A considerable number of diseases, including ischemic heart and limb diseases, cancer, diabetic blindness, age-related macular degeneration and rheumatoid arthritis, are characterized by excessive or insufficient angiogenesis. Vascular endothelial growth factor (VEGF) is a major growth factor that regulates multiple endothelial cell (EC) functions and angiogenesis. The importance of VEGF in angiogenesis has offered new therapeutic opportunities. However, the incomplete understanding of the signaling pathways whereby VEGF directs angiogenesis remains a critical barrier to developing efficient anti-angiogenic cancer therapy or pro-angiogenic treatment for ischemic heart and limb diseases. Emerging evidence from my group and others supports a crucial role of protein kinase D (PKD1) in VEGF signaling and angiogenesis. PKD1 is a member of a novel family of serine/threonine protein kinases, which are potential druggable targets for therapeutics. As such, it is imperative to understand the biological functions of PKD1 and specific signaling events leading to angiogenesis. We are the first to report that VEGF via its receptor 2 stimulated PKD1 phosphorylation and activation in vascular ECs. Subsequently, we found that PKD1, via phosphorylation of histone deacetylases specifically HDAC7, regulates EC migration and tube formation. Nascent observations from my group now reveal that PKD1, through parallel effects on EC survival and new vessel formation, regulates VEGF-mediated angiogenesis. Specifically, using a PKD1 motif-based screening strategy, we identified a novel PKD1 substrate that is involved in the apoptosis pathway. Second, using gene profile analysis we have found that PKD1 is involved in the crosstalk of VEGF signaling and Notch signaling, which plays an essential role in new vessel formation including EC morphological differentiation, sprouting and vascular stabilization. Finally, our preliminary studies indicate that PKD1 inhibition impedes angiogenesis in vitro and in vivo. Therefore, our central hypothesis is that PKD1 activation by VEGF promotes endothelial survival and functions leading to angiogenesis. Three robust and interrelated aims are proposed to test this hypothesis:
Aim 1. Determine the role and signaling mechanisms for PKD1 in VEGF-induced EC survival.
Aim 2. Define the role and molecular mechanisms for PKD1 in the interplay of VEGF and Notch signaling.
Aim 3. Study the role of PKD1 and signaling pathways in a mouse model of ischemia angiogenesis.
Aim 4. Evaluate the biological role of PKD1 and therapeutic effects of a specific PKD inhibitor in a mouse model of tumor angiogenesis. The studies proposed herein will provide mechanistic insights and functional importance of the VEGF-PKD1 pathway in angiogenesis. The results of these studies will facilitate development of new therapeutic approaches to prevent or treat angiogenesis-related diseases.
A considerable number of diseases, including ischemic heart and limb diseases, cancer, diabetic blindness, age-related macular degeneration and rheumatoid arthritis, are characterized by either excessive or insufficient angiogenesis. The studies proposed in this project are designed to elucidate the role of a protein called PKD1 in regulation of vascular endothelial function and new blood vessel formation. The findings from this project will provide a better understanding of cellular signaling mechanisms underlying abnormal blood vessel formation, and will provide an underpinning for the advancement of more effectively targeted interventions aimed at angiogenesis-associated diseases.
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