An increase in VGF expression through a rapid, transcription-independent, autofeedback mechanism improves cognitive function

Translational Psychiatry ARTICLE www.nature.com/tp OPEN An increase in VGF expression through a rapid, transcriptionindependent, autofeedback mechanism improves cognitive function ✉ Wei-Jye Lin1,2,3,4,5 , Yan Zhao3,6,7, Zhe Li 3,6,7, Shuyu Zheng3,6,7, Jin-lin Zou8, Noël A. Warren9, Purva Bali4, Jingru Wu1,2, ✉ ✉ 10 Mengdan Xing , Cheng Jiang 4,5, Yamei Tang1,3,10, Stephen R. Salton 4,5 and Xiaojing Ye 3,6,7 © The Author(s) 2021 The release of neuropeptides from dense core vesicles (DCVs) modulates neuronal activity and plays a critical role in cognitive function and emotion. The granin family is considered a master regulator of DCV biogenesis and the release of DCV cargo molecules. The expression of the VGF protein (nonacronymic), a secreted neuropeptide precursor that also belongs to the extended granin family, has been previously shown to be induced in the brain by hippocampus-dependent learning, and its downregulation is mechanistically linked to neurodegenerative diseases such as Alzheimer’s disease and other mood disorders. Currently, whether changes in translational efficiency of Vgf and other granin mRNAs may be associated and regulated with learning associated neural activity remains largely unknown. Here, we show that either contextual fear memory training or the administration of TLQP-62, a peptide derived from the C-terminal region of the VGF precursor, acutely increases the translation of VGF and other granin proteins, such as CgB and Scg2, via an mTOR-dependent signaling pathway in the absence of measurable increases in mRNA expression. Luciferase-based reporter assays confirmed that the 3′-untranslated region (3′UTR) of the Vgf mRNA represses VGF translation. Consistently, the truncation of the endogenous Vgf mRNA 3′UTR results in substantial increases in VGF protein expression both in cultured primary neurons and in brain tissues from knock in mice expressing a 3′UTR-truncation mutant encoded by the modified Vgf gene. Importantly, Vgf 3′UTR-truncated mice exhibit enhanced memory performance and reduced anxiety- and depression-like behaviors. Our results therefore reveal a rapid, transcription-independent induction of VGF and other granin proteins after learning that are triggered by the VGF-derived peptide TLQP-62. Our findings suggest that the rapid, positive feedforward increase in the synthesis of granin family proteins might be a general mechanism to replenish DCV cargo molecules that have been released in response to neuronal activation and is crucial for memory function and mood stability. Translational Psychiatry (2021)11:383 ; https://doi.org/10.1038/s41398-021-01489-2 INTRODUCTION Neuropeptides play critical roles in the modulation of neural activity and synaptic plasticity, which are required for memory formation and emotional behavior. Neuropeptide precursors are sorted into dense core vesicles (DCVs), subcellular compartments that are present in both axons and dendrites, where they are proteolytically processed into peptides. DCVs have an average diameter of 65 nm, as reported in neurons [1, 2]. The release of DCV components into the extracellular space is achieved by constitutive or activity-regulated secretion. Correct packing and sorting of neuropeptides and neurotrophins have a significant impact on cognitive function. A Val66Met substitution in the BDNF coding sequence, for example, has been widely studied in the human population. BDNF Met66 carriers show increased risks of developing cognitive impairment and mood disorders as a result of impaired BDNF pro-protein sorting and secretion [3–5]. The roles of DCV biogenesis in learning, memory, and emotion are still largely unknown. Proteins of the extended granin family, including VGF (nonacronymic), chromogranin A (CgA), chromogranin B (CgB), secretogranin 2 (Scg2), and secretogranin 3 (Scg3), are the major components of DCVs that are known to play critical roles in DCV biogenesis, sorting, and regulated secretion [6]. Cellular expression of granin proteins induces DCV biogenesis and increases both DCV numbers and 1 Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangdong-Hong Kong Joint Laboratory for RNA Medicine, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou 510120, China. 2Medical Research Center, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou 510120, China. 3 Guangdong Province Key Laboratory of Brain Function and Disease, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong 510080, China. 4Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA. 5Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA. 6Faculty of Forensic Medicine, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China. 7Guangdong Province Translational Forensic Medicine Engineering Technology Research Center, Sun Yat-sen University, Guangzhou 510080, China. 8Department of Gastroenterology, the Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai 519000, China. 9Departments of Neuroscience and Psychiatry, Icahn School of Medicine at Mount Sinai, Addiction Institute of Mount Sinai, New York, NY 10029, USA. 10Department of Neurology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, Guangdong 510080, China. ✉email: ; ; Received: 5 January 2021 Revised: 4 June 2021 Accepted: 21 June 2021 W.-J. Lin et al. 1234567890();,: 2 vesicle sizes in fibroblasts, pheochromocytoma cells, and pancreatic beta-cells [7–9]. For example, overexpression of CgA, CgB, or VGF in fibroblasts that lack a classical regulated secretory pathway results in the de novo production of granulelike structures, while gene silencing studies in DCV-containing cells have revealed reciprocal effects on DCV biogenesis, including decreased DCV number and vesicle sizes [7, 10]. In addition to contributions to DCV biogenesis, granin proteins and their processed peptides are also released into the extracellular space in a regulated manner, where they function in energy and glucose homeostasis and cognition [8]. Expression of the Vgf, ChgA, ChgB, and Scg2 genes has been reported in neurons, while Scg3 is expressed in both neurons and astrocytes [11–15]. VGF (nerve-growth factor inducible, nonacronymic) was originally identified for its robust induction by nerve growth factor (NGF) in PC12 cells [16, 17]. In recent studies, reduced cerebrospinal fluid (CSF) levels or brain expression of VGF, Scg2, CgB, and CgA proteins have been reported in patients with Alzheimer’s disease (AD), with an estimated decrease in CSF VGF levels at a rate of 10.9% per year in a longitudinal study of patients with AD [18–20]. VGF has been identified as a key modulator that regulates diseaseassociated gene and protein networks in the brains of patients with AD and mouse models [21, 22]. Prolonged volunt (...truncated)