Session Type: Poster Session (Sunday)
Session Time: 9:00AM-11:00AM
Background/Purpose: HRES-1/Rab4 is a small GTPase enzyme which regulates endosomal trafficking. The protein is overexpressed in T cells of SLE patients (J Immunol. February 15, 2009, 182 (4): 2063-2073) and mice (Ann Rheum Dis. 2014 Oct;73(10):1888-97.), resulting in mitochondrial accumulation through the inhibition of mitophagy (PLoS One. 2014, 9(1): e84392). Since mitochondrial dysfunction in T cells plays an important role in the pathogenesis of SLE, we investigated whether its mouse homologue, Rab4A, regulates metabolism.
Methods: Metabolic flux analysis is an emerging technique capable of offering insight into intracellular metabolism both on an individual metabolite and on a metabolic pathway level (J Ind Microbiol Biotechnol (2015) 42: 317) which makes it a suitable method for the investigation of T cell metabolism.
To study the effects of Rab4A expression in T cells, a site-specific Cre/Lox recombinase system was employed to knock down Rab4A expression in lupus-prone SLE 1.2.3. mice. The metabolic flux of T cells and other lymphocytes was characterized by feeding 13C-stable isotope labeled nutrients, such as glucose or glutamine, to cells in culture and subsequently measuring isotope labeled metabolites using liquid chromatography-mass spectrometry (LC-MS) after the preparation of cell extracts.
Results: The non-oxidative pentose phosphate pathway (PPP) metabolite, sedoheptulose-7-phosphate (S7P) was accumulated in CD4+ T cells (33% elevation, p=0.002) but it was reduced in B cells (24%, p=0.043) of lupus mice. Rab4A deletion in T cells reversed the accumulation of S7P in CD4 T cells in SLE mice (p=0.035).
Mitochondrial tricarboxylic cycle metabolites, glutamate (18% decrease, p=0.029), citrate/isocitrate (37 % decrease, p=0.004), alpha-ketoglutarate (32 % decrease, p=0.006) and malate (35% decrease, p=0.038) were depleted in CD4+ T cells of SLE mice. Glutamate was also reduced in B cells of SLE mice (7 % decrease, p=0.026).
Conclusion: The results suggest that T cell-specific deletion of Rab4A restores the SLE-induced metabolic changes in CD4+ T cells. Therefore, Rab4A may represent a target for correcting T-cell dysfunction in SLE.
To cite this abstract in AMA style:Faludi T, Huang N, Duarte M, Lewis J, Perl A. Flux Analysis Reveals Influence of Rab4 Expression on Mitochondrial and Pentose Phosphate Pathway Metabolism of Lupus T Cells [abstract]. Arthritis Rheumatol. 2019; 71 (suppl 10). https://acrabstracts.org/abstract/flux-analysis-reveals-influence-of-rab4-expression-on-mitochondrial-and-pentose-phosphate-pathway-metabolism-of-lupus-t-cells/. Accessed April 13, 2021.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/flux-analysis-reveals-influence-of-rab4-expression-on-mitochondrial-and-pentose-phosphate-pathway-metabolism-of-lupus-t-cells/