somatostatin-28 and preproenkephalin

The biosynthesis of neuro and hormonal peptides is in a state of rapid progress. The development of protein microsequencing is making it possible to characterize more and more new important molecules with nanomolar quantities, while the DNA structural studies favor the sequencing of the precursors of all these new peptides. These precursors are often polyproteins containing more than one active end-product. Their maturation processes are following a highly similar pattern with cleavage of the precursors at sites characterized by the presence of pairs of basic amino acid as noted in 1967-68 for the LPH and the pro-insulin models. This now constitutes a general concept which has good chances to be applicable to all the exciting neuro and hormonal peptides recently identified or yet to be discovered.

Topics: Amino Acid Sequence; Animals; Arginine Vasopressin; Calcitonin; Corticotropin-Releasing Hormone; DNA; Endorphins; Enkephalins; Gastrins; Glucagon; Humans; Models, Biological; Neurophysins; Oxytocin; Parathyroid Hormone; Pituitary Gland, Anterior; Pituitary Hormones, Anterior; Pro-Opiomelanocortin; Proglucagon; Proinsulin; Protein Precursors; Somatostatin; Vasopressins

Expression of neuropeptide messenger RNAs in striatal neurons was studied in post mortem human brain tissue by the use of in situ hybridization histochemistry. Clusters of cells expressing high levels of prodynorphin messenger RNA, and less strikingly, preprotachykinin messenger RNA, were prominent in the caudate nucleus and were present but less pronounced in the putamen. Proenkephalin and prosomatostatin messenger RNA-containing cells were more homogeneously distributed throughout the striatum, though the latter were much sparser. The four neuropeptide messenger RNA patterns in the nucleus accumbens were rather homogeneous compared with the dorsal striatum. Of these, prodynorphin messenger RNA showed a higher level of expression per cell in the nucleus accumbens relative to the dorsal striatum. The relationship of neuropeptide-containing cell clusters to the striosomal organization was characterized by looking at the register of these markers with patterns of low acetylcholinesterase activity and dense mu opiate receptor binding. In the caudate and putamen, clusters of cells expressing high levels of dynorphin and preprotachykinin messenger RNAs were clearly in register with the striosomes. The accumbens was defined by high prodynorphin messenger RNA levels, both low and high levels of acetylcholinesterase staining, and very low to absent mu opiate receptor binding. The distribution of high-expressing prodynorphin messenger RNA-containing cells--to the patch compartment and throughout the entire ventral striatum/nucleus accumbens region--defines the limbic domain of the neostriatum and suggests particular relevance to human striatal organization and function, because the distribution of this opioid neuropeptide is considerably more compartmentalized in human than in non-human species.

Topics: Acetylcholinesterase; Adolescent; Adult; Cocaine; Enkephalins; Female; Gene Expression Regulation; Humans; In Situ Hybridization; Male; Middle Aged; Neostriatum; Neurokinin A; Nucleus Accumbens; Protein Precursors; Receptors, Opioid, mu; RNA, Messenger; Somatostatin; Substance P; Tachykinins

The cellular co-expression of adenosine A2a receptor mRNA and preproenkephalin A (PPE A) mRNA and A2a receptor mRNA and prosomatostatin (pSRIF) mRNA in rat striatum was studied using a combination of radioactive and non-radioactive in situ hybridization techniques. Cells containing adenosine A2a receptor mRNA were visualised using an 35S-labelled oligonucleotide whilst those containing PPE A mRNA and pSRIF mRNA were detected using alkaline phosphatase-labelled antisense oligonucleotides; both radioactive and non-radioactive hybridization signals were visualized on the same tissue section. Bright field examination of striatal sections hybridized with both the [35S]adenosine A2a receptor probe and the alkaline phosphatase-labelled PPE A probe revealed dense clusters of silver grains overlying cells containing alkaline phosphatase reaction product demonstrating that the two gene transcripts were expressed by the same medium-sized nerve cells. The cellular expression of the two mRNAs was consistently found to be concordant demonstrating that adenosine A2a receptor mRNA is expressed by medium-sized striatal enkephalin cells. In contrast, clusters of silver grains were never detected overlying striatal cells containing pSRIF mRNA indicating that this population of interneurones do not express the adenosine A2a receptor sub-type. The expression of adenosine A2a receptors by enkephalin cells in striatum suggests that adenosine may play a role in modulating the activity of GABA/enkephalin striatopallidal neurones through interaction with A2a receptors.

Topics: Animals; Corpus Striatum; Enkephalins; In Situ Hybridization; Male; Protein Precursors; Rats; Rats, Wistar; Receptor, Adenosine A2A; Receptors, Purinergic P1; RNA, Messenger; Somatostatin

This study utilized the technique of in situ hybridization histochemistry to identify cells expressing neurotransmitter mRNAs in embryonic striatal tissue grafts implanted into the ibotenic acid-lesioned rat neostriatum. Synthetic 32P- or 35S-labelled oligodeoxyribonucleotide probes specific for prosomatostatin, proneuropeptide Y. proenkephalin, prodynorphin and preprotachykinin mRNAs and a 32P-labelled cRNA probe specific for glutamate decarboxylase mRNA were used to study the regional and cellular changes in these mRNA levels in the normal, lesioned and grafted neostriatum. The levels of neuropeptide Y mRNA and somatostatin mRNA were substantially increased in the striatal grafts compared with the intact control striata. The levels of glutamate decarboxylase mRNA in the grafts also appeared to be slightly elevated over those in the control striata. However, the levels of proenkephalin mRNA, prodynorphin mRNA and preprotachykinin mRNA were significantly lower in the grafts. The increased levels of neuropeptide Y mRNA and somatostatin mRNA in the grafts were due both to an increase in the number of labelled cells and to an increase in the cellular levels of each neuropeptide mRNA. In contrast, the cellular levels of proenkephalin mRNA, prodynorphin mRNA and preprotachykinin mRNA in the grafts were comparable, or elevated relative, to those in the intact striata but the density of cells expressing each of these mRNAs was reduced. Since neuropeptide Y and somatostatin are known to be present in medium to large aspiny striatal neurons (interneurons) and enkephalin, dynorphin and tachykinin peptides and GABA are localized in medium spiny striatal projection neurons, the above findings would indicate that there is a divergence in the levels of activity between these two neuronal populations in the striatal grafts. Our data suggest that the levels of gene expression and hence the functional neurotransmitter-synthesizing and releasing activity in the grafted neuron are different from those in the normal mature striatum.

Topics: Animals; Corpus Striatum; Enkephalins; Female; Gene Expression Regulation; Glutamate Decarboxylase; Neurotransmitter Agents; Nucleic Acid Hybridization; Oligonucleotides; Protein Precursors; Rats; Rats, Inbred Strains; RNA, Messenger; Somatostatin