Biology subjects

Titeca, K.

Publications and source records attributed to Titeca, K..

3 recordsLinked to original sources

bioRxiv2025

Lipid Landscape of human cells

Eukaryotic cells synthesise thousands of lipid species, yet the principles that organise them across compartments remain unclear. Here we introduce PAP-SL, parallel (immuno)affinity purification coupled to shotgun lipidomics, to map [~]300 lipid species across six compartments of human cells and uncover general rules of lipid organisation. Correlation analyses of stoichiometric lipid compositions resolved archetypal distribution trajectories. Biosynthetic origin set the baseline: mitochondrial and lysosomal pathways generated confined pools, whereas the ER acted as a dispatch hub shaping downstream membrane territories. The ER established the saturated plasma membrane through transfer of phosphatidylserine, sphingolipids, and cholesterol, together with species-level selection of more saturated glycerophospholipids across diverse headgroups, while less-saturated species moved unselectively into mitochondria. The ER also channelled ether-linked glycerophospholipids to lysosomes, forming a territory dominated by ether phosphatidylcholine that collapsed under ethanolamine-driven metabolic rewiring. PAP-SL defines a framework to resolve lipid organisation and its metabolic plasticity in health and disease.

systems biology↗

bioRxiv2023

A system-wide analysis of lipid transfer proteins delineates lipid mobility in human cells

Lipid transfer proteins (LTPs) maintain the specialised lipid compositions of biological membranes, and many are associated with disease. In eukaryotes, they support organellar functions by transporting lipids between compartmentalised metabolic pathways. However, for the majority of the hundreds of human LTPs, the cargoes remain unknown. We combined biochemical, lipidomic and computational methods to characterize LTP-lipid complexes assembled in cellulo and in an in vitro biochemical assay. We identified bound lipids for about half of the LTPs analysed, and confirmed known cargoes, while discovering new ones for most LTP families. The data represents a systematic resource that captures the general principles of non-vesicular lipid transport in humans. The specificity of LTPs for lipids involves not only the recognition of specific head groups, but also of specific acyl chains. This selectivity defines lipid species within a lipid class with different metabolic or functional fates. The generalised ability of LTPs to form complexes with more than one class of lipids delineates new relationships between lipids and regulatory mechanisms that may contribute to the coordination of metabolism between different organelles. This work represents a resource and a framework for further analyses in different cell types, in pathological states or following various cellular perturbations.

biochemistry↗

bioRxiv2023

A Mechanistic Model for the Release of Ceramide from the CERT START Domain

Ceramide transfer protein CERT is the mediator of non-vesicular transfer of ceramide from ER to Golgi. In CERT, START is the domain responsible for the binding and transport of ceramide. A wealth of structural data has revealed a helix-grip fold surrounding a large hydrophobic holding the ceramide. Yet little is known about the mechanisms by which START releases the ceramide through the polar region and into the packed environment of cellular membranes. As such events do not lend themselves easily to experimental investigations we used multiple unbiased microsecond-long molecular simulations. We propose a membrane-assisted mechanism in which the passage of the ceramide acyl chains is facilitated by the intercalation of a single phosphatidylcholine lipid in the cavity, practically greasing the ceramide way out. We verify using experimental lipidomics data that CERT forms stable complexes with phosphatidylcholine lipids, in addition to ceramide, thus providing a validation for the proposed computational model.

biophysics↗