|Budget Amount *help
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1997 : ¥1,100,000 (Direct Cost : ¥1,100,000)
Fiscal Year 1996 : ¥1,100,000 (Direct Cost : ¥1,100,000)
Mast cells plays an important role in allergy and inflammatIon. Integrin-mediated adhesion of mast cells to extracellular matrix regulate localization and migration of mast cells, which is thought to influence an intensity and duration of these immune responses. Mast cells adhere to fibronectin (FN) rapidly via integrin VLA-5 only when stimulated with steel factor (SCF) or cross-linking of FcepsilonRI.
In this study, we found that avidity of VLA-5 to FN was regulated by two distinct mechanisms ; spatial modulation and affinity modulation. Cross-linking of FcepsilonRI induced FN bindings by increasing affinity of VLA-5 against FN whereas stimulation with phorbol ester, PMA and SCF induced FN bindings via redistribution of VLA-5 on the cell surface without detectable change of affinity of VLA-5. Induction of affinity modulation of VLA-5 was inhibited with a PI3 kinase specific inhibitor, wortmmanin. Forced expressions of a constitutively active PI3 kinase in mast cells led to both FN bindings and increased affinity of VLA-5. These results indicate that PI3 kinase regulate affinity modulation of VLA-5. So far, known effector molecules downstream PI3 kinase such as Akt, p21Rac, S6 kinase seemed unlikely to be involved in the affinity modulation.
Regarding spatial modulation of VLA-5, the finding that PMA induced diffused distributions of VLA-5, syggests that PKC was involved in spatial modulation. SCF activated PKCalpha, PKCbetaI and PKCbetaII,which all belong to cPKC.Thymeleatoxin, a specific cPKC stimulator, induced FN bindings. These results suggest that cPKC is involved in spatial modulation.