|
|
By admin, on February 20th, 2012
Free Radic Biol Med. 2012 Feb 1;
Berrougui H, Loued S, Khalil A
Paraoxonase-1 (PON1) is a high-density lipoprotein (HDL)-associated serum enzyme thought to make a major contribution to the antioxidant and anti-inflammatory capacities of HDLs. However, the role of PON1 in the modulation of cholesterol efflux is poorly understood. The aim of our study was to investigate the involvement of PON1 in the regulation of cholesterol efflux, especially the mechanism by which it modulates HDL-mediated cholesterol transport. The enrichment of HDL(3) with human PON1 enhanced, in a dose-dependent manner, cholesterol efflux from THP-1 macrophage-like cells and ABCA1-enriched J774 macrophages. Moreover, an additive effect was observed when ABCA1-enriched J774 macrophages were incubated with both PON1 and apo-AI. Interestingly, PON1 alone was able to mediate cholesterol efflux from J774 macrophages and to upregulate ABCA1 expression on J774 macrophages. Immunofluorescence measurement showed an increase in PON1 levels in the cytoplasm of J774 macrophages overexpressing ABCA1. PON1 used an apo-AI-like mechanism to modulate cholesterol efflux from rapid and slow efflux pools derived from the lipid raft and nonraft domains of the plasma membrane, respectively. This was supported by the fact that ABCA1 protein was incrementally expressed by J774 macrophages within the first few hours of incubation with cholesterol-loaded J774 macrophages and that cyclodextrin significantly inhibited the capacity of PON1 to modulate cholesterol efflux from macrophages. This finding suggested that PON1 plays an important role in the antiatherogenic properties of HDLs and may exert its protective function outside the lipoprotein environment.
Read more from the original source:
Purified human paraoxonase-1 interacts with plasma membrane lipid rafts and mediates cholesterol efflux from macrophages.
By admin, on February 10th, 2012
Biochemistry . 2012 Feb 6; Raunest M, Kandt C Playing a major role in antibiotics expulsion and the secretion of cell toxins in conjunction with inner membrane transporters of three protein super families, the outer membrane channel TolC occurs in at least two states blocking or permitting the passage of substrates. The details of the underlying gating mechanism are not fully understood yet.
Original post:
Locked on One Side Only: Ground State Dynamics of the Outer Membrane Efflux Duct TolC.
By admin, on February 10th, 2012
Biochemistry . 2012 Feb 6; Raunest M, Kandt C Playing a major role in antibiotics expulsion and the secretion of cell toxins in conjunction with inner membrane transporters of three protein super families, the outer membrane channel TolC occurs in at least two states blocking or permitting the passage of substrates. The details of the underlying gating mechanism are not fully understood yet.
See the article here:
Locked on One Side Only: Ground State Dynamics of the Outer Membrane Efflux Duct TolC.
By admin, on February 9th, 2012
J Biol Chem. 2012 Feb 6;
Gao J, Takeuchi H, Zhang Z, Fukuda M, Hirata M
Exocytosis is one of the most fundamental cellular events. The basic mechanism of the final step, membrane fusion, is mediated by the formation of the SNARE complex, which is modulated by the phosphorylation of proteins controlled by the concerted actions of protein kinases and phosphatases. We have previously shown that a protein phosphatase-1 (PP1) anchoring protein, PRIP (phospholipase C-related, but catalytically inactive protein), has an inhibitory role in regulated exocytosis. The current study investigated the involvement of PRIP in the phospho-dependent modulation of exocytosis. Dephosphorylation of SNAP-25 (synaptosome-associated protein of 25kDa) was mainly catalyzed by PP1 and the process was modulated by wild-type PRIP, but not by the mutant (F97A) lacking PP1-binding ability in in vitro studies. We then examined the role of PRIP in phospho-dependent regulation of exocytosis in cell-based studies using a pheochromocytoma cell line, PC12 cells, that secrete noradrenalin. Exogenous expression of PRIP accelerated the dephosphorylation process of phosphorylated SNAP-25 after forskolin or phorbol ester treatment of the cells. The phospho-states of SNAP-25 were correlated with noradrenalin secretion, which was enhanced by forskolin or phorbol ester treatment and modulated by PRIP expression in PC12 cells. Both SNAP-25 and PP1 were co-precipitated in anti-PRIP immunocomplex isolated from PC12 cells expressing PRIP. Collectively, together with our previous observation regarding the roles of PRIP in PP1 regulation, these results suggest that PRIP is involved in the regulation of the phospho-states of SNAP-25 by modulating the activity of PP1, thus regulating exocytosis.
See original here:
Phospholipase C-related, but catalytically inactive protein PRIP modulates SNAP-25 phosphorylation and exocytosis.
By admin, on February 8th, 2012
Neurochem Int. 2012 Jan 25;
Nathanson NM
Leukemia inhibitory factor (LIF) and ciliary neurotrophic factor (CNTF) are neurally active cytokines, or neurokines. LIF signals through a receptor consisting of gp130 and the low affinity LIF receptor (LIFR), while the CNTF receptor consists of gp130, LIFR, and the low affinity CNTF receptor (CNTFR). Ser1044 of the LIFR is phosphorylated by Erk1/2 MAP kinase. Stimulation of neural cells with growth factors which strongly activate Erk1/2 decreases LIF-mediated signal transduction due to increased degradation of the LIFR as a consequence of Erk1/2-dependent phosphorylation of the receptor at Ser1044. The gp130 receptor subunit is phosphorylated, at least in part by calmodulin-dependent protein kinase II, at Ser782, which is adjacent to a dileucine internalization motif. Ser782 appears to negatively regulate cytokine receptor expression, as mutagenesis of Ser782 results in increased gp130 expression and cytokine-induced neuropeptide gene transcription. The LIFR and gp130 are transmembrane proteins, while CNTFR is a peripheral membrane protein attached to the cell surface via a glycosylphosphatidylinositol tail. In unstimulated cells, CNTFR but not LIFR and gp130 is localized to detergent-resistant lipid rafts. Stimulation of cells with CNTFR causes translocation of LIFR and gp130 into the lipid rafts, while stimulation with LIF does not induce receptor translocation, raising the possibility that CNTF could induce different patterns of signaling and/or receptor trafficking than caused by LIF. We used a compartmentalized culture system to examine the mechanisms for retrograde signaling by LIF and CNTF from distal neurites to the cell bodies of mouse sympathetic neurons. Stimulation with neurokines of the distal neurites of sympathetic neurons grown in a compartmentalized culture system resulted in the activation and nuclear translocation of the transcription factor Stat3. Retrograde signaling required Jak kinase activity in the cell body but not the distal neurites, and could be blocked by inhibitors of microtubule but not microfilament function. The results are consistent with a signaling endosomes model in which the ctyokine/receptor/Jak kinase complex is transported back to the cell body where Stat3 is activated. While both LIF and CNTF mediate retrograde activation of Stat3, the kinetics for retrograde signaling differ for the two neurokines.
Read the original:
Regulation of neurokine receptor signaling and trafficking.
By admin, on February 4th, 2012
PLoS One . 2012; 7(1): e30767 Nakamura Y, Kitamura N, Shinogi D, Yoshida M, Goda O, Murai R, Kamino H, Arakawa H Mieap, a p53-inducible protein, controls mitochondrial quality by repairing unhealthy mitochondria. During repair, Mieap induces the accumulation of intramitochondrial lysosomal proteins (designated MALM for Mieap-induced accumulation of lysosome-like organelles within mitochondria) by interacting with NIX, leading to the elimination of oxidized mitochondrial proteins
Read the original:
BNIP3 and NIX Mediate Mieap-Induced Accumulation of Lysosomal Proteins within Mitochondria.
By admin, on February 4th, 2012
PLoS One . 2012; 7(1): e30767 Nakamura Y, Kitamura N, Shinogi D, Yoshida M, Goda O, Murai R, Kamino H, Arakawa H Mieap, a p53-inducible protein, controls mitochondrial quality by repairing unhealthy mitochondria. During repair, Mieap induces the accumulation of intramitochondrial lysosomal proteins (designated MALM for Mieap-induced accumulation of lysosome-like organelles within mitochondria) by interacting with NIX, leading to the elimination of oxidized mitochondrial proteins.
Read the original here:
BNIP3 and NIX Mediate Mieap-Induced Accumulation of Lysosomal Proteins within Mitochondria.
By admin, on February 3rd, 2012
Pain. 2012 Jan 30;
Crown ED, Gwak YS, Ye Z, Yu Tan H, Johnson KM, Xu GY, McAdoo DJ, Hulsebosch CE
Chronic central neuropathic pain after central nervous system injuries remains refractory to therapeutic interventions. A novel approach would be to target key intracellular signaling proteins that are known to contribute to continued activation by phosphorylation of kinases, transcription factors, and/or receptors that contribute to changes in membrane excitability. We demonstrate that one signaling kinase, calcium/calmodulin-dependent kinase II (CaMKII), is critical in maintaining aberrant dorsal horn neuron hyperexcitability in the neuropathic pain condition after spinal cord injury (SCI). After contusion SCI at spinal level T10, activated CaMKII (phosphorylated, pCaMKII) expression is significantly upregulated in the T7/8 spinal dorsal horn in neurons, but not glial cells, and in oligodendrocytes in the dorsal column in the same rats that displayed at-level mechanical allodynia. Furthermore, identified spinothalamic neurons demonstrated significant increases of pCaMKII after SCI compared to sham-treated control animals. However, neither astrocytes nor microglia showed pCaMKII expression in either sham-treated or SCI rats. To demonstrate causality, treatment of SCI rats with KN-93, which prevents CaMKII activation, significantly attenuated at-level mechanical allodynia and aberrant wide dynamic range neuronal activity evoked by brush, pressure, and pinch stimuli and a graded series of von Frey stimuli, respectively. Persistent CaMKII activation contributes to chronic central neuropathic pain by mechanisms that involve maintained hyperexcitability of wide dynamic range dorsal horn neurons. Furthermore, targeting key signaling proteins is a novel, useful therapeutic strategy for treating chronic central neuropathic pain.
See the original post:
Calcium/calmodulin dependent kinase II contributes to persistent central neuropathic pain following spinal cord injury.
By admin, on January 31st, 2012
Mol Biosyst. 2012 Jan 27;
Sztolsztener ME, Dobrzyn A, Pikula S, Tylki-Szymanska A, Bandorowicz-Pikula J
The Niemann-Pick type C (NPC) disease is characterized by accumulation of lipids within the late endosome/lysosome (LE/LY) compartment as a result of dysfunctions of the NPC1 or NPC2 proteins and an altered distribution and/or functioning of proteins involved in the regulation of membrane dynamics. In our previous report we isolated membranes of the LE/LY compartment from NPC L1 skin fibroblasts with a mutation in the NPC1 gene (exon 8, R348X) and showed that annexin A6 (AnxA6) may contribute to the impaired dynamics of these membranes in a cholesterol-dependent manner and therefore to the overnormative storage of cholesterol. In this report we show that the LE/LY fraction isolated from NPC L1 cells is characterized by a 4-fold enrichment in cholesterol, 2.5-fold in sphingomyelin and 2-fold in saturated fatty acids. As a result, the fluidity of LE/LY membranes isolated from NPC L1 cells is greatly reduced in comparison to control ones. We conclude that modified lipid composition and properties of this compartment may affect distribution and function of proteins implicated in cellular membrane dynamics. As a consequence, the backward vesicular transport of cholesterol from the LE/LY compartment to the Golgi apparatus, endoplasmic reticulum and finally to plasma membrane is impaired.
Link:
Impaired dynamics of the late endosome/lysosome compartment in human Niemann-Pick type C skin fibroblasts carrying mutation in NPC1 gene.
By admin, on January 25th, 2012
Mol Pharmacol. 2012 Jan 19;
Hoque MT, Robillard KR, Bendayan R
Breast cancer resistance protein (BCRP/ABCG2, an ATP-Binding Cassette (ABC) membrane-associated drug efflux transporter, is known to localize at the blood-brain barrier (BBB) and can significantly restrict xenobiotic permeability in the brain. The objective of this study is to investigate the regulation of BCRP functional expression by peroxisome proliferator-activated receptor alpha (PPARα), a ligand-activated transcription factor primarily involved in lipid metabolism, in a cerebral microvascular endothelial cell culture system (hCMEC/D3), representative of human BBB. We demonstrate that PPARα selective ligands (i.e., clofibrate, GW7647) significantly induce BCRP mRNA and protein expression in a time and concentration-dependent manner, while pharmacological inhibitors (i.e., MK886; GW6471) prevent this induction. Using [3H]-mitoxantrone, an established BCRP substrate, we observe a significant reduction in its cellular accumulation by monolayer cells treated with clofibrate suggesting increased BCRP efflux activity. Furthermore, we show a significant decrease in BCRP protein expression and function when PPARα is downregulated by small interfering RNA. Applying chromatin-immunoprecipitation and quantitative real-time PCR, we observe that clofibrate treatment increases PPARα binding to the peroxisome proliferator response element within ABCG2 gene promoter. This study provides the first evidence of direct BCRP regulation by PPARα in a human in vitro BBB model and suggests new targeting strategies for either improving drug brain bioavailability or increasing neuroprotection.
More here:
Regulation of Breast Cancer Resistant Protein (BCRP) by Peroxisome Proliferator-Activated Receptor Alpha (PPARα) in Human Brain Microvessel Endothelial Cells.
By admin, on January 25th, 2012
Mol Pharmacol. 2012 Jan 19;
Hoque MT, Robillard KR, Bendayan R
Breast cancer resistance protein (BCRP/ABCG2, an ATP-Binding Cassette (ABC) membrane-associated drug efflux transporter, is known to localize at the blood-brain barrier (BBB) and can significantly restrict xenobiotic permeability in the brain. The objective of this study is to investigate the regulation of BCRP functional expression by peroxisome proliferator-activated receptor alpha (PPARα), a ligand-activated transcription factor primarily involved in lipid metabolism, in a cerebral microvascular endothelial cell culture system (hCMEC/D3), representative of human BBB. We demonstrate that PPARα selective ligands (i.e., clofibrate, GW7647) significantly induce BCRP mRNA and protein expression in a time and concentration-dependent manner, while pharmacological inhibitors (i.e., MK886; GW6471) prevent this induction. Using [3H]-mitoxantrone, an established BCRP substrate, we observe a significant reduction in its cellular accumulation by monolayer cells treated with clofibrate suggesting increased BCRP efflux activity. Furthermore, we show a significant decrease in BCRP protein expression and function when PPARα is downregulated by small interfering RNA. Applying chromatin-immunoprecipitation and quantitative real-time PCR, we observe that clofibrate treatment increases PPARα binding to the peroxisome proliferator response element within ABCG2 gene promoter. This study provides the first evidence of direct BCRP regulation by PPARα in a human in vitro BBB model and suggests new targeting strategies for either improving drug brain bioavailability or increasing neuroprotection.
Read more:
Regulation of Breast Cancer Resistant Protein (BCRP) by Peroxisome Proliferator-Activated Receptor Alpha (PPARα) in Human Brain Microvessel Endothelial Cells.
By admin, on January 24th, 2012
J Cell Sci. 2012 Jan 20;
Yip SC, Cotteret S, Chernoff J
Protein tyrosine phosphatase (PTP)1B is an abundant non-transmembrane enzyme that plays a major role in regulating insulin and leptin signaling. Recently, we reported that PTP1B is inhibited by sumoylation, and that sumoylated PTP1B accumulates in a perinuclear distribution, consistent with its known localization in the endoplasmic reticulum (ER) and the contiguous outer nuclear membrane. Here, we report that, in addition to its localization at the ER, PTP1B also is found at the inner nuclear membrane, where it is heavily sumoylated. We also find that PTP1B interacts with emerin, an inner nuclear membrane protein that is known to be tyrosine phosphorylated, and that PTP1B expression levels are inversely correlated with tyrosine phosphorylation levels of emerin. PTP1B sumoylation greatly increases as cells approach mitosis, corresponding to the stage where tyrosine phosphorylation of emerin is maximal. In addition, expression of a non-sumoylatable mutant of PTP1B greatly reduced levels of emerin tyrosine phosphorylation. These results suggest that PTP1B regulates the tyrosine phosphorylation of a key inner nuclear membrane protein in a sumoylation- and cell-cycle-dependent manner.
See more here:
Sumoylated protein tyrosine phosphatase 1B localizes to the inner nuclear membrane and regulates the tyrosine phosphorylation of emerin.
By admin, on January 11th, 2012
Infect Immun . 2012 Jan 9; Roden JA, Wells DH, Chomel BB, Kasten RW, Koehler JE Bartonella species are gram-negative, emerging bacterial pathogens found in two distinct environments. In the gut of the obligately hematophagous arthropod vector, bartonellae are exposed to concentrations of heme that are toxic to other bacteria
Read more here:
Hemin binding protein C is found in outer membrane vesicles and protects Bartonella henselae against toxic concentrations of hemin.
By admin, on December 30th, 2011
PLoS Negl Trop Dis. 2011 Dec; 5(12): e1386
Preet S, Bharati S, Shukla G, Koul A, Rishi P
BACKGROUND: Amoebiasis is a major public health problem in tropical and subtropical countries. Currently, metronidazole is the gold choice medication for the treatment of this disease. However, reports have indicated towards the possibility of development of metronidazole-resistance in Entamoeba strains in near future. In view of the emergence of this possibility, in addition to the associated side effects and mutagenic ability of the currently available anti-amoebic drugs, there is a need to explore newer therapeutics against this disease. In this context, the present study evaluated the amoebicidal potential of cryptdin-2 against E. histolytica. METHODS/PRINCIPAL FINDINGS: In the present study, cryptdin-2 exhibited potent in-vitro amoebicidal activity against E. histolytica in a concentration dependent manner at a minimum amoebicidal concentration (MAC) of 4 mg/L. Scanning electron microscopy as well as phase contrast microscopic investigations of cryptdin-2 treated trophozoites revealed that the peptide was able to induce significant morphological alterations in terms of membrane wrinkling, leakage of the cytoplasmic contents and damaged plasma membrane suggesting a possible membrane dependent amoebicidal activity. N-phenyl napthylamine (NPN) uptake assay in presence of sulethal, lethal as well as twice the lethal concentrations further confirmed the membrane-dependent mode of action of cryptdin-2 and suggested that the peptide could permeabilize the plasma membrane of E. histolytica. It was also found that cryptdin-2 interfered with DNA, RNA as well as protein synthesis of E. histolytica exerting the highest effect against DNA synthesis. Thus, the macromolecular synthesis studies correlated well with the observations of membrane permeabilization studies. SIGNIFICANCE/CONCLUSIONS: The amoebicidal efficacy of cryptdin-2 suggests that it may be exploited as a promising option to combat amoebiasis or, at least, may act as an adjunct to metronidazole and/or other available anti-amoebic drugs.
Original post:
Evaluation of Amoebicidal Potential of Paneth Cell Cryptdin-2 against Entamoeba histolytica.
By admin, on December 29th, 2011
Front Biosci (Schol Ed) . 2012; 4: 1031-43 Singh K, Bayrak B, Riesbeck K A number of microorganisms are capable of binding immunoglobulins (Igs) in a manner, which excludes binding to conventional antigen binding sites. Interaction of such bacterial proteins with surface immunoglobulins leads to polyclonal activation of B-lymphocytes.
See the article here:
A Role for TLRs in Moraxella-superantigen induced polyclonal B cell activation.
By admin, on December 29th, 2011
Pediatr Neurol. 2012 Jan; 46(1): 24-31
Mastrangelo M, Leuzzi V
Early-onset epileptic encephalopathies are severe disorders in which cognitive, sensory, and motor development is impaired by recurrent clinical seizures or prominent interictal epileptiform discharges during the neonatal or early infantile periods. They include Ohtahara syndrome, early myoclonic epileptic encephalopathy, West syndrome, Dravet syndrome, and other diseases, e.g., X-linked myoclonic seizures, spasticity and intellectual disability syndrome, idiopathic infantile epileptic-dyskinetic encephalopathy, epilepsy and mental retardation limited to females, and severe infantile multifocal epilepsy. We summarize recent updates on the genes and related clinical syndromes involved in the pathogenesis of early-onset epileptic encephalopathies: Aristaless-related homeobox (ARX), cyclin-dependent kinase-like 5 (CDKL5), syntaxin-binding protein 1 (STXBP1), solute carrier family 25 member 22 (SLC25A22), nonerythrocytic α-spectrin-1 (SPTAN1), phospholipase Cβ1 (PLCβ1), membrane-associated guanylate kinase inverted-2 (MAGI2), polynucleotide kinase 3'-phosphatase (PNKP), sodium channel neuronal type 1α subunit (SCN1A), protocadherin 19 (PCDH19), and pyridoxamine 5-prime-phosphate oxidase (PNPO).
Follow this link:
Genes of early-onset epileptic encephalopathies: from genotype to phenotype.
|
