Browsing by Author "Lu, TJ"

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Caspase activation of mammalian Sterile 20-like kinase 3 (Mst3) - Nuclear translocation and induction of apoptosis
(2002-09-13)
Huang, CYF
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Wu, YM
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Hsu, CY
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Lee, WS
;
Lai, MD
Mammalian Sterile 20-like kinase 3 (Mst3), the physiological functions of which are unknown, is a member of the germinal center kinase-III family. It contains a conserved kinase domain at its NH2 terminus, whereas there is a regulatory domain at its COOH terminus. In this study we demonstrate that endogenous Mst3 is specifically cleaved when Jurkat cells were treated with anti-Fas antibody or staurosporine and that this cleavage is inhibited by the caspase inhibitor, Ac-DEVD-CHO. Using apoptotic Jurkat cell extracts and recombinant caspases, we mapped the caspase cleavage site, AETD(313), which is at the junction of the NH2-terminal kinase domain and the COOH-terminal regulatory domain. Caspase-mediated cleavage of. Mst3 activates its intrinsic kinase activity, suggesting that the COOH-terminal domain of Mst3 negatively regulates the kinase domain. Furthermore, proteolytic removal of the Mst3 COOH-terminal domain by caspases promotes nuclear translocation. Ectopic expression of either wild-type or COOH-terminal truncated Mst3 in cells results in DNA fragmentation and morphological changes characteristic of apoptosis. By contrast, no such changes were exhibited for catalytically inactive Mst3, implicating the involvement of Mst3 kinase activity for mediation of these effects. Collectively, these results support the notion that caspase-mediated proteolytic activation of Mst3 contributes to apoptosis.
Effects of service quality, customer satisfaction and switching barriers on passenger behavioral intentions in scheduled coach service
(2003)
Jen, W
;
Lu, TJ
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運輸與物流管理系註：原交通所+運管所
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Department of Transportation and Logistics Management
Previous studies only considered the effects of service sacrifice and service value on consumer behavioral intentions, and lack an understanding of the effects of service quality, customer satisfaction and switching barriers. This study attempts to consider all the above-mentioned constructs and further explain passenger behavioral intentions. Linear Structural Relations (LISREL) was employed to test the proposed model and hypotheses. The research subjects were passengers of four companies on the Taipei-Tainan and Taichung-Kaohsiung routes. The survey questionnaires were handed out randomly in the company waiting rooms and passengers were asked to mail the completed questionnaires back to us. According to the analytical results, although the effect of interpersonal relationships of switching barriers on passenger behavioral intentions was not statistically significant, the other hypotheses were verified. This study also provided suggestions for improving the management of scheduled coach service carriers.
Zinc ion acts as a cofactor for serine/threonine kinase MST3 and has a distinct role in autophosphorylation of MST3
(2005-06-01)
Lu, TJ
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Huang, CYF
;
Yuan, CJ
;
Lee, YC
;
Leu, TH
We examined the metal ion cofactor preference for MST3 (mammalian Ste20-like kinase 3) of the Ste20 serine/threonine kinase family. Four metal ions (Mg+2, Mn+2, Zn2+, and Co2+) activate endogenous, exogenous, and baculovirus-expressed recombinant MST3 within the physiological concentration range. In contrast, Fe+2 and Ca+2 do not function as MST3 cofactors. Mn2+, Co2+, and Mg2+-dependent autophosphorylation of MST3 is mainly on threonine residue while Zn2+-stimulated MST3 autophosphorylation is on both serine and threonine residues. The distinct autophosphorylation pattern on MST3 suggests that MST3 may exert various types of kinase reactions depending on the type of metal ion cofactor used. To our knowledge, this is the first report showing Zn2+ as the metal ion cofactor of a recombinant serine/threonine kinase. (C) 2005 Elsevier Inc. All rights reserved.