ABSTRACT
BEHAB (Brain Enriched HyAluronan Binding)/brevican, a brain-specific member of the lectican family of chondroitin sulfate proteoglycans (CSPGs), may play a role in both brain development and human glioma. BEHAB/brevican has been cloned from bovine, mouse and rat. Two isoforms have been reported: a full-length isoform that is secreted into the extracellular matrix (ECM) and a shorter isoform with a sequence that predicts a glycophosphatidylinositol (GPI) anchor. Here, we report the characterization of BEHAB/brevican isoforms in human brain. First, BEHAB/brevican maps to human chromosome 1q31. Second, we report the sequence of both isoforms of human BEHAB/brevican. The deduced protein sequence of full-length, secreted human BEHAB/brevican is 89.7, 83.3 and 83.2% identical to bovine, mouse and rat homologues, respectively. Third, by RNase protection analysis (RPA) we show the developmental regulation of BEHAB/brevican isoforms in normal human cortex. The secreted isoform is highly expressed from birth through 8years of age and is downregulated by 20years of age to low levels that are maintained in the normal adult cortex. The GPI isoform is expressed at uniformly low levels throughout development. Fourth, we confirm and extend previous studies from our laboratory, here demonstrating the upregulation of BEHAB/brevican mRNA in human glioma quantitatively. RPA analysis shows that both isoforms are upregulated in glioma, showing an approximately sevenfold increase in expression over normal levels. In contrast to the developmental regulation of BEHAB/brevican, where only the secreted isoform is regulated, both isoforms are increased in parallel in human glioma. The distinct patterns of regulation of expression of the two isoforms suggest distinct mechanisms of regulation of BEHAB/brevican during development and in glioma.
Subject(s)
Cerebral Cortex/metabolism , Chondroitin Sulfate Proteoglycans/genetics , DNA, Complementary/genetics , Glioma/genetics , Nerve Tissue Proteins/genetics , Amino Acid Sequence , Base Sequence , Brain/metabolism , Brevican , Carrier Proteins/genetics , Cerebral Cortex/growth & development , Chondroitin Sulfate Proteoglycans/metabolism , Chromosome Mapping , Chromosomes, Human, Pair 1/genetics , Cloning, Molecular , DNA, Complementary/chemistry , Gene Expression , Gene Expression Regulation, Developmental , Gene Expression Regulation, Neoplastic , Humans , Lectins, C-Type , Molecular Sequence Data , Nerve Tissue Proteins/metabolism , Protein Isoforms/genetics , Protein Isoforms/metabolism , Proteoglycans/genetics , Proteoglycans/metabolism , RNA/genetics , RNA/metabolism , Transcription, GeneticABSTRACT
Brain-enriched hyaluronan binding (BEHAB)/brevican is a brain-specific extracellular matrix protein containing a cleavage site between Glu(395)-Ser(396), which bears remarkable homology to the "aggrecanase" site in the cartilage proteoglycan aggrecan. Expression of BEHAB/brevican is dramatically increased in human gliomas, notoriously invasive tumors. Recently, we showed that the rat 9L gliosarcoma cell line, which does not express BEHAB/brevican and forms non-invasive tumors when grown as intracranial grafts, can form invasive tumors when transfected with a 5' cDNA fragment of BEHAB/brevican, but not when transfected with the full-length cDNA. In marked contrast, the highly invasive CNS-1 glioma cell line expresses and cleaves BEHAB/brevican protein when grown as an intracranial graft. These results suggest that both synthesis and cleavage of BEHAB/brevican protein may play a role in the invasiveness of gliomas. We report here, using an antibody developed to the neoepitope created by BEHAB/brevican cleavage at the Glu(395)-Ser(396) site, that the CNS-1 cells are able to cleave the protein in vitro. We characterized the CNS-1-derived cleavage activity by assaying its ability to cleave BEHAB/brevican proteoglycan, and determined that the enzyme is a constitutively expressed, secreted activity. Using a variety of protease inhibitors, reverse transcriptase-polymerase chain reaction, and specific antibodies, we determined that this activity is likely to be a member of the ADAMTS family of metalloproteinases, specifically ADAMTS4. These results suggest a novel function for ADAMTS family members in BEHAB/brevican cleavage and glioma and indicate that inhibition of ADAMTS in glioma may provide a novel therapeutic strategy.
Subject(s)
ADAM Proteins/metabolism , Brain/metabolism , Chondroitin Sulfate Proteoglycans/metabolism , Disintegrins/metabolism , Hyaluronic Acid/metabolism , Metalloendopeptidases/metabolism , Nerve Tissue Proteins/metabolism , Thrombospondins/chemistry , ADAM Proteins/antagonists & inhibitors , ADAMTS4 Protein , Animals , Base Sequence , Brevican , DNA Primers , Glioma/metabolism , Glioma/pathology , Humans , Hydrolysis , Lectins, C-Type , Metalloendopeptidases/antagonists & inhibitors , Precipitin Tests , Protease Inhibitors/pharmacology , Rats , Transfection , Tumor Cells, CulturedABSTRACT
The extracellular matrix (ECM) has a prominent role in many physiological processes, including organ development, wound healing, and neoplastic growth and invasion. In each of these processes, changes in the composition of the matrix can lead to increased cell movement. In this review, we discuss the role of ECM components in glioma invasion, with special emphasis on the brain-specific proteoglycan, Brain-Enriched Hyaluronan Binding (BEHAB)/brevican.
Subject(s)
Brain Neoplasms/metabolism , Carrier Proteins/metabolism , Chondroitin Sulfate Proteoglycans/metabolism , Glioma/metabolism , Nerve Tissue Proteins/metabolism , Brain Neoplasms/pathology , Brevican , Extracellular Matrix Proteins/metabolism , Glioma/pathology , Humans , Lectins, C-Type , Neoplasm Invasiveness/pathologyABSTRACT
Several recent findings have advanced our understanding of the composition and function of the brain extracellular matrix (ECM). BEHAB/brevican, a recently identified CNS-specific proteoglycan, is a component of the brain ECM and is upregulated during glial cell motility. It is expressed at high levels during development, in response to injury, and in primary brain tumors. Cleavage of the BEHAB/brevican protein may increase invasion of tumor cells.
