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K Lee

Publications and source records attributed to K Lee.

At least 361 records · Page 20Linked to original sources
PubMed1998

Isoform-specific interaction of the cytoplasmic domains of Na,K-ATPase.

The Na,K-ATPase is a heterodimer consisting of an alpha and a beta subunit, which exchanges intracellular Na+ for extracellular K+ using the energy of ATP hydrolysis. Several studies have demonstrated that the enzyme exists as an (alphabeta)2 heterotetramer, an oligomer of alphabeta dimers within the cell membrane, at least during some portion of the transport cycle although its functional significance is unknown. In our study, we employed the yeast two-hybrid system to identify the cytoplasmic domains of the Na,K-ATPase which might be involved in intersubunit and/or intrasubunit interactions to form higher order oligmers. Our data demonstrate that the N-terminus and the cytoplasmic loop 1 of the alpha2 subunit interact with each other, while those of the alpha1 subunit do not, suggesting that the interaction is isoform-specific. Therefore, the N-terminal and the cytoplasmic loop 1 might be the regions where the alpha2 subunit, which are involved in alpha alpha interactions, stabilize Na,K-ATPase as alphabeta protomer, diprotomer, or higher order oligomer because the interaction can be intrasubunit as well as intersubunit interactions. Our study suggests that there may be an isoform-specific difference in the alpha-alpha interaction and that the isoform-specific interaction may contribute significantly to the differences of the physiological function and regulation among the alpha isoforms.

Animals↗
PubMed1998

Residue leu973 of the rat alpha1 subunit of the Na,K-ATPase is located on the cytoplasmic side of the plasma membrane.

In a previous study (Yoon, K. L., and Guidotti, G., 1994 J. Biol. Chem. 269, 28249-28258), we indicated that the alpha subunit of the Na,K-ATPase has 4 transmembrane segments in the COOH terminal domain between residues Lys769 and Val939, and that both the NH2-terminus and the COOH-terminus are in the cytosol. However, there was insufficient information to determine whether there are more transmembrane segments between residues Val939 and the COOH-terminal Tyr1018. To investigate this question, we inserted the influenza virus hemagglutinin (HA)-epitope between Leu973 and Arg974 of the alpha1 chain, expressed the construct in COS-7 and HeLa cells and determined the membrane arrangement by indirect immunofluorescence. The results indicate that Leu973 is not on the extracellular surface of the plasma membrane. Thus, the alpha1 subunit is likely to possess only four complete transmembrane segments in the COOH terminal domain between residues Lys769 and Tyr1018.

Animals↗
PubMed1998

The parathyroid hormone/parathyroid hormone-related peptide receptor coordinates endochondral bone development by directly controlling chondrocyte differentiation.

During vertebrate limb development, growth plate chondrocytes undergo temporally and spatially coordinated differentiation that is necessary for proper morphogenesis. Parathyroid hormone-related peptide (PTHrP), its receptor, the PTH/PTHrP receptor, and Indian hedgehog are implicated in the regulation of chondrocyte differentiation, but the specific cellular targets of these molecules and specific cellular interactions involved have not been defined. Here we generated chimeric mice containing both wild-type and PTH/PTHrP receptor (-/-) cells, and analyzed cell-cell interactions in the growth plate in vivo. Abnormal differentiation of mutant cells shows that PTHrP directly signals to the PTH/PTHrP receptor on proliferating chondrocytes to slow their differentiation. The presence of ectopically differentiated mutant chondrocytes activates the Indian hedgehog/PTHrP axis and slows differentiation of wild-type chondrocytes. Moreover, abnormal chondrocyte differentiation affects mineralization of cartilaginous matrix in a non-cell autonomous fashion; matrix mineralization requires a critical mass of adjacent ectopic hypertrophic chondrocytes. Further, ectopic hypertrophic chondrocytes are associated with ectopic bone collars in adjacent perichondrium. Thus, the PTH/PTHrP receptor directly controls the pace and synchrony of chondrocyte differentiation and thereby coordinates development of the growth plate and adjacent bone.

Animals↗
PubMed1998

Sonic hedgehog.

Explore the source record for details and available documents.

Animals↗
PubMed1998

Expression profiling of single cells using 3 prime end amplification (TPEA) PCR.

The ability to relate the physiological status of individual cells to the complement of genes they express is limited by current methodological approaches for performing these analyses. We report here the development of a robust and reproducible method for amplifying 3' sequences of mRNA derived from single cells and demonstrate that the amplified cDNA, derived from individual human lymphoblastoma cells, can be used for the expression profiling of up to 40 different genes per cell. In addition, we show that 3 prime end amplification (TPEA) PCR can be used to enable the detection of both high and low abundance mRNA species in samples harvested from live neurons in rat brain slices. This procedure will facilitate the study of complex tissue function at the cellular level.

Animals↗
PubMed1998

Benzylamine-based selective and orally bioavailable inhibitors of thrombin.

A series of p-aminomethylphenylalanine derivatives were investigated as novel thrombin inhibitors. This study led to potent inhibitors of thrombin (Ki up to 3.3 nM) that are trypsin-selective, highly orally bioavailable in rats, and highly permeable across Caco-2 cells. The P1 benzylamine binding mode in the thrombin active site was identified by X-ray crystallographic analysis.

Animals↗
PubMed1998

Identification of an ATP-sensitive potassium channel current in rat striatal cholinergic interneurones.

1. Whole-cell patch-clamp recordings were made from rat striatal cholinergic interneurones in slices of brain tissue in vitro. In the absence of ATP in the electrode solution, these neurones were found to gradually hyperpolarize through the induction of an outward current at -60 mV. This outward current and the resultant hyperpolarization were blocked by the sulphonylureas tolbutamide and glibenclamide and by the photorelease of caged ATP within neurones. 2. This ATP-sensitive outward current was not observed when 2 mM ATP was present in the electrode solution. Under these conditions, 500 microM diazoxide was found to induce an outward current that was blocked by tolbutamide. 3. Using permeabilized patch recordings, neurones were shown to hyperpolarize in response to glucose deprivation or metabolic poisoning with sodium azide (NaN3). The resultant hyperpolarization was blocked by tolbutamide. 4. In cell-attached recordings, metabolic inhibition with 1 mM NaN3 revealed the presence of a tolbutamide-sensitive channel exhibiting a unitary conductance of 44.1 pS. 5. Reverse transcription followed by the polymerase chain reaction using cytoplasm from single cholinergic interneurones demonstrated the expression of the ATP-sensitive potassium (KATP) channel subunits Kir6.1 and SUR1 but not Kir6.2 or SUR2. 6. It is concluded that cholinergic interneurones within the rat striatum exhibit a KATP channel current and that this channel is formed from Kir6.1 and SUR1 subunits.

Adenosine Triphosphate↗
PubMed1998

Potent and efficacious thienylamidine-incorporated thrombin inhibitors.

Novel thrombin inhibitors incorporating thienylamidine at the P1 position were designed and synthesized. These compounds are potent, trypsin-selective and efficacious in the rat model of venous thrombosis. The proposed P1 binding mode in the thrombin active site was confirmed by X-ray crystallographic analysis.

Animals↗
PubMed1998

Isolation of MOAT-B, a widely expressed multidrug resistance-associated protein/canalicular multispecific organic anion transporter-related transporter.

Multidrug resistance-associated protein (MRP) and canalicular multispecific organic anion transporter (cMOAT) are closely related mammalian ATP-binding cassette transporters that export organic anions from cells. Transfection studies have established that MRP confers resistance to natural product cytotoxic agents, and recent evidence suggests the possibility that cMOAT may contribute to cytotoxic drug resistance as well. Based upon the potential importance of these transporters in clinical drug resistance and their important physiological roles in the export of the amphiphilic products of phase I and phase II metabolism, we sought to identify other MRP-related transporters. Using a degenerate PCR approach, we isolated a cDNA that encodes a novel ATP-binding cassette transporter, which we designated MOAT-B. The MOAT-B gene was mapped using fluorescence in situ hybridization to chromosome band 13q32. Comparison of the MOAT-B predicted protein with other transporters revealed that it is most closely related to MRP, cMOAT, and the yeast organic anion transporter YCF1. Although MOAT-B is closely related to these transporters, it is distinguished by the absence of a approximately 200 amino acid NH2-terminal hydrophobic extension that is present in MRP and cMOAT and which is predicted to encode several transmembrane spanning segments. In addition, the MOAT-B tissue distribution is distinct from MRP and cMOAT. In contrast to MRP, which is widely expressed in tissues, including liver, and cMOAT, the expression of which is largely restricted to liver, the MOAT-B transcript is widely expressed, with particularly high levels in prostate, but is barely detectable in liver. These data indicate that MOAT-B is a ubiquitously expressed transporter that is closely related to MRP and cMOAT and raise the possibility that it may be an organic anion pump relevant to cellular detoxification.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

A survey of human serum samples for antibody against Clostridium perfringens type A enterotoxin in humans in Korea.

Serum samples from humans in Chongju City, Korea, were tested for the presence of Clostridium perfringens enterotoxin antibody by enzyme linked immunosorbent assay (ELISA). About half of the 1054 samples tested had high ELISA readings, which could be the result of exposure to enterotoxin produced by C. perfringens. The high prevalence of the antibody among the Korean population suggests that foodborne illnesses caused by C. perfringens may be common in Korea even though the occurrence has not been monitored.

Adolescent↗
PubMed1998

Structure of an aromatic-ring-hydroxylating dioxygenase-naphthalene 1,2-dioxygenase.

BACKGROUND: Pseudomonas sp. NCIB 9816-4 utilizes a multicomponent enzyme system to oxidize naphthalene to (+)-cis-(1R,2S)-dihydroxy-1,2-dihydronaphthalene. The enzyme component catalyzing this reaction, naphthalene 1,2-dioxygenase (NDO), belongs to a family of aromatic-ring-hydroxylating dioxygenases that oxidize aromatic hydrocarbons and related compounds to cis-arene diols. These enzymes utilize a mononuclear non-heme iron center to catalyze the addition of dioxygen to their respective substrates. The present study was conducted to provide essential structural information necessary for elucidating the mechanism of action of NDO. RESULTS: The three-dimensional structure of NDO has been determined at 2.25 A resolution. The molecule is an alpha 3 beta 3 hexamer. The alpha subunit has a beta-sheet domain that contains a Rieske [2Fe-2S] center and a catalytic domain that has a novel fold dominated by an antiparallel nine-stranded beta-pleated sheet against which helices pack. The active site contains a non-heme ferrous ion coordinated by His208, His213, Asp362 (bidentate) and a water molecule. Asn201 is positioned further away, 3.75 A, at the missing axial position of an octahedron. In the Rieske [2Fe-2S] center, one iron is coordinated by Cys81 and Cys101 and the other by His83 and His104. CONCLUSIONS: The domain structure and iron coordination of the Rieske domain is very similar to that of the cytochrome bc1 domain. The active-site iron center of one of the alpha subunits is directly connected by hydrogen bonds through a single amino acid, Asp205, to the Rieske [2Fe-2S] center in a neighboring alpha subunit. This is likely to be the main route for electron transfer.

Amino Acid Sequence↗
PubMed1998

In vivo regulation of cyclin A/Cdc2 and cyclin B/Cdc2 through meiotic and early cleavage cycles in starfish.

In starfish, fertilization occurs naturally at late meiosis I. In the absence of fertilization, however, oocytes complete meiosis I and II, resulting in mature eggs arrested at the pronucleus stage, which are still fertilizable. In this study, we isolated cDNAs of starfish cyclin A and Cdc2, and monitored extensively the cell cycle dynamics of cyclin A and cyclin B levels and their associated Cdc2 kinase activity, Tyr phosphorylation of Cdc2, and Cdc25 phosphorylation states throughout meiotic and early embryonic cleavage cycles in vivo. In meiosis I, cyclin A was undetectable and cyclin B/Cdc2 alone exhibited histone H1 kinase activity, while thereafter both cyclin A/Cdc2 and cyclin B/Cdc2 kinase activity oscillated along with the cell cycle. Cyclin B-, but not cyclin A-, associated Cdc2 was subjected to regulation via Tyr phosphorylation, and phosphorylation states of Cdc25 correlated with cyclin B/Cdc2 kinase activity with some exceptions. Between meiosis I and II and at the pronucleus stage, cyclin A and B levels remained low, Cdc2 Tyr phosphorylation was undetectable, and Cdc25 remained phosphorylated depending on MAP kinase activity, showing a good correlation between these two stages. Upon fertilization of mature eggs, Cdc2 Tyr phosphorylation reappeared and Cdc25 was dephosphorylated. In the first cleavage cycle, under conditions which prevented Cdc25 activity, cyclin A/Cdc2 was activated with a normal time course and then cyclin B/Cdc2 was activated with a significant delay, resulting in the delayed completion of M-phase. Thus, in contrast to meiosis I, both cyclin A and cyclin B appear to be involved in the embryonic cleavage cycles. We propose that regulation of cyclin A/Cdc2 and cyclin B/Cdc2 is characteristic of meiotic and early cleavage cycles.

Amino Acid Sequence↗
PubMed1998

The desmoplastic small round cell tumor t(11;22) translocation produces EWS/WT1 isoforms with differing oncogenic properties.

Structural alterations of the Wilms' tumor locus (WT1) at 11p13 have been implicated in the etiology of two human cancers--Wilms' tumor (WT), a pediatric renal malignancy, and Desmoplastic Small Round Cell Tumor (DSRCT), an aggressive cancer of the abdominal serosal lining with predilection for male adolescents. Germline mutations within the WT1 tumor suppressor gene predispose to WT and are associated with congenital malformations of the urogenital system, and somatic mutations are associated with initiation of transformation in WTs. In DSRCT, a recurrent translocation, t(11;22)(p13;q12), fuses the amino terminal domain of the EWS1 gene product to three of the four WT1 zinc fingers. Two EWS/WT1 isoforms are generated as a result of an alternative splicing event between zinc fingers III and IV, inserting or removing three amino acids (+/- KTS). We demonstrate that introduction of EWS/WT1(-KTS) into NIH3T3 cells causes their tumorigenic transformation as determined by: formation of transformed foci on a monolayer of cells; anchorage-independent growth; and tumor formation in nude mice. EWS/WT1(+KTS) showed no transforming potential in these assays. These results indicate the oncogenic effect of the t(11;22) translocation is mediated by the EWS/WT1(-KTS) isoform and that fusion of the EWS amino terminal domain to the WT1 DNA binding domain produces a chimeric product showing a gain of function.

3T3 Cells↗
PubMed1998

A randomized trial of vascular hemostasis techniques to reduce femoral vascular complications after coronary intervention.

This report details a prospectively randomized clinical trial comparing mechanical clamp compression to hand applied pressure for attaining vascular hemostasis after coronary intervention. Effectiveness was determined by comparing the incidence of femoral vascular complications resulting from each of the 2 techniques. Eligible participants included 778 consecutive patients scheduled for percutaneous coronary intervention over an 8-month period. An unselected cohort of the eligible patients (n = 592), determined by the availability of cross-trained clinicians, underwent follow-up serial physical examinations by blinded observers for the duration of their hospital stay. A second, similarly determined cohort (n = 390), underwent color-duplex ultrasonography within 24 hours of sheath removal. Baseline demographic and clinical characteristics, sheath removal parameters, and subsequent outcomes were collected prospectively. The primary end point was a composite of ultrasound-defined femoral vascular complications: femoral artery thrombosis, echogenic hematoma, pseudoaneurysm, or arteriovenous fistulae formation. Complications diagnosed by physical examination constituted the second fundamental end point and included: persistent oozing, ecchymosis, hematoma, bruit, and pulsatile mass. Compared to manual compression, mechanical clamp hemostasis reduced the primary adverse end point by 63% (p = 0.041). Physical examination detected ecchymosis, oozing, and hematomas at equally high frequencies in the two cohorts. Although 65% of the patients in both treatment groups encountered at least one of these cosmetic complications, the diagnoses made by physical examination did not correlate with ultrasound-defined pathology. Multivariable stepwise logistic regression analysis identified a relationship of advanced age and lower body weight to vascular complications. Utilization of a mechanical clamp rather than conventional hand pressure to attain vascular hemostasis significantly reduces ultrasound-defined femoral vascular pathology. Discrepancies between physical examination and ultrasound diagnoses challenge the utility of clinical assessment alone and establish ultrasound as the diagnostic modality of choice.

Angioplasty, Balloon, Coronary↗
PubMed1998

Solid phase synthesis of benzylamine-derived sulfonamide library.

Using solid phase synthesis, a library has been constructed of benzylamine-derived sulfonamides which have strong inhibitory activity against the blood coagulant thrombin. The library compounds were obtained in good yield and high purity; four of these thrombin inhibitors showed nanomolar potency (Ki 600-10 nM).

Anticoagulants↗
PubMed1998

Shaping the future of global health cooperation: where can we go from here?

A review of recent studies and initiatives on global health cooperation groups their findings into ten key reform issues. In addressing these issues, policy makers need to improve their understanding of what is meant by the shift from international to global health. Attention must also be paid to the fundamental question of what we want from a system of global health cooperation. Three main views currently exist on what priority activities such a system should pursue-traditionalist, essentialist, and social justice. Reconciliation of these views can then be followed by consideration of the structural features of a global health organisation for the 21st century. Achievement of the above will require a reform process that is more broadly participatory, well-informed, and coherent in purpose and direction.

Global Health↗
PubMed1998

Discovery of LB30057, a benzamidrazone-based selective oral thrombin inhibitor.

Systematic variation of the so-called P-pocket moiety of benzamidrazone-based selective thrombin inhibitors led to the discovery of LB30057. It is potent (Ki = 0.38 nM for human thrombin), selective (Ki = 3290 nM for bovine trypsin), and orally bioavailable (58% oral bioavailability in dogs). LB30057 was efficacious in thrombosis animal models.

Animals↗