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R Hosono

Publications and source records attributed to R Hosono.

At least 19 recordsLinked to original sources
PubMed2001

Contribution of neurons to habituation to mechanical stimulation in Caenorhabditis elegans.

In Caenorhabditis elegans, a light touch induces a locomotor response. Repeated touches, however, result in an attenuation of response, that is, habituation. Withdrawal responses elicited by anterior touch are controlled by anterior mechanosensory neurons (AVM and ALMs), and by four pairs of interneurons (AVA, AVB, AVD, and PVC) (Chalfie et al., 1985; White et al., 1986). To identify the neurons that participate in habituation, we ablated these neurons with a laser microbeam and investigated the resulting habituation of the operated animals. The animals lacking both left and right homologues AVDLR were habituated more rapidly than intact animals. We propose that chemical synapses at AVD play a critical role in the habituation of intact animals.

Animals↗
PubMed2001

Effects of high ELF magnetic fields on enzyme-catalyzed DNA and RNA synthesis in vitro and on a cell-free DNA mismatch repair.

Environmental electromagnetic fields have been implicated in human cancers. We examined whether high extremely low frequency (ELF) AC magnetic fields could affect DNA synthesis, transcription or repair, using in vitro model systems with defined sequences. The rate and fidelity of DNA polymerase catalyzed DNA synthesis, as well as of RNA polymerase catalyzed RNA synthesis, were not statistically significantly affected by 60 Hz 0.25-0.5 Tesla magnetic fields. The efficiency of mutS dependent mismatch repair with human cell extracts was also not affected by the magnetic field exposure. The results suggest that the core processes related to the transmission of genetic information are stable under high ELF magnetic fields.

Animals↗
PubMed2001

Exposure of Caenorhabditis elegans to extremely low frequency high magnetic fields induces stress responses.

Responses of the small heat shock protein gene, hsp-16, were examined in transgenic Caenorhabditis elegans exposed to electromagnetic fields. Expression of the hsp-16-lacZ gene was enhanced when transgenic animals were exposed to magnetic fields up to 0.5 T at 60 Hz. The hsp-16 promoter was more efficiently expressed at the embryonic than at the post-embryonic stage irrespective of exposure. Promoter activity was more sensitive to the stimulus in the intestine at the post-embryonic stage. Evidence is presented that the induction occurs at the transcriptional step of hsp-16.

Animals↗
PubMed1999

Regulation of the UNC-18-Caenorhabditis elegans syntaxin complex by UNC-13.

The Caenorhabditis elegans unc-13, unc-18, and unc-64 genes are required for normal synaptic transmission. The UNC-18 protein binds to the unc-64 gene product C. elegans syntaxin (Ce syntaxin). However, it is not clear how this protein complex is regulated. We show that UNC-13 transiently interacts with the UNC-18-Ce syntaxin complex, resulting in rapid displacement of UNC-18 from the complex. Genetic and biochemical evidence is presented that UNC-13 contributes to the modulation of the interaction between UNC-18 and Ce syntaxin.

Alleles↗
PubMed1998

Functional properties of the unc-64 gene encoding a Caenorhabditis elegans syntaxin.

Phenotypes of Caenorhabditis elegans unc-18 and unc-64 gene mutations are similar. While unc-18 is known to be essential for normal synaptic transmission (Hosono, R., Hekimi, S., Kamiya, Y., Sassa, T., Murakami, S., Nishiwaki, S., Miwa, J., Taketo, A., and Kodaira, K.-I. (1992) J. Neurochem. 58, 1517-1525), the function of unc-64 remains unclear. Here we describe the cloning, and the molecular and genetic characterization of the unc-64 gene, especially in relation to unc-18. unc-64 encodes a protein (C. elegans syntaxin) showing sequence and structural similarities to mammalian syntaxin 1A. From unc-64, at least three types of poly(A)+ RNA are transcribed, which encode two types of syntaxin that differ in the deduced transmembrane domain. In gene expression, unc-64 closely resembles unc-18, that is, both are expressed in neural cells, especially in motor neurons and neurons constituting head ganglions. C. elegans syntaxin binds to UNC-18 with high affinity. The unc-64 (e246) mutation producing a mild phenotype causes an Ala-->Val conversion in the conserved COOH-terminal region in mammalian syntaxin 1A or Drosophila syntaxin-1A whose site is included in three types of transcripts. The binding of the mutant C. elegans syntaxin to UNC-18 is greatly reduced, indicating the mutation site contributes to the binding.

Amino Acid Sequence↗
PubMed1996

Expression, purification and characterization of recombinant C. Elegans UNC-18.

The Caenorhabditis elegans unc-18-encoded protein (UNC-18) is implicated in the processes of vesicle targeting, docking, and/or fusion. To further characterize the properties of this important neural protein, we expressed it at a high level in Spodoptera frugiperda Sf21 cells using a baculovirus expressing system. A cDNA containing the coding sequence for UNC-18 was inserted into the transfer vector pBlueBac to yield the recombinant virus pAcNPV/unc-18. At maximal expression, the recombinant virus produces a protein of 67 kDa, which constitutes about one-third of total cell protein. The UNC-18 protein was highly purified and its biochemical and functional properties were assessed. The protein is globular with an isoelectric point of 6.95. Circular dichroism spectroscopy indicated that the alpha-helix and beta-sheet account for 10.0 and 59.0%, respectively. Immunolabeling the Sf21 cells expressing UNC-18 showed that the expressed UNC-18 is predominantly localized in the cytoplasm as a soluble monomer. The protein is phosphorylated by protein kinase C and binds to the recombinant C. elegans syntaxin in vitro. These findings suggest that in vesicle traffic UNC-18 is a regulator factor associated with the plasma membrane through syntaxin, although intrinsically cytoplasmic.

Animals↗
PubMed1996

The synaptic protein UNC-18 is phosphorylated by protein kinase C.

The C. elegans unc-18 encoded protein UNC-18 is implicated in the interactions between synaptic vesicles and presynaptic plasma membrane. To further characterize the neural protein, we investigated the phosphorylation in vitro of the protein expressed in Spodoptera frugiperda Sf21 cells. The UNC-18 protein is selectively phosphorylated by protein kinase C (PKC) but not by casein kinase II and cyclic AMP-dependent protein kinase. The presumed phosphorylation sites determined by manual Edman degradation were serine-2, serine-322, threonine-462 and serine-515, of which the last is highly conserved as a consensus phosphorylation site for PKC in Drosophila and the mammalian homologue. Phosphorylated UNC-18 extracted from C. elegans was also detected, indicating that it has a physiological role in intact nerve terminals. Therefore, the phosphorylation by PKC may play a physiological role in the regulation.

Amino Acid Sequence↗
PubMed1995

Biological responses in Caenorhabditis elegans to high magnetic fields.

Here we describe a device for testing possible influences of high magnetic fields on biological processes, by which alternating-current magnetic stimuli as high as 1.7 T can be administered. Experiments with a simple multicellular organism, the nematode Caenorhabditis elegans, revealed that intermittent exposure to the magnetic fields modestly inhibited the animal's reproduction as well as its post-embryonic development, and caused a marked but transient derangement in its locomotory behavior. Available evidence indicates that alternating high magnetic fields can elicit both chronic and acute biological effects, but that the effects may be well tolerated or compensated for by the living organism.

Animals↗
PubMed1994

Mutations in the unc-41 gene cause elevation of acetylcholine levels.

Mutations in the Caenorhabditis elegans unc-41 gene result in an allele-dependent elevation of acetylcholine content. Eight recessive alleles (cn252, e268, e399, e650, e1175, e1199, e1294, and e870) lead to phenotypes including uncoordinated locomotion, slow growth, a small mature body, and resistance to the acetylcholinesterase inhibitors as well as the elevation of acetylcholine content. The remaining two alleles, e554 and e1162, exhibit normal acetylcholine levels but display the short-body phenotype in a semidominant way. To determine the localization of the elevated acetylcholine content, a method for the isolation of synaptic vesicles from C. elegans was established. The elevation of acetylcholine content in the unc-41 mutants is accompanied by the accumulation of synaptic vesicles. We propose that at least one function of the unc-41 gene relates to the release of neurotransmitters.

Acetylcholine↗
PubMed1993

The C. elegans unc-18 gene encodes a protein expressed in motor neurons.

The C. elegans unc-18 gene is required to maintain normal acetylcholine levels. We determined the complete structure of an unc-18 cDNA that encodes a protein of 591 highly charged and hydrophilic amino acids. The protein shows sequence similarity with elements of the secretory pathway in the yeast S. cerevisiae. Antibodies raised against a portion of the unc-18-encoded protein (UNC-18) detected a 68 kd soluble antigen on immunoblots and intensely stained all vertical cord motor neurons in situ. These findings suggest that UNC-18 participates in the axonal transport system and influences the acetylcholine flow in motor neurons.

Amino Acid Sequence↗
PubMed1992

Mutations in genes for acetylcholinesterase intensify lethality by acrylamide in Caenorhabditis elegans.

Acrylamide inhibits growth and results in death in the nematode Caenorhabditis elegans. The lethargic effect is marked in the mutants defective in genes for acetylcholinesterase (AChE) and the effect is approximately parallel with the decrease in AChE activity by mutations. Although neither the activity nor the localization of the enzyme is affected by acrylamide, the acetylcholine level was significantly elevated.

Acetylcholinesterase↗
PubMed1992

The unc-18 gene encodes a novel protein affecting the kinetics of acetylcholine metabolism in the nematode Caenorhabditis elegans.

Genes affecting acetylcholine (ACh) levels without influencing choline acetyltransferase activity have been identified in Caenorhabditis elegans. We have examined one such gene, unc-18. We isolated a transposon-insertion allele for unc-18 and used it to clone a genomic region containing the unc-18 locus. The unc-18 location within this region was determined by rescuing the unc-18 mutant phenotype in a germ-line transformation experiment and identifying transcripts affected by four independent unc-18 mutations. A single-sized poly(A)+ RNA was synthesized from the gene. Expression of the transcript appears to be stage specific: The transcript is found in abundance at the early larval stage but in decreased amounts at the fourth larval and the adult stages. These results show that the unc-18 gene plays a role in development as well as in the kinetics of ACh metabolism.

Acetylcholine↗
PubMed1991

Additional genes which result in an elevation of acetylcholine levels by mutations in Caenorhabditis elegans.

Four mutant genes (unc-17, unc-18, unc-41 and unc-13) have been identified that result in abnormal accumulation of acetylcholine (ACh). We have now identified 3 more such genes (unc-63, unc-11 and unc-64). In addition to the abnormal accumulation of ACh, mutants in these 7 genes possess common phenotypes in locomotion, resistance to inhibitors of acetylcholinesterase (AChE) and in post-embryonic development. These results suggest that the 7 genes are involved in some related functions.

Acetylcholine↗
PubMed1989

Alterations of life span in the nematode Caenorhabditis elegans under monoxenic culture conditions.

The nematode Caenorhabditis elegans was cultured monoxenically with E. coli as a food source and the influence of the bacterial growth conditions on the life span was studied. When bacterial growth was restricted by reducing the concentration of bactopeptone, which was supplied as the energy source in nematode growth medium (NGM), the nematode's life span tended to be prolonged without a marked effect on postembryonic development. The effect of bactopeptone on the life span was clearly observed during the postreproductive period (that is, after the egg-laying stage of the wild-type C. elegans) rather than during the larval to young adult stage. Evidence is presented that this alteration of the life span was not brought about by any factor in the bactopeptone but by the concentration of bacteria.

Animals↗
PubMed1987

Mutations affecting acetylcholine levels in the nematode Caenorhabditis elegans.

Gene cha-1.unc-17 of the nematode Caenorhabditis elegans is a complex gene, consisting of at least two complementation groups. One part (cha-1 region) of the gene encodes the enzyme choline acetyltransferase (ChAT), but the function of the other part (unc-17 region) is still unclear. We measured the ChAT activity and ACh levels of the cha-1 and unc-17 complex gene mutants. We show here that alterations in ACh levels, rather than the ChAT activity, reflect abnormal phenotypes accompanying cha-1.unc-17 mutations, that is, the decreased ACh levels in cha-1 mutations and abnormal accumulation in unc-17 mutations. Our results suggest that the unc-17 region may encode functions necessary for storage and/or release of ACh at the presynaptic level.

Acetylcholine↗
PubMed1985

Temperature-sensitive mutations causing reversible paralysis in Caenorhabditis elegans.

A method has been developed for the isolation of temperature-dependent paralytic mutants of the nematode Caenorhabditis elegans, based on a screening procedure using short-time exposure to 30 degrees C. Of ten mutants isolated, eight lose their motilities between 30 degrees C and 33 degrees C without prominent changes in body forms. The other two strains that are mainly described in this report are accompanied by alterations in body forms. One mutation, cn101, is recessive and an allele of cha-1. The cn101 mutant shows reversible paralysis at 30 degrees, accompanied by a hypercontracted and coiled body form. At the restrictive temperature, the strain is resistant to all tested inhibitors of acetylcholinesterase (AChE). Another mutation, designated mah-2 (cn110), is a sex-linked semidominant that is mapped as 0.6 map units left of dpy-6. The cn110 mutant is rapidly paralyzed at the restrictive temperature and has a straight and rigid body form; the mutant rapidly recovers when the temperature is lowered. No disorganization of the muscle structure was detected by polarized light and electron microscopic inspection.

Alleles↗
PubMed1982

Life span of the wild and mutant nematode Caenorhabditis elegans. Effects of sex, sterilization, and temperature.

The survival of Caenorhabditis elegans was studied comparing animals of different sexes, sterilized animals, and animals grown at different temperatures as a prelude to more detailed cytological and genetic analysis of aged nematodes. Temperature-sensitive sterile mutants, animals sterilized by 5-fluorodeoxyuridine treatment, and wild-type males showed little difference in life span from that of wild-type hermaphrodites, although slight changes in P (time of beginning of the dying phase) or T1/2 (half-life of the population in the early dying phase) values were observed. At higher temperatures, P and T1/2 values markedly decreased, indicating a shortened life span. Temperature shift between 16 degrees C and 25 degrees C revealed that an increase in life span always involved low temperatures after the adult phase. High temperature treatment during the growing phase or after the adult phase caused an earlier start of the dying phase, but a downward temperature during the adult phase resulted in a great increase in the half-life of the population (T1/2). The results suggest that the life span of C. elegans is rigidly determined by somatic cells and markedly influenced by the effects of temperature on the cells during the post-mitotic state.

Animals↗