Constitutive expression of GlyCAM-1 core protein in the rat cochlea

Glycosylation-dependent cell adhesion molecule-1 (GlyCAM-1) is a mucin-like glycoprotein previously identified on high endothelial venules (HEV) of ly mph nodes and also in lactating mammary glands. A specifically glycosilated form of GlyCAM-1 on HEV has been shown to be a ligand for a leukocyte L-se lectin, which plays an important role in leukocyte rolling along the inflam ed endothelium. Here we report that GlyCAM-1 is also expressed in the cochl ea. Immunohistochemistry revealed the lateral wall of the cochlea, tectoria l membrane, modiolus, organ of corti, and spiral modiolar vein (SMV) to be strongly stained with polyclonal anti-GlyCAM-1 antibody. Moreover, RT-PCR o f the cochlear tissue by the use of specific oligonucleotide primers for ra t GlyCAM-1 generated a 378 bp product which was then verified by nucleotide sequencing to represent GlyCAM-1. Electron microscopic investigation revea led the presence of GlyCAM-1 over the entire lumenal surface of the vessels , and the basolateral infoldings in stria vascularis. However, soluble L-se lectin or mAb MECA-79 which recognizes a carbohydrate epitope on functional L-selectin ligands bound only to the spiral ligament, tectorial membrane a nd modiolus. These observations suggest that GlyCAM-1 expressed in the coch lear region is heterogenous in terms of its glycosylation.