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Integrin alpha 6 beta 4 forms a complex with the cytoskeletal protein HD1 and induces its redistribution in transfected COS-7 cells
被引:59
作者:
Niessen, CM
[1
]
Hulsman, EHM
[1
]
Rots, ES
[1
]
SanchezAparicio, P
[1
]
Sonnenberg, A
[1
]
机构:
[1] NETHERLANDS CANC INST,DIV CELL BIOL,NL-1066 CX AMSTERDAM,NETHERLANDS
关键词:
D O I:
10.1091/mbc.8.4.555
中图分类号:
Q2 [细胞生物学];
学科分类号:
071009 ;
090102 ;
摘要:
The integrin alpha 6 beta 4 is a major component of hemidesmosomes, in which it is linked to intermediate filaments. Its presence in these structures is dependent on the beta 4 cytoplasmic domain but it is not known whether beta 4 interacts directly with keratin filaments or by interaction with other proteins. In this study, we have investigated the interaction of GST-cyto beta 4A fusion proteins with cellular proteins and demonstrate that a fragment of beta 4A, consisting of the two pairs of fibronectin type III repeats, separated by the connecting segment, forms a specific complex containing a 500-kDa protein that comigrates with HD1, a hemidesmosomal plaque protein. A similar protein was also bound by a glutathione S-transferase fusion protein containing the cytoplasmic domain of a variant beta 4 subunit (beta 4B), in which a stretch of 53 amino acids is inserted in the connecting segment. Subsequent immunoblot analysis revealed that the 500-kDa protein is in fact HD1. In COS-7 cells, which do not express alpha 6 beta 4 or the hemidesmosomal components BP230 and BP180, HD1 is associated with the cytoskeleton, but after transfecting the cells with cDNAs for human alpha 6 and beta 4, it was, instead, colocalized with alpha 6 beta 4 at the basal side of the cells. The organization of the vimentin, keratin, actin, and tubulin cytoskeletal networks was not affected by the expression of alpha 6 beta 4 in COS-7 cells. The localization of HD1 at the basal side of the cells depends on the same region of beta 4 that forms a complex containing HD1 in vitro, since the expression of alpha 6 with a mutant beta 4 subunit that lacks the four fibronectin type III repeats and the connecting segment did not alter the distribution of HD1. The results indicate that for association of alpha 6 beta 4 with HD1, the cytoplasmic domain of beta 4 is essential. We suggest that this association may be crucial for hemidesmosome assembly.
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页码:555 / 566
页数:12
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