Rab4A controls the overexpression of CD38 and depletion of IL-2 in CD4+ T cells: Potential involvement in proinflammatory lineage development in systemic lupus erythematosus

Abstract

Rab4A is a GTPase that is overexpressed in systemic lupus erythematosus (SLE) patients’ T cells and enhances cell surface receptor recycling. Increased expression of CD38 and loss of IL-2 production have independently been associated with proinflammatory T cell development in SLE. We investigated the impact of Rab4A on the expression of CD38 and the production of IL-2. Our lab created Rab4A-mutant Jurkat cell lines, containing GFP-expressing vector alone (control), doxycycline-inducible vectors that overexpress Rab4A (Rab4A hi) or the dominant-negative mutant Rab4A S27N(Rab4A DN). They were co-stimulated with anti-CD3 antibody and PMA. After 24 hours, cell surface markers and cytokines were analyzed by flow cytometry and protein levels by western blot. NAD +levels were measured by LC-MS/MS. In the Rab4A hicells compared to the control, CD38 expression was 2-fold upregulated (p=2.49×10 −13), intracellular production and secretion of IL-2 were significantly decreased (fold change=−0.566, p=1.16×10 −7and fold change= −0.481, p=0.0401, respectively), NAD +concentration was decreased (fold change=0.647, p=0.0039), while pSTAT3 levels were 2-fold increased (p=0.0318). CD38 is an NAD +hydrolase, which regulates Sirtuin-1 activity, a NAD +-dependent histone deacetylase that suppresses STAT3 activity. Elevated pSTAT3 levels may underlie diminished IL-2 production by binding to the promoter of FoxO1, which inhibits IL-2 production. The overexpression of Rab4A and CD38, increased pSTAT3, and diminished IL-2 production reflect changes observed in SLE patients. Our results suggest that increased expression of Rab4A may underlie the overexpression of CD38 and diminished secretion of IL-2 in SLE.