The signal mechanism ofTaxus cuspidata(Japanese yew) cells involved in response to shear stress and immobilized matrices was investigated. Western-blot analysis showed that the immobilized cultures altered the degree of phosphorylation of the JNK (c-Jun N-terminal kinase)-like and a 41 kDa p38-like MAPKs (mitogen-activated protein kinases), particularly the 52 and 45 kDa JNK-like MAPKs. The increased rotation speeds up-regulated the degree of phosphorylation of 45 and 47 kDa JNK-like MAPKs, whereas the 41 kDa p38-like MAPK was not significantly changed. The level of phosphorylation of JNK-like MAPKs in the outer zone cells of immobilized matrices was the highest among the different zone cells, which was identical with that ofT. cuspidatacells exposed to hydrodynamic shear stresses. The highly specific p38- or JNK-MAPK inhibitors strongly reduced respectively the p38- or JNK-like MAPK phosphorylation, which also demonstrated that there were no cross-reactions between the p38-like MAPK and JNK-like MAPK inT. cuspidatacells. By a comparison of the effects of the immobilization and laminar shear stress on the phosphorylation of p38- and JNK-like MAPKs inT. cuspidatacells, these findings suggested that the JNK-like MAPK signal pathways may be involved inT. cuspidatacell response to the hydrodynamic shear stress, rather than to the p38-like MAPK.