Gene Cloning of BM180, a Lacrimal Gland Enriched Basement Membrane Protein with a Role in Stimulated Secretion

Abstract

Dry eye is the ocular manifestation of a collective secretory deficiency by lacrimal acinar cells.¹ Lacrimal acinar cells are polarized tear protein factories, with tear protein-filled secretory granules packed in the apical cytoplasm adjacent to the acinar lumen into which tear proteins are released. These cells are wrapped into acini by a poorly characterized basement membrane² sheet, the complex cellular adhesiveness of which is the molecular basis for exocrine cell polarity.³ Abnormality of the basement membrane-cell interface is the primary lesion in several autoimmune and genetic diseases.⁴ In Goodpasture’s syndrome, for example, nephrotoxic autoantibodies appear as a consequence of infection-associated exposure of a sequestered epitope in the α3 chain of collagen IV. In Alport’s syndrome, function-altering point mutations in the collagen IV α3 chain have been detected.