Two-photon momentum density in La2-xSrxCuO4 and Nd2-xCexCuO4.
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Journal Article↗
Biomedical subjects
M Peter
Publications and source records attributed to M Peter.
Mitogen-activated protein kinases phosphorylate nuclear lamins and display sequence specificity overlapping that of mitotic protein kinase p34cdc2.
Members of the mitogen-activated protein (MAP) kinase family are implicated in mediating entry of cells into the cell cycle, as well as passage through meiotic M phase. These kinases have attracted much interest because their activation involves phosphorylation on both tyrosine and threonine residues, but little is known about their physiological targets. In this study, two distinct members of the MAP kinase family (p44mpk and p42mapk) are shown to phosphorylate chicken lamin B2 at a single site identified as Ser16. Moreover, these MAP kinases cause depolymerization of in-vitro-assembled longitudinal lamin head-to-tail polymers. Ser16 was previously shown to be phosphorylated during mitosis in vivo, and to be a target of the mitotic protein kinase p34cdc2 in vitro. Accordingly, lamins were proposed to be direct in vivo substrates of p34cdc2. This proposal is supported by quantitative analyses indicating that lamin B2, when assayed in vitro, is a substantially better substrate for p34cdc2 than for MAP kinases. Nevertheless, a physiological role of MAP kinases in lamin phosphorylation is not excluded. The observation that members of the MAP kinase family display sequence specificities overlapping that of p34cdc2 raises the possibility that some of the purported substrates of p34cdc2 may actually be physiological substrates of MAP kinases.
Animals↗
Cloning and characterization of the Ewing's sarcoma and peripheral neuroepithelioma t(11;22) translocation breakpoints.
Ewing's sarcoma (ES) and peripheral neuroepithelioma (PN) are related tumors, possibly of neural crest origin, which are cytogenetically characterized by the specific translocation t(11;22)(q24;q12). The cos5 locus, previously identified in the vicinity of the chromosome 22 breakpoint of this translocation, was shown by in situ hybridization on interphase nuclei to lie between VIIIF2 and LIF, two loci located on either side of the breakpoint and at a distance of less than 2,000 kb. The progressive expansion of this locus by chromosome walking led to the construction of a 300 kb contig, which finally crossed the breakpoint. The subsequent cloning of the two translocation junction fragments of a PN, followed by the molecular characterization of the translocation breakpoints of 20 ES and PN, showed that most chromosome 22 breakpoints are clustered within a small, 2 kb region. In contrast, the chromosome 11 breakpoints are scattered over a region of at least 40 kb. The translocation leads to the synthesis of chimeric transcript that links sequences from chromosomes 22 and 11. Finally, no evidence was found of any specific difference in the position of ES and PN translocation breakpoints.
Bone Neoplasms↗
Immunological characterization of avian MAP kinases: evidence for nuclear localization.
The subcellular distribution and regulation of MAP kinase isoforms in chicken hepatoma DU249 cells was investigated with antibodies directed against peptides patterned after sequences in the mitogen-activated protein (MAP) kinases, sea star p44mpk, and rat p44erk1. MonoQ chromatography of cytosol from these cells afforded the resolution of at least four peaks of myelin basic protein (MBP) phosphotransferase activity, but only one of these (peak II) was stimulated in extracts from phorbol ester-treated cells. A 40- to 41-kDa (p41) doublet on Western blots detected with three different MAP kinase antibodies was coincident with peak II, and it probably corresponded to the avian homolog of p42mapk/erk2. Immunofluorescent studies with DU249 cells and chicken embryo fibroblasts revealed that most of the cross-reactive protein with at least two different MAP kinase antibodies was distributed in the nucleus. Subcellular fractionation studies confirmed a predominantly nuclear localization for p41 MAP kinase. Nocodazole arrest of DU249 cells was exploited for the detection of an M-phase-activated MBP kinase that was resolved from p41 MAP kinase by phenyl-Superose chromatography. Western blotting analysis with antibodies for the cdc2-encoded protein kinase and p13suc1-agarose binding studies allowed positive identification of this MBP kinase as p34cdc2.
Amino Acid Sequence↗
Can "big" insulin-like growth factor II in serum of tumor patients account for the development of extrapancreatic tumor hypoglycemia?
The pathogenesis of extrapancreatic tumor hypoglycemia has been related to the secretion of big insulin-like growth factor (IGF) II by the tumor. In 25 of 28 patients with this type of hypoglycemia we found 1.5-8-fold elevated serum levels of immunoreactive big (15-25 kD), but decreased levels of normal IGF II. After removal of the tumor, big IGF II disappeared and normal IGF II increased. Tumors contained elevated levels of IGF II, 65-80% in the big form. The insulin-like bioactivity of big IGF II and its affinity towards IGF-binding proteins (IGFBP)-2 and -3 are similar to those of normal IGF II, but two- to threefold higher on a molar basis. Big IGF II is mainly bound to the 50-kD IGFBP complex. The latter contains approximately 10 times more of this peptide than in normal serum and displays three- to fourfold increased insulin-like bioactivity. The formation of the 150-kD IGFBP complex with 125I-recombinant human IGFBP-3 is impaired in tumor serum. This results in sequestration of IGFBP-3 and predominant association of big IGF II with IGFBP-2 and -3 in the 50-kD complex. Increased bioavailability of big IGF II in this complex due to unrestricted capillary passage and enhanced insulin bioactivity of this big IGF II pool provide a continuous increased insulin-like potential available to insulin and type 1 IGF receptors of insulin-sensitive tissues and thus may lead to sustained hypoglycemia.
Biological Availability↗
Isoprenylation of rab proteins on structurally distinct cysteine motifs.
rab proteins are low molecular weight GTP-binding proteins highly related to Ypt1p and Sec4p, which are involved in the control of secretion in yeast Saccharomyces cerevisiae. Morphological and biochemical studies have shown that rab proteins are membrane associated and are localized to specific subcompartments along the exocytic and endocytic pathway. Membrane association requires the presence of C-terminal cysteine residues. The present report indicates that the structurally distinct cysteine motifs of rab proteins are subjected to isoprenylation both in vitro and in vivo. Studies on deletion mutants suggest that an intact C-terminal end is required for the association of rab proteins with the membrane and is necessary for the post-translational modification. Finally, we show that the isoprenoid transferase which modifies rab termini is different from the enzyme which farnesylates nuclear lamins and ras proteins in vitro.
Amino Acid Sequence↗
Influence of different pressure gradients on late clinical outcome after aortic valve replacement.
Late outcome vs. hemodynamic parameters were assessed and compared in a series of 44 patients followed for 10-17 years after aortic valve replacement either with a Starr-Edwards A 1260 (SE) or a Bjork-Shiley 60 degrees (BS) prosthesis. The two groups, 22 patients each, were selected by computer from the data base SG as to be matched for age, sex, underlying lesion, date of implantation, valve size, left ventricular function, and concomitant coronary artery disease. There was no significant difference in mortality and complication rates. Clinical evaluation at a mean of 12.5 +/- 2.2 years postoperatively revealed identical findings of heart size on chest X-rays (CTR 0.50 +/- 0.04 SE vs. 0.50 +/- 0.05 BS) and nearly identical incidence of left ventricular hypertrophy on the ECG (2/22 SE and 1/22 BS). There was a statistically significant difference in Doppler ultrasonic peak pressure gradients between the two valve types (SE 32 +/- 15 mmHg, BS 23 +/- 9 mmHg; p = 0.047), and of fractional shortening on M-mode echocardiograms (SE 30 +/- 9%, BS 37 +/- 8%, p = 0.038), but this was not reflected by a difference in the symptomatic status of the two groups. It is concluded, that in two groups of patients surviving 10-17 years after isolated aortic valve replacement with SE or BS valves, the statistically significant nine mmHg difference in gradient across the two valve types had no effect on long-term clinical outcome.
Aortic Valve↗
[Hemodynamics of various heart valve prostheses].
Modern tilting disc and bileaflet prostheses, and bio-prostheses, perform similarly regarding pressure gradients, discharge coefficient and performance index; however, only bio-prostheses increase their opening area with increasing flow. Ball valve prostheses of the Starr-Edwards type perform less satisfactorily with higher pressure gradients and lower performance indices, which may result in less favorable long-term follow-up. Bio-prostheses show degenerative changes with increasing age which, over a period of 7-10 years, can lead to clinically relevant stenoses necessitating reoperation.
Bioprosthesis↗
Positron annihilation in a single crystal of CoSi2: Experiment and theory.
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Journal Article↗
Positron annihilation on single crystals of YBa2Cu3O7-x.
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Journal Article↗
Disassembly of in vitro formed lamin head-to-tail polymers by CDC2 kinase.
The nuclear lamina is an intermediate filament-type network underlying the inner nuclear membrane. At the onset of mitosis it depolymerizes, presumably in response to phosphorylation of the lamin proteins. Recently, cdc2 kinase, a major regulator of the eukaryotic cell cycle, was shown to induce lamina depolymerization when incubated with isolated nuclei. Here, we have analysed the structural consequences of lamin phosphorylation by cdc2 kinase using lamin head-to-tail polymers reconstituted in vitro from bacterially expressed chicken lamin B2 protein as a substrate. The effects of phosphorylation were monitored by both a pelleting assay and electron microscopy. We show that lamin B2 head-to-tail polymers disassemble in response to phosphorylation of specific sites that are phosphorylated also during mitosis in vivo. These sites are located within SP/TP motifs N- and C-terminal to the central alpha-helical rod domain of lamin proteins. Subsequent dephosphorylation of these sites by purified phosphatase 1 allows reformation of lamin head-to-tail polymers. The relative importance of N- and C-terminal phosphorylation sites for controlling the assembly state of nuclear lamins was assessed by mutational analysis. Polymers formed of lamin proteins carrying mutations in the C-terminal phosphoacceptor motif could still be disassembled by cdc2 kinase. In contrast, a single point mutation in the N-terminal site (Ser16----Ala) rendered head-to-tail polymers resistant to disassembly. These results emphasize the importance of the N-terminal end domain for lamin head-to-tail polymerization in vitro, and they demonstrate that phosphorylation-dephosphorylation is sufficient to control the longitudinal assembly of lamin B2 dimers.
Adenosine Triphosphate↗
Mapping of human chromosome 22 with a panel of somatic cell hybrids.
The adenylosuccinate lyase (ADSL) which is essential for generating adenylate, maps to the long arm of chromosome 22. By using a Chinese hamster ovary cell line deficient in ADSL activity, we have constructed a set of 17 somatic cell hybrids containing defined regions of human chromosome 22. This panel was extended with six additional hybrids, obtained in other laboratories using various methods of selection. Southern analysis of the hybrids with 38 chromosome 22 probes defined 14 different subregions which could be linearly organized on the long arm of chromosome 22. The order of the probes thus deduced is fully compatible with their previous localization and with the genetic map. The ADSL gene was further sublocalized between the MB and D22S22. This panel, which enables the rapid assignment of chromosome 22 single copy probes to small subregions, will be an important tool in the construction of a detailed physical map of this part of the genome.
Adenylosuccinate Lyase↗
p34cdc2 acts as a lamin kinase in fission yeast.
The nuclear lamina is an intermediate filament network that underlies the nuclear membrane in higher eukaryotic cells. During mitosis in higher eukaryotes, nuclear lamins are phosphorylated by a mitosis-specific kinase and this induces disassembly of the lamina structure. Recently, p34cdc2 protein kinase purified from starfish has been shown to induce phosphorylation of lamin proteins and disassembly of the nuclear lamina when incubated with isolated chick nuclei suggesting that p34cdc2 is likely to be the mitotic lamin kinase (Peter, M., J. Nakagawa, M. Dorée, J.C. Labbe, and E.A. Nigg. 1990b. Cell. 45:145-153). To confirm and extend these studies using genetic techniques, we have investigated the role of p34cdc2 in lamin phosphorylation in the fission yeast. As fission yeast lamins have not been identified, we have introduced a cDNA encoding the chicken lamin B2 protein into fission yeast. We report here that the chicken lamin B2 protein expressed in fission yeast is assembled into a structure that associates with the nucleus during interphase and becomes dispersed throughout the cytoplasm when cells enter mitosis. Mitotic reorganization correlates with phosphorylation of the chicken lamin B2 protein by a mitosis-specific yeast lamin kinase with similarities to the mitotic lamin kinase of higher eukaryotes. We show that a lamin kinase activity can be detected in cell-free yeast extracts and in p34cdc2 immunoprecipitates prepared from yeast cells arrested in mitosis. The fission yeast lamin kinase activity is temperature sensitive in extracts and immunoprecipitates prepared from strains bearing temperature-sensitive mutations in the cdc2 gene. These results in conjunction with the previously reported biochemical studies strongly suggest that disassembly of the nuclear lamina at mitosis in higher eukaryotic cells is a consequence of direct phosphorylation of nuclear lamins by p34cdc2.
Animals↗
Expression of chicken lamin B2 in Escherichia coli: characterization of its structure, assembly, and molecular interactions.
Chicken lamin B2, a nuclear member of the intermediate-type filament (IF) protein family, was expressed as a full-length protein in Escherichia coli. After purification, its structure and assembly properties were explored by EM, using both glycerol spraying/low-angle rotary metal shadowing and negative staining for preparation, as well as by analytical ultracentrifugation. At its first level of structural organization, lamin B2 formed "myosin-like" 3.1S dimers consisting of a 52-nm-long tail flanked at one end by two globular heads. These myosin-like molecules are interpreted to represent two lamin polypeptides interacting via their 45-kD central rod domains to form a segmented, parallel and unstaggered 52-nm-long two-stranded alpha-helical coiled-coil, and their COOH-terminal end domains folding into globular heads. At the second level of organization, lamin B2 dimers associated longitudinally to form polar head-to-tail polymers. This longitudinal mode of association of laminin dimers is in striking contrast to the lateral mode of association observed previously for cytoplasmic IF dimers. At the third level of organization, these polar head-to-tail polymers further associated laterally, in an approximately half-staggered fashion, to form filamentous and eventually paracrystal-like structures revealing a pronounced 24.5-nm axial repeat. Finally, following up on recent studies implicating the mitotic cdc2 kinase in the control of lamin polymerization (Peter, M., J. Nakagawa, M. Dorée, J. C. Labbé, and E. A. Nigg. 1990. Cell. 61:591-602), we have examined the effect of phosphorylation by purified cdc2 kinase on the assembly properties and molecular interactions of the bacterially expressed lamin B2. Phosphorylation of chicken lamin B2 by cdc2 kinase interferes with the head-to-tail polymerization of the lamin dimers. This finding supports the notion that cdc2 kinase plays a major, direct role in triggering mitotic disassembly of the nuclear lamina.
Animals↗
Vertebrate cdc2 kinase: its regulation by phosphorylation and its mitotic targets.
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Amino Acid Sequence↗
Ectopic expression of an A-type lamin does not interfere with differentiation of lamin A-negative embryonal carcinoma cells.
The nuclear lamina is an intermediate filament-type network underlying the inner nuclear membrane. It is believed to be important for nuclear envelope integrity and the organization of interphase chromatin. On the basis of biochemical properties and sequence criteria, vertebrate lamin proteins are classified as either A- or B-type. While B-type lamins are expressed in almost all cell types, no A-type lamins are present in early vertebrate embryos or undifferentiated embryonal carcinoma cell lines. Intriguingly, expression of A-type lamins occurs concomitant with cell differentiation and embryonic development. These findings have led to the hypothesis that A-type lamins might play a role in establishing or stabilizing cell-type specific differences in nuclear organization, which in turn might relate to the developmental potential of a cell. To test this hypothesis, we have stably expressed chicken lamin A in undifferentiated murine embryonal carcinoma (P19) cells, and examined the consequences of ectopic lamin A expression for the differentiation state and potential of these cells. Our results demonstrate that the P19 cells, although normally devoid of lamin A, properly incorporate and process chicken lamin A. Moreover, the stably transfected cell lines maintain the properties of undifferentiated cells, demonstrating that expression of lamin A does not directly induce differentiation. Conversely, when exposed to retinoic acid, an inducer of differentiation, lamin A-expressing P19 cells are able to differentiate normally. Taken together, our results suggest that unscheduled expression of A-type lamins is not sufficient to deregulate cell differentiation programs. The implications of these findings for the possible role for lamin A expression during development are discussed.
Animals↗
Improved test to identify heterozygotes for congenital adrenal hyperplasia without index case examination.
In an attempt to improve detection of heterozygote carriers of the gene for congenital adrenal hyperplasia (21-hydroxylase deficiency; CAH) 64 families with at least 1 affected member (72 homozygotes and 191 clinically healthy subjects) were studied by HLA genotyping and by the single-dose corticotropin stimulation test. Plasma samples were drawn immediately before corticotropin and 60 min after its injection, and they were analysed simultaneously for eight adrenal steroids by radioimmunoassay after extraction and automated gel chromatography. Heterozygosity was defined as the presence of one HLA haplotype in common with the affected relative. Of the various basal and corticotropin-stimulated steroid levels and their ratios, the ratio of 17-hydroxyprogesterone to 11-deoxycorticosterone after corticotropin had the greatest power to discriminate between heterozygotes and normal relatives; that ratio was significantly higher in the heterozygotes (n = 116) than in the normal relatives (n = 75) and there was no overlap between the groups (range 12.2-214 vs 1.2-11.9). Thus, it is possible to detect all CAH heterozygotes without examining the index case by means of specific steroid analysis.
17-alpha-Hydroxyprogesterone↗
In vitro disassembly of the nuclear lamina and M phase-specific phosphorylation of lamins by cdc2 kinase.
The nuclear lamina is an intermediate filament-type network underlying the inner nuclear membrane. Phosphorylation of lamin proteins is believed to cause lamina disassembly during meiotic and mitotic M phase, but the M phase-specific lamin kinase has not been identified. Here we show that the cdc2 kinase, a major element implicated in controlling the eukaryotic cell cycle, phosphorylates chicken B-type lamins in vitro on sites that are specifically phosphorylated during M phase in vivo. Concomitantly, cdc2 kinase is capable of inducing lamina depolymerization upon incubation with isolated nuclei. One of the target sites of cdc2 kinase is identified as a motif (SPTR) conserved in the N-terminal domain of all lamin proteins. These results lead us to propose that mitotic disassembly of the nuclear lamina results from direct phosphorylation of lamins by cdc2 kinase.
Amino Acid Sequence↗