Division of Tumor and Cellular Biochemistry, Department of Medical Sciences, University of Miyazaki, Miyazaki, Japan.
Department of Applied Chemistry, Faculty of Engineering, University of Miyazaki, Miyazaki, Japan.
Cancer Sci. 2022 Apr;113(4):1406-1416. doi: 10.1111/cas.15277. Epub 2022 Feb 13.
We have previously reported that the proanthocyanidin (PAC) fraction of blueberry leaf extract (BB-PAC) inhibits the proliferation of HTLV-1-infected adult T-cell leukemia (ATL) by inducing apoptosis. In the present study, we further analyzed the structure of BB-PAC and elucidated the molecular mechanism underlying the inhibitory function of HTLV-1-infected and ATL cells. After hot water extraction with fractionation with methanol-acetone, BB-PAC was found to be concentrated in fractions 4 to 7 (Fr7). The strongest inhibition of ATL cell growth was observed with Fr7, which contained the highest BB-PAC polymerization degree of 14. The basic structure of BB-PAC is mainly B-type bonds, with A-type bonds (7.1%) and cinchonain I units as the terminal unit (6.1%). The molecular mechanism of cytotoxicity observed around Fr7 against ATL cells was the degradation of JAK1 to 3 and the dephosphorylation of STAT3/5, which occurs by proteasome-dependent proteolysis, confirming that PAC directly binds to heat shock protein 90 (HSP90). JAK degradation was caused by proteasome-dependent proteolysis, and we identified the direct binding of PAC to HSP90. In addition, the binding of cochaperone ATPase homolog 1 (AHA1) to HSP90, which is required for activation of the cofactor HSP90, was inhibited by BB-PAC treatment. Therefore, BB-PAC inhibited the formation of the HSP90/AHA1 complex and promoted the degradation of JAK protein due to HSP90 dysfunction. These results suggest that the highly polymerized PAC component from blueberry leaves has great potential as a preventive and therapeutic agent against HTLV-1-infected and ATL cells.
我们之前曾报道，蓝莓叶提取物（BB-PAC）中原花青素（PAC）可通过诱导细胞凋亡抑制 HTLV-1 感染的成人 T 细胞白血病（ATL）的增殖。在本研究中，我们进一步分析了 BB-PAC 的结构，并阐明了其抑制 HTLV-1 感染和 ATL 细胞的分子机制。经过甲醇-丙酮分步热水提取，发现 BB-PAC 集中在第 4 至 7 部分（Fr7）。Fr7 对 ATL 细胞生长的抑制作用最强，其所含 BB-PAC 的聚合度最高，为 14。BB-PAC 的基本结构主要为 B 型键，A 型键（7.1%）和 cinchonain I 单元为末端单元（6.1%）。Fr7 对 ATL 细胞的细胞毒性作用的分子机制是 JAK1 降解为 3 和 STAT3/5 去磷酸化，这是通过蛋白酶体依赖性蛋白水解发生的，证实 PAC 直接与热休克蛋白 90（HSP90）结合。JAK 降解是由蛋白酶体依赖性蛋白水解引起的，我们确定了 PAC 与 HSP90 的直接结合。此外，共伴侣 ATP 酶同源物 1（AHA1）与 HSP90 的结合，这对于 HSP90 辅助因子的激活是必需的，也被 BB-PAC 处理所抑制。因此，BB-PAC 抑制 HSP90/AHA1 复合物的形成，并由于 HSP90 功能障碍而促进 JAK 蛋白的降解。这些结果表明，来自蓝莓叶的高聚合 PAC 成分具有作为预防和治疗 HTLV-1 感染和 ATL 细胞的潜在用途。
