title: Luminal interaction of phogrin with carboxypeptidase E for effective targeting to secretory granules.
abstract: Phogrin, a receptor tyrosine phosphatase-like protein, is localized to dense-core secretory granules (SGs) in various neuroendocrine cells. A previous report showed that the N-terminal luminal domain mediates targeting of this protein to SGs in AtT-20 cells. Here, we show that the luminal domain specifically interacts with carboxypeptidase E (CPE), one of the key proteins involved in peptide hormone sorting, in a weakly acidic condition. The luminal domain consists of pro-sequence domain (pro) and subsequent N-side mature domain and the pro domain was preferentially required for phogrin interaction with CPE and for its targeting to SGs. Small interfering RNA-directed reduction of the CPE protein level resulted in an improper accumulation of phogrin at the trans-Golgi network in AtT-20 cells. This finding indicates that CPE is involved in the sorting process of phogrin to SGs. However, SG localization of CPE was hindered by overexpression of the phogrin mutants that lack the transport motif of binding to clathrin adaptor complexes. Phogrin-depleted AtT-20 cells also exhibited reduced CPE targeting and increased CPE degradation. Our results suggest that the luminal interaction between phogrin and CPE contributes to their targeting to SGs in a cooperative manner in neuroendocrine cells.
authors.affiliation: Laboratory of Secretion Biology, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan.
authors.forename: Naoya
authors.initials: N
authors.lastname: Saito
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Takeuchi
authors.forename: Ayumi
authors.initials: A
authors.lastname: Kawano
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hosaka
authors.forename: Ni
authors.initials: N
authors.lastname: Hou
authors.forename: Seiji
authors.initials: S
authors.lastname: Torii
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D020816:Amino Acid Motifs; D000818:Animals; D043423:Carboxypeptidase H / Q000737:chemistry / Q000378:metabolism*; D002460:Cell Line; D055785:Gene Knockdown Techniques; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009154:Mutation; D055099:Neuroendocrine Cells / Q000378:metabolism; D036361:Peptide Hormones / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D034741:RNA, Small Interfering / Q000096:biosynthesis / Q000235:genetics; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D022142:Secretory Vesicles / Q000201:enzymology / Q000378:metabolism*; D021601:trans-Golgi Network / Q000378:metabolism
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D008565:Membrane Proteins; D036361:Peptide Hormones; D034741:RNA, Small Interfering; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8; C533193:phogrin protein, mouse; D043423:Carboxypeptidase H