Kosaka C, Pears C J
Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
Biochem J. 1997 May 15;324 ( Pt 1)(Pt 1):347-52. doi: 10.1042/bj3240347.
Two homologues of mitogen-activated protein kinases have been identified in Dictyostelium discoideum (ERK1 and EKR2). We here demonstrate transient tyrosine phosphorylation of ERK2 in response to the chemoattractants cAMP and folic acid that correlates with activity. To investigate the signalling pathways, we studied the response in strains with altered cAMP-dependent protein kinase (PKA) status. The degree of cAMP-induced ERK2 tyrosine phosphorylation was increased in cells overexpressing PKA activity but no such increase was observed in the response to folic acid. Our observations suggest that cAMP-induced ERK2 tyrosine phosphorylation is positively modulated by a PKA-regulated step which is not involved in the response to folic acid, suggesting the presence of diverse signalling pathways leading to ERK2 activation.
在盘基网柄菌中已鉴定出两种丝裂原活化蛋白激酶的同源物(ERK1和EKR2)。我们在此证明,响应趋化剂cAMP和叶酸时,ERK2会发生瞬时酪氨酸磷酸化,且这种磷酸化与活性相关。为了研究信号通路,我们研究了cAMP依赖性蛋白激酶(PKA)状态改变的菌株的反应。在过表达PKA活性的细胞中,cAMP诱导的ERK2酪氨酸磷酸化程度增加,但在对叶酸的反应中未观察到这种增加。我们的观察结果表明,cAMP诱导的ERK2酪氨酸磷酸化受到PKA调节步骤的正向调节,该步骤不参与对叶酸的反应,这表明存在导致ERK2激活的多种信号通路。