Understanding the pancake-like morphology of Golgi apparatus compartments.

Abstract

The Golgi Apparatus is a highly conserved membrane-bound organelle involved in a complex cascade of post-translational protein modifications, with the function being closely tied to morphology. Based on bending energy minimization, one would expect membrane compartments of low volume-to-surface ratios, as found in the Golgi compartments (cisterna), to form a cup-like stomatocyte. In nature, however, the Golgi compartments have a flat pancake-like morphology. We investigate additional factors required for this flat pancake-like morphology. Therefore, we adhere giant unilamellar vesicles (GUVs) of varying volume-to-surface ratios to flat surfaces with varying adhesion energies. We find that by combining bending energy with adhesion, pancake-like shapes at lower volume-to-surface ratios can be achieved. However, it does not result in the ultra-flat morphology observed in the Golgi, implying that factors additional to bending and adhesion energy, such as the presence of rim stabilizing proteins or lipids need to be considered.