Cytoplasmic transport signal is involved in phogrin targeting and localization to secretory granules.
Phogrin is an integral glycoprotein primarily expressed in neuroendocrine cells. The predominant localization of phogrin is on dense-core secretory granules, and the lumenal domain has been shown to be involved in its efficient sorting to the regulated secretory pathway. Here, we present data showing that a leucine-based sorting signal [EExxxIL] within the cytoplasmic tail contributes its steady-state localization to secretory granules. Deletion mutants in the tail region failed to represent granular distribution in pancreatic beta-cell line, MIN6, and anterior pituitary cell line, AtT-20. A sorting signal mutant with two glutamic acids substituted into alanines (EE/AA) is primarily accumulated in the Golgi area instead of secretory granules, and another mutant (IL/AA) is trapped at the plasma membrane due to a defect in endocytosis. We further demonstrate that the leucine-based sorting signal of phogrin specifically interacts with both adaptor protein (AP)-1 and AP-2 clathrin adaptor complexes in vitro. These observations, along with previous studies, suggest that distinct domains of phogrin mediate proper localization of this transmembrane protein on secretory granules.
Torii
Seiji
S
Laboratory of Secretion Biology, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan.
Saito
Naoya
N
Kawano
Ayumi
A
Zhao
Shengli
S
Izumi
Tetsuro
T
Takeuchi
Toshiyuki
T
D000818:Animals; D015704:CD4 Antigens / Q000235:genetics; D045744:Cell Line, Tumor; D006801:Humans; D007340:Insulinoma / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009154:Mutation; D010190:Pancreatic Neoplasms / Q000378:metabolism; D021382:Protein Sorting Signals / Q000235:genetics*; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism*; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D022142:Secretory Vesicles / Q000378:metabolism*
D015704:CD4 Antigens; D008565:Membrane Proteins; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; C102889:PTPRN2 protein, human; D017027:Protein Tyrosine Phosphatases; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8