Fluorescence Probes for Imaging Basic Carboxypeptidase Activity in Living Cells with High Intracellular Retention
作者:Hirohisa Iwaki、Mako Kamiya、Minoru Kawatani、Ryosuke Kojima、Tatsuya Yamasoba、Yasuteru Urano
DOI:10.1021/acs.analchem.0c04793
日期:2021.2.23
Basic carboxypeptidases (basic CPs) cleave the C-terminal basic amino acid of peptides, and their activity is upregulated in some types of cancers. Therefore, detecting the activity of basic CPs in living cells would be important not only for studying the physiological functions of these enzymes but also for visualization of cancerous tissues. Here, we report two fluorescein diacetate (FDA)-based activatable fluorescence probes, named 5ArgAF-FDA and 5LysAF-FDA, in which the substrate amino acid arginine or lysine is conjugated to the benzene moiety via an azoformyl linker. In live-cell fluorescence imaging of CPM, one of the seven basic CPs, 5ArgAF-FDA showed a larger intracellular fluorescence increase than did 5LysAF-FDA within a few minutes. This increase was inhibited by coincubation with 2-mercaptomethyl-3-guanidinoethylthiopropanoic acid (MGTA), an inhibitor of basic CPs. When 5ArgAF-FDA was applied to a coculture of two breast cancer cell lines with different CPM activities, the fluorescence increase in individual cells was correlated with the expression level of CPM, suggesting that 5ArgAF-FDA has the ability to distinguish cell lines having different levels of CPM activity, owing to its high intracellular retention. We believe these probes will be useful for imaging cancers with upregulated basic CP activity.
碱性羧肽酶(碱性 CPs)能裂解肽的 C 端碱性氨基酸,在某些类型的癌症中,碱性 CPs 的活性会升高。因此,检测活细胞中碱性羧肽酶的活性不仅对研究这些酶的生理功能很重要,而且对癌症组织的可视化也很重要。在这里,我们报告了两种基于双乙酸荧光素(FDA)的可激活荧光探针,分别命名为 5ArgAF-FDA 和 5LysAF-FDA,其中底物氨基酸精氨酸或赖氨酸通过偶氮甲酰基连接物与苯分子共轭。在七种基本 CPs 之一 CPM 的活细胞荧光成像中,5ArgAF-FDA 在几分钟内显示出比 5LysAF-FDA 更大的细胞内荧光增加。与碱性氯化石蜡抑制剂 2-巯甲基-3-胍基乙基硫代丙酸(MGTA)同时使用可抑制这种增加。当将 5ArgAF-FDA 应用于两种具有不同 CPM 活性的乳腺癌细胞系的共培养时,单个细胞的荧光增加与 CPM 的表达水平相关,这表明 5ArgAF-FDA 由于其在细胞内的高滞留性,能够区分具有不同 CPM 活性水平的细胞系。我们相信,这些探针将有助于对基本 CP 活性上调的癌症进行成像。