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Biomedical subjects

C M Yoshihara

Publications and source records attributed to C M Yoshihara.

7 recordsLinked to original sources
PubMed1993

Increased expression of the 43-kD protein disrupts acetylcholine receptor clustering in myotubes.

The 43-kD protein is a peripheral membrane protein that is in approximately 1:1 stoichiometry with the acetylcholine receptor (AChR) in vertebrate muscle cells and colocalizes with it in the postsynaptic membrane. To investigate the role of the 43-kD protein in AChR clustering, we have isolated C2 muscle cell lines in which some cells overexpress the 43-kD protein. We find that myotubes with increased levels of the 43-kD protein have small AChR clusters and that those with the highest levels of expression have a drastically reduced number of clusters. Our results suggest that the 1:1 stoichiometry of AChR and 43-kD protein found in muscle cells is important for AChR cluster formation.

Animals↗
PubMed1988

Regulation of acetylcholine receptor transcript expression during development in Xenopus laevis.

The level of transcripts encoding the skeletal muscle acetylcholine receptor (AChR) was determined during embryonic development in Xenopus laevis. cDNAs encoding the alpha, gamma, and delta subunits of the Xenopus AChR were isolated from Xenopus embryo cDNA libraries using Torpedo AChR cDNAs as probes. The Xenopus AChR cDNAs have greater than 60% amino acid sequence homology to their Torpedo homologues and hybridize to transcripts that are restricted to the somites of developing embryos. Northern blot analysis demonstrates that a 2.3-kb transcript hybridizes to the alpha subunit cDNA, a 2.4-kb transcript hybridizes to the gamma subunit cDNA, and that two transcripts, of 1.9 and 2.5 kb, hybridize to the delta subunit cDNA. RNase protection assays demonstrate that transcripts encoding alpha, gamma, and delta subunits are coordinately expressed at late gastrula and that the amount of each transcript increases in parallel with muscle-specific actin mRNA during the ensuing 12 h. After the onset of muscle activity the level of actin mRNA per somite remains relatively constant, whereas the level of alpha subunit and delta subunit transcripts decrease fourfold per somite and the level of gamma subunit transcript decreases greater than 50-fold per somite. The decrease in amount of AChR transcripts per somite, however, occurs when embryos are paralyzed with local anaesthetic during their development. These results demonstrate that AChR transcripts in Xenopus are initially expressed coordinately, but that gamma subunit transcript levels are regulated differently than alpha and delta at later stages. Moreover, these results demonstrate that AChR transcript levels in Xenopus myotomal muscle cells are not responsive to electrical activity and suggest that AChR transcript levels are influenced by other regulatory controls.

Amino Acid Sequence↗
PubMed1988

Regulation of transcript encoding the 43K subsynaptic protein during development and after denervation.

The postsynaptic membrane of vertebrate neuromuscular synapses is enriched in the four subunits of the acetylcholine receptor (AChR) and in a peripheral membrane protein of Mr = 43 x 10(3) (43K). Although AChRs are virtually restricted to the postsynaptic membrane of innervated adult muscle, developing and denervated adult muscle contain AChRs at nonsynaptic regions. These nonsynaptic AChRs accumulate because the level of mRNA encoding AChR subunits increases in response to a loss of muscle cell electrical activity. We have determined the level of mRNA encoding the 43K subsynaptic protein in developing muscle and in innervated and denervated adult muscle. We isolated a cDNA that encodes the entire protein-coding region of the 43K subsynaptic protein from Torpedo electric organ and used this cDNA to isolate a cDNA that encodes the 43K subsynaptic protein from Xenopus laevis. We used the Xenopus cDNA to measure the level of transcript encoding the 43K protein in embryonic muscle and in innervated and denervated adult muscle by RNase protection. The level of transcript encoding the 43K protein is low in innervated adult muscle and increases 25- to 30-fold after denervation. The level of transcript encoding the alpha subunit of the AChR increases to a similar extent after denervation. Moreover, during development, transcripts encoding the 43K protein and the alpha subunit are expressed initially at late gastrula and are present in similar quantities in embryonic muscle. These results demonstrate that transcripts encoding the 43K protein and AChR subunits appear coordinately during embryonic development and that the level of mRNA encoding the 43K protein is regulated by denervation.

Amino Acid Sequence↗
PubMed1987

The chicken carbonic anhydrase II gene: evidence for a recent shift in intron position.

The complete nucleotide sequence of the coding region of the chicken carbonic anhydrase II (CA II) gene has been determined from clones isolated from a chicken genomic library. The sequence of a nearly full length chicken CA II cDNA clone has also been obtained. The gene is approximately 17 kilobase pairs (kb) in size and codes for a protein that is comprised of 259 amino acid residues. The 5' flanking region contains consensus sequences commonly associated with eucaryotic genes transcribed by RNA polymerase II. Six introns ranging in size from 0.3 to 10.2 kb interrupt the gene. The number of introns as well as five of the six intron locations are conserved between the chicken and mouse CA II genes. The site of the fourth intron is shifted by 14 base pairs further 3' in the chicken and thus falls between codons 147 and 148 rather than within codon 143 as in the mouse gene. Measurements of CA II RNA levels in various cell types suggest that CA II RNA increases in parallel with globin RNA during erythropoiesis and exists only at low levels, if at all, in non-erythroid cells.

Amino Acid Sequence↗
PubMed1980

Characterization of ACP1TIC-1, an electrophoretic variant of erythrocyte acid phosphatase restricted to the Ticuna Indians of central Amazonas.

A new variant of erythrocyte acid phosphatase, designated ACP1TIC-1, is characterized by a more cathodal electrophoretic mobility than any of the common polymorphic phenotypes, both in the presence and absence of tricarboxylic acids. Individuals of the ACP1TIC-1 phenotype have a level of enzyme activity (4.8 +/- 0.1 mumol/g hemoglobin per min) similar to individuals of the ACP1A phenotype, although no differences in Km values were observed or is the extent of phosphate inhibition different between the ACP1TIC-1 and the ACP1B variants. The thermostability of the enzyme is less than that observed for any of the common variants. The TIC-1 variant is activated by adenine and inhibited by folic acid to the same extent as the type-A enzyme, while the stimulation of the activity of the TIC-1 enzyme by hypoxanthine and the inhibition of it by uric acid is similar to that for the B enzyme. Thus, the TIC-1 variant has a unique combination of kinetic properties, seeming to be a hybrid of A-type and B-type characteristics.

Acid Phosphatase↗
PubMed1979

Electrophoretic variants in three Amerindian tribes: the Baniwa, Kanamari, and Central Pano of western Brazil.

Data are presented on electrophoretic variants of 25 polypeptides found in the blood serum and erythrocytes, in 812 individuals from three Amerindian tribes, the Pano, the Baniwa, and the Kanamari. Two "private polymorphisms" were encountered, of PEPB in the Pano and CAII in the Baniwa. A single example of a different PEPB variant was encountered in the Baniwa, and two possible examples of an unstable variant of HGB A2 in the Kanamari. In addition, the well-known A variant of ACP1, the Duarte variant of GALT, the 2 variant of Hp and the 2 variant of PGM1 occurred in polymorphic proportions in all three tribes, and the TFDChi variant was present as a polymorphism in the Baniwa. These data have recently been incorporated into a treatment which concludes that the eight electrophoretically-defined "private polymorphisms" thus far encountered in Amerindian tribes can be explained by a mutation pressure of 0.7 x 10(-5)/locus/generation on the assumption of neutrality of the phenotypes in question (Neel and Thompson, '78).

Asian People↗