title: Specific depletion of GGA2 causes cathepsin D missorting in HeLa cells.
abstract: Three mammalian GGAs (Golgi-localized, gamma-ear-containing, ARF-binding proteins), GGA1, 2, and 3 have been implicated in the sorting of mannose 6-phosphate receptor (MPR). To investigate the distinct roles of GGA2 in lysosomal enzyme transport, we established two stable cell lines that had a reduced expression of GGA2 by RNA interference. The expression levels of GGA2 were approximately 5% of the control levels, whereas those of non-targeted GGA1 and GGA3 were not apparently reduced. The depletion of GGA2 did not cause changes in the overall distribution of GGA1, GGA3, cation-dependent MPR, or cation-independent MPR. However, the cell lines showed increased secretion of a lysosomal enzyme, cathepsin D. In addition, a moderate expression of the dominant negative VHS-GAT domain of GGA2 had no effect on the trans-Golgi network (TGN) signal of three GGAs, nor was the GGA2 signal affected by the expression of VHS-GAT domain of GGA1 or 3. These results suggest that GGA2 is recruited to the TGN independently of the other GGAs and is required for the efficient sorting of lysosomal enzymes.
authors.affiliation: Department of Conservative Dentistry, Osaka University Faculty of Dentistry, Osaka, Japan.
authors.forename: Tatsuhiro
authors.initials: T
authors.lastname: Hida
authors.forename: Hiroko
authors.initials: H
authors.lastname: Ikeda
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kametaka
authors.forename: Chihiro
authors.initials: C
authors.lastname: Akazawa
authors.forename: Shinichi
authors.initials: S
authors.lastname: Kohsaka
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Ebisu
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Uchiyama
authors.forename: Satoshi
authors.initials: S
authors.lastname: Waguri
mesh_terms: D020727:ADP-Ribosylation Factors / Q000235:genetics / Q000378:metabolism; D033942:Adaptor Proteins, Vesicular Transport / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D020816:Amino Acid Motifs; D002402:Cathepsin D / Q000378:metabolism*; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D034622:RNA Interference; D017527:Receptor, IGF Type 2 / Q000378:metabolism
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; C407306:GGA adaptor proteins; C405944:GGA2 protein, human; D017527:Receptor, IGF Type 2; D002402:Cathepsin D; D020727:ADP-Ribosylation Factors