Magnetic nanoparticle-based isolation of endocytic vesicles reveals a role of the heat shock protein GRP75 in macromolecular delivery.
Proc Natl Acad Sci U S A
; 107(30): 13342-7, 2010 Jul 27.
Article
en En
| MEDLINE
| ID: mdl-20624969
ABSTRACT
An increased understanding of cellular uptake mechanisms of macromolecules remains an important challenge in cell biology with implications for viral infection and macromolecular drug delivery. Here, we report a strategy based on antibody-conjugated magnetic nanoparticles for the isolation of endocytic vesicles induced by heparan sulfate proteoglycans (HSPGs), key cell-surface receptors of macromolecular delivery. We provide evidence for a role of the glucose-regulated protein (GRP)75/PBP74/mtHSP70/mortalin (hereafter termed "GRP75") in HSPG-mediated endocytosis of macromolecules. GRP75 was found to be a functional constituent of intracellular vesicles of a nonclathrin-, noncaveolin-dependent pathway that was sensitive to membrane cholesterol depletion and that showed colocalization with the membrane raft marker cholera toxin subunit B. We further demonstrate a functional role of the RhoA GTPase family member CDC42 in this transport pathway; however, the small GTPase dynamin appeared not to be involved. Interestingly, we provide evidence of a functional role of GRP75 using RNAi-mediated down-regulation of GRP75 and GRP75-blocking antibodies, both of which inhibited macromolecular endocytosis. We conclude that GRP75, a chaperone protein classically found in the endoplasmic reticulum and mitochondria, is a functional constituent of noncaveolar, membrane raft-associated endocytic vesicles. Our data provide proof of principle of a strategy that should be generally applicable in the molecular characterization of selected endocytic pathways involved in macromolecular uptake by mammalian cells.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Proteínas HSP70 de Choque Térmico
/
Vesículas Transportadoras
/
Sustancias Macromoleculares
/
Nanopartículas
/
Magnetismo
/
Proteínas de la Membrana
Límite:
Animals
/
Humans
Idioma:
En
Revista:
Proc Natl Acad Sci U S A
Año:
2010
Tipo del documento:
Article
País de afiliación:
Suecia