title: The ordered and compartment-specfific autoproteolytic removal of the furin intramolecular chaperone is required for enzyme activation.
abstract: The propeptide of furin has multiple roles in guiding the activation of the endoprotease in vivo. The 83-residue N-terminal propeptide is autoproteolytically excised in the endoplasmic reticulum (ER) at the consensus furin site, -Arg(104)-Thr-Lys-Arg(107)-, but remains bound to furin as a potent autoinhibitor. Furin lacking the propeptide is ER-retained and proteolytically inactive. Co-expression with the propeptide, however, restores trans-Golgi network (TGN) localization and enzyme activity, indicating that the furin propeptide is an intramolecular chaperone. Blocking this step results in localization to the ER-Golgi intermediate compartment (ERGIC)/cis-Golgi network (CGN), suggesting the ER and ERGIC/CGN recognize distinct furin folding intermediates. Following transport to the acidified TGN/endosomal compartments, furin cleaves the bound propeptide at a second, internal P1/P6 Arg site (-Arg-Gly-Val(72)-Thr-Lys-Arg(75)-) resulting in propeptide dissociation and enzyme activation. Cleavage at Arg(75), however, is not required for proper furin trafficking. Kinetic analyses of peptide substrates indicate that the sequential pH-modulated propeptide cleavages result from the differential recognition of these sites by furin. Altering this preference by converting the internal site to a canonical P1/P4 Arg motif (Val(72) --> Arg) caused ER retention and blocked activation of furin, demonstrating that the structure of the furin propeptide mediates folding of the enzyme and directs its pH-regulated, compartment-specific activation in vivo.
authors.affiliation: Vollum Institute, Portland, Oregon 97201, USA.
authors.forename: Eric D
authors.initials: ED
authors.lastname: Anderson
authors.forename: Sean S
authors.initials: SS
authors.lastname: Molloy
authors.forename: François
authors.initials: F
authors.lastname: Jean
authors.forename: Hao
authors.initials: H
authors.lastname: Fei
authors.forename: Satoko
authors.initials: S
authors.lastname: Shimamura
authors.forename: Gary
authors.initials: G
authors.lastname: Thomas
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002451:Cell Compartmentation; D002460:Cell Line; D017931:DNA Primers; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004789:Enzyme Activation; D045683:Furin; D006056:Golgi Apparatus / Q000378:metabolism; D006868:Hydrolysis; D018832:Molecular Chaperones / Q000378:metabolism*; D013379:Substrate Specificity; D013381:Subtilisins / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D018832:Molecular Chaperones; D013381:Subtilisins; D045683:Furin