Cellular and Molecular Life Sciences

, Volume 68, Issue 23, pp 3919–3931

Clusterin facilitates in vivo clearance of extracellular misfolded proteins

  • Amy R. Wyatt
  • Justin J. Yerbury
  • Paula Berghofer
  • Ivan Greguric
  • Andrew Katsifis
  • Christopher M. Dobson
  • Mark R. Wilson
Research article

DOI: 10.1007/s00018-011-0684-8

Cite this article as:
Wyatt, A.R., Yerbury, J.J., Berghofer, P. et al. Cell. Mol. Life Sci. (2011) 68: 3919. doi:10.1007/s00018-011-0684-8

Abstract

The extracellular deposition of misfolded proteins is a characteristic of many debilitating age-related disorders. However, little is known about the specific mechanisms that act to suppress this process in vivo. Clusterin (CLU) is an extracellular chaperone that forms stable and soluble complexes with misfolded client proteins. Here we explore the fate of complexes formed between CLU and misfolded proteins both in vitro and in a living organism. We show that proteins injected into rats are cleared more rapidly from circulation when complexed with CLU as a result of their more efficient localization to the liver and that this clearance is delayed by pre-injection with the scavenger receptor inhibitor fucoidan. The CLU–client complexes were found to bind preferentially, in a fucoidan-inhibitable manner, to human peripheral blood monocytes and isolated rat hepatocytes and in the latter cell type were internalized and targeted to lysosomes for degradation. The data suggest, therefore, that CLU plays a key role in an extracellular proteostasis system that recognizes, keeps soluble, and then rapidly mediates the disposal of misfolded proteins.

Keywords

ClusterinExtracellular chaperoneMisfolded proteinReceptor-mediated endocytosisClearance

Supplementary material

18_2011_684_MOESM1_ESM.tif (8.6 mb)
Supplementary Fig. 1 Time-dependent accumulation of the injected dose in the thyroid of Sprague–Dawley rats after injection with 123I-labeled HMW CLU-stressed protein complexes or control proteins. a Pseudocolor images of the distribution of radioactivity in the head and upper body of a rat (orientation indicated by the labels head and abdomen) injected with 123I-HMW CLU–FGN via the tail vein. The times indicated are p.i. Progressively higher levels of radioactivity are indicated by the color gradient starting at blue and moving through green, yellow, red and finally white. The images shown are representative of three different experiments. The arrow indicates the position of the thyroid gland. b Panels shows the proportion of the injected dose per gram of thyroid up to 30 min after the animals were injected with 123I-labeled HMW CLU–client complexes or uncomplexed control protein as indicated. Note, the mass of the rat thyroid is less than 1 g, so the percentage values plotted can exceed 100%. Data points represent means (n = 4 ± standard error) and are corrected for any radioactivity remaining in the tail
18_2011_684_MOESM2_ESM.tif (1.2 mb)
Supplementary Fig. 2 The binding of biotinylated HMW CLU–client protein complexes and control proteins to rat liver cells, assessed by flow cytometry. Enriched preparations of hepatocytes or non-parenchymal liver cells were incubated with biotinylated a FGN, residual soluble heated FGN (FGN#) or HMW CLU–FGN, b GST, residual soluble heated GST (GST#) or HMW CLU-GST, or c CLU or residual soluble heated CLU (CLU#), and then SA-Alexa Fluor® 488. The results shown are the geometric mean of the Alexa Fluor® 488 fluorescence intensity in AU (n = 3 ± standard error)

Copyright information

© Springer Basel AG 2011

Authors and Affiliations

  • Amy R. Wyatt
    • 1
    • 2
  • Justin J. Yerbury
    • 1
    • 2
  • Paula Berghofer
    • 3
  • Ivan Greguric
    • 3
  • Andrew Katsifis
    • 3
  • Christopher M. Dobson
    • 4
  • Mark R. Wilson
    • 1
    • 2
  1. 1.School of Biological SciencesUniversity of WollongongWollongongAustralia
  2. 2.Illawarra Health and Medical Research Institute, University of WollongongWollongongAustralia
  3. 3.Radiopharmaceutical Research InstituteAustralian Nuclear Science and Technology OrganisationLucas HeightsAustralia
  4. 4.Department of ChemistryUniversity of CambridgeCambridgeUK