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Biomedical subjects

H C Seo

Publications and source records attributed to H C Seo.

27 records · Page 2Linked to original sources
PubMed1994

Identification of prosaposin as a neurotrophic factor.

Prosaposin was identified as a neurotrophic factor stimulating neurite outgrowth in murine neuroblastoma (NS20Y) cells and choline acetyltransferase (ChAT) activity in human neuroblastoma (SK-N-MC) cells. The four naturally occurring saposins, which are derived by proteolytic processing of prosaposin, were tested for activity. Saposin C was found to be active, whereas saposins A, B, and D were inactive as neurotrophic factors. Dose-response curves demonstrated that nanomolar concentrations of prosaposin and saposin C stimulated neurite outgrowth and increased ChAT activity. Prosaposin and saposin C exerted activity by a mechanism independent of nerve growth factor, brain-derived neurotrophic factor, and neurotrophin 3. Binding assays utilizing saposin C as a ligand gave two saturable binding constants, a high-affinity (Kd = 19 pM) and a low-affinity (Kd = 1 nM) constant, with 2000 and 15,000 sites per NS20Y cell, respectively. Phosphorylation stimulation experiments demonstrated that brief treatment with prosaposin or saposin C enhanced phosphorylation of a variety of proteins, some of which contained phosphorylated tyrosine(s). Since both cell lines were also stimulated by ciliary neurotrophic factor (CNTF) as well as prosaposin, inhibition was tested by utilizing an anti-gp130 monoclonal antibody, which specifically inhibited CNTF stimulation; this antibody did not inhibit prosaposin or saposin C stimulation. These results indicate that prosaposin and saposin C are neurotrophic factors which initiate signal transduction by binding to a high-affinity receptor that induces protein phosphorylation.

Animals↗
PubMed1993

Identification and purification of a self-associating copper-binding protein from mouse hepatic cytosols.

The proteins which bind copper when it first enters cells and deliver that copper to the cellular sites where copper is incorporated into copper enzymes are unknown. When radiolabeled (64Cu(II)) cytosol proteins were fractionated on Superose columns, two large copper-binding protein fractions were detected which together bound 63% of the total 64Cu recovered from the column. A self-associating, 50-kDa copper-binding protein was identified whose tetramer and dimer appeared to elute in one of the major copper-binding fractions and the monomer eluted in the other. This protein was purified to homogeneity by successive Mono Q, chelating Superose, and phenyl-Superose columns. The concentrated, purified protein showed high amounts of tetramer and monomer plus some dimer, each of which bound copper. Rechromatography of the tetramer-dimer fraction on Superose gave rise to approximately equal amounts of tetramer, dimer, and monomer. Similarly, rechromatography of the monomer fraction gave rise to dimer and tetramer. Thus, the results with the purified protein confirmed that the 50-kDa protein exists as a tetramer-dimer-monomer equilibrium. The 50-kDa protein apparently makes a major contribution to the total copper-binding activity of the mouse hepatic cytosol and may play a significant role in intracellular copper metabolism.

Animals↗
PubMed1993

Purification and properties of a self-associating, 50-kDa copper-binding protein from brindled mouse livers.

The brindled mouse is an animal model of Menkes disease, a fatal, X-linked disease of copper metabolism. A self-associating, 50-kDa copper-binding protein (CuBP) was purified from brindled mouse hepatic cytosols, and some of its properties were determined. When 64Cu-labeled whole hepatic cytosols were fractionated on Superose, statistically significantly less than normal 64Cu binding was detected in both the fraction which contained the tetramer plus dimer (approximately 26% less) and the fraction containing the monomer of CuBP (approximately 37% less). CuBP was purified from brindled mouse hepatic cytosols by successive Mono Q, chelating Superose, and phenyl-Superose columns using the same methods used to purify the protein from normal mice. However, CuBP from the brindled mice was somewhat unstable during the purification. Also, CuBP from the brindled mouse eluted abnormally from the phenyl-Superose column. Thus, while the protein from normal mice eluted at approximately 20 min after starting the final water elution step, the brindled mouse protein eluted by approximately 5 min. This seemed to be due to abnormal self-association in the column buffers. Consistent with the results using whole cytosols, the purified CuBP from the brindled mouse showed decreased copper binding in both the tetramer and monomer fractions from Superose. Moreover, under the same conditions, CuBP from the brindled mice seemed to have relatively less tetramer and more dimer than normal. The results are consistent with a significant role for CuBP in intracellular copper metabolism, and an abnormal structure of CuBP may be the basic defect in the brindled mice and, by inference, Menkes disease.

Animals↗
PubMed1993

Fucosidosis: four new mutations and a new polymorphism.

Fucosidosis is a rare lysosomal storage disease due to a nearly complete deficiency of alpha-L-fucosidase (EC 3.2.1.51). In this study, all 8 exons of the alpha-L-fucosidase structural gene (FUCA-1) were amplified by PCR methods, and the amplified products were subcloned and sequenced. Five patient groups with fucosidosis were selected according to their ethnic backgrounds and haplotypes for RFLPs in FUCA-1. Four presumptive disease causing mutations were detected: 1) A major deletion of DNA containing the last two exons of FUCA-1 in two Algerian siblings. 2) A G to T mutation in exon 6 resulting in an in-frame termination codon (E375X) in eight Hispanic patients from Colorado and New Mexico. 3) A G to A mutation (G60D) in exon 1 in four Italian patients and in three related French-American (Cajun) patients. This G60D mutation creates a unique site for AflIII. 4) A frameshift mutation resulted from a two-base deletion in exon 2 (K151fs) in an Italian patient. This deletion obliterates a unique BstXI site and creates a new BpmI site, and was found in only this patient and in only one allele. The rationale for proposing these defects as disease causing mutations includes pedigree analysis and the predicted consequences of each defect upon the activity and the concentration of the enzyme. An A to G transition (Q281R) in exon 5 was found to be present in homozygous form in affected patients and also in normal subjects; it appears to be a newly identified polymorphism. It causes a charge change and may be responsible for the electrophoretic variant phenotype of fucosidosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Six additional mutations in fucosidosis: three nonsense mutations and three frameshift mutations.

The rare lysosomal storage disease, fucosidosis results from an almost complete deficiency of alpha-L-fucosidase (EC 3.2.1.51). We have identified six new potential disease causing mutations detected by PCR amplification and sequencing of all 8 exons of the alpha-L-fucosidase gene FUCA1. (1) A C to T mutation (Q77X) in exon 1 of two Jewish-Italian siblings. This mutation was present in one allele and was found also in the mother who was of Italian origin. (2) A C to A mutation (W382X) in exon 6 in an Italian patient. This mutation was found in one allele and obliterates a unique Hphl site. (3) A C to A mutation (Y211X) in exon 3 in a Belgian patient. This mutation obliterates a unique Rsal site and was present in both alleles. (4) A homozygous single base (C) deletion in exon 2 in an Italian patient. This deletion results in a frameshift mutation (P141fs) and obliterates a unique Eael site. (5) A homozygous single base (C) deletion in exon 5 in a Portuguese patient, which also results in a frameshift mutation (S265fs). (6) A single base (A) deletion in exon 3 in a Canadian-Indian patient, which also results in a frameshift mutation (S216fs). The S216fs mutation was found in only one allele; the mutation in the other allele is not yet known.

Amino Acid Sequence↗
PubMedDate not supplied

Molecular cloning and characterization of five opsin genes from the marine flatfish Atlantic halibut (Hippoglossus hippoglossus).

Most molecular studies on the visual system in fish have been performed on freshwater teleosts such as goldfish and zebrafish where cones and rods appear simultaneously. Many marine fishes have long larval phase in the upper pelagic zone before transformation into a juvenile and a benthic life style. The retina at the larval stages consists of only single cone cells; later during metamorphosis double cones and rods develop. The flatfish Atlantic halibut (Hippoglossus hippoglossus) is a typical example of a marine species with such a two-step retina development. In this study, we have cloned five different opsins from Atlantic halibut larvae and juvenile retinas. Sequence comparisons with other opsins and phylogenetic analysis show that the five genes belong to the opsins of long-wavelength sensitive (L); middle-wavelength sensitive, M(Cone) and M(Rod); and short-wavelength sensitive, S(Blue) and S(Ultraviolet), respectively. In situ hybridization analysis reveals expression in double cone (L and M(Cone)), single cone (S(Blue) and S(Ultraviolet)), and rod (M(Rod)) types of photoreceptor cells in juvenile halibut retina. The visual system in Atlantic halibut seems therefore to have all four types of cone photoreceptors in addition to rod photoreceptors. This work shows for the first time molecular isolation of a complete set of retinal visual pigment genes from a marine teleost and describes the first cloning of an ultraviolet-sensitive opsin type from a marine teleost.

Amino Acid Sequence↗