Ward Y, Gupta S, Jensen P, Wartmann M, Davis R J, Kelly K
Laboratory of Pathology, National Cancer Institute, Bethesda, Maryland 20892.
Nature. 1994 Feb 17;367(6464):651-4. doi: 10.1038/367651a0.
Intracellular signalling following mitogenic stimulation of quiescent cells involves the initiation of a phosphorylation cascade that leads to the rapid and reversible activation of the mitogen-activated protein (MAP) kinases ERK1 and ERK2. MAP kinase activation is mediated by dual phosphorylation within the motif Thr-Glu-Tyr by MAP kinase kinase (MEK). Following activation, the MAP kinases translocate into the nucleus where they phosphorylate several transduction targets, including transcription factors. We have previously identified PAC1 as an immediate-early mitogen-inducible tyrosine phosphatase in nuclei of T cells. Here we present several lines of evidence indicating that PAC1 is a physiologically relevant MAP kinase phosphatase. Recombinant PAC1 in vitro is a dual-specific Thr/Tyr phosphatase with stringent substrate specificity for MAP kinase. Constitutive expression of PAC1 in vivo leads to inhibition of MAP kinase activity normally stimulated by epidermal growth factor, phorbol myristyl acetate, or T-cell receptor crosslinking. The inactivation of MAP kinase by PAC1 results in inhibition of MAP kinase-regulated reporter gene expression.
静止细胞经有丝分裂原刺激后的细胞内信号传导涉及磷酸化级联反应的启动，该反应导致丝裂原活化蛋白（MAP）激酶ERK1和ERK2快速且可逆的激活。MAP激酶的激活由MAP激酶激酶（MEK）在基序Thr-Glu-Tyr内的双重磷酸化介导。激活后，MAP激酶转位至细胞核，在那里它们使包括转录因子在内的几个转导靶点磷酸化。我们之前已将PAC1鉴定为T细胞核中一种即时早期有丝分裂原诱导型酪氨酸磷酸酶。在此我们提供了几条证据表明PAC1是一种生理相关的MAP激酶磷酸酶。体外重组PAC1是一种对MAP激酶具有严格底物特异性的双特异性Thr/Tyr磷酸酶。体内PAC1的组成型表达导致通常由表皮生长因子、佛波酯肉豆蔻酸酯或T细胞受体交联刺激的MAP激酶活性受到抑制。PAC1使MAP激酶失活导致MAP激酶调节的报告基因表达受到抑制。
