Identification of vascular endothelial growth factor receptor 3 (VEGFR3) as an in vitro and in vivo substrate of the Alzheimer's Disease linked protease BACE2

Schmidt, Andree (2022): Identification of vascular endothelial growth factor receptor 3 (VEGFR3) as an in vitro and in vivo substrate of the Alzheimer's Disease linked protease BACE2. Dissertation, LMU München: Graduate School of Systemic Neurosciences (GSN)

Abstract

The protease ß-Site Amyloid Precursor Protein Cleaving Enzyme 1 (BACE1) is a key drug target in Alzheimer’s disease (AD). It catalyzes the first step in the generation of the pathogenic amyloid ß (Aß) peptide and its inhibition is therefore a promising approach to prevent or delay the onset of AD. To date however, most inhibitory compounds do not discriminate between BACE1 and its close non-amyloidogenic homologue BACE2 and therefore may lead to undesired off target effects, resulting from BACE2 biology. Therefore, future compounds require a higher selectivity for BACE1 and a biomarker is required to confirm unimpaired in vivo BACE2 activity. To replace a long lasting depigmentation assay, which is the current standard for in vivo BACE2 activity monitoring, the blood plasma of BACE2 knockout mice (B2KO) was screened and the tyrosine kinase receptor Vascular Endothelial Growth Factor 3 (VEGFR3) was identified as a putative BACE2 substrate. Subsequently, VEGFR3 was thoroughly validated as an in vitro and in vivo BACE2 substrate and the BACE2 cleavage site was determined. In direct comparison to the pigmentation readout, plasma VEGFR3 performed superior and displayed higher sensitivity and lower variance. Importantly, reduction of VEGFR3 was also detectable in the plasma of BACE inhibitor treated non-human primates (NHP) and clinical trial participants, highlighting potential for applicability in the clinical context. To test whether BACE2 cleavage may be a novel mechanism to control VEGFR3 function, downstream events of VEGFR3 signaling were monitored in primary lymphatic endothelial cells (LECs). Impairment of BACE2 dependent VEGFR3 processing was accompanied by increased activation of the VEGFR3 dependent pathways AKT and ERK and resulted into enhanced transcription of the VEGFR3 inducible genes (FOXC2) and Delta-like 4 (DLL4). As a consequence, alterations in the morphological structure and drainage efficiency of lymphatic vessels and cannot be excluded in the periphery and central nervous system (CNS). Future developments in the BACE inhibitor field need to consider these implications and plasma VEGFR3 levels may be used to control for possible of target effects from BACE2 inhibition.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Keywords: Alzheimer, Protease, BACE, VEGFR, FLT4
• Themengebiete: 500 Naturwissenschaften und Mathematik ; 500 Naturwissenschaften und Mathematik > 570 Biowissenschaften, Biologie
• Fakultäten: Graduate School of Systemic Neurosciences (GSN)
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 18. Januar 2022
• 1. Bericht­erstatter:in: Lichtenthaler, Stefan