Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2020 Jun 1;210(3):107505.
doi: 10.1016/j.jsb.2020.107505. Epub 2020 Apr 1.

Megapinosome: Morphological Description of a Novel Organelle

Affiliations

Megapinosome: Morphological Description of a Novel Organelle

Andrea Bauer et al. J Struct Biol. .

Abstract

The megapinosome is an endocytic cell organel that we observed in human macrophages with electron microscopy. In a previous work we showed that it is formed by an endocytic event that we called megapinocytosis. The megapinosome is filled with a membrane surrounded trabecular meshwork that is topologically part of the cytosol. In this work we used scanning transmission electron tomography on high pressure frozen and freeze substituted human macrophages in order to unravel the three-dimensional structure of both the megapinosome and the adjacent structures. The megapinosome consists of the trabecular meshwork and the lacunae which are connected with and topologically equivalent to the cytosol. The surrounding lumen is topologically equivalent to the structures of the vesicular pathway. In addition, we show the connections of the trabecular meshwork with the cytosol and the connection of the megapinosomes to a complex tubular and cisternal system covering a large part of the macrophages that we named megapinosome complex. We assume that our methodological approach, based on high pressure freezing from a defined physiological state and three-dimensional imaging, renders the tubular components of the macrophages better visible than the classical two-dimensional imaging of chemically fixed cells used as a "blueprint" for textbook illustrations. The cell biological functions of the megapinosome are largely enigmatic. Probably, megapinosomes assures storage of surface membranes that can be promptly made available when a macrophage needs to change shape to move through a tissue, to uptake extracellular material or dead cells as well as to fight against microbes.

Keywords: Electron microscopy; Endocytosis; High pressure freezing; Macrophages; Megapinocytosis; STEM tomography.

Conflict of interest statement

Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Similar articles

See all similar articles

LinkOut - more resources

Feedback