Three-dimensional visualization of arsenic stimulated mouse liver sinusoidal by FIB-SEM approach

Quantitative proteomic study of arsenic treated mouse liver sinusoidal endothelial cells using a reverse super-SILAC method

Liver sinusoidal endothelial cells are the border patrol in the liver. Their open transcellular fenestrations allow the transfer of small and dissolved substances from the blood into the liver parenchymal cells. Fenestrations are dynamic structures, and many drugs and diseases alter their size and number, thus making them an important target for modulation. There is an urgent need to understand how various diseases, toxic substances, and physiological conditions influence liver endothelial cell fenestrations, and how these changes affects liver function. This work represents a straightforward quantitative proteomics study of the in vivo arsenic-stressed liver sinusoidal endothelial cells using a reverse super-SILAC based method. The aim of this study was to identify proteins, which are up- or down-regulated in response to arsenic. This knowledge will aid in identification of potential targets and mechanisms of arsenic toxicity and novel ways to reverse these changes.

Determining the target protein localization in 3D using the combination of FIB-SEM and APEX2

Determining the cellular localization of proteins of interest at nanometer resolution is necessary for elucidating their functions. Besides super-resolution fluorescence microscopy, conventional electron microscopy (EM) combined with immunolabeling or clonable EM tags provides a unique approach to correlate protein localization information and cellular ultrastructural information. However, there are still rare cases of such correlation in three-dimensional (3D) spaces. Here, we developed an approach by combining the focus ion beam scanning electron microscopy (FIB-SEM) and a promising clonable EM tag APEX2 (an enhanced ascorbate peroxidase 2) to determine the target protein localization within 3D cellular ultrastructural context. We further utilized this approach to study the 3D localization of mitochondrial dynamics-related proteins (MiD49/51, Mff, Fis1, and Mfn2) in the cells where the target proteins were overexpressed. We found that all the target proteins were located at the surface of the mitochondrial outer membrane accompanying with mitochondrial clusters. Mid49/51, Mff, and hFis1 spread widely around the mitochondrial surface while Mfn2 only exists at the contact sites.