2006 Fiscal Year Final Research Report Summary
Molecular mechanism of bacterial infection based on the interaction between hosts and pathogens
| Project/Area Number |
17591038
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
膠原病・アレルギー・感染症内科学
|
|---|
| Research Institution | Kyoto University |
|---|
Principal Investigator |
NISHIOKA Hiroaki Kyoto University, Department of Geriatric Medicine, Assistant Professor, 医学研究科, 助手 (20397540)
|
|---|
| Project Period (FY) |
2005 – 2006
|
| Keywords | gram-negative bacteria / Shigella flexneri / effector proteins / Ipa proteins / host cell / mechanism of infection |
|---|
| Research Abstract |
Gram-negative bacteria causes many infectious diseases. Type III secretons (TTSSs) are essential determinants of the interaction of many Gram-negative bacteria with animal and plant hosts. Their major function is to translocate bacterial 'effector' proteins into eukaryotic host cells to manipulate them during infection. Shigella flexneri is the etiological gram-negative bacterium of the endemic form of bacillary dysentery. It also uses a type III secretion apparatus and secretes effector proteins in order to invade eukaryotic cells. The essential proteins of Shigella are IpaB, IpaC, and IpaD. We tried to characterize these Ipaproteins.
Purified secreted IpaB and IpaC formed a stable soluble complex of approximately 200kD. The complex contained a high level of secondary structure. It was monodispersed in solution and of roughly spherical shape with a diameter of 10-20 nm. We could visualize the IpaB/IpaC complex by electron microscopy. The IpaB/IpaC complex displayed a molar ratio of〜1:3-5, which correspond to 176-252 kD. The purified complex bound to red blood cell membranes in a cholesterol-dependent manner. It also bound to cultured mammalian cell membranes in a CD44-and cholesterol-dependent manner. The complex localized to lipid rafts in a cholesterol-dependent but CD44-independent manner. The purified IpaB/IpaC complex interacted with lipid membranes as a function of lipid composition, inserted, and formed pores within liposomes.
As for IpaD, it possessed distinct functional domains. Some ipaD mutants resulted in increased secretion of IpaC. Others showed constitutive secretionf of IpaC and IpaB. Moreover, IpaB and IpaC associated with erythrocyte membranes less effectively in the presence of IpaD mutants. Thus, we showed that IpaD is required for regulation of secretion of IpaB and IpaC and effective insertion of them into host membranes.
|
