BCAP links IL-1R to the PI3K-mTOR pathway and regulates pathogenic Th17 cell differentiation

J Exp Med. 2018 Sep 3;215(9):2413-2428. doi: 10.1084/jem.20171810. Epub 2018 Aug 9.

Abstract

The toll-like receptor (TLR) and interleukin (IL)-1 family of receptors share several signaling components, including the most upstream adapter, MyD88. We previously reported the discovery of B cell adapter for phosphoinositide 3-kinase (BCAP) as a novel toll-IL-1 receptor homology domain-containing adapter that regulates inflammatory responses downstream of TLR signaling. Here we find that BCAP plays a critical role downstream of both IL-1 and IL-18 receptors to regulate T helper (Th) 17 and Th1 cell differentiation, respectively. Absence of T cell intrinsic BCAP did not alter development of naturally arising Th1 and Th17 lineages but led to defects in differentiation to pathogenic Th17 lineage cells. Consequently, mice that lack BCAP in T cells had reduced susceptibility to experimental autoimmune encephalomyelitis. More importantly, we found that BCAP is critical for IL-1R-induced phosphoinositide 3-kinase-Akt-mechanistic target of rapamycin (mTOR) activation, and minimal inhibition of mTOR completely abrogated IL-1β-induced differentiation of pathogenic Th17 cells, mimicking BCAP deficiency. This study establishes BCAP as a critical link between IL-1R and the metabolic status of activated T cells that ultimately regulates the differentiation of inflammatory Th17 cells.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / immunology*
  • Animals
  • Cell Differentiation / genetics
  • Cell Differentiation / immunology*
  • Encephalomyelitis, Autoimmune, Experimental / genetics
  • Encephalomyelitis, Autoimmune, Experimental / immunology
  • Encephalomyelitis, Autoimmune, Experimental / pathology
  • Interleukin-1 / genetics
  • Interleukin-1 / immunology
  • Interleukin-18 / genetics
  • Interleukin-18 / immunology
  • Lymphocyte Activation
  • Mice
  • Mice, Knockout
  • Phosphatidylinositol 3-Kinases / genetics
  • Phosphatidylinositol 3-Kinases / immunology*
  • Proto-Oncogene Proteins c-akt / genetics
  • Proto-Oncogene Proteins c-akt / immunology
  • Receptors, Interleukin-1 / genetics
  • Receptors, Interleukin-1 / immunology*
  • Signal Transduction / genetics
  • Signal Transduction / immunology*
  • TOR Serine-Threonine Kinases / genetics
  • TOR Serine-Threonine Kinases / immunology*
  • Th1 Cells / immunology
  • Th1 Cells / pathology
  • Th17 Cells / immunology*
  • Th17 Cells / pathology

Substances

  • Adaptor Proteins, Signal Transducing
  • Interleukin-1
  • Interleukin-18
  • Pik3ap1 protein, mouse
  • Receptors, Interleukin-1
  • Phosphatidylinositol 3-Kinases
  • TOR Serine-Threonine Kinases
  • mTOR protein, mouse
  • Proto-Oncogene Proteins c-akt