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Cell engineering Cell imaging Cell isolation and culture Cell metabolism Cell movement Cell signaling
Cell staining Cell structure Cell Transplantation Cell viability Cell-based analysis Model organism culture Organelle isolation Single cell analysis Tissue analysisUsing HBmito Crimson to Observe Mitochondrial Cristae Through STED Microscopy
Mitochondrial cristae, formed by folding the mitochondrial inner membrane (IM), are essential for cellular energy supply. However, the observation of the IM is challenging due to the limitations in spatiotemporal resolution offered by conventional microscopy and the absence of suitable in vitro probes specifically targeting the IM. Here, we describe a detailed imaging protocol for the mitochondrial inner membrane using the Si-rhodamine dye HBmito Crimson, which has excellent photophysical properties, to label live cells for imaging via stimulated emission depletion (STED) microscopy. This allows for STED imaging over more than 500 frames (approximately one hour), with a spatial resolution of 40 nm, enabling the observation of cristae dynamics during various mitochondrial processes. The protocol includes detailed steps for cell staining, image acquisition, image processing, and resolution analysis. Utilizing the superior resolution of STED microscopy, the structure and complex dynamic changes of cristae can be visualized.
In vivo Assessment of Lysosomal Stress in the Drosophila Brain Using Confocal Fluorescence Microscopy
Lysosomes play a central role in signaling, nutrient sensing, response to stress, and the degradation and recycling of cellular content. Defects in lysosomal digestive enzymes or structural components can impair lysosomal function with dire consequences to the cell, such as neurodegeneration. A number of methods exist to assess lysosomal stress in the model Drosophila, such as specific driver and reporter strains, transmission electron microscopy, and the investigation of gene expression. These methods, however, can be time consuming and, in some cases, costly. The procedure described here provides a quick, reliable, and low-cost approach to measure lysosomal stress in the Drosophila brain. Using fluorescence confocal microscopy and the LysoTracker staining, this protocol allows for the direct measurement of lysosome size and number. This method can be used to assess lysosomal stress under a number of different genetic and environmental scenarios in the Drosophila brain.
Assessing Mitochondrial Transport via Cytoplasmic Nanotubular Bridges in Cells
Lysosomal Stability Assay
AO is a lipophilic amine that readily diffuses into cells (Figure 1). Inside the cell it enters the acidic lysosomal compartment where it is protonated and sequestered, shifting its emission spectrum towards a longer wavelength (i.e. red). Once inside the lysosomes, the metachromatic AO sensitizes the lysosomal membrane to photo-oxidation by blue light (Brunk et al., 1997). Upon light-induced loss of the lysosomal pH gradient and subsequent leakage of AO into the cytosol, the emission spectrum of AO shifts from red to green (Figure 2). Hence, loss of lysosomal integrity can be measured as a ‘loss of red dots’ or as a quantitative rise in green fluorescence (Petersen et al., 2010; Kirkegaard et al., 2010; Petersen et al., 2013).
Figure 1. Acridine Orange
Figure 2. Snapshots visualizing the U2OS cells at various steps of the recording procedure (Petersen et al., 2010)