Biology subjects

Walther, T. C.

Publications and source records attributed to Walther, T. C..

3 recordsLinked to original sources

bioRxiv2026

Cryo-EM structures reveal the mechanism of phosphatidylserine remodeling by membrane-bound glycerophospholipid O-acyltransferase 1

Lands cycle remodeling of glycerophospholipid acyl chains is crucial for cells to maintain appropriate membrane composition. Glycerophospholipids are cleaved at the glycerol sn2-position by phospholipase A. The lysophospholipids are reacylated by enzymes of the membrane-bound O-acyltransferase (MBOAT) family to incorporate specific fatty-acyl chains to adjust membrane properties. How MBOAT enzymes recognize specific acyl-CoA donors, select lysophospholipid acceptors, and release products is unclear. Phosphatidylserine (PS), a critical anionic phospholipid, controls membrane surface charge, signaling-protein recruitment, and cell-death-associated membrane recognition, and PS acyl-chain remodeling is linked to ferroptosis resistance. Here, we showed that MBOAT1 preferentially generates monounsaturated fatty acid-containing PS from lyso-PS. High-resolution cryo-electron microscopy structures of human MBOAT1 captured distinct binding poses of the fatty acyl donor, lyso-PS acceptor, and PS product. With lipidomics, enzymology and molecular dynamics simulations, these structures reveal the mechanism and pathway of MBOAT1-dependent PS remodeling.

biochemistry↗

bioRxiv2018

A post-transcriptional regulatory code for mRNA stability during the zebrafish maternal-to-zygotic transition

Post-transcriptional regulation is crucial to shape gene expression. During the Maternal-to-Zygotic Transition (MZT), thousands of maternal transcripts are regulated upon fertilization and genome activation. Transcript stability can be influenced by cis-elements and trans-factors, but how these inputs are integrated to determine the overall mRNA stability is unclear. Here, we show that most transcripts are under combinatorial regulation by multiple decay pathways during zebrafish MZT. To identify cis-regulatory elements, we performed a massively parallel reporter assay for stability-influencing sequences, which revealed that 3-UTR poly-U motifs are associated with mRNA stability. In contrast, miR-430 target sequences, UAUUUAUU AU-rich elements (ARE), CCUC and CUGC elements emerged as the main destabilizing motifs in the embryo, with miR-430 and AREs causing mRNA deadenylation in a genome activation-dependent manner. To identify the trans-factors interacting with these cis-elements, we comprehensively profiled RNA-protein interactions and their associated regulatory activities across the transcriptome during the MZT. We find that poly-U binding proteins are preferentially associated with 3-UTR sequences and stabilizing motifs, and that antagonistic sequence contexts for poly-C and poly-U binding proteins shape the binding landscape and magnitude of regulation across the transcriptome. Finally, we integrate these regulatory motifs into a machine learning model that accurately predicts the stability of mRNA reporters in vivo. Our findings reveal how mechanisms of post-transcriptional regulation are coordinated to direct changes in mRNA stability within the early zebrafish embryo.

genomics↗

bioRxiv2018

FIT2 is a lipid phosphate phosphatase crucial for endoplasmic reticulum homeostasis

The endoplasmic reticulum (ER) protein Fat-Induced Transcript 2 (FIT2) has emerged as a key factor in lipid droplet (LD) formation, although its molecular function is unknown. Highlighting its importance, FIT2 orthologs are essential in worms and mice, and FIT2 deficiency causes a deafness/dystonia syndrome in humans. Here we show that FIT2 is a lipid phosphate phosphatase (LPP) enzyme that is required for maintaining the normal structure of the ER. Recombinant FIT2 exhibits LPP activity in vitro and loss of this activity in cells leads to ER membrane morphological changes and ER stress. Defects in LD formation in FIT2 depletion appear to be secondary to membrane lipid abnormalities, possibly due to alterations in phospholipids required for coating forming LDs. Our findings uncover an enzymatic role for FIT2 in ER lipid metabolism that is crucial for ER membrane homeostasis.

cell biology↗