| First Author | Wittrup A | Year | 2010 |
| Journal | Proc Natl Acad Sci U S A | Volume | 107 |
| Issue | 30 | Pages | 13342-7 |
| PubMed ID | 20624969 | Mgi Jnum | J:162567 |
| Mgi Id | MGI:4819318 | Doi | 10.1073/pnas.1002622107 |
| Citation | Wittrup A, et al. (2010) 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 |
| abstractText | 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. |
