Rathinavelu A, Isom G E
Department of Pharmacology and Toxicology, School of Pharmacy and Pharmacal Sciences, Purdue University, West Lafayette, IN 47907.
Biochem Biophys Res Commun. 1991 Mar 29;175(3):1017-22. doi: 10.1016/0006-291x(91)91666-z.
Receptor mediated internalization of 125I-ANF (99-126) and the underlying mechanism was studied in PC12 cells. Phosphorylation of PC12 cell plasma membrane proteins at 0 degrees C or 37 degrees C was not altered in presence of ANF (99-126) or c-ANF (4-23). Exposure of cells to phorbol 12-myristate 13-acetate (PMA, 100 ng/ml) did not alter the endocytic rate or extent of 125I-ANF (99-126) internalization. When cells were treated with a combination of PMA and the calcium ionophore A23187, internalization was not stimulated. Incubation with A23187 (10 microM) alone decreased 125I-ANF (99-126) internalization by 22% in Ca2+ containing medium. Cell surface binding increased 10% in the presence of Ca2+ compared to Ca2+ free medium, irrespective of the presence of A23187. Ca2+ appears to play an important role in the binding of ANF to the receptor and initiation of ligand-receptor complex internalization. Activation of protein kinase C or receptor phosphorylation is not an essential step in initiating ANF receptor internalization.
在PC12细胞中研究了125I-ANF（99-126）的受体介导内化及其潜在机制。在存在ANF（99-126）或c-ANF（4-23）的情况下，0℃或37℃时PC12细胞质膜蛋白的磷酸化未发生改变。将细胞暴露于佛波醇12-肉豆蔻酸酯13-乙酸酯（PMA，100 ng/ml）不会改变125I-ANF（99-126）的内吞速率或内化程度。当用PMA和钙离子载体A23187联合处理细胞时，内化未受到刺激。单独用A23187（10 microM）孵育在含Ca2+的培养基中使125I-ANF（99-126）内化减少22%。与无Ca2+培养基相比，在存在Ca2+的情况下，无论是否存在A23187，细胞表面结合增加10%。Ca2+似乎在ANF与受体的结合以及配体-受体复合物内化的起始中起重要作用。蛋白激酶C的激活或受体磷酸化不是启动ANF受体内化的必要步骤。
