Biology subjects

Lorent, J. H.

Publications and source records attributed to Lorent, J. H..

3 recordsLinked to original sources

bioRxiv2026

Mammalian MemPrep establishes the lipid composition of ER membranes in HEK293T cells

The endoplasmic reticulum (ER) forms a dynamic network of sheets and tubules, whose molecular lipid composition remains incompletely defined. Using an optimized MemPrep workflow, we establish a high-confidence lipidome of the mammalian ER and selectively enrich membrane vesicles originating from ER tubules as a major ER subdomain. Quantitative lipidomics show that ER membranes are dominated by phosphatidylcholine and mono-unsaturated glycerophospholipids, consistent with a highly compressible bilayer. Although proteomics suggests a functional specialization of ER tubules and an enrichment of tubule-associated proteins therein, the lipidome of an ER tubule-enriched isolate is indistinguishable from the general ER, indicating that principal ER architectures share a common lipid composition. Integration of lipidomic data with bioinformatic analyses of transmembrane helices further demonstrates that the physicochemical features of ER lipids mirror those of ER-resident membrane proteins, including reduced hydrophobicity and increased polarity compared to plasma membrane proteins. These findings support a coordinated evolution of ER proteins and lipids based on shared biophysical constraints. Together, this work provides a definitive characterization of the mammalian ER lipidome and suggest that membrane properties are maintained across the entire ER.

cell biology↗

bioRxiv2023

Cell Membranes Sustain Phospholipid Imbalance Via Cholesterol Asymmetry

Membranes are molecular interfaces that compartmentalize cells to control the flow of nutrients and information. These functions are facilitated by diverse collections of lipids, nearly all of which are distributed asymmetrically between the two bilayer leaflets. Most models of biomembrane structure and function often include the implicit assumption that these leaflets have similar abundances of phospholipids. Here, we show that this assumption is generally invalid and investigate the consequences of lipid abundance imbalances in mammalian plasma membranes (PM). Using quantitative lipidomics, we discovered that cytoplasmic leaflets of human erythrocyte membranes have >50% overabundance of phospholipids compared to exoplasmic leaflets. This imbalance is enabled by an asymmetric interleaflet distribution of cholesterol, which regulates cellular cholesterol homeostasis. These features produce unique functional characteristics, including low PM permeability and resting tension in the cytoplasmic leaflet that regulates protein localization. These largely overlooked aspects of membrane asymmetry represent an evolution of classic paradigms of biomembrane structure and physiology.

biophysics↗

bioRxiv2019

The Molecular and Structural Asymmetry of the Plasma Membrane

A fundamental feature of cellular plasma membranes (PM) is asymmetric lipid distribution between the bilayer leaflets. However, neither the detailed, comprehensive compositions of individual PM leaflets, nor how these contribute to structural membrane asymmetries have been defined. We report the distinct lipidomes and biophysical properties of both monolayers in living mammalian PMs. Phospholipid unsaturation is dramatically asymmetric, with the cytoplasmic leaflet being [~]2-fold more unsaturated than the exoplasmic. Atomistic simulations and spectroscopy of leaflet-selective fluorescent probes reveal that the outer PM leaflet is more packed and less diffusive than the inner leaflet, with this biophysical asymmetry maintained in the endocytic system. The structural asymmetry of the PM is reflected in asymmetric structures of protein transmembrane domains (TMD). These structural asymmetries are conserved throughout Eukaryota, suggesting fundamental cellular design principles.

cell biology↗