Expression of insulin-like growth factor binding protein-4 (IGFBP-4) by rat neural cells--comparison to other IGFBPs.
We recently isolated and characterized the 24 kDa and N-glycosylated 28 kDa insulin-like growth factor binding protein-4 (rIGFBP-4) from the B104s rat neuronal cell line (Endocrinology, 129 (1991) 1009-1115). To examine the prevalence of IGFBP-4 secretion by cells of neural origin, we assessed the expression of IGFBP-4 in different neural cell types using ligand blotting, immunoblotting and blot hybridization with relevant cDNAs. A specific IGFBP-4 antibody raised against a synthetic 20 amino acid peptide was used for immunologic recognition. In all the neural cells tested (B104s, C6 astrocytoma, primary neonatal astrocytes and primary fetal neurons), IGFBP-4 was definitively identified by immunoblotting. Blot hybridization using a rat cDNA probe revealed expression of IGFBP-4 mRNA transcripts by all these cells. Using a combination of the same techniques, expression of IGFBP-1, -2, and -3 were also examined. The B104s cells secreted primarily IGFBP-4; C6 cells secreted predominantly IGFBP-3 and small amount of IGFBP-4; both primary neonatal astrocytes and fetal neurons secreted IGFBP-2 as the major IGFBP accompanied by a small quantity of IGFBP-4. IGFBP-1 was not identified in any of the cell media. When probed with the respective IGFBP cDNAs, the mRNA abundance generally reflected the media IGFBP content. The expression of IGFBP-4 mRNA in vivo was examined as well and compared to that of IGFBP-1 and IGFBP-2. Transcripts for both IGFBP-2 and IGFBP-4 were found in all gross anatomical divisions of the rat brain from embryonic day 15 until adulthood, whereas IGFBP-1 was not detected at any time. IGFBP-4 mRNA tended to be more abundant at the youngest ages whereas IGFBP-2 increased during development. These data indicate that IGFBP-4 is produce by a variety of neural cell types and suggest that it may play a role in brain development.
Chernausek
S D
SD
Department of Pediatrics, University of Cincinnati School of Medicine, Children's Hospital Medical Center, OH 45229.
Murray
M A
MA
Cheung
P T
PT
D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D000906:Antibodies; D001253:Astrocytes / Q000378:metabolism*; D001254:Astrocytoma / Q000378:metabolism; D015152:Blotting, Northern; D015153:Blotting, Western; D002352:Carrier Proteins / Q000032:analysis / Q000096:biosynthesis*; D002460:Cell Line; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000378:metabolism*; D005333:Fetus; D015870:Gene Expression; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1; D018971:Insulin-Like Growth Factor Binding Protein 2; D018974:Insulin-Like Growth Factor Binding Protein 4; D008099:Liver / Q000378:metabolism; D008969:Molecular Sequence Data; D009474:Neurons / Q000378:metabolism*; D010455:Peptides / Q000138:chemical synthesis / Q000276:immunology; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D051381:Rats; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D000906:Antibodies; D002352:Carrier Proteins; D018970:Insulin-Like Growth Factor Binding Protein 1; D018971:Insulin-Like Growth Factor Binding Protein 2; D018974:Insulin-Like Growth Factor Binding Protein 4; D010455:Peptides; D012333:RNA, Messenger