Mechanoregulation of clathrin-mediated endocytosis

Insight into Cellular Uptake and Intracellular Trafficking of Nanoparticles

Nanoparticle science is rapidly changing the landscape of various scientific fields and defining new technological platforms. This is perhaps even more evident in the field of nanomedicine whereby nanoparticles have been used as a tool for the treatment and diagnosis of many diseases. However, despite the tremendous benefit conferred, common pitfalls of this technology is its potential short and long-term effects on the human body. To understand these issues, many scientific studies have been carried out. This review attempts to shed light on some of these studies and its outcomes. The topics that were examined in this review include the different possible uptake pathways of nanoparticles and intracellular trafficking routes. Additionally, the effect of physicochemical properties of nanoparticle such as size, shape, charge and surface chemistry in determining the mechanism of uptake and biological function of nanoparticles are also addressed.

Mechanochemical feedback control of dynamin independent endocytosis modulates membrane tension in adherent cells

Plasma membrane tension regulates many key cellular processes. It is modulated by, and can modulate, membrane trafficking. However, the cellular pathway(s) involved in this interplay is poorly understood. Here we find that, among a number of endocytic processes operating simultaneously at the cell surface, a dynamin independent pathway, the CLIC/GEEC (CG) pathway, is rapidly and specifically upregulated upon a sudden reduction of tension. Moreover, inhibition (activation) of the CG pathway results in lower (higher) membrane tension. However, alteration in membrane tension does not directly modulate CG endocytosis. This requires vinculin, a mechano-transducer recruited to focal adhesion in adherent cells. Vinculin acts by controlling the levels of a key regulator of the CG pathway, GBF1, at the plasma membrane. Thus, the CG pathway directly regulates membrane tension and is in turn controlled via a mechano-chemical feedback inhibition, potentially leading to homeostatic regulation of membrane tension in adherent cells.

Plasma membrane tension is an important factor that regulates many key cellular processes. Here authors show that a specific dynamin-independent endocytic pathway is modulated by changes in tension via the mechano-transducer vinculin.

Internalization of large particles by turbot (Scophthalmus maximus) IgM+ B cells mainly depends on macropinocytosis

Increasing evidence has demonstrated support for the endocytic capacities of teleost B cells. In the present study, the ability of turbot IgM⁺ B cells to ingest microspheres of different sizes and the corresponding internalization pathways were investigated. The results showed that IgM⁺ B cells exhibited relatively high endocytic capacities for 0.5 μm and 1 μm latex beads, and that different mechanisms were employed for IgM⁺ and IgM^- cells to uptake 0.5 μm and 1 μm beads. For 0.5 μm beads, IgM⁺ B cells apparently employed macropinocytosis-dependent endocytic pathway, whereas IgM^- cells utilized a different process involving both clathrin- and caveolae-mediated pathways. For the uptake of 1 μm beads, IgM⁺ cells relied mainly on macropinocytosis and partially on caveolae-mediated pathway, while IgM^- cells utilized the routes similar to that of internalizing 0.5 μm beads. Consistently, the internalized microspheres were co-localized with high-molecular-mass dextran in IgM⁺ phagocytic cells. In addition to latex beads, IgM⁺ B cells could also ingest inactivated bacteria predominately through macropinocytosis and caveolae-mediated endocytosis. These results collectively indicated that macropinocytosis is principally responsible for particle uptake by turbot IgM⁺ B cells.