Wang Maggie, Alabi Adekunle, Gu Hong-Mei, Gill Govind, Zhang Ziyang, Jarad Suha, Xia Xiao-Dan, Shen Yishi, Wang Gui-Qing, Zhang Da-Wei
The Department of Pediatrics and Group on the Molecular Cell Biology of Lipids, Faculty of Medicine Dentistry, College of Health Sciences, University of Alberta, Edmonton, AB, Canada.
Department of Orthopedics, The Sixth Affiliated Hospital of Guangzhou Medical University, Qingyuan People's Hospital, Qingyuan, China.
Front Cardiovasc Med. 2022 Aug 25;9:917238. doi: 10.3389/fcvm.2022.917238. eCollection 2022.
Low-density lipoprotein receptor (LDLR) mediates clearance of plasma LDL cholesterol, preventing the development of atherosclerosis. We previously demonstrated that membrane type 1-matrix metalloproteinase (MT1-MMP) cleaves LDLR and exacerbates the development of atherosclerosis. Here, we investigated determinants in LDLR and MT1-MMP that were critical for MT1-MMP-induced LDLR cleavage. We observed that deletion of various functional domains in LDLR or removal of each of the five predicted cleavage sites of MT1-MMP on LDLR did not affect MT1-MMP-induced cleavage of the receptor. Removal of the hemopexin domain or the C-terminal cytoplasmic tail of MT1-MMP also did not impair its ability to cleave LDLR. On the other hand, mutant MT1-MMP, in which the catalytic domain or the MT-loop was deleted, could not cleave LDLR. Further Ala-scanning analysis revealed an important role for Ile at position 167 of the MT-loop in MT1-MMP's action on LDLR. Replacement of Ile167 with Ala, Thr, Glu, or Lys resulted in a marked loss of the ability to cleave LDLR, whereas mutation of Ile167 to a non-polar amino acid residue, including Leu, Val, Met, and Phe, had no effect. Therefore, our studies indicate that MT1-MMP does not require a specific cleavage site on LDLR. In contrast, an amino acid residue with a hydrophobic side chain at position 167 in the MT-loop is critical for MT1-MMP-induced LDLR cleavage.
低密度脂蛋白受体（LDLR）介导血浆低密度脂蛋白胆固醇的清除，从而预防动脉粥样硬化的发展。我们先前证明，膜型1基质金属蛋白酶（MT1-MMP）可切割LDLR并加剧动脉粥样硬化的发展。在此，我们研究了LDLR和MT1-MMP中对MT1-MMP诱导的LDLR切割至关重要的决定因素。我们观察到，LDLR中各种功能域的缺失或LDLR上MT1-MMP的五个预测切割位点中每个位点的去除均不影响MT1-MMP诱导的受体切割。去除MT1-MMP的血红素结合蛋白结构域或C末端细胞质尾巴也不会损害其切割LDLR的能力。另一方面，缺失催化结构域或MT环的突变型MT1-MMP不能切割LDLR。进一步的丙氨酸扫描分析揭示了MT环第167位的异亮氨酸在MT1-MMP对LDLR的作用中的重要作用。将异亮氨酸167替换为丙氨酸、苏氨酸、谷氨酸或赖氨酸会导致切割LDLR的能力明显丧失，而异亮氨酸167突变为非极性氨基酸残基（包括亮氨酸、缬氨酸、甲硫氨酸和苯丙氨酸）则没有影响。因此，我们的研究表明MT1-MMP不需要LDLR上的特定切割位点。相反，MT环中第167位带有疏水侧链的氨基酸残基对于MT1-MMP诱导的LDLR切割至关重要。
