Division of Glyco-Signal Research, Institute of Molecular Biomembrane and Glycobiology, Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai, Miyagi 981-8558, Japan.
Biochem Biophys Res Commun. 2012 Mar 30;420(1):193-8. doi: 10.1016/j.bbrc.2012.02.142. Epub 2012 Mar 3.
Prolonged or repeated agonist activation of G-protein-coupled receptors (GPCRs) initiates their desensitization and internalization, rendering them unresponsive to agonist activation. We analyzed how gangliosides and chondroitin sulfate affect B2 bradykinin (BK) receptors (B2Rs). Gangliosides and chondroitin sulfate did not stimulate intracellular Ca(2+) release from B2R-expressing CHO-K1 cells, but repeated exposure desensitized B2Rs to BK stimulation. Microscopic observation of DsRed-fused B2Rs revealed that several gangliosides and chondroitin sulfate C (CSC) effectively internalized B2Rs. Ganglioside-CSC treatment of B2R mutant-expressing cells failed to desensitize and internalize the mutant receptors. As this mutant lacks the first extracellular domain and cannot activate GPCR kinase (GRK), gangliosides and CSC likely initiate B2R desensitization and endocytosis through GRK-mediated B2R phosphorylation.
蛋白偶联受体（GPCRs）的激动剂持续或反复激活会引发其脱敏和内化，使其对激动剂激活无反应。我们分析了神经节苷脂和硫酸软骨素如何影响 B2 缓激肽（BK）受体（B2R）。神经节苷脂和硫酸软骨素 C （CSC）不会刺激表达 B2R 的 CHO-K1 细胞内 Ca（2+）释放，但反复暴露会使 B2R 对 BK 刺激脱敏。DsRed 融合 B2R 的显微镜观察显示，几种神经节苷脂和 CSC 可有效内化 B2R。B2R 突变体表达细胞的神经节苷脂-CSC 处理不能使突变体受体脱敏和内化。由于这种突变体缺乏第一个细胞外结构域，并且不能激活 GPCR 激酶（GRK），因此神经节苷脂和 CSC 可能通过 GRK 介导的 B2R 磷酸化引发 B2R 脱敏和内吞作用。
