Biology subjects

Ohsaki, Y.

Publications and source records attributed to Ohsaki, Y..

3 recordsLinked to original sources

bioRxiv2025

Dynamics of Fanconi anemia protein D2 in association with nuclear lipid droplet formation

Fanconi anemia (FA) is a rare genetic disease caused by the loss of function of one of the 22 associated genes and is characterized by bone marrow failure, cancer predisposition, and developmental defects. The proteins encoded by these genes (FA proteins) mainly function in DNA damage response and repair. Although FA deficiency has multiple effects on the regulation of lipid metabolism, the molecular function of FA proteins in the context of FA pathology remains unclear. In the present study, we demonstrated that FANCD2, a key component of FA proteins, interacts with lipid metabolism-related factors and that FANCD2 deficiency downregulates the cellular levels of fatty acids. Moreover, a portion of FANCD2 is localized to nuclear lipid droplets in response to oleic acid treatment. These subcellular dynamics are independent of FANCD2 monoubiquitination, which is essential for the DNA damage response. Collectively, these findings demonstrate that FANCD2 responds to not only DNA damage but also oleic acid exposure, providing insights into the pathogenesis of lipid dysregulation in FA.

cell biology↗

bioRxiv2019

Universal phase behaviors of intracellular lipid droplets

Lipid droplets are cytoplasmic micro-scale organelles involved in energy homeostasis and handling of cellular lipids and proteins. The core structure is mainly composed of two kinds of neutral lipids, triglycerides and cholesteryl esters, which are coated by a phospholipid monolayer and proteins. Despite the liquid crystalline nature of cholesteryl esters, the connection between the lipid composition and physical states is poorly understood. Here, we present the first universal intracellular phase diagram of lipid droplets, semi-quantitatively consistent with the in vitro phase diagram, and reveal that cholesterol esters cause the liquid-liquid crystal phase transition under near-physiological conditions. The internal molecules of the liquid crystallized lipid droplets are aligned radially. We moreover combine in vivo and in vitro studies, together with the theory of confined liquid crystals, to suggest that the radial molecular alignments in intracellular lipid droplets are caused by an anchoring force at the droplet surface. Our findings on the phase transition of lipid droplets and resulting molecular organization contribute to a better understanding of their biological functions and diseases.

biophysics↗

bioRxiv2017

Syntaxin 17 promotes lipid droplet formation by regulating the distribution of acyl-CoA synthetase 3

Lipid droplets (LDs) are ubiquitous organelles that contain neutral lipids and are surrounded by a phospholipid monolayer. How proteins specifically localize to the phospholipid monolayer of the LD surface has been a matter of extensive investigations. Here we show that syntaxin 17 participates in LD biogenesis by regulating the distribution of acyl-CoA synthetase 3 (ACSL3), a key enzyme for LD biogenesis that redistributes from the endoplasmic reticulum to LDs during LD formation. Time course experiments revealed that syntaxin 17 binds to ACSL3 in the initial stage of LD formation, and that ACSL3 is released as a consequence of competitive binding of SNAP23 to syntaxin 17 in the maturation stage. We propose a model in which ACSL3 redistributes from the endoplasmic reticulum to LDs through association with syntaxin 17 and SNAP23-mediated dissociation from syntaxin 17. We also provide evidence that lipid raft-like structures are important for LD formation and SNAREs-ACSL3 interactions.

cell biology↗