Biomedical subjects

B Rudy

Publications and source records attributed to B Rudy.

At least 55 records · Page 3Linked to original sources

PubMed1996

NADPH-oxidase and a hydrogen peroxide-sensitive K+ channel may function as an oxygen sensor complex in airway chemoreceptors and small cell lung carcinoma cell lines.

Pulmonary neuroepithelial bodies (NEB) are widely distributed throughout the airway mucosa of human and animal lungs. Based on the observation that NEB cells have a candidate oxygen sensor enzyme complex (NADPH oxidase) and an oxygen-sensitive K+ current, it has been suggested that NEB may function as airway chemoreceptors. Here we report that mRNAs for both the hydrogen peroxide sensitive voltage gated potassium channel subunit (KH2O2) KV3.3a and membrane components of NADPH oxidase (gp91phox and p22phox) are coexpressed in the NEB cells of fetal rabbit and neonatal human lungs. Using a microfluorometry and dihydrorhodamine 123 as a probe to assess H2O2 generation, NEB cells exhibited oxidase activity under basal conditions. The oxidase in NEB cells was significantly stimulated by exposure to phorbol esther (0.1 microM) and inhibited by diphenyliodonium (5 microM). Studies using whole-cell voltage clamp showed that the K+ current of cultured fetal rabbit NEB cells exhibited inactivating properties similar to KV3.3a transcripts expressed in Xenopus oocyte model. Exposure of NEB cells to hydrogen peroxide (H2O2, the dismuted by-product of the oxidase) under normoxia resulted in an increase of the outward K+ current indicating that H2O2 could be the transmitter modulating the O2-sensitive K+ channel. Expressed mRNAs or corresponding protein products for the NADPH oxidase membrane cytochrome b as well as mRNA encoding KV3.3a were identified in small cell lung carcinoma cell lines. The studies presented here provide strong evidence for an oxidase-O2 sensitive potassium channel molecular complex operating as an O2 sensor in NEB cells, which function as chemoreceptors in airways and in NEB related tumors. Such a complex may represent an evolutionary conserved biochemical link for a membrane bound O2-signaling mechanism proposed for other cells and life forms.

Animals↗

PubMed1996

G-protein-gated inward rectifier K+ channel proteins (GIRK1) are present in the soma and dendrites as well as in nerve terminals of specific neurons in the brain.

G-protein-gated inward rectifier potassium (GIRK) channels are coupled to numerous neurotransmitter receptors in the brain and can play important roles in modulating neuronal function, depending on their localization in a given neuron. Site-directed antibodies to the extreme C terminus of GIRK1 (or KGA1), a recently cloned component of GIRK channels, have been used to determine the relative expression levels and distribution of the protein in different regions of the rat brain by immunoblot and immunohistochemical techniques. We report that the GIRK1 protein is expressed prominently in the olfactory bulb, hippocampus, dentate gyrus, neocortex, thalamus, cerebellar cortex, and several brain stem nuclei. In addition to the expected localization in somas and dendrites, where GIRK channels may mediate postsynaptic inhibition, GIRK1 proteins were also found in axons and their terminal fields, suggesting that GIRK channels can also modulate presynaptic events. Furthermore, the distribution of the protein to either somatodendritic or axonal-terminal regions of neurons varied in different brain regions, which would imply distinct functions of these channels in different neuronal populations. Particularly prominent staining of the cortical barrels of layer IV of the neocortex, and the absence of this staining with unilateral kainate lesions of the thalamus, suggest that the GIRK1 protein is expressed in thalamocortical nerve terminals in which GIRK channels may mediate the actions of mu opiate receptors.

Amino Acid Sequence↗

PubMed1996

Specific interaction of (R)-3-hydroxybutyrate dehydrogenase with membrane phosphatidylcholine as studied by ESR spectroscopy in oriented phospholipid multibilayers: coenzyme binding enhances the interaction with phosphatidylcholine.

The interaction of phospholipid with (R)-3-hydroxybutyrate dehydrogenase, a phosphatidylcholine-requiring membrane enzyme, has been studied using ESR spectroscopy of spin-labeled lipids, both as ordered multibilayers and in lipid vesicle suspensions (liposomes). Partially oriented phospholipid multibilayers were prepared from lipid vesicles composed of a 1:1 mixture of phosphatidylcholine (PC) and phosphatidylethanolamine (PE). Vesicles containing (R)-3-hydroxybutyrate dehydrogenase yielded active preparations of the enzyme in such multibilayers. With increasing protein/lipid ratio, the order of the multibilayers was disrupted as monitored by ESR spectroscopy with a spin-labeled analogue of PC, 5-doxyl-PC (5 mol %, 10% of total PC) as a probe. The outer peak separation of 5-doxyl-PC varied with the lipid/protein ratio. The lower the ratio, the larger was the separation, with higher activity enzyme being more effective in exerting this effect. When 5-doxylstearic acid was substituted for 5-doxyl-PC or when the enzyme was inactive, the 2A(zz) value stayed practically constant at its lower limit (about 54 G). Multilayers composed of 81% PE, 11% diphosphatidylglycerol (DPG), and 8% 5-doxyl-PC (no unlabeled PC present) gave similar results. With this lipid mixture, the maximal 2A(zz) value (about 61 G) was reached at lower protein/lipid ratios, although the enzymic activity of (R)-3-hydroxybutyrate dehydrogenase is reduced to 40% in this system. The outer peak separation also depended on the presence of the coenzyme, NAD+, and 2-methylmalonate. The latter enhances binding of NAD+ about 100-fold by forming a ternary complex. With this ternary complex, the 2A(zz) values were increased unless the maximal values had been reached already in the absence of coenzyme. In all these experiments only a single ESR spectral component was observed. Similar results were obtained for the enzyme in liposomes, although the effect was less pronounced apparently due to the higher mobility of the probe. It is concluded that PC is motionally restricted by (R)-3-hydroxybutyrate dehydrogenase and yet is in rapid exchange with the bulk lipid on the ESR time scale. PC is required for formation of tight and functional complexes with NAD [Rudy et al. (1989) Biochemistry 28, 5354-5366], and such complexes strengthen the interaction of the enzyme with PC.

Animals↗

PubMed1996

Developmental expression and functional characterization of the potassium-channel subunit Kv3.1b in parvalbumin-containing interneurons of the rat hippocampus.

The expression of the voltage-gated K(+)-channel subunit Kv3.1b in the developing hippocampus was determined by immunoblot and immunohistochemical techniques. Kv3.1b protein was detected first at postnatal day (P) 8. The Kv3.1b-immunopositive cell number per tissue section reached a maximum at P14 and was maintained through P40. In contrast, the Kv3.1b protein content of isolated membrane vesicles in immunoblots progressively increased through P40, suggesting an increase in Kv3.1b content per cell throughout this time period. Kv3.1b protein was expressed selectively in the somata, proximal dendrites, and axons of cells lying within or near the pyramidal cell layer, consistent with their being GABAergic inhibitory interneurons. Kv3.1b was present in approximately 80% of parvalbumin-positive interneurons. The developmental onset of Kv3.1b and parvalbumin immunoreactivity was identical. In contrast, Kv3.1b was mostly absent from the subset of somatostatin-positive inhibitory interneurons. Electrophysiological recordings were made from stratum pyramidale interneurons in which morphology and Kv3.1b-positive immunoreactivity were confirmed post hoc. Outward currents had voltage-dependent and biophysical properties resembling those of channels formed by Kv3.1b. The current blocked by low concentrations of 4-aminopyridine (4-AP) showed marked inactivation, suggesting that Kv3.1b may coassemble with other members of the Kv3 subfamily. In current-clamp recordings, concentrations of 4-AP that blocked the current through Kv3.1b channels allowed us tentatively to assign a role to Kv3.1b-containing channels in action-potential repolarization. These data demonstrate that Kv3.1b is regulated developmentally in a specific subpopulation of hippocampal interneurons and that channels containing this subunit may be a major determinant in imparting "fast-spiking" characteristics to these and other cells throughout the central nervous system containing the Kv3.1b subunit.

Action Potentials↗

PubMed1996

Cloning of a novel component of A-type K+ channels operating at subthreshold potentials with unique expression in heart and brain.

1. Proteins of the Kv4 or Shal-related subfamily are key components of transient K+ channels (A channels) operating at subthreshold values of the membrane potential. We have cloned and characterized a new mammalian Kv4 or Shal-related cDNA (Kv4.3) that predicts a protein with strong sequence conservation with the other known members of this subfamily. 2. Injection of Kv4.3 transcripts into Xenopus oocytes generates an A type K+ current, with small but physiologically significant differences from the currents expressed by Kv4.2 and Kv4.1 mRNAs. Kv4.3 currents can be modified to resemble native A currents by coinjection with a low molecular weight mRNA fraction from rat brain which does not express detectable currents on its own. Particularly striking is a 7-to-10-fold increase in the rate of recovery from inactivation, a 5- to 10-fold increase in current magnitude and a 3- to 4-fold increase in sensitivity to 4-amino pyridine (4-AP). 3. In situ hybridization histochemistry was used to compare the expression of the three known Kv4 genes. Kv4.2 and Kv4.3 (but not Kv4.1) are abundant in the adult rat brain, with each displaying a specific, but sometimes overlapping pattern of expression. Moreover, a reciprocal gradient of expression of Kv4.2 and Kv4.3 transcripts is seen in some brain areas, such as in the pyramidal cell layers of the hippocampus and the granule cell layer of the cerebellum. Therefore Kv4 proteins may form heteromultimeric channels of distinct subunit composition in different neurons. Moreover, the results suggest that neurons such as pyramidal cells in the hippocampus and granule cells in the cerebellum represent heterogeneous cell populations in terms of their ISA, and hence in their firing patterns. Kv4.2 and Kv4.3 also display complementary expression in the heart, with Kv4.3 being more abundant in atria and Kv4.2 in ventricle. The existence of multiple Kv4 proteins forming channels of variable subunit combinations helps explain the diversity of ISA channels in neurons.

Amino Acid Sequence↗

PubMed1996

Heterologous desensitization of the human endothelin A and neurokinin A receptors in Xenopus laevis oocytes.

Endothelin 1 (ET1) desensitizes endothelin A receptor for 90-110 min while neurokinin A (NKA) desensitizes neurokinin A receptor for 25-35 min in Xenopus laevis oocytes. In the present study, endothelin A receptor and neurokinin A receptor were coexpressed in Xenopus laevis oocytes in an effort to characterize heterologous desensitization of the receptors that activate phospholipase C-beta. ET1 desensitizes both the endothelin A receptor and the neurokinin A receptor for 90-110 min, whereas stimulation with NKA desensitizes the same two receptors for only 25-35 min. Homologous and heterologous desensitization experiments were also carried out with endothelin 3 (ET3), a ligand that exhibits lower affinity to the endothelin A receptor and a quicker dissociation rate than ET1. ET3 was unable to desensitize endothelin A receptor and the neurokinin A receptor; this is in contrast to ET1 that desensitizes both receptors. These results suggests that the receptors that undergo homologous desensitization are able to heterologously desensitize other receptors that activate PLC-beta. Furthermore, the agonist-specific dissociation constant dictates the extent of desensitization and time of recovery of the receptor-mediated response.

Amino Acid Sequence↗

PubMed1995

Protein tyrosine kinase PYK2 involved in Ca(2+)-induced regulation of ion channel and MAP kinase functions.

The protein tyrosine kinase PYK2, which is highly expressed in the central nervous system, is rapidly phosphorylated on tyrosine residues in response to various stimuli that elevate the intracellular calcium concentration, as well as by protein kinase C activation. Activation of PYK2 leads to modulation of ion channel function and activation of the MAP kinase signalling pathway. PYK2 activation may provide a mechanism for a variety of short- and long-term calcium-dependent signalling events in the nervous system.

3T3 Cells↗

PubMed1995

Alternative splicing of the human Shaker K+ channel beta 1 gene and functional expression of the beta 2 gene product.

Mammalian voltage-activated Shaker K+ channels associate with at least three cytoplasmic proteins: Kv beta 1, Kv beta 2 and Kv beta 3. These beta subunits contain variable N-termini, which can modulate the inactivation of Shaker alpha subunits, but are homologous throughout an aldo-keto reductase core. Human and ferret beta 3 proteins are identical with rat beta 1 throughout the core while beta 2 proteins are not; beta 2 also contains a shorter N-terminus and has no reported physiological role. We report that human beta 1 and beta 3 are derived from the same gene and that beta 2 modulates the inactivation properties of Kv1.4 alpha subunits.

Alternative Splicing↗

PubMed1995

Thalamocortical projections have a K+ channel that is phosphorylated and modulated by cAMP-dependent protein kinase.

The finding that some K+ channel mRNAs are restricted to certain populations of neurons in the CNS suggests that there are K+ channels tailored to certain neuronal circuits. One such example are the transcripts from the KV3.2 gene, the majority of which are expressed in thalamic relay neurons. To gain insights into the specific roles of KV3.2 subunits, site specific antibodies were raised to determine their localization in thalamic relay neurons. Immunohistochemical and focal lesioning studies demonstrate that KV3.2 proteins are localized to the terminal fields of thalamocortical projections. It is also shown that KV3.2 channels expressed in vitro are strongly inhibited through phosphorylation by cAMP-dependent protein kinase (PKA). Channels containing KV3.1 subunits, which otherwise exhibit nearly identical electrophysiological properties in heterologous expression systems but have a different and less restricted pattern of expression in the CNS, are not affected by PKA. Therefore, this modulation might be associated with the specific roles of KV3.2 subunits. Furthermore, we demonstrate that KV3.2 proteins can be phosphorylated in situ by intrinsic PKA. KV3.2 subunits display properties and have a localization consistent with a role in the regulation of the efficacy of the thalamocortical synapse, and could thereby participate in the neurotransmitter-mediated control of functional states of the thalamocortical system associated with global states of awareness.

Amino Acid Sequence↗

PubMed1995

The potassium channel subunit KV3.1b is localized to somatic and axonal membranes of specific populations of CNS neurons.

Potassium channels play major roles in the regulation of many aspects of neuronal excitability. These channels are particularly well suited for such multiplicity of roles since there is a large diversity of channel types. This diversity contributes to the ability of specific neurons (and possibly different regions of the same neuron) to respond uniquely to a given input. Neuronal integration depends on the local response of spatially segregated inputs to the cell and the communication of these integration centers with the axon. Therefore, the functional implications of a given set of K+ channels varies depending on their precise location on the neuronal surface. Site-specific antibodies were utilized to characterize the distribution of KV3.1b, a subunit of voltage-gated K+ channels in CNS neurons. KV3.1b subunits are expressed in specific neuronal populations of the rat brain, such as cerebellar granule cells, projecting neurons of deep cerebellar nuclei, the substantia nigra pars-reticulata, the globus pallidus, and the ventral thalamus (reticular thalamic nucleus, ventral lateral geniculate and zona incerta). The KV3.1b protein is also present in various neuronal populations involved in the processing of auditory signals, including the inferior colliculus, the nuclei of the lateral lemniscus, the superior olive, and some parts of the cochlear nuclei; as well as in several other neuronal groups in the brainstem (e.g., in the oculomotor nucleus, the pontine nuclei, the reticulotegmental nucleus of the pons, trigeminal and vestibular nuclei, and the reticular formation) and subsets of neurons in the neocortex, the hippocampus and the caudate-putamen shown by double staining to correspond to neurons containing parvalbumin. KV3.1b subunits are localized predominantly in somatic and axonal membranes (particularly in axonal terminal fields) but are much less prominent in dendritic arborizations. This distribution is different than that of other subunits of voltage gated K+ channels and is consistent with a role in the modulation of action potentials. KV3.1b proteins have a cellular and subcellular distribution different than the related KV3.2 subunits which express in Xenopus oocytes currents similar to those expressed by KV3.1b.

Amino Acid Sequence↗

PubMed1994

Clustering of six human 11p15 gene homologs within a 500-kb interval of proximal mouse chromosome 7.

Homologs of genes mapping to human chromosome 11p15 are located in three distinct, widely separated regions of mouse chromosome 7 (Mmu7). To date, six genes have been localized to the most proximal HSA11p15/Mmu7 homology region, including Ldh3 (encoding lactate dehydrogenase C), Ldh1 (lactate dehydrogenase A), Myod1 (myogenic differentiation factor-1), Tph (tryptophan hydroxylase), Saa1 (serum amyloid-A-1), and Kcnc1 (encoding a Shaw-type voltage-gated potassium channel). To define the overall size and organization of this region of Mmu7, we have established a long-range physical map including the murine Ldh1, Ldh3, Saa, Tph, Kcnc1, and Myod1 genes. Our results demonstrate that these six genes are physically clustered and are distributed throughout a 500-kb interval located just proximal of the pink-eyed dilution (p) locus. These data, together with recent mapping studies within the related region of HSA11p15, demonstrate that gene content and organization within this proximal homology segment have been highly conserved throughout evolution.

Animals↗

PubMed1994

Response to hepatitis B immunization by infants exposed to HIV.

OBJECTIVE: To assess the antibody response to hepatitis B immunization in HIV-infected and uninfected infants. DESIGN: Cohort, comparing hepatitis B surface-antibody responses of HIV-infected infants with HIV-exposed but uninfected infants. SETTING: Urban children's hospital outpatient clinic for families with HIV-infected members. INTERVENTION: All infants received hepatitis B vaccine according to the American Academy of Pediatrics and Centers for Disease Control and Prevention recommended schedule. RESULTS: Forty-one HIV-exposed or infected infants were immunized with hepatitis B vaccine in the first year of life. Twenty-two out of 24 (92%) HIV-exposed but uninfected infants demonstrated an antibody response to hepatitis B immunization, compared with six out of 17 (35%) HIV-infected infants (P < 0.0005). CD4 percentage and CD4 counts were significantly lower in the HIV-infected infants than in the uninfected infants, but there was no significant difference in CD4 count or percentage between HIV-infected responders and nonresponders. CONCLUSION: The humoral immune response to hepatitis B immunization, administered before 12 months of age, is significantly reduced in HIV-infected children and is independent of CD4 count. Given the large number of infants born each year to pregnant women coinfected with HIV and hepatitis B, further studies to assess the efficacy of increased doses of antigen and variations in the dosage schedule are urgently needed.

CD4 Lymphocyte Count↗

PubMed1994

Identification of molecular components of A-type channels activating at subthreshold potentials.

1. Xenopus oocytes injected with rat brain mRNA express a transient K+ current similar to the A current that activates transiently near the threshold for Na+ action potential generation (ISA) seen in somatic recordings from neurons. We used hybrid arrest with antisense oligonucleotides to investigate which of the cloned K+ channel proteins might be components of the channels responsible for the ISA expressed from brain mRNA. An oligonucleotide complementary to a sequence common to all known mammalian Shal-related mRNAs [KV4.1, KV4.2, and KV4.3 (the nomenclature of Sh K+ channel genes of Chandy and colleagues was used in this paper)] blocked the expression of the ISA. An oligonucleotide complementary only to the KV4.2 mRNA, the most abundant Shal-related transcript in rat brain RNA preparations, was also quite efficient in arresting the expression of the ISA from brain. These experiments indicate that Shal-related proteins are important components of the channels carrying the ISA expressed in oocytes injected with brain mRNA. However, there are several significant differences between this ISA and the currents expressed in the same oocytes by in vitro transcribed KV4.1 or KV4.2 cRNA. Most of these differences are eliminated if KV4.1 or KV4.2 cRNA is coinjected with brain poly-(A) RNA treated with antisense oligonucleotides which arrest the expression of the ISA, or with a 2-4Kb rat brain poly-(A) RNA fraction which does not express detectable K+ currents under the same recording conditions. These data support the hypothesis that ISA channels such as those expressed from brain mRNA contain Shal proteins that can be modified by proteins encoded in RNAs that by themselves do not express K+ currents.

Animals↗

PubMed1994

Differential expression of Shaw-related K+ channels in the rat central nervous system.

The family of mammalian genes related to the Drosophila Shaker gene, consisting of four subfamilies, is thought to encode subunits of tetrameric voltage-gated K+ channels. There is compelling evidence that subunits of the same subfamily, but not of different subfamilies, form heteromultimeric channels in vitro, and thus, each gene subfamily is postulated to encode components of an independent channel system. In order to identify cells with native channels containing subunits of one of these subfamilies (Shaw-related or ShIII), the cellular distribution of ShIII transcripts was examined by Northern blot analysis and in situ hybridization. Three of four ShIII genes (KV3.1, KV3.2, and KV3.3) are expressed mainly in the CNS. KV3.4 transcripts are also present in the CNS but are more abundant in skeletal muscle. In situ hybridization studies in the CNS reveal discrete and specific neuronal populations that prominently express ShIII mRNAs, both in projecting and in local circuit neurons. In the cerebral cortex, hippocampus, and caudate-putamen, subsets of neurons can be distinguished by the expression of specific ShIII mRNAs. Each ShIII gene exhibits a unique pattern of expression; however, many neuronal populations expressing KV3.1 transcripts also express KV3.3 mRNAs. Furthermore, KV3.4 transcripts are present, albeit at lower levels, in several of the neuronal populations that also express KV3.1 and/or KV3.3 mRNAs, revealing a high potential for heteromultimer formation between the products of three of the four genes. Expression of ShIII cRNAs in Xenopus oocytes was used to explore the functional consequences of heteromultimer formation between ShIII subunits. Small amounts of KV3.4 cRNA, which expresses small, fast-inactivating currents when injected alone, produced fast-inactivating currents that are severalfold larger when coinjected with an excess of KV3.1 or KV3.3 cRNA. This amplification is due to both an increase in single-channel conductance in the heteromultimeric channels and the observation that less than four, perhaps even a single KV3.4 subunit is sufficient to impart fast-inactivating properties to the channel. The oocyte experiments indicate that the apparently limited, low-level expression of KV3.4 in the CNS is potentially significant. The anatomical studies suggest that heteromultimer formation between ShIII proteins might be a common feature in the CNS. Moreover, the possibility that the subunit composition of heteromultimers varies in different neurons should be considered, since the ratios of overlapping signals change from one neuronal population to another. In order to proceed with functional analysis of native ShIII channels, it is important to known which subunit compositions might occur in vivo. The studies presented here provide important clues for the identification of native homo- and heteromultimeric ShIII channels in neurons.

Animals↗

PubMed1994

Pulmonary veno-occlusive disease. Another vascular disorder associated with human immunodeficiency virus infection?

A variety of arterial lesions in both pulmonary and systemic circulations have been described in association with human immunodeficiency virus infection. Such lesions include plexogenic arteriopathy in patients with primary pulmonary hypertension and fibrocalcific arterial lesions described in a variety of organs. Lesions involving the pulmonary veins, however, have not been previously described. We report a case of pulmonary veno-occlusive disease in a 2-year-old child with human immunodeficiency virus infection. In view of the rarity of these vascular disorders, including pulmonary veno-occlusive disease, it seems unlikely for their association with human immunodeficiency virus infection to occur by chance alone. Further work is needed to elucidate the role that human immunodeficiency virus may have in the pathogenesis of such vascular lesions.

Child, Preschool↗

PubMed1993

Prolonged desensitization of the human endothelin A receptor in Xenopus oocytes. Comparative studies with the human neurokinin A receptor.

Human endothelin (ET) A receptor (hETAR) is a G-protein-mediated receptor that binds ET1 with high affinity and ET2 and ET3 with lower affinities. ET1 is the most potent endogenous vasoconstrictor known at this time. When expressed in Xenopus laevis oocytes, hETAR is rapidly desensitized after stimulation with ET1. This desensitization lasts 90-110 min. Human neurokinin A (hNKAR) and human serotonin type 2 receptors were also expressed in the Xenopus system for comparison to hETAR. hNKAR desensitizes for 25-35 min, while the serotonin receptor does not appear to desensitize. To examine the role of the cytoplasmic tail of hETAR in desensitization, deletion mutations were constructed which remove 11, 36, and 51 amino acids from the cytoplasmic tail. The mutations removing 11 and 36 residues were functional, but the mutation removing 51 amino acids was not functional. The two functional mutations have a resensitization time similar to that of hETAR. In summary, the prolonged desensitization time of hETAR is unique for G-protein-mediated receptors and may attenuate the adverse physiological effects of the endothelin family. In addition, the cytoplasmic tail of hETAR does not appear to play a role in desensitization or resensitization of this receptor.

Amino Acid Sequence↗

PubMed1993

Localization of a highly conserved human potassium channel gene (NGK2-KV4; KCNC1) to chromosome 11p15.

Several genes (the Shaker or Sh gene family) encoding components of voltage-gated K+ channels have been identified in various species. Based on sequence similarities Sh genes are classified into four groups or subfamilies. Mammalian genes of each one of these subfamilies also show high levels of sequence similarity to one of four related Drosophila genes: Shaker, Shab, Shaw, and Shal. Here we report the isolation of human cDNAs for a Shaw-related product (NGK2, KV3.1a) previously identified in rat and mice. A comparison of the nucleotide and deduced amino acid sequence of NGK2 in rodents and humans shows that this product is highly conserved in mammals; the human NGK2 protein shows over 99% amino acid sequence identity to its rodent homologue. The gene (NGK2-KV4; KCNC1) encoding NGK2 was mapped to human chromosome 11p15 by fluorescence in situ hybridization with the human NGK2 cDNAs.

Amino Acid Sequence↗

PubMed1993

Localization of Shaw-related K+ channel genes on mouse and human chromosomes.

Four related genes, Shaker, Shab, Shaw, and Shal, encode voltage-gated K+ channels in Drosophila. Multigene subfamilies corresponding to each of these Drosophila genes have been identified in rodents and primates; this suggests that the four genes are older than the common ancestor of present-day insects and mammals and that the expansion of each into a family occurred before the divergence of rodents and primates. In order to define these evolutionary relationships more precisely and to facilitate the search for mammalian candidate K+ channel gene mutations, we have mapped members of the Shaw-homologous gene family in humans and mice. Fluorescence in situ hybridization analysis of human metaphase chromosomes mapped KCNC2 (KShIIIA, KV3.2) and KCNC3 (KShIIID, KV3.3) to Chromosome (Chr) 19q13.3-q13.4. Inheritance patterns of DNA restriction fragment length variants in recombinant inbred strains of mice placed the homologous mouse genes on distal Chr 10 near Ms15-8 and Mdm-1. The mouse Kcnc1 (KShIIIB, NGK2-KV4, KV3.1) gene mapped to Chr7 near Tam-1. These results are consistent with the hypothesis that the generation of the mammalian KCNC gene family included both duplication events to generate family members in tandem arrays (KCNC2, KCNC3) and dispersion of family members to unlinked chromosomal sites (KCNC1). The KNCN2 and KCNC3 genes define a new synteny group between humans and mice.

Animals↗