Adhesiveness of β5 integrin variant lacking FNK767–769 is similar to that of the prototype containing FNKFNK764–769

Little is known about the functions of two different β5 integrins: repeated-FNK (FNKFNK764–769) and single-FNK (FNK764–766) amino acid sequences in the cytoplasmic domain. We examined whether they occurred as germ line mutations or somatic mutations associated with neoplastic transformation, and whether there were functional alterations. Out of six cultured cell lines, only KATO-III cells had the single-FNK β5 sequence. The single-FNK β5 was found in 9 out of 79 patients with colon carcinoma, but no somatic mutations were detected in cancerous tissues. CHO cells were transformed with expression vectors containing single-FNK or repeated-FNK β5 cDNA, which were derived from KATO-III cells. CHO cells transfected with single-FNK and repeated-FNK showed similar adhesiveness to, and proliferative activity on, vitronectin substrates.