Distribution and second messenger coupling of four somatostatin receptor subtypes expressed in brain

AbstractThe mRNA distribution in the brain and the coupling to cellular effector systems of four somatostatin receptors (SSTR1-4) was studied. All four SRIF receptor subtypes were expressed in cortex and hippocampus. In addition, SSTR1 mRNA was relatively abundant in the spinal cord whereas SSTR2 mRNA was also present in the striatum. The SSTR3 gene was predominantly expressed in the olfactory bulb and in the cerebellum. Conflicting results about the effector coupling of SSTR1-3 have been published previously. We have stably expressed human SSTR1-4 in HEK 293 human embryonal kidney cells. Agonist binding to the receptor subtypes, including the recently cloned SSTR4, inhibited the formation of forskolin-induced cAMP. Is is concluded that, in an appropriate cellular environment, all four receptor subtypes can functionally couple to the inhibition of adenylyl cyclase

Rat brain 5-HT_(1C) receptors are encoded by a 5-6 kbase mRNA size class and are functionally expressed in injected Xenopus oocytes

Injection of rat brain RNA into Xenopus laevis oocytes induces synthesis of receptors that show an electrophysiological response to bath application of serotonin. While there are at least 4 pharmacologically distinct subtypes of 5-HT binding sites in the rat brain, we find that the pharmacological characteristics of the predominant electrophysiologically active receptor synthesized in Xenopus oocytes are most consistent with those of the 5-HT_(1C) subtype. Additional electrophysiologically active 5-HT receptor types could not be detected. Injection of mRNA isolated from a number of rat brain regions shows that the choroid plexus is particularly enriched for 5-HT_(1C) mRNA. Oocytes injected with RNA isolated from this region respond 16 or 8 times more strongly to serotonin than do oocytes injected with RNA isolated from cortex or substantia nigra, respectively. In addition, by fractionation of rat brain mRNA through agarose gels, we have identified a single RNA size class of about 5–6 kbase that encodes this serotonin receptor

Rat brain 5-HT_(1C) receptors are encoded by a 5-6 kbase mRNA size class and are functionally expressed in injected Xenopus oocytes

Injection of rat brain RNA into Xenopus laevis oocytes induces synthesis of receptors that show an electrophysiological response to bath application of serotonin. While there are at least 4 pharmacologically distinct subtypes of 5-HT binding sites in the rat brain, we find that the pharmacological characteristics of the predominant electrophysiologically active receptor synthesized in Xenopus oocytes are most consistent with those of the 5-HT_(1C) subtype. Additional electrophysiologically active 5-HT receptor types could not be detected. Injection of mRNA isolated from a number of rat brain regions shows that the choroid plexus is particularly enriched for 5-HT_(1C) mRNA. Oocytes injected with RNA isolated from this region respond 16 or 8 times more strongly to serotonin than do oocytes injected with RNA isolated from cortex or substantia nigra, respectively. In addition, by fractionation of rat brain mRNA through agarose gels, we have identified a single RNA size class of about 5–6 kbase that encodes this serotonin receptor

Spinal Cord Pathology in Alpha-Synuclein Transgenic Mice

Accumulation of α-synuclein is observed in neurodegenerative diseases like Parkinson's disease and Multiple System Atrophy. In previous studies with transgenic C57BL/6 mice overexpressing α-synuclein carrying the mutations A53T and A30P found in Parkinson's disease or with a parkin-null background, we reported severe mitochondrial impairments in neurons and to a larger extent in glial cells of the mesencephalon. Neuron death was not observed in the brain. Here we show that the mice show severe motor impairments in behavioral tests. In addition, these mice exhibit astrocytic cell death in the spinal cord, accompanied by extensive gliosis and microglial activation. This is shown by cell death staining and immunohistochemistry. Ultrastructural analyses revealed severe mitochondrial impairments not only in astrocytes, but also in oligodendrocytes and, to a small extent, in neurons. Thus, the transgenic mice show a profound pathology in glial cells of the spinal cord

Messenger RNA coding for only the alpha subunit of the rat brain Na channel is sufficient for expression of functional channels in Xenopus oocytes

Several cDNA clones coding for the high molecular weight (alpha) subunit of the voltage-sensitive Na channel have been selected by immunoscreening a rat brain cDNA library constructed in the expression vector lambda gt11. As will be reported elsewhere, the amino acid sequence translated from the DNA sequence shows considerable homology to that reported for the Electrophorus electricus electroplax Na channel. Several of the cDNA inserts hybridized with a low-abundance 9-kilobase RNA species from rat brain, muscle, and heart. Sucrose-gradient fractionation of rat brain poly(A) RNA yielded a high molecular weight fraction containing this mRNA, which resulted in functional Na channels when injected into oocytes. This fraction contained undetectable amounts of low molecular weight RNA. The high molecular weight Na channel RNA was selected from rat brain poly(A) RNA by hybridization to a single-strand antisense cDNA clone. Translation of this RNA in Xenopus oocytes resulted in the appearance of tetrodotoxin-sensitive voltage-sensitive Na channels in the oocyte membrane. These results demonstrate that mRNA encoding the alpha subunit of the rat brain Na channel, in the absence of any beta-subunit mRNA, is sufficient for translation to give functional channels in oocytes

Expression and regulation of human and rat phosphodiesterase type IV isogenes

AbstractType IV phosphodiesterases (PDE IV) specifically hydrolyze cAMP and are inhibited by rolipram. RT-PCR was applied to analyze the expression patterns of mRNAs for four cloned human and rat phosphodiesterase type IV isogenes (PDE IV-A, -B, -C and -D). Although these patterns were mostly coincident for the human and rat PDE IV genes, some differences were found between the two species. PDE IV-A expression was detectable in human blood but not in rat blood, suggesting a species-specific difference in the expression of this PDE IV isogene. PDE IV-C was neither detected in human or rat blood nor in different cell populations of the human immune system. It is further demonstrated that the PDE IV isogene expression is differentially regulated by cAMP in different cell types