A NOVEL STRUCTURAL VARIANT OF THE HUMAN BETA-4 INTEGRIN CDNA

The ability of the alpha 6 beta 4 integrin to function as a laminin receptor appears to be cell-type dependent. We reported that this integrin functions as a laminin receptor on clone A cells, a colon carcinoma cell line (Lee et al., J. Cell Biol., 117:671-678), but this integrin may not function as a laminin receptor on all cell types in which it is expressed. One potential mode of alpha 6 beta 4 regulation resides in the beta 4 cytoplasmic domain because structural variants of this domain exist. We isolated beta 4 clones from a clone A cDNA library and identified a 21 bp (7aa), in-frame deletion not previously reported. This 7aa variant is located within a region that exhibits a relatively high degree of homology (42%) with the 70aa insert previously reported by Tamura et al. (J. Cell Biol., 111:1593-1604). One major difference between these two regions is that the region we have highlighted does not contain the four potential serine/threonine phosphorylation sites that are present in the 210 bp (70aa) insert. PCR analysis revealed that the 7aa variant is also expressed in RNA obtained from normal colon and placenta.