Src Family Kinases Accelerate Prolactin Receptor Internalization, Modulating Trafficking and Signaling in Breast Cancer Cells
Src Family Kinases Accelerate Prolactin Receptor Internalization, Modulating Trafficking and Signaling in Breast Cancer Cells
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DOI：
10.1210/me.2008-0341
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发表时间：
2009-02-01
影响因子：
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通讯作者：
Schuler, Linda A.
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文献类型：
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作者：
Piazza, Timothy M.;Lu, Juu-Chin;Schuler, Linda A.
尽管越来越多的证据支持催乳素 (PRL) 在人类乳腺癌中的作用，但关于 PRL 在这些细胞中对其自身受体的调节知之甚少。配体引发的内吞作用是调节受体可用性和信号级联的关键过程，可能导致致癌作用。尽管暴露于外源性 PRL 会加速 PRL 受体 (IPRLR) 长同工型的降解，但在乳腺癌细胞中，PRL 引发的导致 IPRLR 内化和随后下调的信号以及与下游途径的关系均不清楚。在这项研究中，我们发现，在 MCF-7 细胞中，PRL 诱导的 IPRLR 下调可以通过抑制 src 家族激酶 (SFK) 来减少，但不能通过抑制 Janus 激酶 2 来减少。 SFK 的抑制还导致 PRL 诱导的含有胞外结构域的 PRLR 片段的积累，该片段似乎是由新合成的 PRLR 产生的。 IPRLR 与脂筏中的 SFK 构成相关。 PRL 诱导的 SFK 激活导致鸟苷三磷酸酶 dynamin-2 募集至内化复合物，从而导致内吞作用。通过小干扰 RNA 介导的 dynamin-2 敲低来抑制内吞作用，阻断了 PRL 诱导的 IPRLR 下调，证实内化对于这一过程至关重要。 ERK1/2 和 Akt 的最佳磷酸化也需要内吞作用，但 Janus 激酶 2 或信号转导子和转录激活子 5 不需要内吞作用，这表明内化选择性地调节信号级联。总之，这些数据表明 SFK 是乳腺癌细胞中配体启动的 IPRLR 内化、下调和信号转导的关键介质，并强调了靶细胞背景在受体运输和信号转导中的重要性。 (分子内分泌学 23: 202-212, 2009)
Despite the growing body of evidence supporting prolactin (PRL) actions in human breast cancer, little is known regarding PRL regulation of its own receptor in these cells. Ligand-initiated endocytosis is a key process in the regulation of receptor availability and signaling cascades that may lead to oncogenic actions. Although exposure to exogenous PRL accelerates degradation of the long isoform of the PRL receptor (IPRLR), neither the signals initiated by PRL that lead to IPRLR internalization and subsequent down-regulation, nor the relationship to downstream pathways are understood in breast cancer cells. In this study, we showed that PRL-induced down-regulation of the IPRLR was reduced by inhibition of src family kinases (SFKs), but not Janus kinase 2, in MCF-7 cells. Inhibition of SFKs also resulted in accumulation of a PRL-induced PRLR fragment containing the extracellular domain, which appeared to be generated from newly synthesized PRLR. IPRLR was constitutively associated with SFKs in lipid rafts. PRL-induced SFK activation led to recruitment of the guanosine triphosphatase, dynamin-2, to an internalization complex, resulting in endocytosis. Inhibition of endocytosis by small interfering RNA-mediated knockdown of dynamin-2 blocked PRL-induced down-regulation of IPRLR, confirming that internalization is essential for this process. Endocytosis also was required for optimal phosphorylation of ERK1/2 and Akt, but not for Janus kinase 2 or signal transducer and activator of transcription 5, indicating that internalization selectively modulates signaling cascades. Together, these data indicate that SFKs are key mediators of ligand-initiated IPRLR internalization, down-regulation, and signal transduction in breast cancer cells, and underscore the importance of target cell context in receptor trafficking and signal transduction. (Molecular Endocrinology 23: 202-212, 2009)