RAB4A DRIVES PROINFLAMMATORY CD4⁺ T CELL SIGNALING VIA CD38-DEPENDENT NAD⁺ METABOLISM.

Area of Science:

• Immunology
• Cell Biology
• Metabolism

Background:

• Rab4A GTPase is overexpressed in T cells from systemic lupus erythematosus (SLE) patients.
• Rab4A activates mTOR signaling, promoting T cell inflammation and nephritis in SLE.
• CD38 is implicated in T cell dysfunction and SLE pathogenesis.

Purpose of the Study:

• To elucidate the role of Rab4A in T cell dysfunction in SLE.
• To investigate the link between Rab4A, CD38, NAD+ metabolism, and IL-2 production.
• To identify novel therapeutic targets for SLE.

Main Methods:

• Investigated Rab4A's role in T cell endocytic recycling and surface protein expression.
• Assessed the impact of Rab4A-CD38 axis on NAD+ levels and IL-2 production in CD4+ T cells.
• Analyzed the effects of rapamycin on CD38 expression and IL-2 secretion.
• Examined the influence of Rab4A-CD38 on STAT3 and FOXO1 expression.

Main Results:

• Rab4A facilitates CD38 recycling and surface expression, leading to NAD+ depletion.
• CD38-mediated NAD+ depletion activates mTOR complex 1 and suppresses IL-2 production.
• Rapamycin enhanced CD38 expression and reduced IL-2, indicating an mTOR-independent mechanism.
• Rab4A-driven CD38 upregulation promoted STAT3 and FOXO1 expression, contributing to IL-2 depletion.

Conclusions:

• A novel Rab4A-CD38 signaling axis links T cell receptor trafficking to proinflammatory metabolic pathways in SLE.
• This pathway involves NAD+ depletion, altered STAT3 and FOXO1 expression, and suppressed IL-2 production.
• The Rab4A-CD38 axis represents a potential therapeutic target for SLE treatment.