ORP3 protein identified as key mediator of lysosomal membrane repair through lipid transfer
Researchers have identified ORP3, a lipid transfer protein, as a critical mediator of lysosomal membrane repair following cellular damage. The protein is activated through a signaling cascade involving ubiquitination, TAK1, and p38 MAPK, and works by transferring phosphatidylcholine from the endoplasmic reticulum to damaged lysosomes via interaction with LC3B. The findings reveal a previously unknown mechanism of cellular homeostasis that could have implications for understanding lysosomal storage diseases and cellular stress responses.
In this preprint study, researchers identified ORP3 as a critical component of the cellular response to lysosomal membrane damage. When lysosomes are damaged by chemical agents like LLOME or cationic amphiphilic drugs, ORP3 becomes phosphorylated and recruited to contact sites between the endoplasmic reticulum and lysosomes through a signaling cascade initiated by lysosomal ubiquitination, TAK1, and p38 MAPK. The p38-dependent phosphorylation enables ORP3 to interact directly with LC3B, a protein involved in autophagy, which facilitates the recruitment of autophagic machinery to repair the damaged lysosome. The study demonstrates that ORP3's lipid transfer function—specifically transferring phosphatidylcholine to lysosomes—is essential for restoring lysosomal function, as a lipid transfer-deficient mutant could not rescue lysosomal recovery despite being properly recruited. ORP3 depletion impaired late-stage lysosomal recovery, increased lipid peroxidation, and reduced cell survival, underscoring the protein's importance. The repair process is terminated when VCP/p97 removes ubiquitin marks from lysosomes, allowing the system to reset.
Limitations & open questions
The study's own limitations are not detailed in the provided abstract. Additionally, the clinical relevance to human disease and whether findings in cell culture models translate to whole organisms remain open questions typical of early-stage research.
What different sources said
- bioRxivCenter
Lipid transfer protein ORP3 mediates lysosomal repair via LC3B and ubiquitin-TAK1-p38
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