Expression of neurotrophins and their receptors in primary astroglial cultures: induction by cyclic AMP-elevating agents.
By northern blot analysis and ribonuclease protection assay, we observed the presence of a high level of trkB mRNA in primary brain cultures devoid of neuronal cells and highly enriched in glial fibrillary acidic protein-positive astroglial cells prepared from newborn rat cerebral hemispheres, cerebral cortex, hippocampus, and striatum. In primary astroglial cultures, the more abundant trkB transcripts code for the truncated receptor without tyrosine kinase activity; probes specific for the full-length trkB mRNA did not detect any signal in northern blot analysis. By the sensitive ribonuclease protection assay, we could show the presence of trkC mRNA in cultured astrocytes, whereas no trkA mRNA was detected. We confirmed the presence of relatively high levels of nerve growth factor and neurotrophin-3 mRNA, and very low basal level of brain-derived neurotrophic factor mRNA. Moreover, we demonstrated that another member of the neurotrophin family, neurotrophin-4, is also expressed in cultured astroglial cells. In view of the fact that many functional receptors for conventional neurotransmitters or neuropeptides present on astroglial cells may act via the adenylate cyclase system, we studied also the effect of agents able to increase the intracellular cyclic AMP concentration. A sharp increase in the trkB mRNA level was observed after treatment of primary astroglial cultures with dibutyryl cyclic AMP, 8-bromo-cyclic AMP, or the phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine. On the contrary, trkC mRNA levels were unaffected by treatment with cyclic AMP-elevating agents. All the neurotrophin mRNAs examined, except neutrophin-4, were increased by 3-isobutyl-1-methylxanthine treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
Condorelli
D F
DF
Institute of Biochemistry, Faculty of Medicine, University of Catania, Italy.
Dell'Albani
P
P
Mudò
G
G
Timmusk
T
T
Belluardo
N
N
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001483:Base Sequence; D015152:Blotting, Northern; D001921:Brain / Q000378:metabolism*; D019208:Brain-Derived Neurotrophic Factor; D003994:Bucladesine / Q000494:pharmacology; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D008969:Molecular Sequence Data; D009414:Nerve Growth Factors / Q000096:biosynthesis*; D009419:Nerve Tissue Proteins / Q000096:biosynthesis; D020933:Neurotrophin 3; D015345:Oligonucleotide Probes; D009928:Organ Specificity; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000096:biosynthesis*; D020801:Receptor, Ciliary Neurotrophic Factor; D020917:Receptor, trkA; D020812:Receptor, trkC; D017978:Receptors, Growth Factor / Q000096:biosynthesis*; D017475:Receptors, Nerve Growth Factor / Q000096:biosynthesis*; D014158:Transcription, Genetic / Q000187:drug effects
D019208:Brain-Derived Neurotrophic Factor; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; D020933:Neurotrophin 3; D015345:Oligonucleotide Probes; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D020801:Receptor, Ciliary Neurotrophic Factor; D017978:Receptors, Growth Factor; D017475:Receptors, Nerve Growth Factor; D015124:8-Bromo Cyclic Adenosine Monophosphate; D003994:Bucladesine; D000242:Cyclic AMP; D020794:Receptor Protein-Tyrosine Kinases; D020917:Receptor, trkA; D020812:Receptor, trkC; D015056:1-Methyl-3-isobutylxanthine