Single molecule localization-based analysis of clathrin-coated pit and caveolar dynamics

Caveolae disassemble upon membrane lesioning and foster cell survival

Repair of lesions in the plasma membrane is key to sustaining cellular homeostasis. Cells maintain cytoplasmic as well as membrane-bound stores of repair proteins that can rapidly precipitate at the site of membrane lesions. However, little is known about the origins of lipids and proteins for resealing and repair of the plasma membrane. Here we study the dynamics of caveolar proteins after laser-induced lesioning of plasma membranes of mammalian C2C12 tissue culture cells and muscle cells of intact zebrafish embryos. Single-molecule diffusivity measurements indicate that caveolar clusters break up into smaller entities after wounding. Unlike Annexins and Dysferlin, caveolar proteins do not accumulate at the lesion patch. In caveolae-depleted cavin1a knockout zebrafish embryos, lesion patch formation is impaired, and injured cells show reduced survival. Our data suggest that caveolae disassembly releases surplus plasma membrane near the lesion to facilitate membrane repair after initial patch formation for emergency sealing.

Single-Molecule Imaging of Membrane Proteins on Vascular Endothelial Cells

Transporting substances such as gases, nutrients, waste, and cells is the primary function of blood vessels. Vascular cells use membrane proteins to perform crucial endothelial functions, including molecular transport, immune cell infiltration, and angiogenesis. A thorough understanding of these membrane receptors from a clinical perspective is warranted to gain insights into the pathogenesis of vascular diseases and to develop effective methods for drug delivery through the vascular endothelium. This review summarizes state-of-the-art single-molecule imaging techniques, such as super-resolution microscopy, single-molecule tracking, and protein-protein interaction analysis, for observing and studying membrane proteins. Furthermore, recent single-molecule studies of membrane proteins such as cadherins, integrins, caveolins, transferrin receptors, vesicle-associated protein-1, and vascular endothelial growth factor receptor are discussed.

Bending over backwards: BAR proteins and the actin cytoskeleton in mammalian receptor-mediated endocytosis

The role of the actin cytoskeleton during receptor-mediated endocytosis (RME) has been well characterized in yeast for many years. Only more recently has the interplay between the actin cytoskeleton and RME been extensively explored in mammalian cells. These studies have revealed the central roles of BAR proteins in RME, and have demonstrated significant roles of BAR proteins in linking the actin cytoskeleton to this cellular process. The actin cytoskeleton generates and transmits mechanical force to promote the extension of receptor-bound endocytic vesicles into the cell. Many adaptor proteins link and regulate the actin cytoskeleton at the sites of endocytosis. This review will cover key effectors, adaptors and signalling molecules that help to facilitate the invagination of the cell membrane during receptor-mediated endocytosis, including recent insights gained on the roles of BAR proteins. The final part of this review will explore associations of alterations to genes encoding BAR proteins with cancer.