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Biomedical subjects

D Julius

Publications and source records attributed to D Julius.

45 records · Page 3Linked to original sources
PubMed1989

Ectopic expression of the serotonin 1c receptor and the triggering of malignant transformation.

Neurotransmitter receptors are usually restricted to neuronal cells, but the signaling pathways activated by these receptors are widely distributed in both neural and non-neural cells. The functional consequences of activating a brain-specific neurotransmitter receptor, the serotonin 5HT1c receptor, in the unnatural environment of a fibroblast were examined. Introduction of functional 5HT1c receptors into NIH 3T3 cells results, at high frequency, in the generation of transformed foci. Moreover, the generation and maintenance of transformed foci requires continued activation of the serotonin receptor. In addition, the injection of cells derived from transformed foci into nude mice results in the generation of tumors. The serotonin 5HT1c receptor therefore functions as a protooncogene when expressed in NIH 3T3 fibroblasts.

Animals↗
PubMed1989

5-HT1c receptor is a prominent serotonin receptor subtype in the central nervous system.

Neurons in rat central nervous system (CNS) that express 5-HT1c receptor mRNA have been localized by in situ hybridization histochemistry. The 5-HT1c receptor is expressed in a wide variety of cortical and subcortical neurons including hippocampal pyramidal neurons, neurons within most of the central monoaminergic cell groups, neurons in thalamic sensory relay nuclei, and neurons involved in the central processing and regulation of nociceptive transmission. Therefore, the 5-HT1c receptor is a prominent but poorly characterized central subclass of serotonin (5-HT) receptor. The distribution of the 5-HT1c receptor within the CNS is considerably more widespread than that of the structurally and functionally related 5-HT2 receptor.

Animals↗
PubMed1988

Molecular characterization of a functional cDNA encoding the serotonin 1c receptor.

Neurons that release serotonin as a neurotransmitter project to most regions of the central and peripheral nervous system and mediate diverse neural functions. The physiological effects of serotonin are initiated by the activation of multiple, distinct receptor subtypes. Cloning in RNA expression vectors was combined with a sensitive electrophysiological assay in Xenopus oocytes in order to isolate a functional cDNA clone encoding the 5HTlc serotonin receptor. Injection of RNA transcribed in vitro from this clone into Xenopus oocytes elicits serotonin sensitivity. Mouse fibroblasts transformed with this clone bind serotonin agonists and antagonists and exhibit an increase in intracellular Ca2+ concentrations in response to serotonin. The sequence of the 5HTlc receptor reveals that it belongs to the family of G protein-coupled receptors, which are thought to traverse the cytoplasmic membrane seven times. Moreover, in situ hybridization and RNA blot analysis indicate that the 5HTlc receptor is expressed in neurons in many regions of the central nervous system and suggest that this subclass of receptor may mediate many of the central actions of serotonin.

Amino Acid Sequence↗
PubMed1984

Glycosylation and processing of prepro-alpha-factor through the yeast secretory pathway.

Events in the synthesis and processing of prepro-alpha-factor have been assessed with the aid of mutants blocked at various stages in the yeast secretory pathway. In normal cells treated with tunicamycin, a precursor accumulates which is identical in molecular weight to the primary translation product synthesized in vitro. At the restrictive temperature in a mutant blocked early in the pathway (sec53), a molecule of similar molecular weight accumulates. In mutants affecting translocation into (sec59) and passage from (sec 18) the endoplasmic reticulum, a glycosylated form of the precursor containing three N-linked core oligosaccharides accumulates; however, it appears that the signal peptide is not removed. The glycosylated precursor first experiences proteolytic processing when accumulated in a mutant (sec7) blocked at the stage of the Golgi apparatus. Substantially greater amounts of the mature pheromone are seen in mutants that accumulate secretory vesicles (sec1, sec2, sec3, sec5).

Genotype↗
PubMed1984

Isolation of the putative structural gene for the lysine-arginine-cleaving endopeptidase required for processing of yeast prepro-alpha-factor.

S. cerevisiae kex2 mutants are defective for the production of two biologically active secreted peptides: killer toxin and the mating pheromone, alpha-factor. Both molecules are excised from larger precursor polypeptides. In normal cells, the alpha-factor precursor is core-glycosylated and proteolytically processed intracellularly. In kex2 mutants, however, prepro-alpha-factor is not proteolytically cleaved and is secreted in a highly glycosylated form. All kex2 mutants examined (three independent alleles) lack a Zn++-sensitive membrane-associated endopeptidase with specificity for cleaving on the carboxyl side of a pair of basic residues. Absence of this activity cosegregates with the other phenotypes of a kex2 lesion in genetic crosses. The normal KEX2 gene was isolated by complementation of three of the phenotypes conferred by the kex2-1 mutation. The cloned DNA, either on a multicopy plasmid or integrated into the genome, restores both enzymatic activity in vitro and the normal pattern of proteolytic processing and glycosylation of prepro-alpha-factor in vivo. Gene dosage effects suggest that KEX2 is the structural gene for the endopeptidase.

Arginine↗
PubMed1983

Yeast alpha factor is processed from a larger precursor polypeptide: the essential role of a membrane-bound dipeptidyl aminopeptidase.

Alpha factor mating pheromone is a peptide of 13 amino acids secreted by Saccharomyces cerevisiae alpha cells. Nonmating ("sterile," or ste) alpha-cell mutants bearing defects in the STE13 gene do not produce normal alpha factor, but release a collection of incompletely processed forms (alpha factor) that have a markedly reduced specific biological activity. The major alpha-factor peptides have the structures H2N-GluAlaGluAla-alpha factor and H2N-AspAlaGluAla-alpha factor. The ste13 mutants lack a membrane-bound heat-stable dipeptidyl aminopeptidase (DPAPase A) that specifically cleaves on the carboxyl side of repeating -X-Ala- sequences. Absence of DPAPase A and the other phenotypes of a ste13 lesion cosegregate in genetic crosses. The cloned STE13 gene on a plasmid causes yeast cells to overproduce DPAPase A severalfold. A different cloned DNA segment, which weakly suppresses the ste13 defects, causes overproduction of a heat-labile activity (DPAPase B) by about tenfold. Other experiments indicate that DPAPase A action may be rate-limiting for alpha-factor maturation in normal alpha cells.

Amino Acids↗