Insulin transcytosis across adipose microvascular endothelial cells: Mechanism and physiological implications
Year: 2015
Type: dissertation
Abstract: Transport of insulin across the microvasculature is necessary to reach its target organs (e.g. adipose and muscle) and is rate-limiting in insulin action. We report an approach to study insulin transcytosis across primary human adipose microvascular endothelial cells (HAMEC), involving insulin uptake followed by vesicle-mediated exocytosis visualized by total internal reflection fluorescence microscopy. In this setting, fluorophore-conjugated insulin exocytosis depended on its initial binding and uptake, which was saturable. Unlike its degradation within muscle cells, insulin was stable within HAMEC and escaped lysosomal colocalization. Insulin transcytosis required dynamin but was unaffected by caveolin-1 knockdown or cholesterol depletion. Instead, insulin transcytosis was significantly inhibited by both a clathrin-mediated endocytosis inhibitor and siRNA-mediated clathrin-depletion. Accordingly, insulin internalized for 1 minute in HAMEC colocalized with clathrin far more than with caveolin-1. This study constitutes the first evidence of vesicle-mediated insulin transcytosis and highlights that its initial uptake is clathrin-dependent and caveolae-independent.
Source: TSpace (University of Toronto)
Author: Paymon Azizi
Language: English
Subfield: Cell Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2598338662