Human neuropeptide transmitter systems are dysregulated in Alzheimer's disease pathogenesis - Project Summary Diverse brain neuropeptides, known as neuropeptidomes, comprise the majority of neurotransmitters that are essential for modulating Alzheimer’s disease (AD) deficits in dementia. The gap in the field is that global, unbiased neuropeptidomics analysis of the repertoire of human brain neuropeptides has not yet been achieved, nor have the human brain proteases that produce neuropeptides from their precursors been experimentally identified. Therefore, this project will close this gap by defining human brain neuropeptidomes and their biosynthetic proteases in normal and AD conditions. In support of this research, our group conducted a pilot study that demonstrates dysregulation of synaptic neuropeptidomes in human Alzheimer’s disease (AD) brain cortex compared to age-matched controls, involving proteolytic mechanisms. Furthermore, to identify proteases utilized to synthesize neuropeptidome components, we developed a multi-omics approach which integrates neuropeptidomics, protease cleavage profiling, and proteomics. Given that human-specific mechanisms for neuropeptide production may exist, studies of human brain neuropeptidomes are necessary to understand neurotransmitter regulation in normal human brain and in human AD brain. The goals of this project will be to, firstly, elucidate the full repertoire of neuropeptidome signatures and their biosynthetic proteases in normal human brain hippocampus and cortex subregions that participate in memory functions, combined with the hypothalamus that regulates metabolism and stress. Secondly, human brain regions from AD and the pre-AD stage of mild cognitive impairment (MCI) will be assessed for dysregulation of neuropeptidomes and biosynthetic proteases compared to age-matched controls. Dysregulated neuropeptides, including the chromogranins and VGF, will be assessed for regulating neuronal activities and toxicities. We will assess the hypothesis that synaptic neuropeptidomes are dysregulated in human AD brain, and that they possess biological activities for regulating neuronal functions. The specific aims will (1) study normal human brain regions involved in memory function to define neuropeptidomes and their biosynthetic proteases by multi- omics strategies, (2) evaluate protease production of human neuropeptidomes in young to older ages of human induced neurons (iNs), (3) investigate human AD and MCI brains for dysregulated synaptic neuropeptidomes and their biosynthetic proteases compared to controls, and (4) conduct functional analysis of AD dysregulated neuropeptides for regulating neuronal electrical network activity, metabolism, inflammation, cell death, and molecular pathways of cellular functions in human sporadic AD, MCI, and age-matched iNs. Significant findings will discover normal brain neuropeptides and their biosynthetic protease mechanisms, and, importantly, provide new knowledge of dysregulated human brain AD neuropeptidomes that regulate neuronal deficits related to AD. Such neuropeptides may represent novel AD biomarkers, and biosynthetic proteases may represent new drug targets for future AD drug discovery.
