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Invasin + Listeriolysin
Invasin (INV) plays a key role in the initiation of Yersinia enterocolytica and Yersinia pseudotuberculosis infection. Through interaction with a beta1-integrin receptor present on the surface of eucaryotic cell membranes it triggers a signal-transduction pathway leading to internalisation of the whole bacterium in the endocytosis-dependent manner. The strong affinity of invasin to it’s receptor results in highly selective binding to the target molecule. Mammalian cells depleted of beta1-integrin cannot be infected.
Listeriolysin O (LLO) is a member of a widespread cholesterol-dependent pore-forming cytolysins family (CDCs). It's natural role in Listeria monocytogenes is to provide endosomal escape. The first step of the process involves binding of monomeric listeriolysin molecules to lipid bilayer containing cholesterol. The binding induces conformational change that subsequently leads to the formation of a prepores' oligomeric structures (consisting of 33-50 monomers) converting into large (maximum 350A-diameter) pores. This severely disturbs the stability of endosomal membrane and causes it’s rupture.
LLO is a phagosome-specyfic lysin. The acidic pH is necessary for it’s full hemolytic activity. Neutral pH of cytosol causes premature unfolding of TMH domains responsible for aqueous pore formation. This mechanism prevents Listeria spp from killing the host cell and losing the intracellular environment. In case of any tranformed strain it guarantees the lowest possible level of cytotoxicity, incomparable to this involved with the use of any other protein from CDCs family.
Left: Structural model of the LLO monomer from: P. Schnupf , D.A. Portnoy Listeriolysin O: a phagosome-specific lysin, Microbes and infection (2007) 1176-1187
Construct design.The part consists of B0032 RBS ligated to inv gene from Yersinia pestis (horizontal gene transfer form Yersinia pseudotuberculosis). Following elements are B0032 RBS ligated to synthetic gene encoding Listeriolysin, codon usage optimized for E. coli. Aminoacid sequence identical with mature form of LLO from Listeria monocytogenes. Original signal sequence (secretion signal) is omitted since it does not work in E. coli. The construct is a fragment of the Invasiveness Operon (BBa_K299813 and BBa_K299815) To find out more about it's background and design click here.
SafetyBacteria transformed with this part are invasive microorganisms. All safety precautions must be taken when manipulating with transformed strain. It involves obligatory use of laboratory gloves. Work under laminar is strongly advised. All waste should be autoclaved to avoid accidental gene transfer to other bacteria and potential rise of pathogenic organism.
Function of inv-llo gene on the platform of cyanobacteria
Author: Chiu Hsun-I from NYMU.Taipei, 2012
IntroductionReferences revealed when engineered with invasin(inv) from Yersinia pestis and listeriolysin O(llo) from Listeria monocytogenes, new S. elongatus was able to invade into cultured mammalian cells and was capable of symbiosis with eukaryotic cells. The symbiosis possibility of induced pluripotent stem cells from mice and J774 mouse macrophage cell line were evaluated.</p>
Method and materials Plasmid preparation
Invasin(inv) from Yersinia pestis and listeriolysin O(llo) from Listeria monocytogenes were provided by Pamela A. Silver, Harvard Medical school.Symbiosis experiment
Three types of mammalian cells were evaluated—J774 mouse macrophage cell line and mouse induced pluripotent stem cells in embryonic stem(ES) cells stage and embryoid body(EB) stage.Synechococcus elongatus PCC 7942 was the first cyanobacterial strain which could be transformed by exogenously added DNA.Engineered cyanobacteria which were transformed inv-llo plasmid cocultured with cells under Leibovitz's L-15 medium without antibiotics. After 24 hours, supernatants were discarded and cells were washed with PBS two times and the medium was replaced by L-15 containing antibiotics. Cells were fixed by 4% paraformaldehyde and were observed by fluorescent microscope or confocal laser microscope after 24 hours. Detailed methods were described on NYMU.Taipei wiki.
Discussion and ResultsUnder the fluorescence microscope 530-550 nm excitation filter, red pots were S. elongates PCC7942. Under the transmitted light, round and transparent one was cell.
Figure 1 revealed wildtype and inv-llo transformed type both entered into J774 macrophage cell line by phagocytosis and the help of inv-llo.wildtype, merged image of fluorescence and bright field
Figure 2 showed the coculture results of iPS cells at ES stage. Results showed that inv-llo transformation would increase the recruitment of cyanobacteria on induced pluripotent stem cells instead of the entry.
inv-llo strain, merged image of fluorescence and bright field.
wildtype, merged image of fluorescence and bright field.
On figure 3, there were similar and relative results of the iPS cells at EB stage to iPS cells at ES stage. The symbiosis of stem cells would be more difficult but the recruitment provided a potential for invading mammalian cells.
inv-llo strain, merged image of fluorescence and bright field
ConclusionThe symbiosis possibility of induced pluripotent stem cells from mice and J774 mouse macrophage cell line were evaluated. Results showed that invasin and listeriolysin O transformation would raise the entry speed and escape rate in J774 mouse macrophage cell line, and would increase the recruitment of cyanobacteria on induced pluripotent stem cells.
Towards a Synthetic Chloroplast, Christina M. Agapakis,1 Henrike Niederholtmeyer,1,¤ Ramil R. Noche,1 Tami D. Lieberman,1 Sean G. Megason,1 Jeffrey C. Way,2 and Pamela A. Silver1,2,PLoS One. 2011; 6(4): e18877.
Sequence and Features
- 10COMPATIBLE WITH RFC
- 12Illegal NheI site found at 3936
- 21Illegal BglII site found at 770
- 23COMPATIBLE WITH RFC
- 25Illegal NgoMIV site found at 1387
- 1000COMPATIBLE WITH RFC
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