).Although the risk factors for atherosclerosis are quite variable, localization of atherosclerotic lesions in the arterial tree is surprisingly constant. Atherosclerotic plaques show an increased predilection to areas with complex geometry such as branch points, arches, and bifurcations. Several studies have shown that the pattern of flow in straight portion of the arteries is different from areas of complex geometry. 1,2 While the flow in straight portions of arteries is steady, laminar, and unidirectional, flow in areas of complex geometry is low in magnitude and often changes direction. 3 Although there is evidence that these differences in flow patterns could be responsible for the increased predilection of atherosclerosis to these areas, how these changes are being sensed and transduced to the nucleus is poorly understood. 4Yes-associated protein (YAP) is a recently discovered homolog of Yorkie protein in Drosophila melanogaster which functions as a transcriptional co-activator for transcription enhancer activator domain family member 2 (TEAD II) group of genes that regulate cellular growth. 5 Several studies show that YAP could be involved in the pathogenesis of several diseases including cancers of the breast, pancreas, and liver. 6-8 Some investigators postulate that YAP is a mechanosignaling molecule that transmits mechanical information to the nucleus by detecting changes in actin cytoskeleton induced by changes in shape of the cell. 9 Previous studies have shown that cell shape changes differently with different types of flow. While endothelial cells (ECs) exposed to static conditions were uniformly Keywords ► atherosclerosis ► yes-associated protein ► endothelial cells ► pulsatile flow ► continuous flow ► mechanosignaling
AbstractYes-associated protein (YAP) is a mechanosignaling protein that relays mechanical information to the nucleus by changing its level of phosphorylation. We hypothesize that different flow patterns show differential effect on phosphorylated YAP (pYAP) (S127) and total YAP and could be responsible for flow dependent localization of atherosclerosis. Confluent human umbilical vein endothelial cells (HUVECs) seeded on fibronectin-coated glass slides were exposed to continuous forward flow (CFF) and pulsatile forward flow (PFF) using a parallel plate flow chamber system for 30 minutes. Cell lysates were prepared and immunoblotted to detect the levels of phosphorylated YAP and total YAP. HUVECs exposed to both PFF and CFF showed a mild decrease in the levels of both pYAP (S127) and total YAP. While the levels of pYAP (S127) decreased to 87.85 and 85.21% of static control with PFF and CFF, respectively, the levels of total YAP significantly decreased to 91.31 and 92.27% of static control. No significant difference was seen between CFF and PFF on their effect on pYAP (S127), but both conditions resulted in a significant decrease in total YAP at 30 minutes. The results of this experiment show that the possible effect of different types of flow on YAP is not induced before 30 minutes. E...