The Shear Stress-Induced Transcription Factor KLF2 Affects Dynamics and Angiopoietin-2 Content of Weibel-Palade Bodies

Abstract

BackgroundThe shear-stress induced transcription factor KLF2 has been shown to induce an atheroprotective phenotype in endothelial cells (EC) that are exposed to prolonged laminar shear. In this study we characterized the effect of the shear stress-induced transcription factor KLF2 on regulation and composition of Weibel-Palade bodies (WPBs) using peripheral blood derived ECs.Methodology and Principal FindingsLentiviral expression of KLF2 resulted in a 4.5 fold increase in the number of WPBs per cell when compared to mock-transduced endothelial cells. Unexpectedly, the average length of WPBs was significantly reduced: in mock-transduced endothelial cells WPBs had an average length of 1.7 µm versus 1.3 µm in KLF2 expressing cells. Expression of KLF2 abolished the perinuclear clustering of WPBs observed following stimulation with cAMP-raising agonists such as epinephrine. Immunocytochemistry revealed that WPBs of KLF2 expressing ECs were positive for IL-6 and IL-8 (after their upregulation with IL-1β) but lacked angiopoietin-2 (Ang2), a regular component of WPBs. Stimulus-induced secretion of Ang2 in KLF2 expressing ECs was greatly reduced and IL-8 secretion was significantly lower.Conclusions and SignificanceThese data suggest that KLF2 expression leads to a change in size and composition of the regulated secretory compartment of endothelial cells and alters its response to physiological stimuli.

Yes-associated protein regulates endothelial cell contact-mediated expression of angiopoietin-2

“…Interestingly, ANG-2 is also regulated by mechanical shear-stress on ECs. FoxO1 and KLF2 have been shown to play a role in mediating ANG-2 regulation by shear-stress in different ways 40,41 . Considering the recent finding that YAP plays a key role in cellular mechanotransduction, it is not surprising that ANG-2 is regulated by YAP in ECs.…”

STXBP1 promotes Weibel-Palade body exocytosis through its interaction with the Rab27A effector Slp4-a

“…[11][12][13] The precise composition of mediators stored in WPBs depends crucially on the physical, mechanical, and chemical signals in the local microenvironment; for example, targeting of eotaxin-3, IL-8, and IL-6 has been observed in response to pro-inflammatory mediators such as IL-1b or IL-4, 5,7,14,15 whereas the inclusion of angiopoietin-2 is modulated under conditions that mimic shear stress. 16 Exocytosis of WPBs is triggered by a wide range of physiological secretagogues that trigger Ca 21 -and cyclic adenosine monophosphate (cAMP)-dependent signaling pathways, such as histamine and thrombin or vasopressin and epinephrine, respectively. 3,[17][18][19][20] Several key regulators of WPB exocytosis have been identified, including the small guanosine triphosphates (GTPases) RalA, Rab3A, Rab3D, and Rab27A.…”

MicroRNA-30 mediates anti-inflammatory effects of shear stress and KLF2 via repression of angiopoietin 2

“…Amongst the target mRNAs for miR-30-5p predicted by Targetscan 6.2 was angiopoietin 2 (Ang2). Ang2 is known to enhance ICAM1 and VCAM1 expression [42] and to be downregulated by prolonged flow and KLF2 [5,43], but the mechanism by which this occurs is not clear. First, we confirmed that lentiviral KLF2 overexpression reduces Ang2 levels in HUVECs, as measured by Western blot analysis (Fig.…”

“…One of the factors that is responsible for inhibiting pro-inflammatory activation in ECs exposed to laminar shear stress is the transcription factor KLF2 [4]. KLF2 was shown to inhibit the expression of Ang2 in blood outgrowth ECs, but the mechanism is unknown [5].…”