Schubert Shay Y, Ilan Neta, Shushy Moran, Ben-Izhak Ofer, Vlodavsky Israel, Goldshmidt Orit
Cancer and Vascular Biology Research Center, Rappaport Faculty of Medicine, Technion, Haifa, Israel.
Lab Invest. 2004 May;84(5):535-44. doi: 10.1038/labinvest.3700084.
In previous studies, we have demonstrated that human heparanase (endo-beta-D-glucuronidase) is localized primarily in a perinuclear pattern within lysosomes and late endosomes, and occasionally may be surface associated and secreted. The presence of two potential nuclear localization sequences in human heparanase, led us to investigate heparanase translocation into the nucleus and subsequent degradation of nuclear heparan sulfate. Applying cell fractionation, Western blot analysis, determination of heparanase activity and confocal microscopy, we identified heparanase within the nuclei of human glioma and breast carcinoma cells and estimated its amount to be about 7% of the cytosolic enzyme. Our results indicate that nuclear heparanase colocalizes with nuclear heparan sulfate and is enzymaticaly active. Moreover, following uptake of latent 65 kDa heparanase by cells that do not express the enzyme, an active 50 kDa heparanase was detected in the cell nucleus, capable of degrading both nuclear and extracellular matrix-derived heparan sulfate. Immunohistochemical examination of human squamous cell carcinoma specimens revealed a prominent granular staining of heparanase within the nuclei of the epithelial tumor cells vs no nuclear staining in the adjacent stromal cells. Taken together, it appears that heparanase is translocated into the cell nucleus where it may degrade the nuclear heparan sulfate and thereby affect nuclear functions that are thought to be regulated by heparan sulfate. Nuclear localization of heparanase suggests that the enzyme may fulfill nontraditional functions (ie, regulation of gene expression and signal transduction) apart of its well-documented involvement in cancer metastasis, angiogenesis and inflammation.
在先前的研究中，我们已经证明人乙酰肝素酶（内切-β-D-葡糖醛酸酶）主要定位于溶酶体和晚期内体中的核周模式，偶尔可能与表面相关并分泌。人乙酰肝素酶中存在两个潜在的核定位序列，这促使我们研究乙酰肝素酶向细胞核的转运以及随后细胞核硫酸乙酰肝素的降解。通过细胞分级分离、蛋白质印迹分析、乙酰肝素酶活性测定和共聚焦显微镜检查，我们在人胶质瘤和乳腺癌细胞的细胞核中鉴定出了乙酰肝素酶，并估计其含量约为胞质酶的7%。我们的结果表明，细胞核乙酰肝素酶与细胞核硫酸乙酰肝素共定位且具有酶活性。此外，在不表达该酶的细胞摄取潜伏的65 kDa乙酰肝素酶后，在细胞核中检测到一种活性50 kDa乙酰肝素酶，它能够降解细胞核和细胞外基质来源的硫酸乙酰肝素。对人鳞状细胞癌标本的免疫组织化学检查显示，上皮肿瘤细胞的细胞核内乙酰肝素酶有明显的颗粒状染色，而相邻基质细胞的细胞核无染色。综上所述，似乎乙酰肝素酶被转运到细胞核中，在那里它可能降解细胞核硫酸乙酰肝素，从而影响被认为受硫酸乙酰肝素调节的核功能。乙酰肝素酶的核定位表明，该酶除了在癌症转移、血管生成和炎症中已被充分证明的作用外，可能还具有非传统功能（即基因表达调控和信号转导）。
