ANALYSES OF THE SIGNAL TRANSDUCTION OF NOVEL ANTI-ARTHRITIC FACTOR, FRP, AND ITS EFFECTS ON IMMUNE SYSTEM

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1. Molecular interaction analysis of FRP receptor, A7: Our BIACORE studies disclosed that FRP actually bound to A7 and CD14, and also to activin A, follistatin, TGF-beta1. Their K_D values were calculated as follows: 4.20×10^<-6>M for FRP and A7, 1.72×10^<-4>M for FRP and CD14, 1.43×10^<-6>M for FRP and activin A, 1.88×10^<-4>M for FRP and follistatin, 1.28×10^<-8>M for FRP and TGF-beta1. K_D values for other binding pairs could not be decided. FRP was characterized by having extremely high speed and comparatively low affinity binding activity for partner molecules except for TGF-beta. Activin A and CD14 didn't bind to A7, however, follistatin bound weekly and quite slowly to A7, and they all interfered with FRP binding to A7. Interestingly, TGF-beta1 also bound to A7 with relatively-high affinity. However, bound TGF-beta1 seemed to be substituted by a larger amount of FRP, judging from its characteristic rectangular sensorgram. FRP trivially interfered TGF-beta1 binding to TGF-beta1sRII with a little competition, therefore, it seemed that FRP could hardly impede TGF-beta signaling. Taken together, FRP seems to interact with TGF-beta family proteins, and thereby play an important part in the tissue formation including the immune system.2. Cloning of second messengers in FRP signaling system: All of the resultant two-hybrid clone cells, SA240, SA263, SB224, SC21, SC23 proved to lack prey vectors, probably because their product proteins could be toxic to host cells. This brought us to consider cloning by another two-hybrid system not with yeast but with bacteria, whose species is more distant from the mammals.