NSF is required for transport from early to late endosomes.
Protein transport between early and late endosomes is a major membrane trafficking pathway in the cell followed by many proteins, including all down-regulated receptors. Yet, little is known at the molecular level about the mechanisms regulating membrane interactions in the endocytic pathway beyond early endosomes. In this study, we have used an in vitro transport assay to study the biochemical properties of endosome docking/fusion events. Our data demonstrate that N-ethylmaleimide (NEM) sensitive factor (NSF) and its soluble associated proteins (SNAPs) are required for transport from early to late endosomes, as well as at all other steps of endosomal membrane transport. We also find that these proteins are enriched on endosomal membranes. In addition, our studies suggest that besides NSF/SNAPs, another NEM-sensitive component may also be involved in docking/fusion at this late stage of the pathway. Finally, we find that, in contrast to Golgi membranes, NSF association to both early and late endosomal membranes occurs via an ATP-independent mechanism, indicating that the binding properties of endosomal and biosynthetic NSF are different. Our data thus show that NSF/SNAPs, perhaps together with another NEM-sensitive factor, are part of the basic molecular machinery which controls docking/fusion events during transport from early to late endosomes, along the lysosomal degradation pathway.
Robinson
L J
LJ
Department of Biochemistry, University of Geneva, Switzerland.
Aniento
F
F
Gruenberg
J
J
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002352:Carrier Proteins / Q000032:analysis / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry; D006224:Cricetinae; D004705:Endocytosis / Q000502:physiology; D011992:Endosomes / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology; D007668:Kidney / Q000166:cytology; D008247:Lysosomes / Q000378:metabolism; D008274:Magnesium / Q000494:pharmacology; D008565:Membrane Proteins / Q000032:analysis / Q000378:metabolism; D052066:N-Ethylmaleimide-Sensitive Proteins; D009687:Nuclear Proteins / Q000032:analysis / Q000378:metabolism; D012680:Sensitivity and Specificity; D052067:Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins; D013347:Subcellular Fractions / Q000737:chemistry; D033921:Vesicular Transport Proteins
D002352:Carrier Proteins; D008565:Membrane Proteins; D009687:Nuclear Proteins; D052067:Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins; D033921:Vesicular Transport Proteins; C094680:nuclear protein import factor p97; D000255:Adenosine Triphosphate; D052066:N-Ethylmaleimide-Sensitive Proteins; D008274:Magnesium; D005033:Ethylmaleimide