1. Phosphatidylserine enrichment in the nuclear membrane regulates key enzymes of phosphatidylcholine synthesis.
- Author
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Niu, Yang, Pemberton, Joshua G, Kim, Yeun Ju, and Balla, Tamas
- Subjects
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NUCLEAR matrix , *CELL membranes , *ENDOPLASMIC reticulum , *PHOSPHATIDYLSERINES , *OLEIC acid - Abstract
Phosphatidylserine (PS) is an important anionic phospholipid that is synthesized within the endoplasmic reticulum (ER). While PS shows the highest enrichment and serves important functional roles in the plasma membrane (PM) but its role in the nucleus is poorly explored. Using three orthogonal approaches, we found that PS is also uniquely enriched in the inner nuclear membrane (INM) and the nuclear reticulum (NR). Nuclear PS is critical for supporting the translocation of CCTα and Lipin1α, two key enzymes important for phosphatidylcholine (PC) biosynthesis, from the nuclear matrix to the INM and NR in response to oleic acid treatment. We identified the PS-interacting regions within the M-domain of CCTα and M-Lip domain of Lipin1α, and show that lipid droplet formation is altered by manipulations of nuclear PS availability. Our studies reveal an unrecognized regulatory role of nuclear PS levels in the regulation of key PC synthesizing enzymes within the nucleus. Synopsis: Phosphatidylserine (PS) is a phospholipid mainly enriched in the inner leaflet of the plasma membrane; however, its role in the nucleus remains unclear. This study describes the presence of PS in the inner nuclear membrane and nuclear reticulum, where it promotes nuclear membrane association of two key enzymes of phosphatidylcholine (PC) biosynthesis in response to oleic acid treatment. PS biosensors show its enrichment in the inner nuclear membrane (INM) and the nuclear reticulum (NR). PS in the inner nuclear membrane is synthesized at the endoplasmic reticulum. Nuclear PS interacts with two PC biosynthetic enzymes, CCTα and Lipin1α, promoting their translocation to the inner nuclear membrane. Nuclear PS biases PC biosynthesis toward membrane expansion rather than lipid droplet formation. Phosphatidylserine supports inner nuclear membrane enrichment of phosphatidylcholine biosynthetic enzymes, CCTα and Lipin1α, for nuclear membrane expansion. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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