A Novel Structural Variant of the Human β4 Integrin cDNA

Abstract

The ability of the α6β4 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 α6β4 regulation resides in the β4 cytoplasmic domain because structural variants of this domain exist. We isolated β4 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.