The low-density lipoprotein receptor–mTORC1 axis coordinates CD8+ T cell activation

Abstract

Activation of T cells relies on the availability of intracellular cholesterol for an effective response after stimulation. We investigated the contribution of cholesterol derived from extracellular uptake by the low-density lipoprotein (LDL) receptor in the immunometabolic response of T cells. By combining proteomics, gene expression profiling, and immunophenotyping, we described a unique role for cholesterol provided by the LDLR pathway in CD8+ T cell activation. mRNA and protein expression of LDLR was significantly increased in activated CD8+ compared to CD4+ WT T cells, and this resulted in a significant reduction of proliferation and cytokine production (IFNγ, Granzyme B, and Perforin) of CD8+ but not CD4+ T cells from Ldlr −/− mice after in vitro and in vivo stimulation. This effect was the consequence of altered cholesterol routing to the lysosome resulting in a lower mTORC1 activation. Similarly, CD8+ T cells from humans affected by familial hypercholesterolemia (FH) carrying a mutation on the LDLR gene showed reduced activation after an immune challenge.

Decoding the crosstalk between mevalonate metabolism and T cell function

“…Whether a similar mechanism exists in T cells remains unclear, as variable results have been reported between the correlation of cholesterol levels and mTORC1 activation. In support of this mechanism, deletion of LDLR in CD8 T cells was associated with decreased cholesterol at the lysosome and lower mTORC1 activation 169 . In other studies, the adding MβCD cholesterol to SCAP‐deficient and HDAC‐deficient T cells rescues proliferation without altering mTORC1 signaling, suggesting that alternative mechanisms exist to couple intracellular cholesterol with T cell growth and metabolism 1,164 .…”

“…In support of this mechanism, deletion of LDLR in CD8 T cells was associated with decreased cholesterol at the lysosome and lower mTORC1 activation. 169 In other studies, the adding MβCD cholesterol to SCAP-deficient and HDAC-deficient T cells rescues proliferation without altering mTORC1 signaling, suggesting that alternative mechanisms exist to couple intracellular cholesterol with T cell growth and metabolism. 1,164 Loss of ABCG1 causes an accumulation of cholesterol; however, studies also found decreased mTORC1 signaling.…”

“…The different metabolic routes by which T cells acquire requisite cellular cholesterol may be better indicators of their fitness and proliferative capacity than plasma membrane or total cellular levels. In support of this concept, CD8 T cells deficient for LDLR were defective in proliferation and IFNγ production, insinuating that de novo cholesterol synthesis could not compensate for a complete loss of LDL uptake 169 . Loss of LDLR resulted in decreased cholesterol in the lysosome.…”

“…In support of this concept, CD8 T cells deficient for LDLR were defective in proliferation and IFNγ production, insinuating that de novo cholesterol synthesis could not compensate for a complete loss of LDL uptake. 169 Loss of LDLR resulted in decreased cholesterol in the lysosome. Notably, LDLR-deficient T cells had no difference in PM cholesterol levels or proximal TCR signaling.…”

Regional Differences in the Small Intestinal Proteome of Control Mice and of Mice Lacking Lysosomal Acid Lipase

“…A total of 10 μg of proteins was completely dried in a vacuum concentrator at 45 °C for 45 min. Afterward, the dried protein pellet was resuspended in 10 μL of water plus 10 μL of 50 mM ammonium bicarbonate solution (final pH 8.5), followed by protein reduction with 5 mM DTT for 20 min at 55 °C, as previously described. , Proteins were then alkylated at room temperature by incubation with 15 mM iodoacetamide for 30 min in the dark. Trypsin (#T7575-1KT, Merck Millipore, Billerica, MA) digestion with a 1:20 enzyme/protein ratio was performed overnight at 37 °C and terminated by acidification with trifluoroacetic acid (final concentration 1%).…”