Targeting PCBP1 to Ameliorate Pathological Angiogenesis - Abstract Various human diseases rely on blood vessels to carry oxygen and nutrients to fuel disease initiation and progression. While they are crucial for normal development in humans, blood vessels are also vital for the progression of diseases such as cancer and blinding eye disorders. It is thought that the most important signal to induce blood vessel growth is vascular endothelial growth factor (VEGF), which activates quiescent endothelial cells (ECs) and promotes the formation of new blood vessels. Exuberant VEGF signaling is known to play a foundational role in propelling the progression of cancer and diabetic retinopathy and targeting VEGF results in reduced tumor burden due to regression of tumor vessels and improved drug delivery. However, the development of resistance resulting from the upregulation of other angiogenic factors significantly dampens the clinical benefits of this treatment strategy. Therefore, uncovering new molecular targets that regulate VEGF signaling should considerably advance the field. Here, we propose to determine the novel role of Pcbp1, an RNA-binding protein abundantly expressed in the endothelium but possessing high cell and tissue type specificity in terms of its downstream targets and its splicing target Aars2 in regulating VEGF signaling in physiological and pathological settings. Our team has recently discovered that the Pcbp1-Aars2 axis plays a crucial role in cardiomyopathy. Yet, their importance in the vascular system and their novel function in neovascularization and blood vessel growth remain unknown. To this end, we have created unique mice with inducible endothelial knockouts of Pcbp1 and Aars2 and found VEGF signaling and neovascularization are impaired upon loss of Pcbp1 or Aars2 in ECs, suggesting that these proteins are novel regulators of VEGF signaling. We also found that endothelial Pcbp1 interacts with the 5’UTR of VEGFR2 mRNA, and a lack of Pcbp1 diminishes VEGFR2 protein expression. Loss of endothelial Aars2 reduces mitochondrial membrane potential, leading to decreased acetyl-CoA production and attenuated histone acetylation of the VEGFR2 promoter, resulting in downregulation of VEGFR2 gene expression. We hypothesize that VEGFR2 mRNA stabilization and/or translation is regulated by Pcbp1, and VEGFR2 epigenetic activation is modulated by Aars2 in ECs. We will determine the molecular mechanisms by which Pcbp1 regulates VEGF translation, determine molecular mechanisms by which Aars2 promotes VEGFR epigenetic activation, and identify the therapeutic potential of inhibiting Pcbp1 and Aars2 in pathological angiogenesis. Our proposal addresses an important scientific problem, fills a significant knowledge gap, and initiates paradigm-shifting and innovative translational research.
