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Transmembrane-4 superfamily proteins CD81 (TAPA-1), CD82, CD63, and CD53 specifically associated with integrin alpha

B A Mannion1, F Berditchevski, S K Kraeft

  • 1Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA.

Journal of Immunology (Baltimore, Md. : 1950)
|September 1, 1996
PubMed

Insights

Researchers found that CD81, a cell surface protein, interacts with alpha 4 integrins. This interaction is crucial for alpha 4 integrin function and may involve other transmembrane-4 superfamily members.

Area of Science:

  • Immunology
  • Cell Biology
  • Molecular Biology

Background:

  • Integrins are critical cell surface receptors involved in cell adhesion and signaling.
  • Alpha 4 integrins (e.g., alpha 4 beta 1 and alpha 4 beta 7) play key roles in immune cell trafficking and function.
  • The transmembrane-4 superfamily (TM4SF) includes proteins like CD81, CD53, CD63, and CD82, involved in cell surface interactions.

Purpose of the Study:

  • To investigate the molecular interactions between alpha 4 integrins and CD81.
  • To determine if other TM4SF members associate with alpha 4 integrins.
  • To elucidate the functional relevance of the alpha 4 integrin-CD81 association.

Main Methods:

  • Co-immunoprecipitation assays using specific monoclonal antibodies (mAbs) against alpha 4 integrins and CD81.
  • Reciprocal immunoprecipitation experiments.
  • Confocal microscopy to visualize protein localization.
  • Analysis of alpha 4 integrin adhesion-deficient mutants.

Main Results:

  • Anti-alpha 4 integrin mAb coprecipitated CD81 from various hematopoietic cell lines.
  • Reciprocal experiments confirmed alpha 4 beta 1 integrin precipitation from CD81 immunoprecipitates.
  • CD81 and CD82 were found to colocalize with alpha 4 beta 1 in cell surface clusters.
  • The association between alpha 4 beta 1 and CD81 was independent of the integrin's cytoplasmic domain, divalent cations, or integrin activation.
  • Alpha 4 adhesion-deficient mutants showed reduced association with CD81.
  • Other TM4SF members (CD53, CD63, CD82) also coprecipitated alpha 4 beta 1.

Conclusions:

  • CD81 directly associates with alpha 4 integrins (alpha 4 beta 1 and alpha 4 beta 7).
  • The interaction between alpha 4 integrins and CD81 is functionally significant, as indicated by studies with adhesion-deficient mutants.
  • TM4SF proteins, including CD81 and CD82, may play a role in regulating alpha 4 integrin-mediated cellular functions.

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