| 20674546 |
COPI-mediated retrograde trafficking from the Golgi to the ER regulates EGFR nuclear transport |
10.1016/j.bbrc.2010.07.096. |
Biochem Biophys Res Commun |
COPI-mediated retrograde trafficking from the Golgi to the ER regulates EGFR nuclear transport
Abstract
- Emerging evidence indicates that cell surface receptors, such as the entire epidermal growth factor receptor (EGFR) family, have been shown to localize in the nucleus. A retrograde route from the Golgi to the endoplasmic reticulum (ER) is postulated to be involved in the EGFR trafficking to the nucleus; however, the molecular mechanism in this proposed model remains unexplored. Here, we demonstrate that membrane-embedded vesicular trafficking is involved in the nuclear transport of EGFR. Confocal immunofluorescence reveals that in response to EGF, a portion of EGFR redistributes to the Golgi and the ER, where its NH(2)-terminus resides within the lumen of Golgi/ER and COOH-terminus is exposed to the cytoplasm. Blockage of the Golgi-to-ER retrograde trafficking by brefeldin A or dominant mutants of the small GTPase ADP-ribosylation factor, which both resulted in the disassembly of the coat protein complex I (COPI) coat to the Golgi, inhibit EGFR transport to the ER and the nucleus. We further find that EGF-dependent nuclear transport of EGFR is regulated by retrograde trafficking from the Golgi to the ER involving an association of EGFR with gamma-COP, one of the subunits of the COPI coatomer. Our findings experimentally provide a comprehensive pathway that nuclear transport of EGFR is regulated by COPI-mediated vesicular trafficking from the Golgi to the ER, and may serve as a general mechanism in regulating the nuclear transport of other cell surface receptors.
|
| 20675137 |
Proline isosteres in a series of 2,4-disubstituted pyrrolo[1,2-f][1,2,4]triazine inhibitors of IGF-1R kinase and IR kinase |
10.1016/j.bmcl.2010.07.045. |
Bioorg Med Chem Lett |
Proline isosteres in a series of 2,4-disubstituted pyrrolo[1,2-f][1,2,4]triazine inhibitors of IGF-1R kinase and IR kinase
Abstract
- Pyrrolidine, pyrrolidinone, carbocyclic, and acyclic groups were used as isosteric proline replacements in a series of insulin-like growth factor I receptor kinase/insulin receptor kinase inhibitors. Examples that were similar in potency to proline-containing reference compounds were shown to project a key fluoropyridine amide into a common space, while less potent compounds were not able to do so for reasons of stereochemistry or structural rigidity.
|
| 20691407 |
Haploinsufficiency of HDAC4 causes brachydactyly mental retardation syndrome, with brachydactyly type E, developmental delays, and behavioral problems. |
10.1016/j.ajhg.2010.07.011 |
Am. J. Hum. Genet. |
Haploinsufficiency of HDAC4 causes brachydactyly mental retardation syndrome, with brachydactyly type E, developmental delays, and behavioral problems.
Abstract
- Brachydactyly mental retardation syndrome (BDMR) is associated with a deletion involving chromosome 2q37. BDMR presents with a range of features, including intellectual disabilities, developmental delays, behavioral abnormalities, sleep disturbance, craniofacial and skeletal abnormalities (including brachydactyly type E), and autism spectrum disorder. To date, only large deletions of 2q37 have been reported, making delineation of a critical region and subsequent identification of candidate genes difficult. We present clinical and molecular analysis of six individuals with overlapping deletions involving 2q37.3 that refine the critical region, reducing the candidate genes from >20 to a single gene, histone deacetylase 4 (HDAC4). Driven by the distinct hand and foot anomalies and similar cognitive features, we identified other cases with clinical findings consistent with BDMR but without a 2q37 deletion, and sequencing of HDAC4 identified de novo mutations, including one intragenic deletion probably disrupting normal splicing and one intragenic insertion that
Results in a frameshift and premature stop codon. HDAC4 is a histone deacetylase that regulates genes important in bone, muscle, neurological, and cardiac development. Reportedly, Hdac4(-/-) mice have severe bone malformations resulting from premature ossification of developing bones. Data presented here show that deletion or mutation of HDAC4
Results in reduced expression of RAI1, which causes Smith-Magenis syndrome when haploinsufficient, providing a link to the overlapping findings in these disorders. Considering the known molecular function of HDAC4 and the mouse knockout phenotype, taken together with deletion or mutation of HDAC4 in multiple subjects with BDMR, we conclude that haploinsufficiency of HDAC4
Results in brachydactyly mental retardation syndrome.
|
| 20702409 |
Tyrosine phosphorylation of integrin beta3 regulates kindlin-2 binding and integrin activation |
10.1074/jbc.C110.134247. |
J Biol Chem |
Tyrosine phosphorylation of integrin beta3 regulates kindlin-2 binding and integrin activation
Abstract
- Kindlins are essential for integrin activation in cell systems and do so by working in a cooperative fashion with talin via their direct interaction with integrin β cytoplasmic tails (CTs). Kindlins interact with the membrane-distal NxxY motif, which is distinct from the talin-binding site within the membrane-proximal NxxY motif. The Tyr residues in both motifs can be phosphorylated, and it has been suggested that this modification of the membrane-proximal NxxY motif negatively regulates interaction with the talin head domain. However, the influence of Tyr phosphorylation of the membrane-distal NxxY motif on kindlin binding is unknown. Using mutational analyses and phosphorylated peptides, we show that phosphorylation of the membrane-distal NITY(759) motif in the β(3) CT disrupts kindlin-2 recognition. Phosphorylation of this membrane-distal Tyr also disables the ability of kindlin-2 to coactivate the integrin. In direct binding studies, peptides corresponding to the non-phosphorylated β(3) CT interacted well with kindlin-2, whereas the Tyr(759)-phosphorylated peptide failed to bind kindlin-2 with measurable affinity. These observations indicate that transitions between the phosphorylated and non-phosphorylated states of the integrin β(3) CT determine reactivity with kindlin-2 and govern the role of kindlin-2 in regulating integrin activation.
|
| 20704304 |
Cytotoxic halogenated macrolides and modified peptides from the apratoxin-producing marine cyanobacterium Lyngbya bouillonii from Guam |
10.1021/np1004032. |
J Nat Prod |
Cytotoxic halogenated macrolides and modified peptides from the apratoxin-producing marine cyanobacterium Lyngbya bouillonii from Guam
Abstract
- Collections of the marine cyanobacterium Lyngbya bouillonii from shallow patch reefs in Apra Harbor, Guam, afforded three hitherto undescribed analogues of the glycosidic macrolide lyngbyaloside, namely, 2-epi-lyngbyaloside (1) and the regioisomeric 18E- and 18Z-lyngbyalosides C (2 and 3). Concurrently we discovered two new analogues of the cytoskeletal actin-disrupting lyngbyabellins, 27-deoxylyngbyabellin A (4) and lyngbyabellin J (5), a novel macrolide of the laingolide family, laingolide B (6), and a linear modified peptide, lyngbyapeptin D (7), along with known lyngbyabellins A and B, lyngbyapeptin A, and lyngbyaloside. The structures of 1-7 were elucidated by a combination of NMR spectroscopic and mass spectrometric analysis. Compounds 1-6 were either brominated (1-3) or chlorinated (4-6), consistent with halogenation being a hallmark of many marine natural products. All extracts derived from these L. bouillonii collections were highly cytotoxic due to the presence of apratoxin A or apratoxin C. Compounds 1-5 showed weak to moderate cytotoxicity to HT29 colorectal adenocarcinoma and HeLa cervical carcinoma cells.
|
| 20715250 |
Backbone dynamics of cyclotide MCoTI-I free and complexed with trypsin |
10.1002/anie.201002906. |
Angew Chem Int Ed Engl |
Backbone dynamics of cyclotide MCoTI-I free and complexed with trypsin
Abstract
|
| 20732855 |
cDNA cloning of conotoxins with framework XII from several Conus species |
10.1093/abbs/gmq066. |
Acta Biochim Biophys Sin (Shanghai) |
cDNA cloning of conotoxins with framework XII from several Conus species
Abstract
- In our efforts for cloning novel I(2)-superfamily conotoxins using the signal peptide sequence, we identified a novel conotoxin Lt12.4 from Conus litteratus. This gene has a framework XII (-C-C-C-C-CC-C-C-), which is distinct from the cysteine pattern I(2)-superfamily conotoxin (-C-C-CC-CC-C-C-). Subsequently, we found the signal peptide sequence of Lt12.4 by 5'-RACE. Using this new sequence, we identified another five novel conotoxins with this cysteine pattern from four Conus species (Conus eburneus, Conus imperialis, Conus marmoreus, and C. litteratus). These novel conotoxins have the same cysteine pattern as the reported Gla-TxX and Gla-MII, and may contain Gla residues. Furthermore, they have the highly conserved signal peptide and hypervariable mature peptide sequences, and widely exist in Conus species. Therefore, it could be defined as a new superfamily of E-conotoxins.
|
| 20801649 |
Parallel synthesis and anti-inflammatory activity of cyclic peptides cyclosquamosin D and Met-cherimolacyclopeptide B and their analogs |
10.1016/j.bmcl.2010.08.033. |
Bioorg Med Chem Lett |
Parallel synthesis and anti-inflammatory activity of cyclic peptides cyclosquamosin D and Met-cherimolacyclopeptide B and their analogs
Abstract
- We report the parallel synthesis of two natural cyclopeptides, isolated from the seeds of Annona squamosa, cyclosquamosin D (A1), and Met-cherimolacyclopeptide B (B) and their analogs. All of the compounds were screened for anti-inflammatory activity by evaluating their inhibitory effects on the production of pro-inflammatory cytokines using the lipopolysaccharide stimulated macrophage J774A.1 cell line. Compounds having significant anti-inflammatory activity in suppressing the secretion of IL-6 and TNF-α have been identified, some of which exhibit activity superior to that observed with the natural products.
|
| 20837704 |
Structural evidence for loose linkage between ligand binding and kinase activation in the epidermal growth factor receptor |
10.1128/MCB.00742-10. |
Mol Cell Biol |
Structural evidence for loose linkage between ligand binding and kinase activation in the epidermal growth factor receptor
Abstract
- The mechanisms by which signals are transmitted across the plasma membrane to regulate signaling are largely unknown for receptors with single-pass transmembrane domains such as the epidermal growth factor receptor (EGFR). A crystal structure of the extracellular domain of EGFR dimerized by epidermal growth factor (EGF) reveals the extended, rod-like domain IV and a small, hydrophobic domain IV interface compatible with flexibility. The crystal structure and disulfide cross-linking suggest that the 7-residue linker between the extracellular and transmembrane domains is flexible. Disulfide cross-linking of the transmembrane domain shows that EGF stimulates only moderate association in the first two α-helical turns, in contrast to association throughout the membrane over five α-helical turns in glycophorin A and integrin. Furthermore, systematic mutagenesis to leucine and phenylalanine suggests that no specific transmembrane interfaces are required for EGFR kinase activation. These results suggest that linkage between ligand-induced dimerization and tyrosine kinase activation is much looser than was previously envisioned.
|
| 20845912 |
Palmyrolide A, an unusually stabilized neuroactive macrolide from Palmyra Atoll cyanobacteria |
10.1021/ol101752n. |
Org Lett |
Palmyrolide A, an unusually stabilized neuroactive macrolide from Palmyra Atoll cyanobacteria
Abstract
- Palmyrolide A (1) is a new neuroactive macrolide isolated from a marine cyanobacterial assemblage composed of Leptolyngbya cf. and Oscillatoria spp. collected from Palmyra Atoll. It features a rare N-methyl enamide and an intriguing t-butyl branch; the latter renders the adjacent lactone ester bond resistant to hydrolysis. Consistent with its significant suppression of calcium influx in cerebrocortical neurons (IC(50) = 3.70 μM), palmyrolide A (1) showed a relatively potent sodium channel blocking activity in neuro-2a cells (IC(50) = 5.2 μM), without appreciable cytotoxicity.
|
| 20848010 |
Revisiting the Kinnel-Scheuer hypothesis for the biosynthesis of palau'amine |
10.1039/c0cc02214d. |
Chem Commun (Camb) |
Revisiting the Kinnel-Scheuer hypothesis for the biosynthesis of palau'amine
Abstract
- We propose herein an alternative biosynthetic pathway for palau'amine in order to resolve the stereochemical issue from the original Kinnel-Scheuer hypothesis. Furthermore, we use this revised hypothesis as a guide toward the laboratory synthesis of palau'amine.
|
| 20854656 |
Molecular characterization of tlyA gene product, Rv1694 of Mycobacterium tuberculosis: a non-conventional hemolysin and a ribosomal RNA methyl transferase. |
10.1186/1471-2091-11-35 |
BMC Biochem. |
Molecular characterization of tlyA gene product, Rv1694 of Mycobacterium tuberculosis: a non-conventional hemolysin and a ribosomal RNA methyl transferase.
Abstract
- Background: Mycobacterium tuberculosis is a virulent bacillus causing tuberculosis, a disease responsible for million deaths each year worldwide. In order to understand its mechanism of pathogenesis in humans and to help control tuberculosis, functions of numerous Mycobacterium tuberculosis genes are being characterized. In this study we report the dual functionality of tlyA gene product of Mycobacterium tuberculosis annotated as Rv1694, a 268 amino acid long basic protein.
Results: The recombinant purified Rv1694 protein was found to exhibit hemolytic activity in vitro. It showed concentration and time-dependent hemolysis of rabbit and human erythrocytes. Multiple oligomeric forms (dimers to heptamers) of this protein were seen on the membranes of the lysed erythrocytes. Like the oligomers of conventional, well-known, pore-forming toxins, the oligomers of Rv1694 were found to be resistant to heat and SDS, but were susceptible to reducing agents like β-mercaptoethanol as it had abolished the hemolytic activity of Rv1694 indicating the role of disulfide bond(s). The Rv1694 generated de novo by in vitro transcription and translation also exhibited unambiguous hemolysis confirming the self assembly and oligomerization properties of this protein. Limited proteolytic digestion of this protein has revealed that the amino terminus is susceptible while in solution but is protected in presence of membrane. Striking feature of Rv1694 is its presence on the cell wall of E. coli as visualized by confocal microscopy. The surface expression is consistent with the contact dependent haemolytic ability of E. coli expressing this protein. Also, immune serum specific to this protein inhibits the contact dependent hemolysis. Moreover, Rv1694 protein binds to and forms stable oligomers on the macrophage phagosomal membranes. In addition to all these properties, E. coli expressing Rv1694 was found to be susceptible to the antibiotic capreomycin as its growth was significantly slower than mock vector transformed E. coli. The S30 extract of E. coli expressing the Rv1694 had poor translational activity in presence of capreomycin, further confirming its methylation activity. Finally, incorporation of methyl group of [3H]-S-adenosylmethionine in isolated ribosomes also confirmed its methylation activity. Conclusions: The Rv1694 has an unusual dual activity. It appears to contain two diverse functions such as haemolytic activity and ribosomal RNA methylation activity. It is possible that the haemolytic activity might be relevant to intra-cellular compartments such as phagosomes rather than cell lysis of erythrocytes and the self-assembly trait may have a potential role after successful entry into macrophages by Mycobacterium tuberculosis.
|
| 20864147 |
The cyclopentapeptide plactin enhances cellular binding and autoactivation of the serine protease plasma hyaluronan-binding protein |
10.1016/j.thromres.2010.08.016. |
Thromb Res |
The cyclopentapeptide plactin enhances cellular binding and autoactivation of the serine protease plasma hyaluronan-binding protein
Abstract
- Plactin, a family of cyclopentapeptides of fungal origin, enhances fibrinolytic activity by promoting of single-chain urokinase-type plasminogen activator (scu-PA) activation on the cell surface. For this activity, factor(s) in the blood plasma is absolutely required. In the previous studies, we identified prothrombin as a plasma cofactor involved in this mechanism, while the presence of another independent cofactor was suggested. The objective of this study was to identify the second cofactor and investigate the mechanism involved. Using plactin-affinity and ion-exchange chromatographies, we purified plasma hyaluronan-binding protein (PHBP) ~4,000-fold from human plasma as an independent plactin cofactor. PHBP, at ~10nM, was effective in plactin-dependent promotion of scu-PA activation by U937 cells. PHBP is a serine protease that is produced as a single-chain proenzyme (pro-PHBP) and autoproteolytically converted to an active two-chain form. Pro-PHBP was comparable to PHBP in activity to promote plactin-dependent scu-PA activation by U937 cells. Plactin enhanced both cellular binding and autoproteolytic activation of pro-PHBP. The two activities were obtained with a plactin concentration at ~30μM, which resulted in a significant increase in intrinsic fluorescence and self association of pro-PHBP. Thus, it is suggested that such changes account for both enhanced cellular binding and autoactivation of pro-PHBP, resulting in an enhancement of scu-PA activation.
|
| 20889720 |
Colocalization of amanitin and a candidate toxin-processing prolyl oligopeptidase in Amanita basidiocarps |
10.1128/EC.00161-10. |
Eukaryot Cell |
Colocalization of amanitin and a candidate toxin-processing prolyl oligopeptidase in Amanita basidiocarps
Abstract
- Fungi in the basidiomycetous genus Amanita owe their high mammalian toxicity to the bicyclic octapeptide amatoxins such as α-amanitin. Amatoxins and the related phallotoxins (such as the heptapeptide phalloidin) are encoded by members of the "MSDIN" gene family and are synthesized on ribosomes as short (34- to 35-amino-acid) proproteins. Antiamanitin antibodies and confocal microscopy were used to determine the cellular and subcellular localizations of amanitin accumulation in basidiocarps (mushrooms) of the Eastern North American destroying angel (Amanita bisporigera). Consistent with previous studies, amanitin is present throughout the basidiocarp (stipe, pileus, lamellae, trama, and universal veil), but it is present in only a subset of cells within these tissues. Restriction of amanitin to certain cells is especially marked in the hymenium. Several lines of evidence implicate a specific prolyl oligopeptidase, A. bisporigera POPB (AbPOPB), in the initial processing of the amanitin and phallotoxin proproteins. The gene for AbPOPB is restricted taxonomically to the amatoxin-producing species of Amanita and is clustered in the genome with at least one expressed member of the MSDIN gene family. Immunologically, amanitin and AbPOPB show a high degree of colocalization, indicating that toxin biosynthesis and accumulation occur in the same cells and possibly in the same subcellular compartments.
|
| 20924384 |
Bioconversion of AS1387392: bioconversion studies involving Amycolatopsis azurea JCM 3275 |
10.1038/ja.2010.108. |
J Antibiot (Tokyo) |
Bioconversion of AS1387392: bioconversion studies involving Amycolatopsis azurea JCM 3275
Abstract
- We screened actinomycetes capable of converting AS1387392 to AS1429716 and identified those strains capable of hydroxylation. Amycolatopsis azurea JCM 3275 was found to be a particularly efficient strain, capable of converting AS1387392 to AS1429716, with a yield of 44% after 9 h. This strain can metabolize not only the hydroxylation of phenylalanine at the meta and para positions but also the reduction of hydroxyketones, as shown by the isolation of bioconversion products. Examination of more suitable conversion conditions showed that pH 7.8 and 25 °C were the optimum pH and temperature for bioconversion, respectively. We also demonstrated the effect of carbon and nitrogen sources in the culture media on hydroxylation. Using this strain, we were able to efficiently produce AS1429716 as a chemical template. Further derivatization studies may provide more effective, safer immunosuppressants than those that are currently on-market.
|
