MHC I Expression Regulates Co-clustering and Mobility of Interleukin-2 and -15 Receptors in T Cells

Biophys J. 2016 Jul 12;111(1):100-12. doi: 10.1016/j.bpj.2016.05.044.

Abstract

MHC glycoproteins form supramolecular clusters with interleukin-2 and -15 receptors in lipid rafts of T cells. The role of highly expressed MHC I in maintaining these clusters is unknown. We knocked down MHC I in FT7.10 human T cells, and studied protein clustering at two hierarchic levels: molecular aggregations and mobility by Förster resonance energy transfer and fluorescence correlation spectroscopy; and segregation into larger domains or superclusters by superresolution stimulated emission depletion microscopy. Fluorescence correlation spectroscopy-based molecular brightness analysis revealed that the studied molecules diffused as tight aggregates of several proteins of a kind. Knockdown reduced the number of MHC I containing molecular aggregates and their average MHC I content, and decreased the heteroassociation of MHC I with IL-2Rα/IL-15Rα. The mobility of not only MHC I but also that of IL-2Rα/IL-15Rα increased, corroborating the general size decrease of tight aggregates. A multifaceted analysis of stimulated emission depletion images revealed that the diameter of MHC I superclusters diminished from 400-600 to 200-300 nm, whereas those of IL-2Rα/IL-15Rα hardly changed. MHC I and IL-2Rα/IL-15Rα colocalized with GM1 ganglioside-rich lipid rafts, but MHC I clusters retracted to smaller subsets of GM1- and IL-2Rα/IL-15Rα-rich areas upon knockdown. Our results prove that changes in expression level may significantly alter the organization and mobility of interacting membrane proteins.

MeSH terms

  • Cell Line
  • Gene Expression Regulation*
  • Gene Knockdown Techniques
  • Histocompatibility Antigens Class I / chemistry
  • Histocompatibility Antigens Class I / genetics
  • Histocompatibility Antigens Class I / metabolism*
  • Humans
  • Interleukin-15 Receptor alpha Subunit / metabolism*
  • Interleukin-2 Receptor alpha Subunit / metabolism*
  • Movement*
  • Protein Aggregates
  • Protein Multimerization
  • Protein Structure, Quaternary
  • Protein Transport
  • T-Lymphocytes / metabolism*

Substances

  • Histocompatibility Antigens Class I
  • Interleukin-15 Receptor alpha Subunit
  • Interleukin-2 Receptor alpha Subunit
  • Protein Aggregates