ハブトビンは、血小板凝集初期のFAKTyr³⁹⁷リン酸化を抑制する

抄録

In previous study, we demonstrated that habutobin, thrombin-like enzyme, bound to β₃subunit of integrin α_IIbβ₃on rabbit washed platelet, and then habutobin inhibited the collagen-induced aggregation. FAK tyrosine-phosphorylation (pTyr) was inhibited at an early stage of collagen-induced aggregation in the presence of habutobin. FAK contains six tyrosine (Tyr)-residues, which are phosphorylated in response to diverse stimuli. However, it was not cleared that habutobin was concerned in which tyrosine residues. In order to investigate the signal transduction pathway being concerned with habutobin-induced inhibition of platelet aggregation, the pTyr³⁹⁷and pTyr⁸⁶¹of FAK were studied from Western blotting using the antibodies against pTyr³⁹⁷and pTyr⁸⁶¹of FAK. From results of Western blot, pTyr³⁹⁷and pTyr⁸⁶¹of FAK were prominently observed on collagen-induced aggregation in the absence of habutobin. The pTyr³⁹⁷of FAK, however, was decreased in a concentration dependent manner by habutobin, and it was not detectable in the presence of high concentration of habutobin (final 5 μg/ml) on an early stage of collagen-induced aggregation. While, the pTyr⁸⁶¹of FAK was detectable in the presence of high concentration of habutobin. From these results, it was clarified that habutobin inhibited the phosphorylation of Tyr³⁹⁷of FAK. pTyr³⁹⁷of FAK included the activation of adaptor protein Shc and the p85 subunit of PI3K. It was suggested that habutobin inhibited the phosphorylation of PI3K. [J Physiol Sci. 2007;57 Suppl:S217]