51
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Rajaram S, Sedensky MM, Morgan PG. Unc-1: a stomatin homologue controls sensitivity to volatile anesthetics in Caenorhabditis elegans. Proc Natl Acad Sci U S A 1998; 95:8761-6. [PMID: 9671752 PMCID: PMC21150 DOI: 10.1073/pnas.95.15.8761] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
To identify sites of action of volatile anesthetics, we are studying genes in a functional pathway that controls sensitivity to volatile anesthetics in the nematode Caenorhabditis elegans. The unc-1 gene occupies a central position in this pathway. Different alleles of unc-1 have unique effects on sensitivity to the different volatile anesthetics. UNC-1 shows extensive homology to human stomatin, an integral membrane protein thought to regulate an associated ion channel. We postulate that UNC-1 has a direct effect on anesthetic sensitivity in C. elegans and may represent a molecular target for volatile anesthetics.
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Affiliation(s)
- S Rajaram
- Departments of Anesthesiology and Genetics, University Hospitals, Case Western Reserve University, Cleveland, OH 44106, USA
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52
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Snyers L, Umlauf E, Prohaska R. Oligomeric nature of the integral membrane protein stomatin. J Biol Chem 1998; 273:17221-6. [PMID: 9642292 DOI: 10.1074/jbc.273.27.17221] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The 31-kDa integral membrane protein stomatin (protein 7.2b) is not only an important component of the red cell membrane but can also be found in abundance in different tissues and cell lines. The protein is thought to be anchored to the membrane by a hydrophobic domain while both N and C termini are exposed to the cytoplasm. We have previously shown in the human cell line UAC that stomatin concentrates preferentially in plasma membrane folds and protrusions. There is also evidence that stomatin is linked to the cortical actin cytoskeleton, suggesting a role in cortical morphogenesis of the cell. In this study, we demonstrate that the fundamental structure of stomatin is oligomeric. Whereas interaction of stomatin with itself was suggested by cross-linking experiments, we show by density gradient centrifugation analysis that soluble homo-oligomeric complexes of this protein are present in Triton X-100 extracts of UAC cells. We also show the existence of these oligomers by co-immunoprecipitation of the endogenous stomatin and a recombinantly expressed myc-tagged stomatin, using an anti-myc antibody. The data indicate that these complexes comprise between 9 and 12 monomers of stomatin. Two C-terminally truncated forms of stomatin do not incorporate into these oligomers, suggesting an involvement of the C terminus in the homo-oligomeric interaction.
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Affiliation(s)
- L Snyers
- Institute of Biochemistry, University of Vienna, Vienna Biocenter, A-1030 Vienna, Austria
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53
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Mayer H, Salzer U, Breuss J, Ziegler S, Marchler-Bauer A, Prohaska R. Isolation, molecular characterization, and tissue-specific expression of a novel putative G protein-coupled receptor. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1395:301-8. [PMID: 9512664 DOI: 10.1016/s0167-4781(97)00178-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We isolated a 40 kDa integral membrane protein (p40) from human erythrocyte ghosts by affinity chromatography, using a C-terminal peptide of stomatin, and obtained partial sequences which enabled us to isolate two full-length cDNAs from human bone marrow and fetal brain cDNA libraries. The cDNA sequences were identical and encoded a novel putative G protein-coupled receptor (399 amino acids). Northern and RNA dot blot analyses demonstrated that the major 4.8 kb-transcript is predominantly expressed in brain. In situ hybridization studies of tissue sections revealed high expression in neurons of the brain and spinal cord, in thymocytes, megakaryocytes, and macrophages.
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Affiliation(s)
- H Mayer
- Institute of Biochemistry, University of Vienna, Austria
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54
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Abstract
Mechanosensation, the transduction of mechanical forces into a cellular electrochemical signal, enables living organisms to detect touch; vibrations, such as sound; accelerations, including gravity; body movements; and changes in cellular volume and shape. Ion channels directly activated by mechanical tension are thought to mediate mechanosensation in many systems. Only one channel has been cloned that is unequivocably mechanically gated: the MscL channel in bacteria. Genetic screens for touch-insensitive nematodes or flies promise to identify the proteins that constitute a mechanosensory apparatus in eukaryotes. In Caenorhabditis elegans, the mec genes thus identified encode molecules for a candidate structure, which includes a "degenerin" channel tethered to specialized extracellular and intracellular structural proteins. In hair cells of the inner ear, evidence suggests that an extracellular tip link pulls on a channel, which attached intracellularly to actin via a tension-regulating myosin 1beta. The channel and the tip link have not been cloned. Because degenerins and MscL homologs have not been found outside of nematodes and prokaryotes, respectively, and because intracellular and extracellular accessory structures apparently differ among organs and species, it may be that mechanosensory channel complexes evolved multiple times.
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Affiliation(s)
- J Garcia-Anoveros
- Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston 02114, USA
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55
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Tavernarakis N, Driscoll M. Molecular modeling of mechanotransduction in the nematode Caenorhabditis elegans. Annu Rev Physiol 1997; 59:659-89. [PMID: 9074782 DOI: 10.1146/annurev.physiol.59.1.659] [Citation(s) in RCA: 200] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Genetic and molecular studies of touch avoidance in the nematode Caenorhabditis elegans have resulted in a molecular model for a mechanotransducing complex. mec-4 and mec-10 encode proteins hypothesized to be subunits of a mechanically gated ion channel that are related to subunits of the vertebrate amiloride-sensitive epithelial Na+ channel. Products of mec-5, a novel collagen, and mec-9, a protein that includes multiple Kunitz-type protease inhibitor repeats and EGF repeats, may interact with the channel in the extracellular matrix. Inside the cell, specialized 15-protofilament microtubules composed of mec-12 alpha-tubulin and mec-7 beta-tubulin may be linked to the mechanosensitive channel by stomatin-homologous MEC-2. MEC-4 and MEC-10 are members of a large family of C. elegans proteins, the degenerins. Two other degenerins, UNC-8 and DEL-1, are candidate components of a stretch-sensitive channel in motor neurons. Implications for advancing understanding of mechanotransduction in other systems are discussed.
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Affiliation(s)
- N Tavernarakis
- Department of Molecular Biology and Biochemistry, Rutgers University, New Brunswick, New Jersey 08855, USA
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56
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Schlegel W, Unfried I, Prohaska R. Cloning and analysis of a cDNA encoding the BALB/c murine erythrocyte band 7 integral membrane protein. Gene 1996; 178:115-8. [PMID: 8921901 DOI: 10.1016/0378-1119(96)00347-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
cDNA clones encoding the BALB/c murine erythrocyte band 7 integral membrane protein (also termed protein 7.2b, or 'stomatin') were isolated by the screening of a corresponding bone-marrow lambda gt11 cDNA library with a human cDNA probe, and by 5'-RACE PCR cloning. Comparison of the murine, human and Caenorhabditis elegans protein 7.2b amino acid (aa) sequences revealed overall identities of 88% (human) and 61% (C. elegans), with the N-terminal domains showing only little similarity. The 7.2b protein sequences of the two mouse strains, BALB/c and C57BL/6J (B6), showed six rather conservative aa substitutions, three of them in the hydrophobic domain. The BALB/c murine mRNA, about 3.5 kb in size, is widely expressed in various tissues, most notably in spleen, lung and testis.
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Affiliation(s)
- W Schlegel
- Institute of Biochemistry, University of Vienna, Austria
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57
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Gu G, Caldwell GA, Chalfie M. Genetic interactions affecting touch sensitivity in Caenorhabditis elegans. Proc Natl Acad Sci U S A 1996; 93:6577-82. [PMID: 8692859 PMCID: PMC39067 DOI: 10.1073/pnas.93.13.6577] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
At least 13 genes (mec-1, mec-2, mec-4-10, mec-12, mec-14, mec-15, and mec-18) are needed for the response to gentle touch by 6 touch receptor neurons in the nematode Caenorhabditis elegans. Several, otherwise recessive alleles of some of these genes act as dominant enhancer mutations of temperature-sensitive alleles of mec-4, mec-5, mec-6, mec-12, and mec-15. Screens for additional dominant enhancers of mec-4 and mec-5 yielded mutations in previously known genes. In addition, some mec-7 alleles showed allele-specific, dominant suppression of the mec-15 touch-insensitive (Mec) phenotype. The dominant enhancement and suppression exhibited by these mutations suggest that the products of several touch genes interact. These results are consistent with a model, supported by the known sequences of these genes, that almost all of the touch function genes contribute to the mechanosensory apparatus.
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Affiliation(s)
- G Gu
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
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58
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Huang M, Gu G, Ferguson EL, Chalfie M. A stomatin-like protein necessary for mechanosensation in C. elegans. Nature 1995; 378:292-5. [PMID: 7477350 DOI: 10.1038/378292a0] [Citation(s) in RCA: 218] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The mec-2 gene is required for the function of a set of six touch receptor neurons in the nematode Caenorhabditis elegans; mec-2 mutants, which are touch-insensitive, have touch cells that appear morphologically normal. Gene interaction studies suggest that mec-2 positively regulates the activity of the putative mechanosensory transduction channel (and the present paper), comprised in part of proteins encoded by the two degenerin genes mec-4 and mec-10 The central region of the mec-2 protein (MEC-2) is very similar to stomatin, an integral membrane protein (band 7.2b) in human red blood cells that is thought to regulate cation conductance. MEC-2-LacZ fusions are distributed along the touch receptor axons. This axonal distribution, which is mediated by the mec-2-specific amino terminus, is disrupted by mutations in mec-12, an alpha-tubulin gene needed for touch cell function. Our results indicate that MEC-2 links the mechanosensory channel and the microtubule cytoskeleton of the touch receptor neurons. Such linkage provides the basis for a mechanism of mechanosensation whereby microtubule displacement leads to channel opening.
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Affiliation(s)
- M Huang
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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59
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Gallagher PG, Forget BG. Structure, organization, and expression of the human band 7.2b gene, a candidate gene for hereditary hydrocytosis. J Biol Chem 1995; 270:26358-63. [PMID: 7592848 DOI: 10.1074/jbc.270.44.26358] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Band 7.2b is an integral membrane phosphoprotein absent from the erythrocyte membranes of patients with hereditary hydrocytosis, a hemolytic anemia inherited in an autosomal dominant fashion and characterized by stomatocytic red blood cells with abnormal permeability to Na+ and K+. The precise role of band 7.2b is unknown, but it may interact with other proteins of the junctional complex of the membrane skeleton. To gain additional insight into the structure and function of this protein and to provide the necessary tools for further genetic studies of hydrocytosis patients, we determined the sequence of the full-length human band 7.2b cDNA, characterized the genomic structure of the band 7.2b gene, studied its pattern of expression in different tissues, and characterized the promoter of the gene. The composite band 7.2b gene cDNA was 3047 base pairs in length. Northern blot analysis revealed a wide tissue distribution of expression of the band 7.2b gene, with utilization of alternative polyadenylation signals generating transcripts of 2.2 and 3.1 kilobases. Cloning of the band 7.2b chromosomal gene revealed that it is composed of seven exons distributed over 40 kilobases of DNA. The band 7.2b gene promoter was identified as a TATA-less, (G+C)-rich promoter with a typical InR recognition sequence and a single transcription initiation site. It directed high level expression of a reporter gene in both erythroid and nonerythroid cells. An imperfect simple sequence repeat polymorphism was identified in the 5'-flanking DNA, and an assay was developed for its analysis by PCR.
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MESH Headings
- 3T3 Cells
- Amino Acid Sequence
- Anemia, Hemolytic/blood
- Anemia, Hemolytic/genetics
- Animals
- Base Sequence
- Blood Proteins/biosynthesis
- Blood Proteins/genetics
- Blotting, Northern
- Cell Line
- Consensus Sequence
- DNA Primers
- DNA, Complementary
- Exons
- Gene Expression
- Genetic Variation
- Hominidae/genetics
- Humans
- Introns
- Leukemia, Erythroblastic, Acute
- Membrane Proteins/genetics
- Mice
- Molecular Sequence Data
- Polymerase Chain Reaction
- Polymorphism, Genetic
- Promoter Regions, Genetic
- RNA, Messenger/analysis
- RNA, Messenger/biosynthesis
- Recombinant Fusion Proteins/biosynthesis
- Regulatory Sequences, Nucleic Acid
- Restriction Mapping
- Transfection
- Tumor Cells, Cultured
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Affiliation(s)
- P G Gallagher
- Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut 06520-8021, USA
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60
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MESH Headings
- Adaptation, Physiological
- Amino Acid Sequence
- Anemia, Dyserythropoietic, Congenital/genetics
- Anemia, Hemolytic, Congenital/blood
- Anemia, Hemolytic, Congenital/classification
- Anemia, Hemolytic, Congenital/genetics
- Animals
- Base Sequence
- Blood Group Antigens/genetics
- Blood Proteins/chemistry
- Blood Proteins/genetics
- Blood Proteins/metabolism
- Disease Models, Animal
- Elliptocytosis, Hereditary/genetics
- Erythrocyte Membrane/metabolism
- Erythrocyte Membrane/ultrastructure
- Erythrocytes, Abnormal/metabolism
- Hemoglobinuria, Paroxysmal/genetics
- Humans
- Immunity, Innate
- Malaria
- Membrane Lipids/blood
- Membrane Proteins/blood
- Membrane Proteins/chemistry
- Membrane Proteins/genetics
- Molecular Sequence Data
- Spherocytosis, Hereditary/genetics
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Affiliation(s)
- J Delaunay
- CNRS URA 1171, Institut Pasteur de Lyon, France
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