Document Type

Dissertation

Date of Degree

Fall 2015

Degree Name

PhD (Doctor of Philosophy)

Degree In

Molecular and Cell Biology

First Advisor

Charles Yeaman

Second Advisor

Amit Choudhury

Abstract

Angiogenesis is a crucial process under both physiological and pathological conditions. Vascular endothelial growth factor (VEGF) A and its cognate receptor, vascular endothelial growth factor receptor 2 (VEGFR2) are key regulators of angiogenesis. Plasma membrane (PM) levels of VEGFR2 are regulated by de novo synthesis, and by both exocytic and endocytic trafficking. VEGF-binding to VEGFR2 induces phosphorylation of key tyrosine residues located in the cytosolic domain of the receptor, followed by clathrin-mediated endocytosis and signal transduction leading to vascular morphogenesis. Disabled protein 2 (Dab2) is a cytosolic, clathrin-adaptor protein that is known to regulate endocytosis of certain cell surface receptors. Studies of Dab2 function have revealed its role in the development of embryonic vasculature. However, the mechanism of Dab2 function, particularly in conjunction with endosomal VEGFR2, remains poorly understood. Our results show that Dab2 interacts with VEGFR2 and that upon VEGF stimulation the two proteins co-localize within Rab5-positive early endosomes. Knockdown of Dab2 reduces levels of VEGF-induced phosphorylation of VEGFR2 at residue Y1175. This is significant because phosphorylation of VEGFR2-Y1175 is crucial for pro-angiogenic signal transduction. Moreover, knockdown of Dab2 causes an increased trafficking of VEGFR2 to late endosomes (LE). Finally, this altered VEGFR2 trafficking following Dab2 knockdown has major functional consequences for endothelial cells, as they are unable to undergo morphogenesis into tube-like structures in an in vitro assay of angiogenesis. Collectively, our data show that Dab2 plays a crucial role in VEGFR2 trafficking in the endocytic system and this impacts receptor signaling and endothelial cell morphogenesis during angiogenesis.

Keywords

Dab2, Early endosome, Endocytosis, Late endosome, tube formation assay, VEGFR2

Pages

xiii, 85 pages

Bibliography

Includes bibliographical references (pages 75-79).

Comments

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Copyright

Copyright © 2015 Shivangi Makarand Inamdar

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Cell Biology Commons

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