Team:Kyoto/CiC/Method

1. Home
2. Cells in Cells
3. Mechanism

Method

Method for Subgoal A --- Liposomes with HIV-1 TAT peptide

Subgoal A is construction of liposome that penetrate through cell membranes.

Construction of Liposomes with HIV-1 TAT peptide

We designed liposomes with HIV-1 TAT peptide.

HIV-1 TAT is a Protein Transduction Domain(PTD)[2]. Liposomes made of peptidolipid with HIVｰ1 TAT is known to penetrate through cell membrane[1]. It is suggested that HIV-1 TAT promotes endocytosis,though the precise mechanism remains unclear.

Then we fused HIV-1 TAT with potential anchor protein (LALAAAALALAAAALALAAAA)[3]. The LALAAAA side of this fusion protein is expected to be anchored in the lipid barrier of liposome. And the TAT side of the protein will be exposed to water so that TAT domain can touches the cell membrane. When exposed to cells, liposomes with this fusion protein will promote endocytosis and be taken into the cell. If such liposomes are fluorescent stained, they will show fluorescence in the cells.

We constructed plasmids encoding this fusion protein. When this plasmid is mixed with mixture of liposomes and cell-free protein synthesis system, the fusion proteins will be synthesized and anchored on Liposomes[4].

We also performed similar experiments with chemically synthesized TAT-LALAAAA protein.

Host cells

We chose HeLa cells for this experiment.

Method for Subgoal B --- Liposomes with Mitochondrial Translocases

Subgoal B is construction of liposome with mitochondrial translocases and confirming whether mitochondrial proteins are imported into them.

Construction of Liposomes with Mitochondrial Translocases

Mitochondria have several types of translocases: TOM40 complex on outer membrane, TIM22 complex, TIM23 complex and OXA complex on Inner membrane. They catalyze protein transport across mitochondrial membrane. Precursor proteins with signal sequence for mitochondrial protein import are selectively sent to mitochondria.

We aimed to reconstitute all types of mitochondrial translocases on liposomes but later found it too difficult. Mitochondria have double-membraned sturucture, which we can hardly construct well. So, we decided to construct liposomes which correspond to mitochondrial Inner membrane.

It is known that mitochondria without their outer membrane, which is called mitoplasts, can efficiently import precursor proteins into the matrix space. It means that TIM23 can recognize signal sequence and catalyze protein tranport if exposed on their surface.

So if we successfully reconstitute liposomes with TIM23 , these liposomes will take in proteins with mitochondrial signal sequence too. We named such liposomes "Prepared Liposome"

Prepared liposome is constructed in the ways described below.

1. Isolate mitochondrial fraction.

2. Disrupt outer membrane.

3. Mix mitoplasts with detergent.

4. Mix liposomes with mixture of the 3 step

5. Get rid of detergent.

GFP with Mitochondrial Signal Sequence

We designed GFP with mitochondrial signal sequence, which we named this sig-GFP, and constructed plasmids encoding it. And we isolated mitochondrial fraction from yeast to confirm whether sig-GFP is imported into mitochondria in vitro. Mitochondrial fraction is mixed with cell-free protein synthesis system expressing sig-GFP. If sig-GFP works well, mitochondria will be filled with GFP. And it means sig-GFP can be imported into prepared liposome too .

Method for Subgoal C --- Liposomes with HIV-1 TAT and Mitochondrial Translocases

reference

Subgoal A

[1] Nobuhiro Yagi: Furukute atarashi miwakuno nanoryuusi Liposome(Classic yet new and attractive nanoparticle:liposome).yakuzaigaku, 68 (5),(2008).

[2] Hideki MATSUI, Kazuhito TOMIZAWA and Masayuki MATSUSHITA: Protein transduction by poly-arginine.. Jpn.121，(2003)

[3] Yoshiaki Yano, Tomokazu Takemoto, Satoe Kobayashi, Hiroyuki Yasui, Hiromu Sakurai,Wakana Ohashi, Miki Niwa, Shiroh Futaki, Yukio Sugiura, and Katsumi Matsuzaki: Topological Stability and Self-Association of a Completely Hydrophobic Model Transmembrane Helix in Lipid Bilayers.Biochemistry, 2002, 41(9)

[4] Shin-ichiro M. Nomura, Satoshi Kondoha, Wakiko Asayamaa, Akikazu Asada, Shigemichi. Nishikawa and Kazunari Akiyoshia: Direct preparation of giant proteo-liposomes by in vitro membrane protein synthesis.Journal of Biotechnology Volume 133, Issue 2, 20 January 2008.

Subgoal B

Subgoal C