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.