SARAF and Orai1 Contribute to Endothelial Cell Activation and Angiogenesis.

Isabel Galeano-Otero,Isabel Galeano-Otero,Isabel Galeano-Otero,Antonio Ordóñez-Fernández,Tarik Smani,Tarik Smani,Tarik Smani,Juan Antonio Rosado,Abdel-Majid Khatib,Raquel Del Toro,Raquel Del Toro,Raquel Del Toro

doi:10.3389/fcell.2021.639952

Abstract

Angiogenesis is a multistep process that controls endothelial cells (ECs) functioning to form new blood vessels from preexisting vascular beds. This process is tightly regulated by pro-angiogenic factors, such as vascular endothelial growth factor (VEGF), which promote signaling pathways involving the increase in the intracellular Ca2+ concentration ([Ca2+]i). Recent evidence suggests that store-operated calcium entry (SOCE) might play a role in angiogenesis. However, little is known regarding the role of SARAF, SOCE-associated regulatory factor, and Orai1, the pore-forming subunit of the store-operated calcium channel (SOCC), in angiogenesis. Here, we show that SOCE inhibition with GSK-7975A blocks aorta sprouting, as well as human umbilical vein endothelial cell (HUVEC) tube formation and migration. The intraperitoneal injection of GSK-7975A also delays the development of retinal vasculature assessed at postnatal day 6 in mice, since it reduces vessel length and the number of junctions, while it increases lacunarity. Moreover, we find that SARAF and Orai1 are involved in VEGF-mediated [Ca2+]i increase, and their knockdown using siRNA impairs HUVEC tube formation, proliferation, and migration. Finally, immunostaining and in situ proximity ligation assays indicate that SARAF likely interacts with Orai1 in HUVECs. Therefore, these findings show for the first time a functional interaction between SARAF and Orai1 in ECs and highlight their essential role in different steps of the angiogenesis process.

Highlights

Angiogenesis is defined as the formation of new blood vessels from existing vasculature for the purpose of expanding vascular networks to the tissues (Stapor et al, 2014)
Angiogenesis is a dynamic multiphase process that includes the formation of new vessels from preexisting vascular beds, involving endothelial cell (EC) proliferation and migration, vascular patterning, and a final remodeling phase that ends in a stabilization of the new network for blood circulation (Ucuzian et al, 2010)
The process of angiogenesis is tightly regulated by proangiogenic factors such as vascular endothelial growth factor (VEGF) which binds to its receptors on ECs and mediates [Ca2+]i increase (Munaron et al, 2008)

Summary

Introduction

Angiogenesis is defined as the formation of new blood vessels from existing vasculature for the purpose of expanding vascular networks to the tissues (Stapor et al, 2014). SARAF’s Role in Angiogenesis displays fine-tuned regulation that is mainly stimulated by oxygen deficiency, which may happen in both physiological (e.g., reproduction (Logsdon et al, 2014) or tissue repair (Ingason et al, 2018)) and pathological situations (e.g., diabetic retinopathy (Li et al, 2011) or cancer (Folkman, 1971)) This process requires the action of several growth factors, including vascular endothelial growth factor (VEGF), considered as the most pro-angiogenic factor, and fibroblast growth factor (FGF) and epidermal growth factor (EGF), which are secreted by parenchymal cells and triggered by the hypoxic environment (Adair and Montani, 2010). It has been proved that siRNA-mediated inhibition of Orai and STIM1 affected angiogenesis in vitro using human umbilical vein EC (HUVEC) and endothelial progenitor cells (Lodola et al, 2012)

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