Selective reduction of bis(monoacylglycero)phosphate ameliorates the storage burden in a THP-1 macrophage model of Gaucher disease

Stephen Duplock,Maria Fuller,Leanne K. Hein

doi:10.1194/jlr.m038232

Abstract

Bis(monoacylglycero)phosphate (BMP) assists lysosomal function by facilitating interaction of hydrolases and activator proteins with sphingolipid substrates. Impaired lysosomal degradation of the sphingolipid glucosylceramide (GC) occurs in Gaucher disease due to an inherited deficiency of acid β-glucosidase, with secondary BMP alterations. We investigated the nature of BMP accumulation and whether its correction reduced the storage burden in a THP-1 macrophage model of Gaucher disease. Using sucrose gradients and detergent solubility, 98% of BMP resided in the detergent-soluble membranes (DSM) rather than in the detergent-resistant membranes (DRM) where 73% of GC predominated. There was a 2-fold widespread elevation in BMP, including the saturated, mono- and polyunsaturated species. Linoleic acid in the culture media selectively reduced BMP from 4.2 nmol/mg to 0.49 nmol/mg (except 18:1/18:2) and prevented up to one third of GC, dihexosylceramide (DHC), and trihexosylceramide (THC) from accumulating. The 2-fold reduction in these sphingolipids occurred only in the DRM and did not reduce 18:1/16:0. However, once GC had accumulated, linoleic acid could not reverse it, DHC, or THC, despite effectively reducing BMP. These results imply a causative link for BMP in the pathobiology of Gaucher disease and demonstrate that linoleic acid can shield the cell from excessive substrate accumulation.

Highlights

Bis(monoacylglycero)phosphate (BMP) assists lysosomal function by facilitating interaction of hydrolases and activator proteins with sphingolipid substrates
We show that BMP accumulates in different membrane microdomains from the primary substrate, GC, in a Gaucher THP-1 macrophage model and that BMP could be lowered by manipulating its synthesis with an excessive amount of linoleic acid added to the culture media
With the exception of the fully saturated BMP 16:0/16:0, PC 32:0, PG 32:0, and PS 16:0/16:0, which did not correlate, the remaining species measured in the membrane microdomains correlated (Pearson >0.8) and were summed

Summary

Introduction

Bis(monoacylglycero)phosphate (BMP) assists lysosomal function by facilitating interaction of hydrolases and activator proteins with sphingolipid substrates. Once GC had accumulated, linoleic acid could not reverse it, DHC, or THC, despite effectively reducing BMP. Selective reduction of bis(monoacylglycero)phosphate ameliorates the storage burden in a THP-1 macrophage model of Gaucher disease. The negative charge of BMP, coupled with its proposed cone-shaped structure, enables it to participate in the organization of the membranes of the lysosomal network, contributing to its multivesicular/multilamellar morphology [6, 7]. These properties of BMP facilitate lysosomal lipid degradation, which takes place on the surface of the inner membranes of lysosomes.

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Conclusion