Yanagawa Takashi, Funasaka Tatsuyoshi, Tsutsumi Soichi, Hu Huankai, Watanabe Hideomi, Raz Avraham
Tumor Progression and Metastasis Program, Karmanos Cancer Institute, School of Medicine, Wayne State University, Detroit, Michigan 48201, USA.
Cancer Res. 2007 Sep 15;67(18):8682-9. doi: 10.1158/0008-5472.CAN-07-1586.
Phosphoglucose isomerase (PGI; EC 5.3.1.9) is a ubiquitous cytosolic enzyme essential for glycolysis and gluconeogenesis. PGI is a multifunctional dimeric protein that extracellularly acts as a cytokine [autocrine motility factor (AMF)] eliciting mitogenic, motogenic, and differentiation functions through binding to its cell surface receptor gp78/AMF receptor (AMFR). AMFR contains a seven-transmembrane domain with RING-H2 and leucine zipper motifs showing ubiquitin protein ligase (E3) activity and is exposed on the endoplasmic reticulum surface. Augmented expressions of both PGI/AMF and AMFR have been implicated in tumor progression and metastasis, and an intracellular binding partner of PGI/AMF is expected to regulate in part its diverse biological functions. Thus, we screened a cDNA library using a yeast two-hybrid system to search for interacting protein(s) and report on the finding of poly(ADP-ribose) polymerase-14 (PARP-14) to be a binding partner with PGI/AMF. PARP-14-PGI/AMF interaction was confirmed by coimmunoprecipitation and immunolocalization. We also report that PGI/AMF degradation is mainly regulated by the ubiquitin-lysosome system and RNA interference experiments revealed that PARP-14 inhibits PGI/AMF ubiquitination, thus contributing to its stabilization and secretion. This newly characterized PARP-14 protein should assist in understanding the regulation of PGI/AMF intracellular function(s) and may provide a new therapeutic target for inhibition of PGI/AMF inducing tumor cell migration and invasion during metastasis.
磷酸葡萄糖异构酶（PGI；EC 5.3.1.9）是一种普遍存在的胞质酶，对糖酵解和糖异生至关重要。PGI是一种多功能二聚体蛋白，在细胞外作为一种细胞因子[自分泌运动因子（AMF）]，通过与细胞表面受体gp78/AMF受体（AMFR）结合发挥促有丝分裂、促运动和分化功能。AMFR含有一个七跨膜结构域，带有RING-H2和亮氨酸拉链基序，具有泛素蛋白连接酶（E3）活性，且暴露于内质网表面。PGI/AMF和AMFR的表达增加均与肿瘤进展和转移有关，预计PGI/AMF的细胞内结合伴侣可部分调节其多种生物学功能。因此，我们使用酵母双杂交系统筛选cDNA文库以寻找相互作用蛋白，并报告发现聚（ADP-核糖）聚合酶-14（PARP-14）是与PGI/AMF的结合伴侣。通过免疫共沉淀和免疫定位证实了PARP-14与PGI/AMF的相互作用。我们还报告PGI/AMF的降解主要受泛素-溶酶体系统调节，RNA干扰实验表明PARP-14抑制PGI/AMF的泛素化，从而有助于其稳定和分泌。这种新鉴定的PARP-14蛋白应有助于理解PGI/AMF细胞内功能的调节，并可能为抑制PGI/AMF在转移过程中诱导肿瘤细胞迁移和侵袭提供新的治疗靶点。
