Synergistic factors control kinase-phosphatase organization in B-cells engaged with supported bilayers

Mol Biol Cell. 2020 Mar 19;31(7):667-682. doi: 10.1091/mbc.E19-09-0507. Epub 2019 Dec 26.

Abstract

B-cells become activated by ligands with varying valency and mode of presentation to the B-cell receptor (BCR). We previously demonstrated that clustering the immunoglobulin M (IgM) isotype of BCR with an artificial soluble cross-linker stabilized an ordered phase-like domain that enriched kinases and depleted phosphatases to promote receptor tyrosine phosphorylation. BCR is also activated by ligands presented at surfaces, and here we activate B-cells via supported bilayers of phosphatidylcholine lipids, a natural ligand for the IgM BCR expressed in the CH27 cells used. Using superresolution fluorescence localization microscopy, along with a quantitative cross-correlation analysis, we find that BRCs engaged with bilayers sort minimal peptide markers of liquid-ordered and liquid-disordered phases, indicating that ordered-domain stabilization is a general feature of BCR clustering. The phosphatase CD45 is more strongly excluded from bilayer-engaged BRCs than a transmembrane peptide, indicating that mechanisms other than domain partitioning contribute to its organization. Experimental observations are assembled into a minimal model of receptor activation that incorporates both ordered domains and direct phosphatase exclusion mechanisms to produce a more sensitive response.

Publication types

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

MeSH terms

  • Animals
  • B-Lymphocytes / enzymology*
  • Biomarkers / metabolism
  • Cell Line
  • Computer Simulation
  • Immunoglobulin M / metabolism
  • Leukocyte Common Antigens / metabolism
  • Ligands
  • Lipid Bilayers / metabolism*
  • Membrane Microdomains / metabolism
  • Mice
  • Peptides / metabolism
  • Phosphatidylcholines / metabolism
  • Phosphorylation
  • Phosphotyrosine / metabolism
  • Protein Tyrosine Phosphatases / metabolism*
  • Protein-Tyrosine Kinases / metabolism*
  • Receptors, Antigen, B-Cell / metabolism

Substances

  • Biomarkers
  • Immunoglobulin M
  • Ligands
  • Lipid Bilayers
  • Peptides
  • Phosphatidylcholines
  • Receptors, Antigen, B-Cell
  • Phosphotyrosine
  • Protein-Tyrosine Kinases
  • Leukocyte Common Antigens
  • Protein Tyrosine Phosphatases