Characterization of a Nonclathrin Endocytic Pathway: Membrane Cargo and Lipid RequirementsD⃞
AUTOR(ES)
Naslavsky, Naava
FONTE
The American Society for Cell Biology
RESUMO
Clathrin-independent endocytosis internalizes plasma membrane proteins that lack cytoplasmic sequences recognized by clathrin adaptor proteins. There is evidence for different clathrin-independent pathways but whether they share common features has not been systematically tested. Here, we examined whether CD59, an endogenous glycosylphosphatidyl inositol-anchored protein (GPI-AP), and major histocompatibility protein class I (MHCI), an endogenous, integral membrane protein, entered cells through a common mechanism and followed a similar itinerary. At early times of internalization, CD59 and MHCI were found in the same Arf6-associated endosomes before joining clathrin cargo proteins such as transferrin in common sorting endosomes. CD59 and MHCI, but not transferrin, also were observed in the Arf6-associated tubular recycling membranes. Endocytosis of CD59 and MHCI required free membrane cholesterol because it was inhibited by filipin binding to the cell surface. Expression of active Arf6 stimulated endocytosis of GPI-APs and MHCI to the same extent and led to their accumulation in Arf6 endosomes that labeled intensely with filipin. This blocked delivery of GPI-APs and MHCI to early sorting endosomes and to lysosomes for degradation. Endocytosis of transferrin was not affected by any of these treatments. These observations suggest common mechanisms for endocytosis without clathrin.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=491817Documentos Relacionados
- Syp1 is a conserved endocytic adaptor that contains domains involved in cargo selection and membrane tubulation
- Navigating the secretory pathway: Conference on exocytosis membrane structure and dynamics
- Visualization of cargo concentration by COPII minimal machinery in a planar lipid membrane
- The association of epsin with ubiquitinated cargo along the endocytic pathway is negatively regulated by its interaction with clathrin
- Carbohydrate- and Conformation-dependent Cargo Capture for ER-ExitD⃞