Dynein functions in galectin-3 mediated processes of clathrin-independent endocytosis.

Multiple endocytic processes operate in cells in tandem to uptake multiple cargoes involved in diverse cellular functions, including cell adhesion and migration. The best-studied clathrin-mediated endocytosis (CME) involves the formation of a well-defined cytoplasmic clathrin coat to facilitate cargo uptake. According to the glycolipid-lectin (GL-Lect) hypothesis, galectin-3 (Gal3) binds to glycosylated membrane receptors and glycosphingolipids (GSLs) to drive membrane bending and tubular membrane invaginations that undergo scission to form a morphologically distinct class of uptake structures, termed clathrin-independent carriers (CLICs). Which components from cytoskeletal machinery are involved in the scission of CLICs remains to be explored. In this study, we propose that dynein is recruited onto Gal3-induced tubular endocytic pits and provides the pulling force for friction-driven scission. The uptake of Gal3 and its cargoes (CD98/CD147) is significantly dependent on dynein activity, whereas only transferrin (CME marker) is slightly affected upon dynein inhibition. Our study reveals that Gal3 and Gal3-dependent (CD98 and CD147) clathrin-independent cargoes require dynein for the clathrin-independent endocytosis.

Cationic lipid modification of DNA tetrahedral nanocages enhances their cellular uptake.

Self-assembled DNA nanocages are among the most promising candidates for bioimaging and payload delivery into cells. DNA nanocages have great potential to efficiently address drug resistance and nucleic acid delivery problems due to precise control of their shape and size, and excellent biocompatibility. Although DNA nanostructures demonstrate some cellular uptake, because they bear a highly negative charge, the uptake of tetrahedral nanostructures is hindered by electrostatic repulsion. In this study, we describe a method to enhance the cellular uptake of DNA nanostructures using a binary system containing DNA and a positively charged head group with a hydrophobic lipid chain containing lipids for cellular internalization. Here we represent the functionalization of a model cage, DNA tetrahedron (TD) with a cationic lipid, N-[1-(2,3-dioleyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTMA). Atomic force microscopy (AFM) and other standard characterization techniques were used to explore the co-assembly of the DNA tetrahedron and DOTMA. We revealed a simple confocal microscopy-based approach to show the enhancement in the cellular uptake of DNA nanocages. This new method will find multiple applications in delivery applications such as gene transfection, drug delivery and targeted bioimaging.

The roles of dynein and myosin VI motor proteins in endocytosis.

Endocytosis is indispensable for multiple cellular processes, including signalling, cell adhesion, migration, as well as the turnover of plasma membrane lipids and proteins. The dynamic interplay and regulation of different endocytic entry routes requires multiple cytoskeletal elements, especially motor proteins that bind to membranes and transport vesicles along the actin and microtubule cytoskeletons. Dynein and kinesin motor proteins transport vesicles along microtubules, whereas myosins drive vesicles along actin filaments. Here, we present a brief overview of multiple endocytic pathways and our current understanding of the involvement of these motor proteins in the regulation of the different cellular entry routes. We particularly focus on structural and mechanistic details of the retrograde motor proteins dynein and myosin VI (also known as MYO6), along with their adaptors, which have important roles in the early events of endocytosis. We conclude by highlighting the key challenges in elucidating the involvement of motor proteins in endocytosis and intracellular membrane trafficking.