Susarla Radhika, Watkinson John C, Eggo Margaret C
Division of Medical Sciences, University of Birmingham, Birmingham, UK.
J Cell Physiol. 2007 Sep;212(3):643-54. doi: 10.1002/jcp.21060.
Human thyroid cells in culture take up and organify (125)I when cultured in TSH (acting through cAMP) and insulin. They also secrete urokinase (uPA) and tissue-type (tPA) plasminogen activators (5-100 IU/10(6)cells/day). TSH and insulin both decreased secreted PA activity (PAA), uPA and tPA protein and their mRNAs. Autocrine fibroblast growth factor increased secreted PAA and inhibited thyroid cell (125)I uptake. Epidermal growth factor (EGF) and the protein kinase C (PKC) activator, TPA significantly increased PAA and inhibited thyroid differentiated function, (TPA > EGF). For TPA, effects were rapid, increased PAA secretion and decreased (125)I uptake being seen at 4 h whereas for EGF, a 24 h incubation was required. qRT-PCR showed significantly increased mRNA expression of uPA with lesser effects on tPA. Aprotinin, which inhibits PAA, increased (125)I uptake but did not abrogate the effects of TPA and EGF. The MEKK inhibitor, PD98059 partially reversed the effects of EGF and TPA on PAA, and largely reversed the effects of EGF but not TPA on differentiated function. PKC inhibitors bisindoylmaleimide 1, and the specific PKCbeta inhibitor, LY379196 completely reversed the effects of TPA on (125)I uptake and PAA whereas EGF effects were unaffected. TPA inhibited follicle formation and this effect was blocked by LY379196 but not PD98059. We conclude that in thyroid cells, MAPK activation inversely correlates with (125)I uptake and directly correlates with PA expression, in contrast to the effects of cAMP. TPA effects on iodide metabolism, dissolution of follicles and uPA synthesis are mediated predominantly through PKCbeta whereas EGF exerts its effects through MAPK but not PKCbeta.
培养的人甲状腺细胞在促甲状腺激素（通过环磷酸腺苷起作用）和胰岛素存在的情况下培养时会摄取并有机化（125）I。它们还分泌尿激酶（uPA）和组织型（tPA）纤溶酶原激活剂（5 - 100 IU/10（6）个细胞/天）。促甲状腺激素和胰岛素均降低分泌的纤溶酶原激活剂活性（PAA）、uPA和tPA蛋白及其mRNA。自分泌成纤维细胞生长因子增加分泌的PAA并抑制甲状腺细胞摄取（125）I。表皮生长因子（EGF）和蛋白激酶C（PKC）激活剂佛波酯（TPA）显著增加PAA并抑制甲状腺分化功能（TPA > EGF）。对于TPA，作用迅速，4小时时可见PAA分泌增加和（125）I摄取减少，而对于EGF，则需要24小时孵育。定量逆转录聚合酶链反应显示uPA的mRNA表达显著增加，对tPA的影响较小。抑制PAA的抑肽酶增加（125）I摄取，但未消除TPA和EGF的作用。MEKK抑制剂PD98059部分逆转了EGF和TPA对PAA的作用，并在很大程度上逆转了EGF对分化功能的作用，但未逆转TPA的作用。PKC抑制剂双吲哚马来酰胺1和特异性PKCβ抑制剂LY379196完全逆转了TPA对（125）I摄取和PAA的作用，而EGF的作用未受影响。TPA抑制滤泡形成，这种作用被LY379196阻断，但未被PD98059阻断。我们得出结论，在甲状腺细胞中，与环磷酸腺苷的作用相反，丝裂原活化蛋白激酶（MAPK）激活与（125）I摄取呈负相关，与PA表达呈正相关。TPA对碘代谢、滤泡溶解和uPA合成的作用主要通过PKCβ介导，而EGF通过MAPK而非PKCβ发挥其作用。
