Fluorescent markers for studying phagosome-lysosome fusion

Area of Science:

• Cell biology
• Immunology
• Biochemistry

Background:

• Lysosomotropic fluorescent aminoacridines, such as acridine orange and quinacrine, are widely used to study lysosome-phagosome fusion.
• These markers are particularly prominent in macrophage research.

Purpose of the Study:

• To evaluate the reliability of aminoacridines as markers for lysosome-phagosome fusion.
• To identify limitations and propose alternative markers for accurate fusion studies.

Main Methods:

• Experimental investigation of aminoacridine diffusion across biological membranes.
• Assessment of aminoacridine accumulation in phagosomes.
• Description of alternative fluorescent lysosomal markers.

Main Results:

• Aminoacridines readily traverse biological membranes, leading to diffusion throughout the cellular system.
• Intra- and extracellular accumulation of aminoacridines occurs where they bind most efficiently.
• Phagosomal presence or absence of aminoacridines is not a definitive indicator of fusion or nonfusion.

Conclusions:

• The membrane permeability of aminoacridines compromises their specificity as lysosome-phagosome fusion markers.
• Alternative fluorescent lysosomal markers are necessary for reliable fusion assessment.
• Specific experimental systems are defined where aminoacridines may still be cautiously employed.