Memory formation requires de novo protein synthesis, and memory disorders may result from misregulated synthesis of critical proteins that remain largely unidentified. Plasma membrane ion channels and receptors are likely candidates given their role in regulating neuron excitability, a candidate memory mechanism. Here we conduct targeted molecular monitoring and quantitation of hippocampal plasma membrane proteins from mice with intact or impaired contextual fear memory to identify putative candidates. Here we report contextual fear memory deficits correspond to increased Trpc3 gene and protein expression, and demonstrate TRPC3 regulates hippocampal neuron excitability associated with memory function. These data provide a mechanistic explanation for enhanced contextual fear memory reported herein following knockdown of TRPC3 in hippocampus. Collectively, TRPC3 modulates memory and may be a feasible target to enhance memory and treat memory disorders.

Alzheimer’s disease (AD), the most common form of dementia in the elderly, has no cure. Thus, the identification of key molecular mediators of cognitive decline in AD remains a top priority. As aging is the most significant risk factor for AD, the goal of this study was to identify altered proteins and pathways associated with the development of ‘normal’ aging and AD memory deficits, and identify unique proteins and pathways that may contribute to AD-specific symptoms. We used contextual fear conditioning to diagnose 8-month-old 5XFAD and non-transgenic (Ntg) mice as having either intact or impaired memory, followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to quantify hippocampal membrane proteins across groups. Subsequent analysis detected 113 proteins differentially expressed relative to memory status (intact vs impaired) in Ntg mice and 103 proteins in 5XFAD mice. Thirty-six proteins, including several involved in neuronal excitability and synaptic plasticity (e.g., GRIA1, GRM3, and SYN1), were altered in both ‘normal’ aging and AD. Pathway analysis highlighted HDAC4 as a regulator of observed protein changes in both genotypes and identified the REST epigenetic regulatory pathway and Gi intracellular signaling as AD-specific pathways involved in regulating the onset of memory deficits. Comparing the hippocampal membrane proteome of Ntg versus AD, regardless of cognitive status, identified 138 differentially expressed proteins, including confirmatory proteins APOE and CLU. Overall, we provide a novel list of putative targets and pathways with therapeutic potential, including a set of proteins associated with cognitive status in normal aging mice or gene mutations that cause AD.

Summary How lifespan and body weight vary as a function of diet and genetic differences is not well understood. Here we quantify the impact of differences in diet in a genetically diverse family of female mice, split into matched isogenic cohorts fed a low-fat chow (CD, n = 663) or a high-fat diet (HFD, n = 685). We further generate key metabolic data in a parallel cohort sacrificed at four time points. HFD feeding shortens lifespan by 12%— equivalent to a decade in humans. Initial body weight and early weight gains account for longevity differences of ~4–6 days/g. At 500 days, animals on a HFD typically gain 4× as much weight as control, but variation in weight gain does not correlate with lifespan. Classic serum metabolites, often regarded as health biomarkers, are not necessarily strong predictors of longevity. Our data indicate that responses to a high fat diet are substantially modulated by gene-by-environmental interactions, highlighting the importance of genetic variation in making accurate individualized dietary recommendations.

An individual’s genetic makeup plays an important role in determining susceptibility to cognitive aging. Identifying the specific genes that contribute to cognitive aging may aid in early diagnosis of at-risk patients, as well as identify novel therapeutics targets to treat or prevent development of symptoms. Challenges to identifying these specific genes in human studies include complex genetics, difficulty in controlling environmental factors, and limited access to human brain tissue. Here, we identify Hp1bp3 as a novel modulator of cognitive aging using a genetically diverse population of mice, and confirm that HP1BP3 protein levels are significantly reduced in the hippocampi of cognitively impaired elderly humans relative to cognitively intact controls. Deletion of functional Hp1bp3 in mice recapitulates memory deficits characteristic of aged impaired mice and humans, further supporting the idea that Hp1bp3 and associated molecular networks are modulators of cognitive aging. Overall, our results suggest Hp1bp3 may serve as a potential target against cognitive aging and demonstrate the utility of genetically diverse animal models for the study of complex human disease.

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly population. More than 80% of AMD cases are of the dry-AMD classification, which characteristically features geographic atrophy resulting from the loss of retinal pigment epithelial (RPE) cells (1, 2). Dry-AMD often converts to wet-AMD, which is visionthreatening. Accumulation of undigested cellular debris (e.g., drusen), oxidative stress, and subsequent death and degeneration of RPE cells are important contributors to AMD pathology (3,4). Accumulating evidence suggests that the cellular sphingolipid mediator, ceramide (Cer), which acts as a second messenger to induce apoptosis, might play a role in RPE cell death (5-7). Here, we investigate for the first time the role of Cer in human RPE-derived ARPE19 cells under oxidative stress by removing excess cellular Cer via genetic manipulation of Cer-hydrolyzing enzymes.In addition to being a critical component of membrane structure and function, Cer serves as a vital intracellular second messenger. A steady-state level of Cer is necessary for cell proliferation and differentiation (8,9), while excessive amounts of Cer are often toxic and can result in cellular apoptosis (10). High concentrations of Cer can result in the induction of cell death, leading to tissue damage and organ failure, such as what is observed in retinal degeneration Sph) is the major source for Sph 1-phosphate production, which has an opposing role to Cer and provides cytoprotection. Here, we investigated the role of Cer in human RPE-derived ARPE19 cells under hydrogen peroxide-induced oxidative stress, and show that Cer and hexosyl-Cer levels increase in the oxidatively stressed ARPE19 cells, which can be prevented by overexpression of lysosomal ASAH1. This study demonstrates that oxidative stress generates sphingolipid death mediators in retinal cells and that induction of ASAH1 could rescue retinal cells from oxidative stress by hydrolyzing excess Overexpression of acid ceramidase (ASAH1) protects retinal cells (ARPE19) from oxidative stress. J. Lipid Res. 2019. 60: 30-43. Abstract Over 11 million people in the United States alone have some form of age-related macular degeneration (AMD). Oxidative stress, cell death, and the degeneration of retinal pigment epithelial (RPE) cells contribute to AMD pathology. Recent evidence suggests that ceramide (Cer), a cellular sphingolipid mediator that acts as a second messenger to induce apoptosis, might play a role in RPE cell death. The lysosomal breakdown of Cer by acid ceramidase [N-acylsphingosine amidohydrolase (ASAH)1] into sphingosine (Supplementary key words N-acylsphingosine amidohydrolase 1 • ceramide • hexosyl-ceramide • lysosome, retinal pigment epithelium • retinal degeneration • age-related macular degeneration