I. Determinants for the interactions between the cytoplasmic regions of the Interleukin-3 receptor subunits α and βc and JAK kinases and JAK kinasesII.Roles of the p38 pathway in cell differentiation and growth inhibition

• Main Authors: Ya-Li Lee, 李雅莉
• Other Authors: Huei-Mei Huang
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/798y58

碩士 === 臺北醫學大學 === 細胞及分子生物研究所 === 94 === Abstract IL-3, a member of cytokine family, is involved in the cell growth, proliferation, differentiation and apoptosis. IL-3 stimulates its biological effects by binding to a heterodimeric receptor composed of α and β subunits. JAK1 and JAK2 are rapidly activated after binding of IL-3 to their receptors, and are essential for the initiation of intracellular signaling. Previously, we reported that JAK1 and JAK2 were associated with the IL-3 receptor β and α subunits, respectively. In addition to the JH1 domain（kinase domain）, the JAK family contains the JH2-JH7 domains. JH2 has been shown to have a negative regulatory effect on JAK2 kinase activity. JH3-JH7 domains have been implicated in receptor association. However, which regions of JAKs interact with IL-3 receptors is now unclear. In this study, I demonstrated that the JH3-JH7 domains of JAK1 interacted with βc subunit, but had weak interaction with IL-3 receptor α subunit by GST-pull down assay. The deletion of JH7 domain or JH6-JH7 domains of JAK2 did not affect the interaction with IL-3 receptors. Abstract p38 play a central role in cellular responses such as cell proliferation, differentiation and apoptosis. We have previously reported that Activin A-induced globin promoters and cell growth inhibition were inhibited by p38 inhibitor SB203580. The p38 inhibitor SB203580 targets both p38α and p38β. To further investigate that p38α, p38β or both kinases are involved in cytokine-mediated cell proliferation and differentiation, we performed the RT-PCR to analyze the expression of four p38 isoforms on K562 and Jurkat cells. We showed that p38α, p38β, p38γ and p38δ transcripts are expressed in K562 and Jurkat cells. Expression of the exogenous p38 dominant negative mutants, p38αAF and p38βAF, reduced Activin A-induced α- and ζ-globin promoters activity, indicating that Activin A activated α- and ζ-globin gene promoters through p38α and p38β. In addition, the expression of c-Jun, a blocker of erythroid differentiation, was up-regulated by SB203580 in K562 cells. At last IFN-α inhibited Jurkat cell growth through p38 pathway. Together, these results suggest that p38 plays an important role in regulating cell proliferation and differentiation.