Neilson Lynn M, Zhu Jianquong, Xie Jianwu, Malabarba M Grazia, Sakamoto Kazuhito, Wagner Kay-Uwe, Kirken Robert A, Rui Hallgeir
Kimmel Cancer Center, Department of Cancer Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
Mol Endocrinol. 2007 Sep;21(9):2218-32. doi: 10.1210/me.2007-0173. Epub 2007 Jun 5.
Prolactin (PRL) receptors (PRLRs) have been considered selective activators of Janus tyrosine kinase (Jak)2 but not Jak1, Jak3, or Tyk2. We now report marked PRL-induced tyrosine phosphorylation of Jak1, in addition to Jak2, in a series of human breast cancer cell lines, including T47D, MCF7, and SKBR3. In contrast, PRL did not activate Jak1 in immortalized, noncancerous breast epithelial lines HC11, MCF10A, ME16C, and HBL-100, or in CWR22Rv1 prostate cancer cells or MDA-MB-231 breast cancer cells. However, introduction of exogenous PRLR into MCF10A, ME16C, or MDA-MB-231 cells reconstituted both PRL-Jak1 and PRL-Jak2 signals. In vitro kinase assays verified that PRL stimulated enzymatic activity of Jak1 in T47D cells, and PRL activated Jak1 and Jak2 with indistinguishable time and dose kinetics. Relative Jak2 deficiency did not cause PRLR activation of Jak1, because overexpression of Jak2 did not interfere with PRL activation of Jak1. Instead, PRL activated Jak1 through a Jak2-dependent mechanism, based on disruption of PRL activation of Jak1 after Jak2 suppression by 1) lentiviral delivery of Jak2 short hairpin RNA, 2) adenoviral delivery of dominant-negative Jak2, and 3) AG490 pharmacological inhibition. Finally, suppression of Jak1 by lentiviral delivery of Jak1 short hairpin RNA blocked PRL activation of ERK and signal transducer and activator of transcription (Stat)3 and suppressed PRL activation of Jak2, Stat5a, Stat5b, and Akt, as well as tyrosine phosphorylation of PRLR. The data suggest that PRL activation of Jak1 represents a novel, Jak2-dependent mechanism that may serve as a regulatory switch leading to PRL activation of ERK and Stat3 pathways, while also serving to enhance PRL-induced Stat5a/b and Akt signaling.
催乳素（PRL）受体（PRLRs）一直被认为是Janus酪氨酸激酶（Jak）2的选择性激活剂，而非Jak1、Jak3或Tyk2的激活剂。我们现在报告，在一系列人乳腺癌细胞系中，包括T47D、MCF7和SKBR3，PRL除了能诱导Jak2酪氨酸磷酸化外，还能显著诱导Jak1的酪氨酸磷酸化。相比之下，PRL在永生化的非癌性乳腺上皮细胞系HC11、MCF10A、ME16C和HBL - 100中，以及在CWR22Rv1前列腺癌细胞或MDA - MB - 231乳腺癌细胞中均未激活Jak1。然而，将外源性PRLR导入MCF10A、ME16C或MDA - MB - 231细胞中可重建PRL - Jak1和PRL - Jak2信号。体外激酶分析证实，PRL刺激了T47D细胞中Jak1的酶活性，并且PRL激活Jak1和Jak2的时间和剂量动力学难以区分。相对Jak2缺陷不会导致PRLR对Jak1的激活，因为Jak2的过表达不会干扰PRL对Jak1的激活。相反，基于以下情况，PRL通过Jak2依赖性机制激活Jak1：在通过1）慢病毒递送Jak2短发夹RNA、2）腺病毒递送显性负性Jak2以及3）AG490药物抑制来抑制Jak2后，PRL对Jak1的激活受到破坏。最后，通过慢病毒递送Jak1短发夹RNA抑制Jak1可阻断PRL对ERK和信号转导及转录激活因子（Stat）3的激活，并抑制PRL对Jak2、Stat5a、Stat5b和Akt的激活，以及PRLR的酪氨酸磷酸化。数据表明，PRL对Jak1的激活代表了一种新的、Jak2依赖性机制，该机制可能作为一种调节开关，导致PRL激活ERK和Stat3途径，同时也有助于增强PRL诱导的Stat5a/b和Akt信号传导。
