Regulation of Vascular Endothelial Growth Factor Receptor Function in Angiogenesis by Numb and Numb-Like

Abstract

Objective— Vascular endothelial growth factor (VEGF) signaling is a major regulator of physiological and pathological angiogenesis. VEGF receptor activity is strongly controlled by endocytosis, which can terminate or enhance signal transduction in the angiogenic endothelium, but the exact molecular regulation of these processes remains incompletely understood. We have therefore examined the function of Numb family clathrin-associated sorting proteins in angiogenesis. Approach and Results— We show that Numb proteins are expressed by endothelial cells during retinal angiogenesis in mice. Inducible inactivation of the Numb / Numbl genes in the postnatal endothelium led to impaired vessel growth, reduced endothelial proliferation and sprouting, and decreased VEGF receptor activation. Biochemistry and cell biology experiments established that Numb can interact with VEGFR2 and VEGFR3 and controls VEGF receptor activation in response to ligand stimulation. Experiments in cultured endothelial cells showed that Numb proteins counteract VEGF receptor degradation and promote VEGFR2 recycling back to the plasma membrane. Conclusions— Numb proteins control VEGF receptor endocytosis, signaling, and recycling in endothelial cells, which promotes the angiogenic growth of blood vessels.

The endosomal RIN2/Rab5C machinery prevents VEGFR2 degradation to control gene expression and tip cell identity during angiogenesis

“…Depletion of Numb or Rab GTPasebinding effector protein-2 (RABEP-2) also enhances VEGFR2 degradation, resulting in lower VEGFR2 levels and reduced VEGF signaling [27,33]. Interestingly, genetic deletion of RABEP-2 in mice disturbs arteriogenesis but not angiogenesis, while the deletion of Numb induces angiogenic defects [27,57]. It remains to be determined how different proteins along trafficking pathways can mediate such very diverse outcomes of VEGFR2 signaling.…”

“…Internalization of activated VEGFR2 and its subsequent flux through the endosomal system are regulated by endocytic adapters, as well as by cell-surface receptors that associate with VEGFR2 [14,23,[25][26][27][28][29][30][31]. Although it is known that VEGFR2 can signal from endosomal compartments [2,18], the interrelation between VEGFR2 endocytosis and signaling is complex.…”

Endothelium

“…Full VEGF receptor signaling and recycling of VEGFR2 to the endothelial cell surface requires the clathrin-associated sorting proteins numb and numb-like. 30 Finally, Pi et al 31 bring strong evidence that nicotinamide adenine dinucleotide phosphate (NADPH) oxidases are novelpositive regulators of endothelial migration and angiogenesis induced by stromal cell-derived factor 1α a potent angiogenic chemokine. Reactive oxygen species generated by NADPH oxidases oxidize and inhibit the protein tyrosine phosphatases MKP7, thereby regulating stromal cell-derived factor 1α-dependent JNK3 activity and angiogenesis.…”

The Spatiotemporal Expression of Notch1 and Numb and Their Functional Interaction during Cardiac Morphogenesis

“…Whether NFPs’ deletion in Tie2 expressing cells will affect angiogenesis is not extensively examined. Indeed, a study shows that NFPs regulate VEGF receptor endocytosis, signaling, and recycling in endothelial cells to promote the angiogenic growth of blood vessels [ 79 ]. The epicardium, as the outer layer of the heart, is forged from a single layer of epicardial cells.…”