β1 integrin cytoplasmic domain regulates the constitutive conformation detected by MAb 15/7, but not the ligand-induced conformation
✍ Scribed by Deirdre Crommie; Martin E. Hemler
- Book ID
- 101258844
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 198 KB
- Volume
- 71
- Category
- Article
- ISSN
- 0730-2312
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✦ Synopsis
The anti-integrin 1 MAb 15/7 sometimes may be a reporter of integrin activation or ligand occupancy. However, certain 1 tail deletions eliminate ligand binding despite inducing maximal constitutive 15/7 expression : J Biol Chem 271:16580-16585]. Here we describe 1 tail mutations (e.g., double point mutations [D759L/F763L, F766L/E769L], or replacement of the 1 tail by the 5 tail) that prevent rather than induce constitutive appearance of the 15/7 epitope. Despite variable losses of constitutive 15/7 epitope, these mutants all retained a similar inducible 15/7 epitope component as seen upon incubation with GRGDSP peptide ligand. In addition, constitutive 15/7 expression did not correlate with integrin localization into focal adhesions. In conclusion, we show for the first time for a fully functional integrin that specific mutations within the 1 tail can down-regulate the constitutive appearance of an extracellular conformation defined by MAb 15/7. Because this regulation occurs away from the ligand binding site and does not correlate with responsiveness to integrin ligand, cell adhesion, or localization into focal adhesions, a novel type of conformational regulation is suggested.