Year: 2026
Type: preprint
Abstract: Microglial activation in response to lipopolysaccharide (LPS) requires Toll-like receptor 4 (TLR4) redistribution into cholesterol- and sphingolipid-rich membrane domains, yet the lipid determinants of this process remain unclear. Here, we identify cholesterol accessibility as a key driver of TLR4-dependent microglial activation. We show that LPS increases cholesterol uptake and mobilization, whereas inhibition of intracellular cholesterol trafficking or the plasma membrane-to-ER cholesterol transporter Aster attenuates inflammatory responses. Scavenger receptor class B type 1 (SR-B1) mediates LPS-induced cholesterol uptake, and its inhibition suppresses TLR4 signaling, receptor recruitment to detergent-resistant membrane domains, and TLR4 endocytosis without altering bulk cellular cholesterol. Instead, SR-B1 inhibition remodels the sphingolipidome and expands the sphingomyelin-associated cholesterol pool, as detected by OlyA, while LPS promotes remodeling of this pool and increases accessible cholesterol detected by D4H. Manipulation of sphingomyelin-cholesterol interactions alters membrane properties and TLR4 trafficking, while stabilization of these complexes suppresses inflammatory activation. In vivo, LPS induces remodeling of sphingomyelin-associated cholesterol in microglia, whereas Alzheimer’s disease-related ApoE4/Trem2 R47H microglia show impaired cholesterol-pool remodeling and enhanced inflammatory responses. Together, these findings establish sphingolipid-dependent cholesterol accessibility as a key regulatory layer controlling TLR4 organization and microglial inflammatory activation, positioning SR-B1 as an upstream regulator of this lipid-signaling axis.
Source: Research Square
Language: English
Subfield: Neurology
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
Awards: G1081089216, G1105844351, G1175115578, G1321079107, G1422035950, G2262748287, G24120701, G2601397997, G294895050, G300979063, G3179677927, G3220251042, G3480869486, G3565621276, G3681454997, G3857581125, G4042783231, G410571670, G4208431586, G4212894969, G425668148, G451917667, G4825891670, G491712853, G5080475149, G5195188938, G523076202, G5539308778, G5635532810, G5742496722, G5749886754, G593054264, G5967599077, G6033112984, G6082289184, G7084143925, G717256432, G7395345766, G7398047371, G7434936867, G7780475403, G7805626310, G7863371703, G8497050386, G8667377315
OpenAlex ID: W7213210192