title: Peroxisomal targeting signal receptor Pex5p interacts with cargoes and import machinery components in a spatiotemporally differentiated manner: conserved Pex5p WXXXF/Y motifs are critical for matrix protein import.
abstract: Two isoforms of the peroxisomal targeting signal type 1 (PTS1) receptor, termed Pex5pS and (37-amino-acid-longer) Pex5pL, are expressed in mammals. Pex5pL transports PTS1 proteins and Pex7p-PTS2 cargo complexes to the initial Pex5p-docking site, Pex14p, on peroxisome membranes, while Pex5pS translocates only PTS1 cargoes. Here we report functional Pex5p domains responsible for interaction with peroxins Pex7p, Pex13p, and Pex14p. An N-terminal half, such as Pex5pL(1-243), comprising amino acid residues 1 to 243, bound to Pex7p, Pex13p, and Pex14p and was sufficient for restoring the impaired PTS2 import of pex5 cell mutants, while the C-terminal tetratricopeptide repeat motifs were required for PTS1 binding. N-terminal Pex5p possessed multiple Pex14p-binding sites. Alanine-scanning analysis of the highly conserved seven (six in Pex5pS) pentapeptide WXXXF/Y motifs residing at the N-terminal region indicated that these motifs were essential for the interaction of Pex5p with Pex14p and Pex13p. Moreover, mutation of several WXXXF/Y motifs did not affect the PTS import-restoring activity of Pex5p, implying that the binding of Pex14p to all of the WXXXF/Y sites was not a prerequisite for the translocation of Pex5p-cargo complexes. Pex5p bound to Pex13p at the N-terminal part, not to the C-terminal SH3 region, via WXXXF/Y motifs 2 to 4. PTS1 and PTS2 import required the interaction of Pex5p with Pex14p but not with Pex13p, while Pex5p binding to Pex13p was essential for import of catalase with PTS1-like signal KANL. Pex5p recruited PTS1 proteins to Pex14p but not to Pex13p. Pex14p and Pex13p formed a complex with PTS1-loaded Pex5p but dissociated in the presence of cargo-unloaded Pex5p, implying that PTS cargoes are released from Pex5p at a step downstream of Pex14p and upstream of Pex13p. Thus, Pex14p and Pex13p very likely form mutually and temporally distinct subcomplexes involved in peroxisomal matrix protein import.
authors.affiliation: Department of Biology, Faculty of Sciences, Kyushu University Graduate School, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
authors.forename: Hidenori
authors.initials: H
authors.lastname: Otera
authors.forename: Kiyoko
authors.initials: K
authors.lastname: Setoguchi
authors.forename: Maho
authors.initials: M
authors.lastname: Hamasaki
authors.forename: Toshitaka
authors.initials: T
authors.lastname: Kumashiro
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Shimizu
authors.forename: Yukio
authors.initials: Y
authors.lastname: Fujiki
mesh_terms: D020816:Amino Acid Motifs / Q000502:physiology; D000818:Animals; D016466:CHO Cells; D002352:Carrier Proteins / Q000378:metabolism; D002374:Catalase / Q000378:metabolism; D017124:Conserved Sequence; D006224:Cricetinae; D005982:Glutathione Transferase / Q000235:genetics; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D000074437:Peroxisomal Targeting Signal 2 Receptor; D000074435:Peroxisome-Targeting Signal 1 Receptor; D020675:Peroxisomes / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins; D014162:Transfection
chemical_list: D002352:Carrier Proteins; D008565:Membrane Proteins; C101884:PEX13 protein, human; C455539:PEX14 protein, human; C000614264:PEX5 protein, human; D000074437:Peroxisomal Targeting Signal 2 Receptor; D000074435:Peroxisome-Targeting Signal 1 Receptor; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D002374:Catalase; D005982:Glutathione Transferase