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Efficient transport of Shiga toxin to the Golgi apparatus is dependent on newly synthesized glycosphingolipids
Abstracts / Chemistry and Physics of Lipids 149S (2007) S74–S91
S87
PO 148
PO 149
QSAR analysis on antimicrobial peptides
Efficient transport of Shiga toxin to the Golgi apparatus is dependent on newly synthesized glycosphingolipids
Stefano Piotto, Erminia Bianchino Department of Pharmaceutical Sciences, University of Salerno, Italy Antimicrobial peptides (AMP) have raised interest as pathogens become resistant against conventional antibiotics. Indeed, one of the major strengths of this class of molecules is their ability to kill multidrug-resistant bacteria. They usually act through relatively non-specific mechanisms resulting in membranolytic activity but they can also stimulate the innate immune response. Unlike conventional antibiotics which microbes readily circumvent, it has been claimed that acquisition of resistance by a sensitive microbial strain against AMPs is highly improbable due to the deep changes in membrane structure that would be needed to confer effective resistance and their great diversity. Certain microbial pathogens are inherently more resistant to AMPs due to stable structural or functional properties or pathogenesis strategies. The diversity of AMPs discovered is so great that it is difficult to categorize them except broadly on the basis of their secondary structure. The main assumption of the present work is that AMPs interact with specific regions of the cellular membrane modulating their physical state (MPS). The MPS perturbation can alter the activity of domain localized membranes or, in extreme cases, lead to membrane permeabilization and destruction. The molecular mechanism of membrane permeation and disruption of AMPs depends on a number of parameters such as the amino acid sequence, membrane lipids and peptide concentration. Here is presented a QSAR investigation based on genetic function analysis. An element of novelty is the use of the outcome from molecular dynamics simulation of lipid membranes as molecular descriptor. This analysis permitted to identify several details of the action of well known AMPs and led us to the complete design of novel antimicrobial agents. doi:10.1016/j.chemphyslip.2007.06.199
Hilde Raa 1 , Stine Grimmer 2 , Kirsten Sandvig 1 1 Department
of Biochemistry, The Norwegian Radium Hospital and University of Oslo, Norway; 2 Department of Biochemistry, The Norwegian Radium Hospital and University of Oslo, Norway (Present affiliation: Matforsk AS, Oslo, Norway) The bacterial toxin Shiga toxin binds to globotriasylceramide (Gb3 ) receptors on the target cell surface. To gain entry to the cell cytosol, Shiga toxin relies on endocytic uptake and retrograde transport to the Golgi apparatus and further to the ER before translocation to the cytosol. Depletion of cholesterol from cells has previously been demonstrated to inhibit transport of Shiga toxin from endosomes to the Golgi apparatus, indicating that recruitment of Gb3 to cholesterol- and sphingolipidenriched lipid rafts is essential for this transport step. Here, we have investigated the importance of newly synthesized glycosphingolipids on uptake and intracellular transport of Shiga toxin. Inhibition of glycosphingolipid synthesis in HEp-2 cells, brought about by treatment with either dl-PDMP or Fumonisin B1, protected the cells against Shiga toxin cytotoxicity, even under conditions when the toxin could still bind Gb3 . It also strongly reduced the fraction of Shiga toxin reaching the Golgi apparatus. Together, our results indicate that efficient transport of Shiga toxin to the Golgi apparatus is dependent on newly synthesized glycosphingolipids. doi:10.1016/j.chemphyslip.2007.06.200 PO 150 Withdrawn. PO 151
Self-assembly of sodium dodecyl sulfate: A simulation study of micellization Maria Sammalkorpi 1 , Mikko Karttunen 2 , Mikko Haataja 1 1 Mechanical
and Aerospace Engineering, Princeton University, USA; 2 Department of Applied Mathematics, University of Western Ontario, Canada Surfactants (e.g., lipids and detergents) are important interfacial agents in many biological and industrial systems. They consist of a polar head group and one or more hydrophobic tails, and self-aggregate above a criti-
S87
PO 148
PO 149
QSAR analysis on antimicrobial peptides
Efficient transport of Shiga toxin to the Golgi apparatus is dependent on newly synthesized glycosphingolipids
Stefano Piotto, Erminia Bianchino Department of Pharmaceutical Sciences, University of Salerno, Italy Antimicrobial peptides (AMP) have raised interest as pathogens become resistant against conventional antibiotics. Indeed, one of the major strengths of this class of molecules is their ability to kill multidrug-resistant bacteria. They usually act through relatively non-specific mechanisms resulting in membranolytic activity but they can also stimulate the innate immune response. Unlike conventional antibiotics which microbes readily circumvent, it has been claimed that acquisition of resistance by a sensitive microbial strain against AMPs is highly improbable due to the deep changes in membrane structure that would be needed to confer effective resistance and their great diversity. Certain microbial pathogens are inherently more resistant to AMPs due to stable structural or functional properties or pathogenesis strategies. The diversity of AMPs discovered is so great that it is difficult to categorize them except broadly on the basis of their secondary structure. The main assumption of the present work is that AMPs interact with specific regions of the cellular membrane modulating their physical state (MPS). The MPS perturbation can alter the activity of domain localized membranes or, in extreme cases, lead to membrane permeabilization and destruction. The molecular mechanism of membrane permeation and disruption of AMPs depends on a number of parameters such as the amino acid sequence, membrane lipids and peptide concentration. Here is presented a QSAR investigation based on genetic function analysis. An element of novelty is the use of the outcome from molecular dynamics simulation of lipid membranes as molecular descriptor. This analysis permitted to identify several details of the action of well known AMPs and led us to the complete design of novel antimicrobial agents. doi:10.1016/j.chemphyslip.2007.06.199
Hilde Raa 1 , Stine Grimmer 2 , Kirsten Sandvig 1 1 Department
of Biochemistry, The Norwegian Radium Hospital and University of Oslo, Norway; 2 Department of Biochemistry, The Norwegian Radium Hospital and University of Oslo, Norway (Present affiliation: Matforsk AS, Oslo, Norway) The bacterial toxin Shiga toxin binds to globotriasylceramide (Gb3 ) receptors on the target cell surface. To gain entry to the cell cytosol, Shiga toxin relies on endocytic uptake and retrograde transport to the Golgi apparatus and further to the ER before translocation to the cytosol. Depletion of cholesterol from cells has previously been demonstrated to inhibit transport of Shiga toxin from endosomes to the Golgi apparatus, indicating that recruitment of Gb3 to cholesterol- and sphingolipidenriched lipid rafts is essential for this transport step. Here, we have investigated the importance of newly synthesized glycosphingolipids on uptake and intracellular transport of Shiga toxin. Inhibition of glycosphingolipid synthesis in HEp-2 cells, brought about by treatment with either dl-PDMP or Fumonisin B1, protected the cells against Shiga toxin cytotoxicity, even under conditions when the toxin could still bind Gb3 . It also strongly reduced the fraction of Shiga toxin reaching the Golgi apparatus. Together, our results indicate that efficient transport of Shiga toxin to the Golgi apparatus is dependent on newly synthesized glycosphingolipids. doi:10.1016/j.chemphyslip.2007.06.200 PO 150 Withdrawn. PO 151
Self-assembly of sodium dodecyl sulfate: A simulation study of micellization Maria Sammalkorpi 1 , Mikko Karttunen 2 , Mikko Haataja 1 1 Mechanical
and Aerospace Engineering, Princeton University, USA; 2 Department of Applied Mathematics, University of Western Ontario, Canada Surfactants (e.g., lipids and detergents) are important interfacial agents in many biological and industrial systems. They consist of a polar head group and one or more hydrophobic tails, and self-aggregate above a criti-