Distinct lipid transport proteins are regulated by innate immune stimuli

Lipid transport plays a critical role in the distribution of lipids across subcellular compartments. This is pivotal during infection and other stress stimuli that increase metabolic demands. While lipid biosynthesis is regulated by immune stimuli, whether immune signalling also influences lipid transport mechanisms remains unexplored.

We examined the effect of TLR and IFN-γ signalling on the gene expression of lipid transport proteins in human monocytic THP-1 cell line and compared these responses with those in primary bone marrow-derived mouse macrophages.

Our data demonstrate that TLR4 signalling selectively modulates the expression of oxysterol-binding protein-related proteins (ORPs), a key family of proteins that transport lipids between organelles. Remarkably, TLR4 activation led to the downregulation of several ORP family members in human THP-1-derived macrophages. However, this response was less profound in mouse macrophages. In contrast, the expression of steroidogenic acute regulatory domain (STARD) proteins, many of which transport lipids between mitochondria and other compartments, exhibited no statistical difference. Moreover, IFN-γ, a cytokine that plays a key role in the immune response, did not considerably impact human ORP or STARD expression levels, either alone or in combination with LPS.

Together, these results reveal that TLR signalling exerts selective and critical control over lipid trafficking pathways with important biological differences. These findings provide new insights into the crosstalk between immune signalling and lipid metabolism, which may offer novel targets to treat diseases characterized by dysregulated lipid pathways.