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By admin, on May 15th, 2012
Neuron. 2012 May 10; 74(3): 504-16
Slezak M, Grosche A, Niemiec A, Tanimoto N, Pannicke T, Münch TA, Crocker B, Isope P, Härtig W, Beck SC, Huber G, Ferracci G, Perraut M, Reber M, Miehe M, Demais V, Lévêque C, Metzger D, Szklarczyk K, Przewlocki R, Seeliger MW, Sage-Ciocca D, Hirrlinger J, Reichenbach A, Reibel S, Pfrieger FW
Glial cells release molecules that influence brain development, function, and disease. Calcium-dependent exocytosis has been proposed as potential release mechanism in astroglia, but the physiological relevance of “gliotransmission” in vivo remains controversial. We focused on the impact of glial exocytosis on sensory transduction in the retina. To this end, we generated transgenic mice to block exocytosis by Cre recombinase-dependent expression of the clostridial botulinum neurotoxin serotype B light chain, which cleaves vesicle-associated membrane protein 1-3. Ubiquitous and neuronal toxin expression caused perinatal lethality and a reduction of synaptic transmission thus validating transgene function. Toxin expression in Müller cells inhibited vesicular glutamate release and impaired glial volume regulation but left retinal histology and visual processing unaffected. Our model to study gliotransmission in vivo reveals specific functions of exocytotic glutamate release in retinal glia.
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Relevance of exocytotic glutamate release from retinal glia.
By admin, on May 15th, 2012
J Biol Chem. 2012 May 10;
Lopez Sambrooks C, Carpio MA, Hallak ME
Post-translational modifications of proteins are important for the regulation of cell fate and functions; one of these post-translational modifications is arginylation. We have previously established that calreticulin (CRT), an endoplasmic reticulum (ER) resident, is also one of the arginylated substrates found in the cytoplasm. In the present study, we describe that arginylated CRT (R-CRT) binds to the cell membrane and identified its role as a pre-apoptotic signal. We also show that cells lacking arginyl-tRNA protein transferase (ATE1-/- cells) are less susceptible to apoptosis than WT cells. Under these conditions R-CRT is present on the cell membrane, but at early stages is differently localized in stress granules (SGs). Moreover, cells induced to undergo apoptosis by arsenite show increased R-CRT on their cell surface. Exogenously applied R-CRT binds to the cell membrane and is able both to increase the number of cells undergoing apoptosis in WT cells and overcome apoptosis resistance in ATE1-/- cells that express R-CRT on the cell surface. Thus, these results demonstrate the importance of surface R-CRT in the apoptotic response of cells, implying that post-translational arginylation of CRT can regulate its intracellular localization, cell function and survival.
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Arginylated calreticulin at the plasma membrane increases the susceptibility of cells to apoptosis.
By admin, on May 15th, 2012
Open Biochem J. 2012; 6: 40-2
Contag B
A new hypothesis is discussed, which describes the initiation of the carcinogenesis through polycyclic aromatic hydrocarbons (PAHs) and aminoazo dyes (AZOs) as a two-step process: the oncogenic proteins of the ras or ras-like on-cogenes activated by mutation (“initiation A “) co-operate with the complexes in the plasma membrane formed during the “initiation B ” stage from the parent compounds of the PAHs or AZOs with cholesterol and apolipoprotein A-I. The final result of this co-operation, or the “complete initiation”, is an irreversibly modified membrane architecture with negative consequences for growth control.
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Hypothetical two-step initiation of experimental carcinogenesis by polycyclic aromatic hydrocarbons and aminoazo dyes.
By admin, on May 15th, 2012
PLoS One. 2012; 7(5): e36526
Anand K, Maeda K, Gavin AC
Pleckstrin homology (PH) domains are common membrane-targeting modules and their best characterized ligands are a set of important signaling lipids that include phosphatidylinositol phosphates (PtdInsPs). PH domains recognize PtdInsPs through two distinct mechanisms that use different binding pockets on opposite sides of the β-strands 1 and 2: i) a canonical binding site delimited by the β1-β2 and β3-β4loops and ii) a non-canonical binding site bordered by the β1-β2 and β5-β6loops. The PH domain-containing protein Slm1 from budding yeast Saccharomyces cerevisiae is required for actin cytoskeleton polarization and cell growth. We recently reported that this PH domain binds PtdInsPs and phosphorylated sphingolipids in a cooperative manner.To study the structural basis for the Slm1-PH domain (Slm1-PH) specificity, we co-crystallized this domain with different soluble compounds that have structures analogous to anionic lipid head groups of reported Slm1 ligands: inositol 4-phosphate, which mimics phosphatidylinositol-4-phosphate (PtdIns(4)P), and phosphoserine as a surrogate for dihydrosphingosine 1-phosphate (DHS1-P). We found electron densities for the ligands within the so-called non-canonical binding site. An additional positively charged surface that contacts a phosphate group was identified next to the canonical binding site.Our results suggest that Slm1-PH utilizes a non-canonical binding site to bind PtdInsPs, similar to that described for the PH domains of β-spectrin, Tiam1 and ArhGAP9. Additionally, Slm1-PH may have retained an active canonical site. We propose that the presence of both a canonical and a non-canonical binding pocket in Slm1-PH may account for the cooperative binding to PtdInsPs and DHS-1P.
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Structural Analyses of the Slm1-PH Domain Demonstrate Ligand Binding in the Non-Canonical Site.
By admin, on May 15th, 2012
PLoS One. 2012; 7(5): e36526
Anand K, Maeda K, Gavin AC
Pleckstrin homology (PH) domains are common membrane-targeting modules and their best characterized ligands are a set of important signaling lipids that include phosphatidylinositol phosphates (PtdInsPs). PH domains recognize PtdInsPs through two distinct mechanisms that use different binding pockets on opposite sides of the β-strands 1 and 2: i) a canonical binding site delimited by the β1-β2 and β3-β4loops and ii) a non-canonical binding site bordered by the β1-β2 and β5-β6loops. The PH domain-containing protein Slm1 from budding yeast Saccharomyces cerevisiae is required for actin cytoskeleton polarization and cell growth. We recently reported that this PH domain binds PtdInsPs and phosphorylated sphingolipids in a cooperative manner.To study the structural basis for the Slm1-PH domain (Slm1-PH) specificity, we co-crystallized this domain with different soluble compounds that have structures analogous to anionic lipid head groups of reported Slm1 ligands: inositol 4-phosphate, which mimics phosphatidylinositol-4-phosphate (PtdIns(4)P), and phosphoserine as a surrogate for dihydrosphingosine 1-phosphate (DHS1-P). We found electron densities for the ligands within the so-called non-canonical binding site. An additional positively charged surface that contacts a phosphate group was identified next to the canonical binding site.Our results suggest that Slm1-PH utilizes a non-canonical binding site to bind PtdInsPs, similar to that described for the PH domains of β-spectrin, Tiam1 and ArhGAP9. Additionally, Slm1-PH may have retained an active canonical site. We propose that the presence of both a canonical and a non-canonical binding pocket in Slm1-PH may account for the cooperative binding to PtdInsPs and DHS-1P.
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Structural Analyses of the Slm1-PH Domain Demonstrate Ligand Binding in the Non-Canonical Site.
By admin, on May 15th, 2012
Biochem J. 2012 Jun 1; 444(2): e3-5
Kirchhofer D, Vucic D
Constitutive NF-κB (nuclear factor κB) activation in B-cell lymphomas relies greatly on the CARMA1 [CARD (caspase recruitment domain)-containing MAGUK (membrane-associated guanylate kinase) 1]-Bcl10-MALT1 (mucosa-associated lymphoid tissue translocation gene 1) signalling complex. Within this protein complex, MALT1 possesses a rather unique enzymatic activity, which allows it to cleave Bcl10, RelB and CYLD, among other substrates. The catalytic activity of MALT1 promotes activation of canonical and non-canonical NF-κB as well as other signalling pathways. However, even after a decade of intense research on MALT1, many mechanistic aspects of its enzymatic activity remain elusive. A recent article by Hachmann, Snipas, van Raam, Cancino, Houlihan, Poreba, Kasperkiewicz, Drag and Salvesen [(2012) Biochem. J. 443, 287-295] provides novel insight into the activation mechanism and the substrate specificity of MALT1. These intriguing findings convincingly demonstrate the importance of MALT1 dimerization for its catalytic activity and pave the way for novel therapeutic approaches that target this crucial regulator of lymphoma survival and proliferation.
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Protease activity of MALT1: a mystery unravelled.
By admin, on May 15th, 2012
Biochem J. 2012 Jun 1; 444(2): e3-5
Kirchhofer D, Vucic D
Constitutive NF-κB (nuclear factor κB) activation in B-cell lymphomas relies greatly on the CARMA1 [CARD (caspase recruitment domain)-containing MAGUK (membrane-associated guanylate kinase) 1]-Bcl10-MALT1 (mucosa-associated lymphoid tissue translocation gene 1) signalling complex. Within this protein complex, MALT1 possesses a rather unique enzymatic activity, which allows it to cleave Bcl10, RelB and CYLD, among other substrates. The catalytic activity of MALT1 promotes activation of canonical and non-canonical NF-κB as well as other signalling pathways. However, even after a decade of intense research on MALT1, many mechanistic aspects of its enzymatic activity remain elusive. A recent article by Hachmann, Snipas, van Raam, Cancino, Houlihan, Poreba, Kasperkiewicz, Drag and Salvesen [(2012) Biochem. J. 443, 287-295] provides novel insight into the activation mechanism and the substrate specificity of MALT1. These intriguing findings convincingly demonstrate the importance of MALT1 dimerization for its catalytic activity and pave the way for novel therapeutic approaches that target this crucial regulator of lymphoma survival and proliferation.
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Protease activity of MALT1: a mystery unravelled.
By admin, on May 14th, 2012
J Mol Biol . 2012 May 7; Zerbes RM, Bohnert M, Stroud DA, von der Malsburg K, Kram A, Oeljeklaus S, Warscheid B, Becker T, Wiedemann N, Veenhuis M, van der Klei IJ, Pfanner N, van der Laan M The mitochondrial inner membrane contains a large protein complex crucial for membrane architecture, the mitochondrial inner membrane organizing system (MINOS).
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Role of MINOS in Mitochondrial Membrane Architecture: Cristae Morphology and Outer Membrane Interactions Differentially Depend on Mitofilin Domains.
By admin, on May 14th, 2012
J Mol Biol . 2012 May 7; Zerbes RM, Bohnert M, Stroud DA, von der Malsburg K, Kram A, Oeljeklaus S, Warscheid B, Becker T, Wiedemann N, Veenhuis M, van der Klei IJ, Pfanner N, van der Laan M The mitochondrial inner membrane contains a large protein complex crucial for membrane architecture, the mitochondrial inner membrane organizing system (MINOS). MINOS is required for keeping cristae membranes attached to the inner boundary membrane via crista junctions and interacts with protein complexes of the mitochondrial outer membrane.
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Role of MINOS in Mitochondrial Membrane Architecture: Cristae Morphology and Outer Membrane Interactions Differentially Depend on Mitofilin Domains.
By admin, on May 14th, 2012
Ann Dermatol. 2012 May; 24(2): 168-74
Lee Y, Je YJ, Lee SS, Li ZJ, Choi DK, Kwon YB, Sohn KC, Im M, Seo YJ, Lee JH
Aquaporins (AQPs) are a family of water transporting proteins present in many mammalian epithelial and endothelial cell types. Among the AQPs, AQP3 is known to be a water/glycerol transporter expressed in human skin.The relationship between the expression level of AQP3 and transpidermal water loss (TEWL) in the lesional and peri-lesional skin of psoriasis-affected patients, and skin hydration in the lesional and peri-lesional skin of psoriasis patients, was investigated.The expression of AQP3 in psoriasis-affected and healthy control skin was determined using immunohistochemical and immunofluroscence staining. TEWL and skin hydration were measured using a Tewameter® TM210 (Courage & Khazaka, Cologne, Germany) and a Corneometer® CM 820 (Courage & Khazaka), respectively.AQP3 was mainly expressed in the plasma membrane of stratum corneum and the stratum spinosum in normal epidermis. Unlike the normal epidermis, AQP3 showed decreased expression in the lesional and peri-lesional epidermis of psoriasis. TEWL was increased, and skin hydration was decreased, in the lesional and peri-lesional skin of psoriasis patients, compared with the healthy control sample.Although various factors contribute to reduced skin hydration in the lesional and peri-lesional skin of psoriasis, AQP3 appears to be a key factor in the skin dehydration of psoriasis-affected skin.
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Changes in transepidermal water loss and skin hydration according to expression of aquaporin-3 in psoriasis.
By admin, on May 14th, 2012
Ann Dermatol. 2012 May; 24(2): 168-74
Lee Y, Je YJ, Lee SS, Li ZJ, Choi DK, Kwon YB, Sohn KC, Im M, Seo YJ, Lee JH
Aquaporins (AQPs) are a family of water transporting proteins present in many mammalian epithelial and endothelial cell types. Among the AQPs, AQP3 is known to be a water/glycerol transporter expressed in human skin.The relationship between the expression level of AQP3 and transpidermal water loss (TEWL) in the lesional and peri-lesional skin of psoriasis-affected patients, and skin hydration in the lesional and peri-lesional skin of psoriasis patients, was investigated.The expression of AQP3 in psoriasis-affected and healthy control skin was determined using immunohistochemical and immunofluroscence staining. TEWL and skin hydration were measured using a Tewameter® TM210 (Courage & Khazaka, Cologne, Germany) and a Corneometer® CM 820 (Courage & Khazaka), respectively.AQP3 was mainly expressed in the plasma membrane of stratum corneum and the stratum spinosum in normal epidermis. Unlike the normal epidermis, AQP3 showed decreased expression in the lesional and peri-lesional epidermis of psoriasis. TEWL was increased, and skin hydration was decreased, in the lesional and peri-lesional skin of psoriasis patients, compared with the healthy control sample.Although various factors contribute to reduced skin hydration in the lesional and peri-lesional skin of psoriasis, AQP3 appears to be a key factor in the skin dehydration of psoriasis-affected skin.
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Changes in transepidermal water loss and skin hydration according to expression of aquaporin-3 in psoriasis.
By admin, on May 14th, 2012
Comp Biochem Physiol A Mol Integr Physiol. 2012 May 2;
Notch EG, Chapline C, Flynn E, Lameyer T, Lowell A, Sato D, Shaw JR, Stanton BA
The Atlantic killifish (Fundulus heteroclitus) is an environmental sentinel organism used extensively for studies of environmental toxicants and osmoregulation. Previous research in our laboratory has shown that acute acclimation to seawater is mediated by an increase in SGK1. SGK1 promotes the trafficking of CFTR chloride channels from intracellular vesicles to the plasma membrane of the gill within the first hour in seawater resulting in increased chloride secretion. Although we have shown that the increase in gill SGK1 does not require activation of the glucocorticoid receptor, the mechanisms that mediate the rise SGK1 during acute acclimation is unknown. To test the hypothesis that mitogen activated protein kinase (MAPK14) is responsible for the rise in SGK1 we identified the coding sequence of killifish MAPK14-1 and designed a translational blocking vivo-morpholino targeting MAPK14-1. Injection of the MAPK14-1 vivo-morpholino resulted in a 30% reduction of MAPK14-1 and a 45% reduction in phosphorylated-MAPK14-1 protein in the gill of killifish transitioned from freshwater to seawater. Knock down of phosphorlyated-MAPK14-1 completely blocked the rise in SGK1 mRNA and protein in the killifish gill, providing the first direct and in vivo evidence that MAPK14-1 is necessary for acute seawater acclimation.
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Mitogen activated protein kinase 14-1 regulates serum glucocorticoid kinase 1 during seawater acclimation in Atlantic killifish, Fundulus heteroclitus.
By admin, on May 14th, 2012
Comp Biochem Physiol A Mol Integr Physiol. 2012 May 2;
Notch EG, Chapline C, Flynn E, Lameyer T, Lowell A, Sato D, Shaw JR, Stanton BA
The Atlantic killifish (Fundulus heteroclitus) is an environmental sentinel organism used extensively for studies of environmental toxicants and osmoregulation. Previous research in our laboratory has shown that acute acclimation to seawater is mediated by an increase in SGK1. SGK1 promotes the trafficking of CFTR chloride channels from intracellular vesicles to the plasma membrane of the gill within the first hour in seawater resulting in increased chloride secretion. Although we have shown that the increase in gill SGK1 does not require activation of the glucocorticoid receptor, the mechanisms that mediate the rise SGK1 during acute acclimation is unknown. To test the hypothesis that mitogen activated protein kinase (MAPK14) is responsible for the rise in SGK1 we identified the coding sequence of killifish MAPK14-1 and designed a translational blocking vivo-morpholino targeting MAPK14-1. Injection of the MAPK14-1 vivo-morpholino resulted in a 30% reduction of MAPK14-1 and a 45% reduction in phosphorylated-MAPK14-1 protein in the gill of killifish transitioned from freshwater to seawater. Knock down of phosphorlyated-MAPK14-1 completely blocked the rise in SGK1 mRNA and protein in the killifish gill, providing the first direct and in vivo evidence that MAPK14-1 is necessary for acute seawater acclimation.
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Mitogen activated protein kinase 14-1 regulates serum glucocorticoid kinase 1 during seawater acclimation in Atlantic killifish, Fundulus heteroclitus.
By admin, on May 14th, 2012
J Biol Chem. 2012 May 10;
Oh HJ, Abraham LS, van Hengel J, Stove C, Proszynski TJ, Gevaert K, Dimario JX, Sanes JR, van Roy F, Kim H
The dystrophin complex is a multimolecular membrane-associated protein complex whose defects underlie many forms of muscular dystrophy. The dystrophin complex is postulated to function as a structural element that stabilizes the cell membrane by linking the contractile apparatus to the extracellular matrix. A better understanding of how this complex is organized and localized will improve our knowledge of the pathogenic mechanisms of diseases that involve the dystrophin complex. In a Caenorhabditis elegans genetic study, we demonstrate that CTN-1/α-catulin, a cytoskeletal protein, physically interacts with DYB-1/α-dystrobrevin (a component of the dystrophin complex), and that this interaction is critical for the localization of the dystrophin complex near dense bodies, structures analogous to mammalian costameres. We further show that in mouse α-catulin is localized at the sarcolemma and neuromuscular junctions and interacts with α-dystrobrevin, and that the level of α-catulin is reduced in α-dystrobrevin-deficient mouse muscle. Intriguingly, in the skeletal muscle of mdx mice lacking dystrophin, we discover that the expression of α catulin is increased, suggesting a compensatory role of α-catulin in dystrophic muscle. Together, our study demonstrates that the interaction between α-catulin and α-dystrobrevin is evolutionarily conserved in C. elegans and mammalian muscles, and strongly suggests that this interaction contributes to the integrity of the dystrophin complex.
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The interaction of alpha-catulin with dystrobrevin contributes to the integrity of the dystrophin complex in muscle.
By admin, on May 14th, 2012
J Biol Chem. 2012 May 10;
Oh HJ, Abraham LS, van Hengel J, Stove C, Proszynski TJ, Gevaert K, Dimario JX, Sanes JR, van Roy F, Kim H
The dystrophin complex is a multimolecular membrane-associated protein complex whose defects underlie many forms of muscular dystrophy. The dystrophin complex is postulated to function as a structural element that stabilizes the cell membrane by linking the contractile apparatus to the extracellular matrix. A better understanding of how this complex is organized and localized will improve our knowledge of the pathogenic mechanisms of diseases that involve the dystrophin complex. In a Caenorhabditis elegans genetic study, we demonstrate that CTN-1/α-catulin, a cytoskeletal protein, physically interacts with DYB-1/α-dystrobrevin (a component of the dystrophin complex), and that this interaction is critical for the localization of the dystrophin complex near dense bodies, structures analogous to mammalian costameres. We further show that in mouse α-catulin is localized at the sarcolemma and neuromuscular junctions and interacts with α-dystrobrevin, and that the level of α-catulin is reduced in α-dystrobrevin-deficient mouse muscle. Intriguingly, in the skeletal muscle of mdx mice lacking dystrophin, we discover that the expression of α catulin is increased, suggesting a compensatory role of α-catulin in dystrophic muscle. Together, our study demonstrates that the interaction between α-catulin and α-dystrobrevin is evolutionarily conserved in C. elegans and mammalian muscles, and strongly suggests that this interaction contributes to the integrity of the dystrophin complex.
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The interaction of alpha-catulin with dystrobrevin contributes to the integrity of the dystrophin complex in muscle.
By admin, on May 13th, 2012
Chem Commun (Camb) . 2012 May 11; Basit H, Shivaji Sharma K, Van der Heyden A, Gondran C, Breyton C, Dumy P, Winnik FM, Labbé P Biotinylated amphipol was used to entrap FhuA (an E. coli outer membrane protein) and immobilize the FhuA-amphipol complex on streptavidin surfaces.
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Amphipol mediated surface immobilization of FhuA: a platform for label-free detection of the bacteriophage protein pb5.
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