| Budget Amount *help |
¥2,652,000 (Direct Cost: ¥2,040,000、Indirect Cost: ¥612,000)
Fiscal Year 2010: ¥1,261,000 (Direct Cost: ¥970,000、Indirect Cost: ¥291,000)
Fiscal Year 2009: ¥1,391,000 (Direct Cost: ¥1,070,000、Indirect Cost: ¥321,000)
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| Research Abstract |
Toll-like receptor s(TLRs) sense a variety of microbial products. TLRs activate innate immune responses and prime adaptive immune responses. TLR4/MD-2, a sensor for LPS, delivers the MyD88-dependent signal from the cellsurface, then traffics to endolysosomes and delivers the TRIF/TICAM-1-dependent signal. Both signals are thought to be dependent on cell surface TLR4/MD-2. Although TLR4/MD-2 is located also in recycling endosomes, the Golgi apparatus or the endoplasmic reticulum, little is known abouta role for intracellular TLR4/MD-2 in LPS responses. We here studied intracellular LPS sensing in macrophages. PRAT4A (protein associated with TLR4 A) is a cochaperone for a general chaperone gp96 and required for cell surface expression of TLR4/MD-2. Cell surface TLR4/MD-2 was undetectable on PRAT4A deficient thioglycollate-elicited peritoneal macrophage cells (P-Macs) and bone marrow-derived macrophages (BM-Macs). LPS responses were all abolished in PRAT4A deficient P-Macs, whereas a part of LPS responses remained detectable in PRAT4A deficient BM-Macs. Of note, LPS responses in PRAT4A deficient BM-Macs were not necessarily dependent on TRIF/TICAM-1 signaling. PRAT4A deficient BM-Macs showed unimpaired production of both TRIF/TICAM-1-dependent chemokine RANTES (CCL5) and MyD88-dependent chemokine MCP-1 (CCL2). Moreover, up-regulation of co-stimulatory molecules, CD40 and CD86 was notaltered. In contrast, TRIF/TICAM-1-dependent production of type I IFN was profoundly impaired. These results demonstrate that intracellular TLR4/MD-2 is responsible for unique set of LPS responses.
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