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β1 integrin cytoplasmic domain regulates the constitutive conformation detected by MAb 15/7, but not the ligand‐induced conformation
Author(s) -
Crommie Deirdre,
Hemler Martin E.
Publication year - 1998
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/(sici)1097-4644(19981001)71:1<63::aid-jcb7>3.0.co;2-#
Subject(s) - integrin , epitope , ligand (biochemistry) , mutant , microbiology and biotechnology , focal adhesion , cytoplasm , chemistry , biology , receptor , biochemistry , antigen , signal transduction , gene , genetics
The anti‐integrin β1 MAb 15/7 sometimes may be a reporter of integrin activation or ligand occupancy. However, certain β1 tail deletions eliminate ligand binding despite inducing maximal constitutive 15/7 expression [Puzon‐Mclaughlin et al. (1996): J Biol Chem 271:16580–16585]. Here we describe β1 tail mutations (e.g., double point mutations [D759L/F763L, F766L/E769L], or replacement of the β1 tail by the β5 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 β1 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. J. Cell. Biochem. 71:63–73, 1998. © 1998 Wiley‐Liss, Inc.