Class I PI3K Provide Lipid Substrate in T Cell Autophagy Through Linked Activity of Inositol Phosphatases

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Autophagy is a conserved cellular process vital for T lymphocyte homeostasis.
• The precise molecular mechanisms regulating autophagy in T cells are not fully understood.

Purpose of the Study:

• To elucidate the role of phosphatidylinositol-3 kinases (PI3K) in T cell receptor (TCR)-mediated autophagy.
• To identify key regulators and pathways involved in autophagy induction in T lymphocytes.

Main Methods:

• Investigated autophagy induction via starvation and TCR stimulation in T cells.
• Utilized PI3K-deficient T cells and assessed PI(3)P production.
• Analyzed the role of inositol phosphatases (Inpp4, SHIP) in autophagy.
• Examined the effect of exogenous PI(3,4)P2 and TCR complex internalization.
• Assessed autophagy in HIV-infected CD4+ T cells.

Main Results:

• TCR-mediated autophagy requires class I PI3K activity for PI(3)P production.
• Common gamma chain cytokines suppress autophagy, despite activating PI3K.
• T cells lacking PI3KI subunits show impaired TCR-mediated autophagy and PI(3)P production.
• Inositol phosphatases Inpp4 and SHIP are essential for TCR-mediated autophagy.
• Exogenous PI(3,4)P2 can rescue PI(3)P levels and enhance autophagy.
• HIV-induced bystander CD4+ T cell autophagy depends on PI3KI.

Conclusions:

• TCR activation induces autophagy through PI3KI activity and inositol phosphatase upregulation, leading to PI(3)P production.
• This pathway is critical for T lymphocyte homeostasis and is implicated in HIV pathogenesis.