# Phosphatidylcholine with C26:0 moiety, a precursor of a diagnostic marker for X-ALD, is synthesized by LPLAT10/LPEAT2

## TL;DR

This study identifies LPLAT10 as the enzyme responsible for producing a key diagnostic marker for X-ALD, a genetic disorder affecting myelin and adrenal function.

## Contribution

The study reveals LPLAT10's role in synthesizing C26:0-LPC, a diagnostic marker for X-ALD, and its mechanism of action.

## Key findings

- LPLAT10/LPEAT2 synthesizes PC with C26:0 moiety by transferring C26:0-CoA into 2-acyl-LPC.
- LPLAT10 deficiency reduces C26:0-LPC levels in X-ALD patient fibroblasts.
- C26:0 FFA-d4 is preferentially incorporated into sphingolipids when LPLAT10 is absent.

## Abstract

X-linked adrenoleukodystrophy (X-ALD) is a congenital metabolic disorder characterized mainly by inflammatory demyelination and adrenal insufficiency. Newborn screening using hexacosanoyl lysophosphatidylcholine (C26:0-LPC) in dried blood spots as a diagnostic marker can successfully identify potential patients with X-ALD and prevent disease onset. C26:0-LPC accumulates in patients with X-ALD, although the machinery synthesizing it has remained unclear. In this study, we focused on phosphatidylcholine (PC) with C26:0 moiety as a precursor of C26:0-LPC. We identified that lysophospholipid (LPL) acyltransferase 10 (LPLAT10)/LPCAT4/LPEAT2/AGPAT7 (1-acylglycerol-3-phosphate O-acyltransferase 7) is the responsible LPL acyltransferase that produces PC with C26:0 moiety by transferring C26:0-CoA into 2-acyl-LPC. We also found that LPLAT10 deficiency decreased the amount of C26:0-LPC in fibroblasts from X-ALD patients. Mechanistically, LPLAT10 introduced saturated fatty acid-CoA of various chain lengths as substrates into the sn-1 position of LPC but did not transfer C26:0-CoA to other LPL classes, such as lysophosphatidylethanolamine. Structural analysis revealed that a trimethylamine group of PC was placed between two tryptophan residues (W242 and W244), forming a W-X-W motif, possibly through cation-π interaction. Finally, it was shown that exogenously administered C26:0 FFA-d4 was preferentially incorporated into sphingolipids in the absence of LPLAT10. These results suggest that C26:0-LPC is produced through acyl-chain remodeling of PC catalyzed by LPLAT10 and accumulates in the plasma from X-ALD patients.