Eckel, R. H. | Search bioRxiv

bioRxiv2026

ApoE Lipidation State Directs Immunometabolic Reprogramming of Human Microglia

IntroductionApoE4 is the strongest genetic risk factor for Alzheimers disease (AD). Emerging evidence suggests that ApoE4 increases AD risk by disrupting microglial metabolism and function. However, whether ApoE lipidation state contributes to microglial dysfunction remains poorly understood. MethodsHuman microglia were treated with lipid-free or lipid-bound ApoE3 or ApoE4. Label-free live-cell holotomography and global proteomics were used to assess isoform- and lipidation-specific effects on lipid droplet dynamics, mitochondrial morphology, and microglial phenotype. ResultsApoE4 treatment resulted in fewer but enlarged lipid droplets and increased mitochondrial fragmentation compared to ApoE3, effects that were enhanced by lipid-bound ApoE4. Proteomic analyses revealed a strong type I interferon response in cells exposed to lipid-free ApoE, which was exacerbated by lipid-free ApoE4. DiscussionThese findings indicate that lipid-bound ApoE4 drives metabolic reprogramming, whereas lipid-free ApoE4 promotes inflammatory signaling, identifying ApoE lipidation as a critical modifier of ApoE4-associated AD risk.

neuroscience↗

bioRxiv2025

Lipoprotein lipase requires a flexible lid and stable C-terminal, both maintained by ApoC-II peptide binding

Lipoprotein lipase (LPL) is the rate-limiting enzyme responsible for hydrolyzing triglycerides in circulating lipoproteins. Reduced LPL activity contributes to hypertriglyceridemia, a major cardiovascular risk factor. LPL activity is thought to depend on the conformation of the lid domain, the lipid pore, N- and C-terminal domains (NTD, CTD), and stabilization of these domains by endogenous activators such as apolipoprotein C-II (ApoC-II). Despite major clinical significance, the structure-function relationship of LPLs functional domains and cofactors remain incompletely understood. To address this, we performed the longest known (1-{micro}s) molecular dynamics simulations of LPL independently and in complex with an ApoC-II mimetic peptide (ApoC-II-P). For the first time, we show that LPLs flexible lid can adopt multiple orientations, transitioning between open and closed states that regulate lipid pore access and catalytic activity. We also observed flipping of [~]180{degrees} by the CTD, a unique characteristic that dictates LPL activity when not in a closed lid state. Furthermore, ApoC-II-P stabilizes LPL by bridging its NTD and CTD, while maintaining an optimal lid orientation. Biochemical and cellular assays corroborate these findings, demonstrating that ApoC-II-P enhances LPL hydrolysis and supports noncanonical LPL functions. Together, these insights reveal previously unrecognized mechanisms governing LPL regulation and activity dynamics.

molecular biology↗