标记物 Lamp-1 的共定位在切应力刺激的细胞中增加。切应力减少了野生型小鼠 ECs（未剪切对照的 18±3%，P<0.01）而非 Cav1(-/-) ECs（90±10%）对荧光 AngII 的标记，证实 AT1R 的内化需要 Cav1。切应力使 ERK1/2 激活了 2 倍（P<0.01），这一过程被 AT1R 阻滞剂 losartan 所阻止。apocynin 抑制 NADPH 氧化酶可防止 AT1R 与 Cav1 的共定位和切应力诱导的 ERK1/2 激活。此外，与表达野生型 AT1Ra 的 CHO 细胞相比，表达不内化的 AT1Ra 突变体的细胞中，切应力依赖性 ERK1/2 激活最小（P<0.05）。因此，AT1R 可能是 ERK1/2 依赖于切应力激活的重要转导器。
