Immunological and partial sequence identity of mouse BM180 with wheat alpha-gliadin.

BM180, a novel 180-kDa basement membrane protein enriched in guanidine-HCl extracts of lacrimal and parotid exocrine secretory glands, was immunopurified using the secretion inhibitory monoclonal antibody 3E12. The N-terminal amino acid sequence was found to be VRVPVPQLQPQNP. An identical sequence comprises the N-terminus of the wheat storage protein alpha-gliadin. The presence of a gliadin-like protein in basement membranes was confirmed using a monoclonal and several polyclonal anti-gliadin antibodies, the former of which detected a 180-kDa protein in basement membrane blots. A full-length alpha-gliadin cDNA was found to hybridize at high stringency with mouse and human genomic DNA; and in lacrimal gland Northern blots with a 2.3-kb message. Since BM180 appears to be required for stimulus-secretion coupling by lacrimal acinar cells, circulating anti-alpha-gliadin antibodies associated with Sjögren's syndrome ('Dry Eye') and more commonly in Coeliac disease, may be secretion inhibitory.