Endothelial cell-specific phosphatase VE-PTP in regulation of endothelial biology

• Autor(a) principal: Oliveira, Filipa Viviana Rocha Martinez
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/132078
• topic: VE-PTP; VEGFA; VEGFR2; Erk 1/2; OIR; retinopathy; Domínio/Área Científica::Engenharia e Tecnologia::Outras Engenharias e Tecnologias

Vascular endothelial growth factor (VEGF)-A signal transduction is a central mediator of angiogenesis in development and in pathological conditions, such as ischemic retinopathies. The role of VEGFA in pathophysiological processes including neovascularization and vascular permeability, and the therapeutic benefit of targeting VEGFA and its main receptor on endothelial cells, VEGF receptor 2 (VEGFR2), has been well documented. However, the significant treatment burden for the patient and the transient efficacy of anti-VEGF/VEGFR2 drugs in retinal vascular diseases create a need for new therapeutic targets to improve the diseases´ outcome. Vascular endothelial protein tyrosine phosphatase (VE-PTP, also known as PTPRB) is an endothelial specific tyrosine phosphate that interacts with VEGFR2 and Tie2, thereby regulating their activity. Here, we evaluated the efficiency of a siRNA targeting human PTPRB and identified commercially available antibodies specific for VE-PTP to be used in in vitro studies. Immunofluorescence analyses of human umbilical vein endothelial cells showed colocalization of VE-PTP with vascular endothelial (VE)-cadherin at endothelial cell junctions, where VE-PTP is known to interact with VEGFR2, Tie2 and VE-cadherin. Silencing of PTPRB expression in vitro was accompanied by increased VEGFA-induced VEGFR2 phosphorylation at tyrosine site 1175, which unexpectedly was accompanied by decreased phosphorylation of the downstream extracellular regulated kinase (Erk) 1/2. Moreover, endothelial specific genetic deletion of the murine VE-PTP codifying gene, denoted Ptprb, impaired retina vascular development, negatively affecting retina vessel density, vessel outgrowth and tip cell density. These effects on the retina vasculature did not depend on changes in expression levels of Flk1, Tie2 or Cdh5. In a mouse model of oxygen-induced retinopathy (OIR), genetic Ptprb deficiency reduced vessel obliteration but had no effect on formation of neovascular tufts. In conclusion, we demonstrate that VE-PTP is required in vivo for normal development of the retinal vasculature and inhibition of PTPRB expression in vitro markedly enhances VEGFR2 phosphorylation in response to VEGFA while subsequent activation of its downstream signalling transducer Erk 1/2 is suppressed. This suggests a potential mechanism by which targeting VE-PTP may reduce vessel obliteration observed in ischemic eye diseases. However, more in-depth analyses are warranted.