Lymphangiogenesis requires Ang2/Tie/PI3K signaling for VEGFR3 cell-surface expression
Emilia A. Korhonen, … , Taija Mäkinen, Kari Alitalo
Emilia A. Korhonen, … , Taija Mäkinen, Kari Alitalo
Published June 28, 2022
Citation Information: J Clin Invest. 2022;132(15):e155478. https://doi.org/10.1172/JCI155478.
View: Text | PDF
Research Article Vascular biology

Lymphangiogenesis requires Ang2/Tie/PI3K signaling for VEGFR3 cell-surface expression

Abstract

Vascular endothelial growth factor C (VEGF-C) induces lymphangiogenesis via VEGF receptor 3 (VEGFR3), which is encoded by the most frequently mutated gene in human primary lymphedema. Angiopoietins (Angs) and their Tie receptors regulate lymphatic vessel development, and mutations of the ANGPT2 gene were recently found in human primary lymphedema. However, the mechanistic basis of Ang2 activity in lymphangiogenesis is not fully understood. Here, we used gene deletion, blocking Abs, transgene induction, and gene transfer to study how Ang2, its Tie2 receptor, and Tie1 regulate lymphatic vessels. We discovered that VEGF-C–induced Ang2 secretion from lymphatic endothelial cells (LECs) was involved in full Akt activation downstream of phosphoinositide 3 kinase (PI3K). Neonatal deletion of genes encoding the Tie receptors or Ang2 in LECs, or administration of an Ang2-blocking Ab decreased VEGFR3 presentation on LECs and inhibited lymphangiogenesis. A similar effect was observed in LECs upon deletion of the PI3K catalytic p110α subunit or with small-molecule inhibition of a constitutively active PI3K located downstream of Ang2. Deletion of Tie receptors or blockade of Ang2 decreased VEGF-C–induced lymphangiogenesis also in adult mice. Our results reveal an important crosstalk between the VEGF-C and Ang signaling pathways and suggest new avenues for therapeutic manipulation of lymphangiogenesis by targeting Ang2/Tie/PI3K signaling.

Authors

Emilia A. Korhonen, Aino Murtomäki, Sawan Kumar Jha, Andrey Anisimov, Anne Pink, Yan Zhang, Simon Stritt, Inam Liaqat, Lukas Stanczuk, Laura Alderfer, Zhiliang Sun, Emmi Kapiainen, Abhishek Singh, Ibrahim Sultan, Anni Lantta, Veli-Matti Leppänen, Lauri Eklund, Yulong He, Hellmut G. Augustin, Kari Vaahtomeri, Pipsa Saharinen, Taija Mäkinen, Kari Alitalo

×

Figure 10

Schematic summary of how Ang2/Tie/PI3K signaling controls lymphangiogenesis via regulation of VEGFR3 cell-surface expression.

Options: View larger image (or click on image) Download as PowerPoint
Schematic summary of how Ang2/Tie/PI3K signaling controls lymphangiogene...
Ang2 is shown as a tetramer of 2 asymmetric dimers binding to and activating the Tie2-Tie1 cluster (30, 66–68). Ang/Tie signaling promotes activation or PI3K and Akt, leading to inhibition of FoxO1 and its target genes, such as Angpt2 (24, 27). In LECs, VEGF-C increased Ang2 release from stimulated cells and subsequent Tie2 and Akt activation. Disruption of Ang2/Tie signaling in Ang2 Ab–treated or Tie1- or Tie1/-2–deleted pups resulted in increased Angpt2 gene expression, suggesting that Ang2 acts as an agonistic Tie2 ligand in LECs that promotes PI3K activation. VEGF-C induces internalization of VEGFR3 and its vesicular trafficking for degradation or recycling, which are regulated by PI3K (40–42). VEGF-C stimulation led to cotrafficking of VEGFR3 and Tie1 into EEA1/RAB5-positive early/sorting endosomes and, subsequently, to the RAB7-positive late endosomal degradative vesicle route. Our results show that inhibition or deletion of Ang2 or PI3K, or deletion of Tie receptors, promoted loss of VEGFR3 from the LEC surface and its increased degradation, leading to decreased lymphangiogenesis.