Emerging Concepts in Ion Channel Biophysics

Emerging Concepts in Ion Channel Biophysics

Wednesday Speaker Abstracts

Imaging the Nanometer-scale Structure of the Plasma Membrane with Correlative Superresolution Light and Electron Microscopy Justin Taraska , Kem Sochacki. NHLBI, NIH, Bethesda, MD, USA. Clathrin mediated endocytosis (CME) is the cell’s primary internalization mechanism and is central for nutrient uptake, cellular signaling and homeostasis. For an endocytic vesicle to develop, dozens of unique proteins work together to recruit cargo and stabilize clathrin as a nanoscale honeycomb lattice on the membrane. Factors that associate with the lattice must then regulate the growth and curvature of the pit and finally cut the coated-vesicle free from the surface. Due to the technical difficulty of localizing proteins at the nanoscale across large areas of the cell the spatial organization of the vast and complex endocytic protein machinery at the plasma membrane is unknown. Here, with a large-scale correlative superresolution light and electron microscopy study, we map 19 key proteins involved in endocytosis. Our data provide a comprehensive molecular architecture of endocytic structures with nano-precision across cells. We discover a distinct spatial organization within clathrin coated pits; some factors localize only to the edge (eps15, fcho2, dynamin, amphiphysin, syndapin, snx9), or center of the lattice (epsin, NECAP, CALM, hip1r, receptor cargo), but several have discrete subpopulations in both regions (AP-2, dab2, stonin2, β2-arrestin, intersectin). Furthermore, the presence or concentration of many factors within these zones changes during organelle maturation. We propose that endocytosis is driven by the recruitment, re-organization, and loss of proteins within these partitioned nano-scale zones. These data provide a framework for understanding the dynamic formation and regulation of endocytosis and a way forward to study the spatial organization of the plasma membrane.

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