Neurovascular protein lifetime in health, aging and Alzheimer's disease

University Of California, San Diego, La Jolla CA

Investigators

Abstract

PROJECT SUMMARY/ABSTRACT In the central nervous system (CNS), blood vessels have specialized functions that are critical for maintenance of CNS homeostasis. These include the blood-brain barrier (BBB), which tightly controls the access of ions, molecules, and cells to the CNS, and neurovascular coupling, a process by which blood flow is transiently increased to regions of elevated neural activity. Further, vascular cells regulate development and function of neurons and glia, and perivascular spaces serve as conduits for cerebrospinal fluid circulation, which may be important for waste clearance. These processes rely on the coordinated function of many cell types, including endothelial cells, pericytes, vascular smooth muscle cells, perivascular fibroblasts, astrocyte endfeet, and immune cells, which together constitute a neurovascular unit (NVU). Emerging evidence suggests that many NVU properties are dynamically regulated by physiological cues, including circadian rhythms and neural activity. This suggests that the CNS vasculature achieves a balance between the stability required to achieve continuous, highly tuned oxygen and nutrient delivery, and the plasticity required to dynamically modulate function. Importantly, NVU dysfunction is observed in aging and neurological diseases, including Alzheimer's disease, and such dysfunction contributes to the associated CNS pathology. A better understanding of the molecular mechanisms underlying neurovascular stability and plasticity in health, and age- and Alzheimer’s disease- associated dysfunction, may reveal new molecular targets for treating this dysfunction. This project will address this knowledge gap by quantifying the lifetimes of neurovascular proteins in health, aging, and Alzheimer’s disease. Protein lifetime is a fundamental parameter that profoundly influences protein function, and thereby influences cell and tissue function: long-lived proteins can stabilize cellular structures, but are also susceptible to accumulated damage; short-lived proteins are amenable to rapid modulation by physiological cues, but have high energetic burden. Changes to protein lifetimes are potential mechanisms of aging- and disease-associated cellular dysfunction. Although protein lifetimes have been measured in the CNS, the vast majority of neurovascular protein lifetimes have not been quantified due to the low vascular fraction in whole brain tissue. This project will generate a comprehensive atlas of neurovascular protein lifetimes in health, aging, and a tauopathy-based model of Alzheimer’s disease. Aim 1 will employ stable isotope labeling in mammals (SILAM), nonenzymatic vessel isolation, and mass spectrometry-based proteomics to quantify protein lifetimes, and identify changes in aging and Alzheimer’s disease. In Aim 2, single nucleus RNA-seq will be used to define the cellular and transcriptomic composition of isolated microvessels, and allow inference of cell type(s) of origin of proteins detected in Aim 1. Together, this work will advance understanding of the molecular bases of neurovascular function and yield new hypotheses for molecular mechanisms underlying age- and Alzheimer’s disease-associated neurovascular dysfunction.