Retinoic acid-induced IgG production in TLR-activated human primary B cells involves ULK1-mediated autophagy

Autophagy. 2015;11(3):460-71. doi: 10.1080/15548627.2015.1009797.

Abstract

In the present study we have established a vital role of autophagy in retinoic acid (RA)-induced differentiation of toll-like receptor (TLR)-stimulated human B cells into Ig-secreting cells. Thus, RA enhanced autophagy in TLR9- and CD180-stimulated peripheral blood B cells, as revealed by increased levels of the autophagosomal marker LC3B-II, enhanced colocalization between LC3B and the lysosomal marker Lyso-ID, by a larger percentage of cells with more than 5 characteristic LC3B puncta, and by the concomitant reduction in the level of SQSTM1/p62. Furthermore, RA induced expression of the autophagy-inducing protein ULK1 at the transcriptional level, in a process that required the retinoic acid receptor RAR. By inhibiting autophagy with specific inhibitors or by knocking down ULK1 by siRNA, the RA-stimulated IgG production in TLR9- and CD180-mediated cells was markedly reduced. We propose that the identified prominent role of autophagy in RA-mediated IgG-production in normal human B cells provides a novel mechanism whereby vitamin A exerts its important functions in the immune system.

Keywords: ATG, autophagy-related; B lymphocytes; BDS, bright detail similarity; CD180; CD180, CD180 molecule; CVID, common variable immune deficiency; ELISA, enzyme-linked immunosorbent assay; IL, interleukin; Ig, immunoglobulin; MAP1LC3B/LC3B, microtubule-associated protein 1 light chain 3 β; MTOR, mechanistic target of rapamycin (serine/threonine kinase); PAMP, pathogen-associated molecular pattern, PML/RARA, promyelocytic leukemia/ retinoic acid receptor α; RA, all-trans retinoic acid; RAR, retinoic acid receptor; RP105; SQSTM1, sequestosome 1; TLR, toll-like receptor; TLR9; ULK1; ULK1, unc-51 like autophagy activating kinase 1; antibody secretion; autophagy; plasma cell differentiation; retinoic acid.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, CD / metabolism
  • Antigens, CD19 / metabolism
  • Autophagy*
  • Autophagy-Related Protein-1 Homolog
  • B-Lymphocytes / immunology
  • B-Lymphocytes / metabolism*
  • Cell Differentiation / drug effects
  • CpG Islands
  • Humans
  • Immune System
  • Immunoglobulin G / biosynthesis*
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Lymphocyte Activation / immunology
  • Lysosomes / metabolism
  • Microtubule-Associated Proteins / metabolism
  • Oligonucleotides / chemistry
  • Protein-Serine-Threonine Kinases / metabolism*
  • RNA, Small Interfering / chemistry
  • Receptors, Retinoic Acid / metabolism
  • Signal Transduction / drug effects
  • Toll-Like Receptor 9 / metabolism
  • Toll-Like Receptors / metabolism*
  • Transcription, Genetic
  • Tretinoin / chemistry*

Substances

  • Antigens, CD
  • Antigens, CD19
  • CD180 protein, human
  • Immunoglobulin G
  • Intracellular Signaling Peptides and Proteins
  • MAP1LC3B protein, human
  • Microtubule-Associated Proteins
  • Oligonucleotides
  • RNA, Small Interfering
  • Receptors, Retinoic Acid
  • TLR9 protein, human
  • Toll-Like Receptor 9
  • Toll-Like Receptors
  • Tretinoin
  • Autophagy-Related Protein-1 Homolog
  • Protein-Serine-Threonine Kinases
  • ULK1 protein, human