Autophagy-related protein Vps34 controls the homeostasis and function of antigen cross-presenting CD8α⁺dendritic cells

Abstract

The class III PI3K Vacuolar protein sorting 34 (Vps34) plays a role in both canonical and noncanonical autophagy, key processes that control the presentation of antigens by dendritic cells (DCs) to naive T lymphocytes. We generated DC-specific Vps34-deficient mice to assess the contribution of Vps34 to DC functions. We found that DCs from these animals have a partially activated phenotype, spontaneously produce cytokines, and exhibit enhanced activity of the classic MHC class I and class II antigen-presentation pathways. Surprisingly, these animals displayed a defect in the homeostatic maintenance of splenic CD8α + DCs and in the capacity of these cells to cross-present cell corpse-associated antigens to MHC class I-restricted T cells, a property that was associated with defective expression of the T-cell Ig mucin (TIM)-4 receptor. Importantly, mice deficient in the Vps34-associated protein Rubicon, which is critical for a noncanonical form of autophagy called "Lightchain 3 (LC3)-associated phagocytosis" (LAP), lacked such defects. Finally, consistent with their defect in the cross-presentation of apoptotic cells, DC-specific Vps34-deficient animals developed increased metastases in response to challenge with B16 melanoma cells. Collectively, our studies have revealed a critical role of Vps34 in the regulation of CD8α + and CD4 + T cells, respectively. MHC class II-associated peptides are typically generated by proteolysis of endocytosed proteins (1), whereas MHC class I-associated peptides are predominantly generated by proteolysis of cytosolic proteins (2). However, in specialized antigen-presenting cells (APCs) such as a DC subset expressing CD8α and CD103, extracellular antigens can be presented in the context of MHC class I molecules via a cross-presentation pathway whose mechanism is incompletely understood (3).In recent years, the process of autophagy has been implicated in controlling antigen processing (4). Autophagy is a conserved catabolic process that maintains cellular energy homeostasis in response to a wide spectrum of cellular stresses (5, 6). Autophagy ensures continuous degradation of long-lived proteins, damaged cellular organelles, and protein aggregates to facilitate recycling of nutrients and hence promote cellular metabolism. The formation of autophagosomes requires an interplay between autophagyrelated (Atg) gene products, which have been well characterized in yeast and are conserved in mammals (7). Defective autophagy in mammalian cells results in the accumulation of damaged cellular organelles and protein aggregates, leading to stress with pathological consequences (8). Autophagy has common features with endocytosis, with which it shares effector molecules (9). However, how these processes and their shared machinery regulate antigen presentation remains incompletely understood.Vacuolar protein sorting 34 (Vps34) is a class III PI3K that plays a role in endocytosis, intracellular vesicular trafficking, and autophagosome formation during autophagy (10). Vps34-deficient cells display defec...

The multifaceted role of autophagy in cancer and the microenvironment

“…In line with this role of autophagy in presenting appropriate antigenic peptides, knockout of the autophagy‐regulator VPS34 in DCs abrogated the induction of B16 melanoma‐specific CTLs in vivo, yielding a significantly higher incidence of lung metastases . In this setting, cross‐presentation of OVA peptides derived from apoptotic cells was strongly reduced, although VPS34‐deficient DCs did present higher levels of cytoplasmic OVA‐derived antigens .…”

Autophagy: A Potential Therapeutic Target for Reversing Sepsis-Induced Immunosuppression

“…Mice with Atg5 deficient in DCs exhibited impaired activities of CD4 + T cells as a result of reduced interleukin (IL)-2 and interferon (IFN)-γ production, but without affecting costimulatory molecule expressions on DCs, which were different from Beclin-1 and vacuolar protein sorting 34 (Vps34). The DCs exhibited long-standing dysfunction and massive loss in animals with Beclin-1 or Vps34 deficient ( 34 – 36 ). However, Bhattacharya and colleagues found that the loss of Atg7 gene displayed protective effects against autoimmune encephalomyelitis in mice ( 37 ).…”

Disabled-2 (DAB2) Overexpression Inhibits Monocyte-Derived Dendritic Cells' Function in Vogt-Koyanagi-Harada Disease

“…17 Src, PI3K, and Akt are key genes affecting autophagy, and autophagy has been implicated in the antigen presentation ability and cytokine response of DCs. 34,35 Earlier reports showed that DAB2 was found to be an autophagy inhibitor by blocking the interaction between vacuolar protein sorting 34 and beclin-1. 36 To find out whether DAB2 affects the function of DCs through autophagy, we measured the autophagy proteins LC3 and P62 after overexpression of DAB2 in DCs but did not find a difference compared with controls.…”

“…Autophagy can directly affect the maturation of DCs, 34,35 and DAB2 has been mentioned as an inhibitor of autophagy. 36 To investigate the role of DAB2 in the autophagy of DCs, we used Western blots to measure the autophagy proteins LC3 and P62 in DCs overexpressing DAB2.…”