Laboratory of Receptor Cell Biology, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia.
Biochimie. 2010 Apr;92(4):418-22. doi: 10.1016/j.biochi.2010.01.015. Epub 2010 Jan 25.
Calcium-independent receptor of alpha-latrotoxin (CIRL-1) is an adhesion G protein-coupled receptor implicated in the regulation of exocytosis. CIRL-1 biosynthesis involves constitutive proteolytic processing that takes place in the endoplasmic reticulum, requires the receptor's GPS domain, and yields heterologous two-subunit receptor complexes. It was proposed that the GPS-directed cleavage is based on cis-autoproteolysis. In this study, we demonstrate that activators of protein kinase C - PMA and ionomycin, can inhibit the cleavage of CIRL-1 precursor in transfected cells. Both reagents also downregulate trafficking of CIRL-1 to the cell surface that results in accumulation of the uncleaved receptor precursor inside the cells. Experiments with a non-cleavable soluble mutant of CIRL-1 showed that the downregulation of the receptor trafficking is independent of its cleavage. Our data suggest that the GPS proteolysis of CIRL-1 is not a purely autocatalytic process and may involve auxiliary proteins or factors that become available in the course of CIRL-1 trafficking.
钙非依赖性α- latrotoxin 受体（CIRL-1）是一种黏附 G 蛋白偶联受体，参与调控胞吐作用。CIRL-1 的生物合成涉及内质网中组成性蛋白水解加工，需要受体的 GPS 结构域，并产生异源二聚体受体复合物。有人提出，GPS 定向切割是基于顺式自切割。在这项研究中，我们证明蛋白激酶 C 的激活剂 - PMA 和离子霉素可以抑制转染细胞中 CIRL-1 前体的切割。这两种试剂还下调了 CIRL-1 向细胞表面的运输，导致未切割的受体前体在内细胞内积累。用不可切割的可溶性 CIRL-1 突变体进行的实验表明，受体运输的下调不依赖于其切割。我们的数据表明，CIRL-1 的 GPS 水解不是一个纯粹的自催化过程，可能涉及辅助蛋白或因子，这些蛋白或因子在 CIRL-1 运输过程中变得可用。
