A novel membrane-associated glycovariant of BEHAB/brevican is up-regulated during rat brain development and in a rat model of invasive glioma

BEHAB (brain-enriched hyaluronan-binding protein)/ brevican is the most abundant chondroitin sulfate proteoglycan in the extracellular matrix of the adult rat brain. BEHAB/brevican expression is up-regulated coincident with glial cell proliferation and/or motility, including during early central nervous system development and in invasive glioma. An understanding of the molecular interactions that mediate BEHAB/brevican function is still in its infancy because of the existence of several BEHAB/brevican isoforms, each of which may mediate different functions. Here, we describe a novel BEHAB/brevican isoform, B/b(130), and demonstrate that it is neither the glycosylphosphatidylinositol-linked splice variant of BEHAB/brevican nor a cleavage product of the full-length protein (B/b(150)). B/b(130) is an underglycosylated isoform of BEHAB/brevican, lacking glycosaminoglycan chains as well as most of the sugars that invest B/b(150). B/b(130) localizes exclusively to the particulate fraction of rat brain and associates with the cell membrane by a previously undescribed calcium-independent mechanism. In addition, B/b(130) is the major isoform of BEHAB/brevican that is up-regulated in a rat model of invasive glioma and may therefore contribute to the invasive ability of glioma cells. Further understanding of BEHAB/brevican isoforms will advance our knowledge of the function of this ECM component and may help identify new potential therapeutic targets for primary brain tumors.