Identification of a novel truncated αIIb integrin

Integrin alpha IIb beta 3 requires its cytoplasmic tails to participate in tumor cell adhesion, spreading, and migration. Using 3' rapid amplification of cDNA ends, we have amplified two alpha IIb cDNAs from human Leukemia, prostate adenocarcinoma, and melanoma cells. One of these is the predicted wild-type alpha IIb cDNA, and the other is a novel truncated alpha IIb variant. This variant is unique in that it lacks the transmembrane and cytoplasmic portions of the alpha IIb light chain. The truncated alpha IIb integrin protein is expressed by human leukemia, prostate adenocarcinoma, and melanoma cells but not by platelets or normal prostate epithelial or normal breast epithelial cells. Tumor cells secrete this protein and deposit it on the extracellular matrix. To our knowledge, this is the first report of a naturally occurring variant of an cu integrin that lacks the transmembrane and cytoplasmic tail.