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CD9, but not other tetraspans, associates with the beta1 integrin precursor
E Rubinstein1, V Poindessous-Jazat, F Le Naour
1INSERM U268, Hôpital Paul Brousse, Villejuif, France. erubin@infobiogen.fr
European Journal of Immunology
|August 1, 1997
Summary
CD9 protein associates with the precursor of beta1 integrin (pre beta1) early in its development, independent of Golgi processing. This specific interaction involves multiple regions of CD9 and suggests calnexin may aid CD9 processing.
Area of Science:
- Cell Biology
- Molecular Biology
- Protein Interactions
Background:
- Tetraspanins are cell surface proteins with four transmembrane domains.
- They form complexes with other proteins, including beta1 integrins.
Purpose of the Study:
- To investigate the association between CD9 and the precursor of beta1 integrin (pre beta1).
- To identify the molecular regions of CD9 responsible for this interaction.
- To explore the role of calnexin in CD9 processing.
Main Methods:
- Metabolic labeling and co-immunoprecipitation assays.
- Use of Brefeldin A to assess Golgi-independent interactions.
- Generation of chimeric CD9/CD82 molecules.
- Site-directed mutagenesis of CD9.
- Investigation of CD9 association with calnexin.
Main Results:
- CD9 specifically associates with pre beta1 integrin within 15 minutes of synthesis, independent of Golgi modifications.
- Other tetraspans (CD63, CD81, CD82) do not associate with pre beta1.
- The large extracellular loop and/or the fourth transmembrane domain of CD9 mediate association with mature beta1 integrin.
- Association with pre beta1 requires at least two regions of CD9.
- CD9 associates with calnexin independently of beta1 integrin association.
Conclusions:
- CD9 forms a specific, early association with pre beta1 integrin.
- Multiple regions of CD9 are involved in pre beta1 integrin binding.
- Calnexin may play a role in the cellular processing of CD9.
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