Quantitative proteomics identifies PTP1B as modulator of B cell antigen receptor signaling

Life Sci Alliance. 2021 Sep 15;4(11):e202101084. doi: 10.26508/lsa.202101084. Print 2021 Nov.

Abstract

B cell antigen receptor (BCR) signaling is initiated by protein kinases and limited by counteracting phosphatases that currently are less well studied in their regulation of BCR signaling. Here, we used the B cell line Ramos to identify and quantify human B cell signaling components. Specifically, a protein tyrosine phosphatase profiling revealed a high expression of the protein tyrosine phosphatase 1B (PTP1B) in Ramos and human naïve B cells. The loss of PTP1B leads to increased B cell activation. Through substrate trapping in combination with quantitative mass spectrometry, we identified 22 putative substrates or interactors of PTP1B. We validated Igα, CD22, PLCγ1/2, CBL, BCAP, and APLP2 as specific substrates of PTP1B in Ramos B cells. The tyrosine kinase BTK and the two adaptor proteins GRB2 and VAV1 were identified as direct binding partners and potential substrates of PTP1B. We showed that PTP1B dephosphorylates the inhibitory receptor protein CD22 at phosphotyrosine 807. We conclude that PTP1B negatively modulates BCR signaling by dephosphorylating distinct phosphotyrosines in B cell-specific receptor proteins and various downstream signaling components.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • B-Lymphocytes / metabolism
  • Cell Line
  • GRB2 Adaptor Protein / metabolism
  • Mass Spectrometry / methods
  • Phosphorylation
  • Protein Binding
  • Protein Tyrosine Phosphatase, Non-Receptor Type 1 / genetics
  • Protein Tyrosine Phosphatase, Non-Receptor Type 1 / metabolism*
  • Protein Tyrosine Phosphatase, Non-Receptor Type 1 / physiology
  • Protein-Tyrosine Kinases / metabolism
  • Proteomics / methods
  • Proto-Oncogene Proteins c-vav / metabolism
  • Receptors, Antigen, B-Cell / metabolism*
  • Receptors, Antigen, B-Cell / physiology
  • Sialic Acid Binding Ig-like Lectin 2 / metabolism
  • Signal Transduction / genetics

Substances

  • CD22 protein, human
  • GRB2 Adaptor Protein
  • GRB2 protein, human
  • Proto-Oncogene Proteins c-vav
  • Receptors, Antigen, B-Cell
  • Sialic Acid Binding Ig-like Lectin 2
  • VAV1 protein, human
  • Protein-Tyrosine Kinases
  • PTPN1 protein, human
  • Protein Tyrosine Phosphatase, Non-Receptor Type 1