BIN1 is a key regulator of proinflammatory and neurodegeneration-related activation in microglia

• Type of Material: Article
• Authors: Ari Sudwarts, University of South Florida; Supriya Ramesha, Emory University; Tianwen Gao, Emory University; Moorthi Ponnusamy, University of South Florida; Shuai Wang, University of South Florida; Mitchell Hansen, University of South Florida; Alena Kozlova, North Shore Univ Hlth Syst; Sara Bitarafan, Georgia Institute of Technology; Prateek Kumar, Emory University; David Beaulieu-Abdelahad, University of South Florida; Xiaolin Zhang, University of South Florida; Lisa Collier, University of South Florida; Charles Szekeres, University of South Florida; Levi B Wood, Georgia Institute of Technology; Jubao Duan, North Shore University Health System; Gopal Thinakaran, University of South Florida; Srikant Rangaraju, Emory University
• Language: English
• Date: 2022-05-07
• Publisher: BMC
• Publication Version: Final Published Version
• Copyright Statement: © The Author(s) 2022
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1186/s13024-022-00535-x
• Title of Journal or Parent Work: MOLECULAR NEURODEGENERATION
• Volume: 17
• Issue: 1
• Start Page: 33
• End Page: 33
• Grant/Funding Information: This work was supported by National Institutes of Health Grants RF1 AG054223 and RF1 AG056061 (to G.T.), R01 NS114130-01A1, RF1 AG071587, and K08 NS099474 (to S.R.), R01 AG063175 (to J.D. and G.T.), R01 MH106575 (to J.D.), and R01 R01NS115994 (to L.W.), and National Science Foundation CAREER 1944053 (to L.W.).
• Keywords: ALZHEIMER-DISEASE; PROTEIN EXPRESSION; BIN1; Neurosciences & Neurology; Neurosciences; LPS; Neuroinflammation; Microglia; Innate immunity; REVEALS; MOUSE; IFITM3; PU.1 EXPRESSION; IDENTIFICATION; GWAS risk factor; PU.1; CX3CR1; ASTROCYTES; BRAIN; IRF1; IRF7; Science & Technology; Life Sciences & Biomedicine; TRANSCRIPTION FACTOR; Alzheimer's disease; AMPHIPHYSIN-2 BIN1
• Research Categories: Engineering, Mechanical; Health Sciences, Medicine and Surgery

Abstract

Background: The BIN1 locus contains the second-most significant genetic risk factor for late-onset Alzheimer’s disease. BIN1 undergoes alternate splicing to generate tissue- and cell-type-specific BIN1 isoforms, which regulate membrane dynamics in a range of crucial cellular processes. Whilst the expression of BIN1 in the brain has been characterized in neurons and oligodendrocytes in detail, information regarding microglial BIN1 expression is mainly limited to large-scale transcriptomic and proteomic data. Notably, BIN1 protein expression and its functional roles in microglia, a cell type most relevant to Alzheimer’s disease, have not been examined in depth. Methods: Microglial BIN1 expression was analyzed by immunostaining mouse and human brain, as well as by immunoblot and RT-PCR assays of isolated microglia or human iPSC-derived microglial cells. Bin1 expression was ablated by siRNA knockdown in primary microglial cultures in vitro and Cre-lox mediated conditional deletion in adult mouse brain microglia in vivo. Regulation of neuroinflammatory microglial signatures by BIN1 in vitro and in vivo was characterized using NanoString gene panels and flow cytometry methods. The transcriptome data was explored by in silico pathway analysis and validated by complementary molecular approaches. Results: Here, we characterized microglial BIN1 expression in vitro and in vivo and ascertained microglia expressed BIN1 isoforms. By silencing Bin1 expression in primary microglial cultures, we demonstrate that BIN1 regulates the activation of proinflammatory and disease-associated responses in microglia as measured by gene expression and cytokine production. Our transcriptomic profiling revealed key homeostatic and lipopolysaccharide (LPS)-induced inflammatory response pathways, as well as transcription factors PU.1 and IRF1 that are regulated by BIN1. Microglia-specific Bin1 conditional knockout in vivo revealed novel roles of BIN1 in regulating the expression of disease-associated genes while counteracting CX3CR1 signaling. The consensus from in vitro and in vivo findings showed that loss of Bin1 impaired the ability of microglia to mount type 1 interferon responses to proinflammatory challenge, particularly the upregulation of a critical type 1 immune response gene, Ifitm3. Conclusions: Our convergent findings provide novel insights into microglial BIN1 function and demonstrate an essential role of microglial BIN1 in regulating brain inflammatory response and microglial phenotypic changes. Moreover, for the first time, our study shows a regulatory relationship between Bin1 and Ifitm3, two Alzheimer’s disease-related genes in microglia. The requirement for BIN1 to regulate Ifitm3 upregulation during inflammation has important implications for inflammatory responses during the pathogenesis and progression of many neurodegenerative diseases. Graphical Abstract: [Figure not available: see fulltext.]