Fresno Vara J A, Carretero M V, Gerónimo H, Ballmer-Hofer K, Martín-Pérez J
Instituto de Investigaciones Biomédicas, C.S.I.C., Arturo Duperier 4, 28029 Madrid, Spain.
Biochem J. 2000 Jan 1;345 Pt 1(Pt 1):17-24. doi: 10.1042/0264-6021:3450017.
Interaction of prolactin (PRL) with its receptor (PRLR) leads to activation of Jak and Src family tyrosine kinases. The PRL/growth hormone/cytokine receptor family conserves a proline-rich sequence in the cytoplasmic juxtamembrane region (Box 1) required for association and subsequent activation of Jaks. In the present work, we studied the mechanisms underlying c-Src kinase activation by PRL and the role that Jak2 plays in this process. PRL addition to chicken embryo fibroblasts (CEF) expressing the rat PRLR long form resulted in activation of c-Src and Jak2 and in tyrosine phosphorylation of the receptor. Receptor phosphorylation was due to associated Jak2, since in cells expressing either a Box 1 mutated PRLR (PRLR(4P-A)), which is unable to interact with Jak2, or a kinase-domain-deleted Jak2 (Jak2Deltak), PRL did not stimulate receptor phosphorylation. Interestingly, addition of PRL to cells expressing PRLR(4P-A) resulted in an activation of c-Src equivalent to that observed with the wild-type receptor. These findings indicate that PRL-mediated stimulation of c-Src was independent of Jak2 activation and of receptor phosphorylation. Our results suggest that PRL-activated Src could send signals to downstream cellular targets independently of Jak2.
催乳素（PRL）与其受体（PRLR）相互作用会导致Jak和Src家族酪氨酸激酶的激活。PRL/生长激素/细胞因子受体家族在细胞质近膜区域保留了一个富含脯氨酸的序列（框1），这是Jak结合及随后激活所必需的。在本研究中，我们探究了PRL激活c-Src激酶的潜在机制以及Jak2在此过程中所起的作用。向表达大鼠PRLR长型的鸡胚成纤维细胞（CEF）中添加PRL，会导致c-Src和Jak2的激活以及受体的酪氨酸磷酸化。受体磷酸化是由相关的Jak2引起的，因为在表达无法与Jak2相互作用的框1突变PRLR（PRLR(4P-A)）或激酶结构域缺失的Jak2（Jak2Deltak）的细胞中，PRL不会刺激受体磷酸化。有趣的是，向表达PRLR(4P-A)的细胞中添加PRL会导致c-Src的激活，其程度与野生型受体相当。这些发现表明，PRL介导的c-Src刺激独立于Jak2激活和受体磷酸化。我们的结果表明，PRL激活的Src可以独立于Jak2向细胞下游靶点发送信号。
