Endocytosis without clathrin coats

c-Src trafficking and co-localization with the EGF receptor promotes EGF ligand-independent EGF receptor activation and signaling

“…The current study emphasizes the importance of c-Src tyrosine kinase activity for this event; kinase-dead c-SrcGFP formed membrane ruffles that did not circularize or internalize into vesicles. Macropinocytosis occurs both constitutively and in response to growth factor stimulation [31,33] and requires the small G proteins Rac and Rab34 [46,47] as well as second messengers such as phosphoinositide 3-kinase and phospholipase C [48]. Our findings here, as well as those presented by others [38], indicate that c-Src not only is present on macropinosomes but also contributes to their formation via its tyrosine kinase activity.…”

“…We propose that some of this internal pool represents c-Src that has internalized via macropinocytosis. Other studies have documented that macropinocytosis is an internalization event that is distinct from clathrin mediated endocytosis [31][32][33]. In A431 cells, macropinosomes remain as discrete intracellular vesicles that do not fuse with either early or late endosomes or with lysosomes [33,49].…”

“…Multiple venues exist for internalization from the plasma membrane into the cell interior, including clathrin mediated endocytosis, caveolin-mediated endocytosis, clathrin and caveolin-independent endocytosis, phagocytosis and macropinocytosis [31,32]. Previous studies have documented that v-Src expression induces constitutive macropinocytosis -an actin-driven, clathrin-independent endocytic process promoting the uptake of fluid-phase solute [33][34][35].…”

Enlargeosome, an Exocytic Vesicle Resistant to Nonionic Detergents, Undergoes Endocytosis via a Nonacidic Route

“…This result excludes the involvement of the endosomes generated from coated pits and vesicles, characterized by their classical acidic lumen (Maxfield and McGraw, 2004); however, it seems insufficient for the identification of the organelles involved. Various types of nonacidic endosomes have in fact been described, trafficking independently or coordinately with each other and with acidic endosomes along multiple intracellular pathways (Nichols and Lippincott-Schwartz, 2001;Nabi and Le, 2003;Nichols, 2003;Parton and Richards, 2003;Massol et al, 2004). Finally, a sequence of the events occurring within 30 min after the generation of the d/A-positive endocytic vesicles could be deduced from the ultrastructural study of cells that had internalized antibody in the course of ionomycin stimulation.…”

Introduction to the Special Issue: traveling the intracellular highway to gene therapy

“…8,9 Such pathways, including nonclathrinmediated routes of endocytosis, might avoid delivery to degradative compartments of the cell, and thus could be paths exploited for vector use. 10 Our aim here is not only to provide a comprehensive overview of vector trafficking, but in a larger sense, provide a foundation of knowledge in intracellular trafficking as it relates to gene and molecular therapy so as to inspire the continual and creative development of improved vector design.…”