tailieunhanh - Báo cáo khoa học: A di-leucine sorting signal in ZIP1 (SLC39A1) mediates endocytosis of the protein

It has been demonstrated that the plasma membrane expression of ZIP1 is regulated by endocytic mechanisms. In the zinc-replete condition, the level of surface expressed ZIP1 is low due to the rapid internalization of ZIP1. The present study aimed to identify a sorting signal(s) in ZIP1 that medi-ated endocytosis of ZIP1. | ễFEBS Journal A di-leucine sorting signal in ZIP1 SLC39A1 mediates endocytosis of the protein Liping Huang1 2 and Catherine P. Kirschke1 1 United States Department of Agriculture Agriculture Research Service Western Human Nutrition Research Center Davis CA USA 2 Department of Nutrition and Rowe Program in Genetics University of California at Davis CA USA Keywords di-leucine endocytosis Golgi apparatus SLC39 zinc transporters Correspondence L. Huang 430 West Health Sciences Drive Davis CA 95616 USA Fax 1 530 752 5295 Tel 1 530 754 5756 E-mail lhuang@ Received 9 April 2007 revised 31 May 2007 accepted 11 June 2007 doi It has been demonstrated that the plasma membrane expression of ZIP1 is regulated by endocytic mechanisms. In the zinc-replete condition the level of surface expressed ZIP1 is low due to the rapid internalization of ZIP1. The present study aimed to identify a sorting signal s in ZIP1 that mediated endocytosis of ZIP1. Four potential sorting signals three di-leucine-and one tyrosine-based were found by searching the eukaryotic linear motif resource for functional sites in proteins http . Site-directed mutagenesis and immunofluorescence microscopic analyses demonstrated that the di-leucine sorting signal ETRALL144-149 located in the variable loop region of ZIP1 was required for the ZIP1 internalization and lysosomal degradation. Substitutions of alanines for the di-leucine residues LL148 149 AA severely impaired the internalization of ZIP1 and subsequent protein degradation leading to an accumulation of the mutant ZIP1 on the cell surface as well as inside the cell. Using chimeric proteins composed of an a-chain of interleukin-2 receptor fused to the peptides derived from the variable loop region of ZIP1 we found that the di-leucine sorting signal of ZIP1 was required and sufficient for endocytosis of the chimeric proteins. Intracellular zinc homeostasis is achieved through coordinated regulations

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