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Updated: Jul 24, 2025

Investigating Mast Cell Secretory Granules; from Biosynthesis to Exocytosis
Published on: January 26, 2015
Receptor-mediated internalization promotes increased endosome size and number in a RAB4- and RAB5-dependent manner
Naava Naslavsky1, Steve Caplan1
1Department of Biochemistry & Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198, USA; Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA.
Abstract:
Despite their significance in receptor-mediated internalization and continued signal transduction in cells, early/sorting endosomes (EE/SE) remain incompletely characterized, with many outstanding questions that surround the dynamics of their size and number. While several studies have reported increases in EE/SE size and number resulting from endocytic events, few studies have addressed such dynamics in a methodological and quantitative manner. Herein we apply quantitative fluorescence microscopy to measure the size and number of EE/SE upon internalization of two different ligands: transferrin and epidermal growth factor. Additionally, we used siRNA knock-down to determine the involvement of 5 different endosomal RAB proteins (RAB4, RAB5, RAB8A, RAB10 and RAB11A) in EE/SE dynamics. Our study provides new information on the dynamics of endosomes during endocytosis, an important reference for researchers studying receptor-mediated internalization and endocytic events.
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