ALG2 regulates type I interferon responses by inhibiting STING trafficking.

Area of Science:

• Immunology
• Molecular Biology
• Cellular Signaling

Background:

• The Stimulator of Interferon Genes (STING) protein is crucial for detecting cytosolic DNA and initiating type I interferon responses.
• STING activation requires its translocation from the endoplasmic reticulum (ER) to perinuclear vesicles after binding cyclic GMP-AMP (cGAMP).

Purpose of the Study:

• To investigate the role of apoptosis-linked gene 2 (ALG2, also known as PDCD6) in regulating STING-mediated innate immune signaling.
• To elucidate the mechanism by which ALG2 influences STING trafficking and downstream interferon production.

Main Methods:

• Utilized THP-1 monocyte cell lines with ALG2 knockout (KO) to assess STING pathway activation.
• Stimulated cells with cGAMP or herpes simplex virus-1 (HSV-1) to mimic cytosolic DNA presence.
• Analyzed STING protein localization, interaction with ALG2, and calcium (Ca2+) coordination.

Main Results:

• ALG2 knockout significantly enhanced type I interferon expression in response to cGAMP or HSV-1.
• ALG2 directly associated with the C-terminal tail of STING, inhibiting its ER to perinuclear trafficking.
• The calcium-coordinating ability of ALG2 was essential for its regulatory function in STING trafficking and DNA-induced immunity.

Conclusions:

• Apoptosis-linked gene 2 (ALG2) acts as a negative regulator of the STING signaling pathway.
• ALG2 suppresses DNA-induced innate immune responses by inhibiting STING's critical trafficking step.
• This study identifies ALG2 as a novel modulator of the STING pathway, with potential implications for immune response modulation.