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Different states of integrin LFA-1 aggregation are controlled through its association with tetraspanin CD9

Raquel Reyes1, Alicia Monjas2, María Yánez-Mó3

  • 1Centro de Biología Molecular Severo Ochoa (CSIC-UAM), 28049 Madrid, Spain; Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain.

Biochimica Et Biophysica Acta
|May 25, 2015
PubMed

Insights

The tetraspanin CD9 directly binds to the LFA-1 integrin on leukocytes, inhibiting cell adhesion and cytotoxic activity by altering LFA-1 aggregation, not affinity.

Area of Science:

  • Immunology
  • Cell Biology
  • Molecular Interactions

Background:

  • Tetraspanin CD9 is known to interact with β1 and β3 integrins, modulating cell functions.
  • Integrins, like LFA-1, are crucial for leukocyte adhesion, migration, and immune responses.

Purpose of the Study:

  • To investigate the interaction between CD9 and the β2 integrin LFA-1 in leukocytes.
  • To elucidate the functional consequences of CD9-LFA-1 association on leukocyte activity.

Main Methods:

  • Confocal microscopy for co-localization studies.
  • Co-immunoprecipitation and chemical crosslinking to confirm interaction.
  • In situ Proximity Ligation Assays and pull-down experiments.
  • Functional assays measuring cell adhesion and cytotoxic activity.

Main Results:

  • CD9 associates directly with LFA-1 in T cells, B cells, and monocytic cells.
  • The interaction is mediated by the Large Extracellular Loop of CD9 and is resistant to harsh solubilization.
  • CD9 inhibits LFA-1 adhesive function and LFA-1-dependent cytotoxicity.
  • Inhibition is linked to altered LFA-1 aggregation, not changes in binding affinity.

Conclusions:

  • CD9 directly interacts with LFA-1 in various leukocytes.
  • This interaction negatively regulates LFA-1-mediated functions, including adhesion and cytotoxicity.
  • CD9's inhibitory mechanism involves modulating LFA-1 aggregation state.

Keywords:
AdhesionCD9CytotoxicityIntegrinLFA-1Tetraspanin

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