Mammary serine protease inhibitor (maspin) binds directly to interferon regulatory factor 6 - Identification of a novel serpin partnership
Mammary serine protease inhibitor (maspin) binds directly to interferon regulatory factor 6 - Identification of a novel serpin partnership
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DOI：
10.1074/jbc.m503523200
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发表时间：
2005-10-07
影响因子：
4.8
通讯作者：
Hendrix, MJC
中科院分区：
文献类型：
--
作者：
Bailey, CM;Khalkhali-Ellis, Z;Hendrix, MJC
自1994年发现以来，maspin（乳腺丝氨酸蛋白酶抑制剂）已被鉴定为II类肿瘤抑制剂，具有促进细胞凋亡和抑制细胞侵袭的能力。Maspin在正常乳腺上皮细胞中高度表达，但在侵袭性乳腺癌中减少或缺失。然而，尽管努力表征maspin作为肿瘤抑制因子的作用机制，但其分子表征仍然有些难以捉摸。因此，在试图确定maspin相互作用的蛋白质，从而深入了解maspin的功能途径，我们采用amaspin诱饵酵母双杂交系统，随后确定干扰素调节因子6（IRF 6）作为maspin结合蛋白。IRF 6属于IRF转录因子家族，其最为人所知的是在致病刺激后对干扰素和干扰素诱导基因的调节。虽然许多IRF家族成员已被很好地表征，但IRF 6仍然知之甚少。我们报告说，IRF 6在正常乳腺上皮细胞中表达，它直接与maspin在酵母双杂交系统和体外。这种相互作用通过保守的IRF蛋白结合结构域发生，并受IRF 6磷酸化的调节。我们已经表明，与maspin相似，IRF 6表达与乳腺癌侵袭性呈负相关。我们进一步证明，乳腺癌细胞中IRF 6的短暂重新表达导致N-钙粘蛋白的增加和与细胞形态变化相称的波形蛋白的重新分布，表明上皮细胞向间充质转化事件。同时，我们发现maspin在这个过程中起负调节作用。这些发现有助于阐明maspin的分子机制，并表明maspin和IRF 6在调节细胞表型中的相互作用，其损失可导致肿瘤转化。
Since its reported discovery in 1994, maspin ( mammary serine protease inhibitor) has been characterized as a class II tumor suppressor by its ability to promote apoptosis and inhibit cell invasion. Maspin is highly expressed in normal mammary epithelial cells but reduced or absent in aggressive breast carcinomas. However, despite efforts to characterize the mechanism(s) by which maspin functions as a tumor suppressor, its molecular characterization has remained somewhat elusive. Therefore, in an attempt to identify maspin-interacting proteins and thereby gain insight into the functional pathways of maspin, we employed amaspin-baited yeast two-hybrid system and subsequently identified Interferon Regulatory Factor 6 (IRF6) as a maspin-binding protein. IRF6 belongs to the IRF family of transcription factors, which is best known for its regulation of interferon and interferon-inducible genes following a pathogenic stimulus. Although many of the IRF family members have been well characterized, IRF6 remains poorly understood. We report that IRF6 is expressed in normal mammary epithelial cells and that it directly associates with maspin in a yeast two-hybrid system and in vitro. The interaction occurs via the conserved IRF protein association domain and is regulated by phosphorylation of IRF6. We have shown that, similar to maspin, IRF6 expression is inversely correlated with breast cancer invasiveness. We further demonstrated that the transient re-expression of IRF6 in breast cancer cells results in an increase of N-cadherin and a redistribution of vimentin commensurate with changes in cell morphology, suggestive of an epithelial-to-mesenchymal transition event. Concomitantly, we showed that maspin acts as a negative regulator of this process. These findings help to elucidate the molecular mechanisms of maspin and suggest an interactive role between maspin and IRF6 in regulating cellular phenotype, the loss of which can lead to neoplastic transformation.