Megapinocytosis: a novel endocytic pathway

A Bauer, N Subramanian, C Villinger… - Histochemistry and Cell …, 2016 - Springer
A Bauer, N Subramanian, C Villinger, G Frascaroli, T Mertens, P Walther
Histochemistry and Cell Biology, 2016Springer
M2 macrophages showed large endocytotic structures, very different from classical
macropinosomes that we named megapinosomes. As observed in the scanning electron
microscope, megapinosome formation started with a large (diameter of several micrometers)
invagination of the plasma membrane. When the invagination was almost completed, the
remaining opening was closed by an actinomorphous centripetal arrangement of many
(about 50–100) microvilli-like structures. In transmission electron microscopy using high …
Abstract
M2 macrophages showed large endocytotic structures, very different from classical macropinosomes that we named megapinosomes. As observed in the scanning electron microscope, megapinosome formation started with a large (diameter of several micrometers) invagination of the plasma membrane. When the invagination was almost completed, the remaining opening was closed by an actinomorphous centripetal arrangement of many (about 50–100) microvilli-like structures. In transmission electron microscopy using high-pressure freezing, we observed that the megapinosome was filled with a trabecular meshwork that originated from the highly structured plasma membrane. The trabecular meshwork was topologically part of the cytosol and separated from the extracellular fluid by a lipid bilayer. According to ultrastructural features, we could define different phases of megapinosome formation and decay. Megapinosomes became more frequent when M2 macrophages were inoculated with human cytomegalovirus. We did not find megapinosome formation in M1 macrophages.
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