Annexin VI is a mannose-6-phosphate-independent endocytic receptor for bovine beta-glucuronidase

作者：Ramirez Mata Alberto; Michalak Colette; Mendoza Hernandez Guillermo; Leon Del Rio Alfonso; Gonzalez Noriege Alfonso^*

来源：Experimental Cell Research, 2011, 317(16): 2364-2373.

DOI：10.1016/j.yexcr.2011.05.025

• Receptor-mediate endocytosis
• Annexin VI
• B-glucuronidase
• Mannose 6-phosphate-independent
• endocytosis

Endocytosis and transport of bovine liver beta-glucuronidase to lysosomes in human fibroblasts are mediated by two receptors: the well-characterized cation-independent mannose 6-phosphate receptor (IGF-II/Man6PR) and an IGF-II/Man6PR-independent receptor, which recognizes a Ser-Trp*-Ser sequence present on the ligand. The latter receptor was detergent extracted from bovine liver membranes and purified. LC/ESI-MS/MS analysis revealed that this endocytic receptor was annexin VI (AnxA6). Several approaches were used to confirm this finding. First, the binding of bovine beta-glucuronidase to the purified receptor from bovine liver membranes and His-tagged recombinant human AnxA6 protein was confirmed using ligand-blotting assays. Second, western blot analysis using antibodies raised against IGF-II/Man6PR-independent receptor as well as commercial antibodies against AnxA6 confirmed that the receptor and AnxA6 were indeed the same protein. Third, double immunofluorescence experiments in human fibroblasts confirmed a complete colocalization of the bovine beta-glucuronidase and the AnxA6 receptor on the plasma membrane. Lastly, two cell lines were stably transfected with a plasmid containing the cDNA for human AnxA6. In both transfected cell lines, an increase in cell surface AnxA6 and in mannose 6-phosphate-independent endocytosis of bovine beta-glucuronidase was detected. These results indicate that AnxA6 is a novel receptor that mediates the endocytosis of the bovine beta-glucuronidase.

• 出版日期2011-10-1