Dedicator of cytokinesis protein 2 couples with lymphoid enhancer-binding factor 1 to regulate expression of CD21 and B-cell differentiation

J Allergy Clin Immunol. 2019 Nov;144(5):1377-1390.e4. doi: 10.1016/j.jaci.2019.05.041. Epub 2019 Aug 9.

Abstract

Background: B-cell receptor (BCR) signaling, combined with CD19 and CD21 signals, imparts specific control of B-cell responses. Dedicator of cytokinesis protein 2 (DOCK2) is critical for the migration and motility of lymphocytes. Although absence of DOCK2 leads to lymphopenia, little is known about the signaling mechanisms and physiologic functions of DOCK2 in B cells.

Objective: We sought to determine the underlying molecular mechanism of how DOCK2 regulates BCR signaling and peripheral B-cell differentiation.

Methods: In this study we used genetic models for DOCK2, Wiskott-Aldrich syndrome protein (WASP), and lymphoid enhancer-binding factor 1 deficiency to study their interplay in BCR signaling and B-cell differentiation.

Results: We found that the absence of DOCK2 led to downregulation of proximal and distal BCR signaling molecules, including CD19, but upregulation of SH2-containing inositol 5 phosphatase 1, a negative signaling molecule. Interestingly, DOCK2 deficiency reduced CD19 and CD21 expression at the mRNA and/or protein levels and was associated with reduced numbers of marginal zone B cells. Additionally, loss of DOCK2 reduced activation of WASP and accelerated degradation of WASP, resulting into reduced actin accumulation and early activation of B cells. Mechanistically, the absence of DOCK2 upregulates the expression of lymphoid enhancer-binding factor 1. These differences were associated with altered humoral responses in the absence of DOCK2.

Conclusions: Overall, our study has provided a novel underlying molecular mechanism of how DOCK2 deficiency regulates surface expression of CD21, which leads to downregulation of CD19-mediated BCR signaling and marginal zone B-cell differentiation.

Keywords: B cell; B-cell receptor; CD21; Dedicator of cytokinesis protein 2; lymphoid enhancer–binding factor 1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigens, CD19 / genetics
  • Antigens, CD19 / metabolism
  • B-Lymphocytes / physiology*
  • Cell Differentiation
  • Cells, Cultured
  • GTPase-Activating Proteins / genetics
  • GTPase-Activating Proteins / metabolism*
  • Gene Expression Regulation
  • Guanine Nucleotide Exchange Factors / genetics
  • Guanine Nucleotide Exchange Factors / metabolism*
  • Humans
  • Lymphoid Enhancer-Binding Factor 1 / genetics
  • Lymphoid Enhancer-Binding Factor 1 / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Protein Binding
  • Receptors, Antigen, B-Cell / metabolism
  • Receptors, Complement 3d / genetics
  • Receptors, Complement 3d / metabolism
  • Signal Transduction
  • Wiskott-Aldrich Syndrome / genetics
  • Wiskott-Aldrich Syndrome / metabolism*
  • Wiskott-Aldrich Syndrome Protein / genetics
  • Wiskott-Aldrich Syndrome Protein / metabolism*

Substances

  • Antigens, CD19
  • DOCK2 protein, mouse
  • GTPase-Activating Proteins
  • Guanine Nucleotide Exchange Factors
  • Lymphoid Enhancer-Binding Factor 1
  • Receptors, Antigen, B-Cell
  • Receptors, Complement 3d
  • Wiskott-Aldrich Syndrome Protein