Johannes Löwer

Publications (2)5.63 Total impact

• Source

  Available from: Vincenzo Mattei

  Article: Paracrine diffusion of PrP(C) and propagation of prion infectivity by plasma membrane-derived microvesicles.

  Vincenzo Mattei, Maria Grazia Barenco, Vincenzo Tasciotti, Tina Garofalo, Agostina Longo, Klaus Boller, Johannes Löwer, Roberta Misasi, Fabio Montrasio, Maurizio Sorice
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  ABSTRACT: Cellular prion protein (PrP(C)) is a physiological constituent of eukaryotic cells. The cellular pathways underlying prions spread from the sites of prions infection/peripheral replication to the central nervous system are still not elucidated. Membrane-derived microvesicles (MVs) are submicron (0.1-1 microm) particles, that are released by cells during plasma membrane shedding processes. They are usually liberated from different cell types, mainly upon activation as well as apoptosis, in this case, one of their hallmarks is the exposure of phosphatidylserine in the outer leaflet of the membrane. MVs are also characterized by the presence of adhesion molecules, MHC I molecules, as well as of membrane antigens typical of their cell of origin. Evidence exists that MVs shedding provide vehicles to transfer molecules among cells, and that MVs are important modulators of cell-to-cell communication. In this study we therefore analyzed the potential role of membrane-derived MVs in the mechanism(s) of PrP(C) diffusion and prion infectivity transmission. We first identified PrP(C) in association with the lipid raft components Fyn, flotillin-2, GM1 and GM3 in MVs from plasma of healthy human donors. Similar findings were found in MVs from cell culture supernatants of murine neuronal cells. Furthermore we demonstrated that PrP(Sc) is released from infected murine neuronal cells in association with plasma membrane-derived MVs and that PrP(Sc)-bearing MVs are infectious both in vitro and in vivo. The data suggest that MVs may contribute both to the intercellular mechanism(s) of PrP(C) diffusion and signaling as well as to the process of prion spread and neuroinvasion.
  PLoS ONE 02/2009; 4(4):e5057. · 4.09 Impact Factor
• Article: Oligonucleotide and plasmid DNA packaging into polyoma VP1 virus‐like particles expressed in Escherichia coli

  Helene Braun, Klaus Boller, Johannes Löwer, Wolf Martin Bertling, Andreas Zimmer
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  ABSTRACT: The drug delivery system described here is based on the properties of the capsoid or capsid-like structure resulting from the assembly of polyoma virus capsid protein VP1 expressed in Escherichia coli. The capsid protein VP1 was expressed as a fusion protein with a completely removable N-terminal His6 affinity tag. The pentameric morphology of the recombinant VP1 protein was confirmed by electron microscopy after affinity chromatography and factor Xa cleavage under conditions of low ionic strength. The self-assembly of VP1 capsoids can be induced from purified VP1 pentamers by increasing the ionic strength with (NH4)2SO4. These VP1 capsoid particles were packed in vitro with anti-sense oligonucleotides and plasmid DNA. The loading with DNA was pH-dependent. We observed the highest efficiency at pH 5. DNase I treatment of particles with encapsidated material showed that 37–55% of the bound oligonucleotides and fragments of 1.5–1.8 kb double-stranded DNA were protected against degradation.
  Biotechnology and Applied Biochemistry 01/1999; 29(1):31 - 43. · 1.53 Impact Factor