Biomedical subjects

Cheng-Han Huang

Publications and source records attributed to Cheng-Han Huang.

6 recordsLinked to original sources

PubMed2006

Dusty protein kinases: primary structure, gene evolution, tissue specific expression and unique features of the catalytic domain.

Ser/Thr- and Tyr-Protein kinases constitute a key switch underlying the dynamic nature and graded regulation of signal transduction and pathway activities in cellular organization. Here we describe the identification and characterization of Dusty, a single-copy gene that arose in metazoan evolution and encodes a putative dual Ser/Thr and Tyr protein kinase with unique structural features. Dusty is widely expressed in vertebrates, broadly distributed in the central nervous system, and deregulated in certain human cancers. Confocal imaging of transiently expressed human Dusty-GFP fusion proteins showed a cytoplasmic distribution. Dusty proteins from lower to higher species display an increasing degree of sequence conservation from the N-terminal non-catalytic domain to C-terminal catalytic domain. The non-catalytic region has eight conserved cysteine residues, multiple potential kinase-docking motifs and phosphorylation sites, whereas the catalytic domain is divergent and about equally distant of Ser/Thr and Tyr protein kinases. Homology analyses identified the essential catalytic residues, suggesting that Dusty homologues all possess the enzymatic activity of a protein kinase. Taken together, Dusty is a unique evolutionarily selected group of divergent protein kinases that may play important functional roles in the brain and other tissues of vertebrates.

Amino Acid Sequence↗

PubMed2006

CeRh1 (rhr-1) is a dominant Rhesus gene essential for embryonic development and hypodermal function in Caenorhabditis elegans.

Rhesus (Rh) proteins share a conserved 12-transmembrane topology and specify a family of putative CO(2) channels found in diverse species from microbes to human, but their functional essentiality and physiological importance in metazoans is unknown. To address this key issue and analyze Rh-engaged physiologic processes, we sought to explore model organisms with fewer Rh genes yet are tractable to genetic manipulations. In this article, we describe the identification in nematodes of two Rh homologues that are highly conserved and similar to human Rh glycoproteins, and we focus on their characterization in Caenorhabditis elegans. RNA analysis revealed that CeRh1 is abundantly expressed in all developmental stages, with highest levels in adults, whereas CeRh2 shows a differential and much lower expression pattern. In transient expression in human cells, both CeRh1 and CeRh2-GFP fusion proteins were routed to the plasma membrane. Transgenic analysis with GFP or LacZ-fusion reporters showed that CeRh1 is mainly expressed in hypodermal tissue, although it is also in other cell types. Mutagenesis analysis using deletion constructs mapped a minimal promoter region driving CeRh1 gene expression. Although CeRh2 was dispensable, RNA interference with CeRh1 caused a lethal phenotype mainly affecting late stages of C. elegans embryonic development, which could be rescued by the CbRh1 homologue from the worm Caenorhabditis briggsae. Taken together, our data provide direct evidence for the essentiality of the CeRh1 gene in C. elegans, establishing a useful animal model for investigating CO(2) channel function by cross-species complementation.

Amino Acid Sequence↗

PubMed2005

Evolutionary conservation and diversification of Rh family genes and proteins.

Rhesus (Rh) proteins were first identified in human erythroid cells and recently in other tissues. Like ammonia transporter (Amt) proteins, their only homologues, Rh proteins have the 12 transmembrane-spanning segments characteristic of transporters. Many think Rh and Amt proteins transport the same substrate, NH(3)/NH(4)(+), whereas others think that Rh proteins transport CO(2) and Amt proteins NH(3). In the latter view, Rh and Amt are different biological gas channels. To reconstruct the phylogeny of the Rh family and study its coexistence with and relationship to Amt in depth, we analyzed 111 Rh genes and 260 Amt genes. Although Rh and Amt are found together in organisms as diverse as unicellular eukaryotes and sea squirts, Rh genes apparently arose later, because they are rare in prokaryotes. However, Rh genes are prominent in vertebrates, in which Amt genes disappear. In organisms with both types of genes, Rh had apparently diverged away from Amt rapidly and then evolved slowly over a long period. Functionally divergent amino acid sites are clustered in transmembrane segments and around the gas-conducting lumen recently identified in Escherichia coli AmtB, in agreement with Rh proteins having new substrate specificity. Despite gene duplications and mutations, the Rh paralogous groups all have apparently been subject to strong purifying selection indicating functional conservation. Genes encoding the classical Rh proteins in mammalian red cells show higher nucleotide substitution rates at nonsynonymous codon positions than other Rh genes, a finding that suggests a possible role for these proteins in red cell morphogenetic evolution.

Amino Acid Sequence↗

PubMed2005

Magmas gene structure and evolution.

Magmas is a nuclear encoded protein found in the mitochondria of mammalian cells. It participates in granulocyte-macrophage-colony stimulating factor (GM-CSF) signaling in hematopoietic cells and has an essential role in invertebrate development. In order to characterize the protein structural features and gene evolution of Magmas, a dataset containing 61 Magmas homologs from 52 species distributed among animals, plants and fungi was analyzed. All Magmas members were found to possess three novel sequence motifs in addition to a conserved leader peptide. Phylogenetic tree and dN/dS rate ratios showed that Magmas was evolutionarily conserved. Analysis of Magmas gene organization demonstrated incremental intron acquisition in plants and vertebrates. Significant genetic diversity in Magmas was observed from kingdom specific amino acid signatures, the presence of predicted signal peptides that target the protein to other intracellular locations besides the mitochondria, and the detection of multiple isoforms in higher animals. These studies demonstrate that Magmas members constitute an important family of conserved proteins having multifunctional activities, and provide a basis for future experiments.

Alternative Splicing↗

PubMed2003

Mutations in GYPB exon 5 drive the S-s-U+(var) phenotype in persons of African descent: implications for transfusion.

BACKGROUND: The S-s-U- phenotype in African Americans is due to a GYPB deletion, however the molecular basis for the S-s-U+var phenotype is poorly understood. Variable reactivity of S-s-U+var RBCs with monoclonal anti-He or by anti-U has been demonstrated, however the underlying molecular bases for this phenotype remain to be established. STUDY DESIGN AND METHODS: Hemagglutination was performed on 104 S-s- blood samples using monoclonal anti-He and anti-U. GYPB was sequenced from selected samples. Allele and exon-specific PCR analysis was used to identify wild-type and mutant alleles. RESULTS: The RBCs of 49-percent S-s- samples were identified as S-s-U+var by hemagglutination. Sequencing analysis of 41 samples revealed 1) a point mutation at +5 (g > t) of intron 5 that resulted in skipping of exon 5 in 34 samples; 2) two mutations (208G > T and 230C > T) caused partial skipping of exon 5 in four samples due to activation of a cryptic 3' splice site that resulted from a C > G transversion at nt251 present in all GYPB*S alleles and most GYPB*s alleles tested. Three samples were heterozygous for the mutated alleles. DISCUSSION: The S-s-U+var phenotype arises from changes in or around GYPB exon 5. The weak expression of U and in most examples, He, may be due to low levels of normal transcription of the variant gene or to posttranscriptional down regulation.

Black or African American↗

PubMed2002

Rhesus expression in a green alga is regulated by CO(2).

The function of the Rhesus (Rh) complex in the human red cell membrane has been unknown for six decades. Based on the organismal, organ, and tissue distribution of Rh proteins, and on our evidence that their only known paralogues, the ammonium and methylammonium transport proteins (also called methylammonium permeases), are gas channels for NH(3), we recently speculated that Rh proteins are biological gas channels for CO(2). Like NH(3), CO(2) differs from other gases in being readily hydrated. We have now tested our speculation by studying expression of the RH1 gene in the photosynthetic microbe Chlamydomonas reinhardtii. Expression of RH1 was high for cells grown in air supplemented with 3% CO(2) or shifted from air to high CO(2) (3%) for 3 h. Conversely, RH1 expression was low for cells grown in air (0.035% CO(2)) or shifted from high CO(2) to air for 3 h. These results make viable the hypothesis that Rh1 and Rh proteins generally are gas channels for CO(2).

Amino Acid Sequence↗