Primate-specific regulation of the human glycosphingolipid gatekeeper UGCG.
This study reveals the structural complexity of UGCG, which may influence glycosphingolipid diversity and has implications for understanding lipid metabolism in humans.
Where it sits
this study against the rest of the vasopressin corpusSummary and findings
This study investigates the regulation of UDP-glucose ceramide glucosyltransferase (UGCG) in humans, focusing on its structural properties and functional states. The research utilized cryogenic electron microscopy to analyze UGCG in eight functional states. Findings reveal a unique transmembrane architecture and a primate-specific element affecting lipid affinity.
Abstract
Glycosphingolipids are essential membrane components that organize lipid microdomains and orchestrate cellular signalling, differentiation and neuronal function1-4. In humans, these functions arise from a repertoire of several hundred glycosphingolipid species generated through stepwise glycan elaboration5,6. Entry into this network is controlled by a single committed reaction catalysed by UDP-glucose ceramide glucosyltransferase (UGCG), the gatekeeper that dictates the scale and composition of glycosphingolipid diversity. Despite its biological and therapeutic importance7,8, its mechanism and regulation have remained unknown. Here we report cryogenic electron microscopy structures of full-length human UGCG in eight functional states at 2.9-3.4 Å resolution. UGCG adopts a previously unrecognized triple-pass transmembrane architecture that anchors a GT-A core at the membrane interface and creates a bipartite active site engaging soluble and membrane-embedded substrates. Contrary to canonical GT-A enzymes, UGCG uses a metal-independent catalytic mechanism driven by an arginine network. We identify a primate-specific steric element that tunes lipid affinity and catalytic turnover, modulating glycosphingolipid entry. Structures with clinically used inhibitors reveal how this architecture governs their potency and selectivity. Together, these findings define the structural and evolutionary logic by which one enzyme controls glycosphingolipid diversity and provide a framework for precision modulation of membrane lipid homeostasis in disease.
Background
Not reported in abstract.
Methods
Not reported in abstract.
Results
Not reported in abstract.
Interpretation
Not reported in abstract.
Limitations
Not reported in abstract.