Soft X-ray tomography to map and quantify organelle interactions at the mesoscale

Valentina Loconte,Jitin Singla,Angdi Li,Jian-Hua Chen,Axel Ekman,Gerry Mcdermott,Andrej Sali,Mark Le Gros,Kate L White,Carolyn A Larabell

doi:10.1016/j.str.2022.01.006

Abstract

Inter-organelle interactions are a vital part of normal cellular function; however, these have proven difficult to quantify due to the range of scales encountered in cell biology and the throughput limitations of traditional imaging approaches. Here, we demonstrate that soft X-ray tomography (SXT) can be used to rapidly map ultrastructural reorganization and inter-organelle interactions in intact cells. SXT takes advantage of the naturally occurring, differential X-ray absorption of the carbon-rich compounds in each organelle. Specifically, we use SXT to map the spatiotemporal evolution of insulin vesicles and their co-localization and interaction with mitochondria in pancreatic β cells during insulin secretion and in response to different stimuli. We quantify changes in the morphology, biochemical composition, and relative position of mitochondria and insulin vesicles. These findings highlight the importance of a comprehensive and unbiased mapping at the mesoscale to characterize cell reorganization that would be difficult to detect with other existing methodologies.

Highlights

Organelles are traditionally described as intracellular membrane compartments that separate biochemical processes in the cell (Valm et al, 2017; Cohen et al, 2018a)
To demonstrate the capability of soft X-ray tomography (SXT) to map and quantify interactions between organelles, we examined the co-localization of insulin vesicles and mitochondria
INS-1E architecture by SXT We used SXT to investigate alterations in cell morphology and molecular density of INS-1E rat insulinoma cells at three different time points representing the early stage of the biphasic secretory process (1 min), the late stage of the first phase of secretion (5 min), and the early stage of the second phase of secretion (30 min) compared with unstimulated cells

Summary

Introduction

Organelles are traditionally described as intracellular membrane compartments that separate biochemical processes in the cell (Valm et al, 2017; Cohen et al, 2018a). Each compartment is characterized by highly specialized functions that regulate cell homeostasis, division, and response to outside stimuli (Henne, 2021). Their functions are coordinated, and inter-organelle interactions facilitate the communication among different compartments. High-resolution imaging techniques provide an accurate identification of organelle interactions (Scorrano et al, 2019), and three-dimensional (3D) maps of entire cells are required to characterize the frequency of the interactions, to identify the number and location of inter-organelle contacts, and to determine whether they are altered during specific pathological conditions (Dıaz et al, 2021)

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