Selective degradation of PU.1 during autophagy represses the differentiation and antitumour activity of T(H)9 cells

Autophagy, a catabolic mechanism that involves degradation of cellular components, is essential for cell homeostasis. Although autophagy favours the lineage stability of regulatory T cells, the contribution of autophagy to the differentiation of effector CD4 T cells remains unclear. Here we show that autophagy selectively represses T helper 9 (T(H)9) cell differentiation. CD4 T cells lacking Atg3 or Atg5 have increased interleukin-9 (IL-9) expression upon differentiation into T(H)9 cells relative to Atg3- or Atg5-expressing control cells. In addition, the T(H)9 cell transcription factor, PU.1, undergoes K63 ubiquitination and degradation through p62-dependent selective autophagy. Finally, the blockade of autophagy enhances T(H)9 cell anticancer functions in vivo, and mice with T cell-specific deletion of Atg5 have reduced tumour outgrowth in an IL-9-dependent manner. Overall, our findings reveal an unexpected function of autophagy in the modulation of T(H)9 cell differentiation and antitumour activity, and prompt potential autophagy-dependent modulations of T(H)9 activity for cancer immunotherapy.