Transglutaminase 2 kinase activity facilitates protein kinase A-induced phosphorylation of retinoblastoma protein
Transglutaminase 2 kinase activity facilitates protein kinase A-induced phosphorylation of retinoblastoma protein
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DOI：
10.1074/jbc.m607413200
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发表时间：
2007-06-22
影响因子：
4.8
通讯作者：
Murphy, Liam J.
中科院分区：
文献类型：
--
作者：
Mishra, Suresh;Melino, Gerry;Murphy, Liam J.
转谷氨酰胺酶2(TG2，组织转谷氨酰胺酶)是一种多功能蛋白质，参与多种蛋白质的交联，包括视网膜母细胞瘤蛋白(Rb)。在这里，我们表明Rb也是最近发现的TG2丝氨酸/苏氨酸激酶活性的底物，并且TG2在关键的Ser(780)残基上磷酸化Rb。此外，TG2对Rb的磷酸化破坏了Rb中心点E2F1复合体的稳定性。高浓度的Ca~(2+)抑制Rb的TG2磷酸化，而ATP则抑制TG2的转氨酶活性。TG2自身被蛋白激酶A(PKA)磷酸化。PKA对TG2的磷酸化可减弱其转胺化活性，增强其激酶活性。用二丁酰cAMP激活小鼠胚胎成纤维细胞(MEF)中的PKA可促进TG2和RB的磷酸化，这一过程可被PKA抑制剂H89抑制。二丁酰cAMP可促进MEFtg2+/+细胞的Rb磷酸化，但对MEFtg2-/-细胞无明显影响。这些数据表明Rb是TG2激酶活性的底物，并提示Rb的磷酸化是间接的，需要TG2激酶活性。
Transglutaminase 2 (TG2, tissue transglutaminase) is a multifunctional protein involved in cross-linking a variety of proteins, including retinoblastoma protein (Rb). Here we show that Rb is also a substrate for the recently identified serine/threonine kinase activity of TG2 and that TG2 phosphorylates Rb at the critically important Ser(780) residue. Furthermore, phosphorylation of Rb by TG2 destabilizes the Rb center dot E2F1 complex. TG2 phosphorylation of Rb was abrogated by high Ca2+ concentrations, whereas TG2 transamidating activity was inhibited by ATP. TG2 was itself phosphorylated by protein kinase A (PKA). Phosphorylation of TG2 by PKA attenuated its transamidating activity and enhanced its kinase activity. Activation of PKA in mouse embryonic fibroblasts (MEF) with dibutyryl-cAMP enhanced phosphorylation of both TG2 and Rb by a process that was inhibited by the PKA inhibitor H89. Treatment with dibutyryl-cAMP enhanced Rb phosphorylation in MEFtg2+/+ cells but not in MEFtg2-/- cells. These data indicate that Rb is a substrate for TG2 kinase activity and suggest that phosphorylation of Rb, which results from activation of PKA in fibroblasts, is indirect and requires TG2 kinase activity.