Schematic of cell structure with expanded view of a lysosome

Lysosomes are membrane-bound organelles that are involved in several cellular processes such as biomolecule degradation, apoptosis, cell signaling, metabolism, and plasma membrane repair. Lysosome markers are effective tools for identifying and tracking lysosomes. While LysoTracker markers target acid contents and localize within lysosomes, CellLight fluorescent fusion proteins target to the lysosomal membrane for locating and tracking of lysosomes.

See lysosomal markers selection guide

Lysosome introduction

Lysosomes are membrane-bound organelles that contain enzymes which degrade biomolecules such as carbohydrates, lipids, nucleic acids, and peptides [1–3]. Intracellular molecules are digested through a process called autophagy while extracellular material that are taken up by endocytosis are digested through a process called phagocytosis [1, 2]. Lysosomes are also involved in the digestion of viral particles or bacteria through phagocytosis. Lysosomes have been shown to be involved in other cellular processes including intracellular transport of internal and external material, signaling to regulate proliferation and growth, and cellular metabolism [3].

Selection guide for lysosomal markers

 
TargetTargets acidic organelles
ReadoutLocalization of lysosomes by fluorescence imaging
Common filter setDAPIFITCTRITCCy5
LabelsLysoTracker BlueLysoTracker GreenLysoTracker RedLysoTracker Deep Red
Ex/Em (nm)373/422504/511577/590647/668
Signal-to-noise ratio
Photostability
MultiplexingYesYesYesYes
Live cellsYesYesYesYes
Fixed cellsNoNoNoNo
FixableNoNoYesNo
Format20 x 50 uL20 x 50 uL20 x 50 uL5 x 50 uL
Cat. No.L7525L7526L7528L12492

LysoTracker lysosome markers

LysoTrackers are cell-permeable lysosome markers that target and track acidic organelles in live cells. LysoTracker markers are comprised of a fluorophore bound to weakly basic amines. Though the mechanism of LysoTracker retention is relatively unknown, it is likely due to protonation with retention in the organelles’ membrane. These lysosomal markers accumulate in organelles that have a low pH and are only partially protonated at neutral pH. LysoTracker lysosomal markers are available in a range of colors to allow for multiplexing with other fluorescent markers (Figures 1 and 2).

Microscopic image of cells stained with red lysosomes and green mitochondria
Figure 1. Multi-color imaging of lysosomes and mitochondria. Bovine pulmonary artery endothelial cells (BPAEC) incubated simultaneously with 50 nM LysoTracker Red DND-99 and 75 nM MitoTracker Green FM at 37°C for 30 minutes. Both dyes showed excellent cellular retention, even after cells were fixed in 3% glutaraldehyde for 30 minutes. The image was deconvolved using Huygens software.
Microscopic image of cells stained with red lysosomes, green endocytosis, and blue nuclei
Figure 2. Multi-color imaging of lysosomes and endocytosis. A549 cells were labeled with Hoechst 33342 and 50 nM LysoTracker Deep Red for 15 minutes in complete media. Cells were then washed with warm DPBS and incubated in DPBS containing 40 µg/mL pHrodo Green 10k-dextran for 90 minutes at 37°C. Imaged using standard DAPI/FITC/Cy5 filter sets. Images were pseudo colored as Hoechst 33342 (blue), LysoTracker Deep Red (red), and pHrodo Green 10k-dextran (green).

CellLight lysosome fusion proteins

CellLight fluorescent fusion proteins are lysosome membrane constructs that label lysosomes in live cells to follow the dynamics of intracellular behavior. CellLight fluorescent proteins use the Lamp1 (lysosomal associated membrane protein 1) construct fused to emGFP (Figure 3) or TagRFP (Figure 4). CellLight lysosome membrane markers are available in green or red fluorescent fusion proteins and can be multiplexed with other fluorescent dyes and proteins. Additionally, fluorescent staining is retained after fixation and permeabilization.

Lysosome membrane markers also serve as tools for tracking fusion with the autophagosome prior to degradation of the autolysosome.

Learn more about other autophagy markers here

Microscopic image of cells stained with green lysosomes, orange oxidation, and blue nuclei
Figure 3. Live cell imaging with CellLight Lysosome-GFP. Human osteosarcoma (U2-OS) cells expressing CellLight Lysosomes-GFP were treated with 200 µM tert-Butyl hydroperoxide for two hours. A stain solution containing 5 µM CellROX Orange and 2 drops/ml of NucBlue Live Cell Stain was applied for 30 min at 37°C. Cells were washed and imaged with Live Cell Imaging Solution.
Microscopic image of cell stained with red lysosomes, green microtubules, and blue nucleus

Figure 4. Live cell imaging with CellLight fluorescent fusion proteins. Cascade Biologics human aortic smooth muscle cells (HASMC) were transduced with CellLight Lysosomes-RFP, CellLight MAP4-GFP, and Hoechst 33342. Imaging was performed on live cells using a DeltaVision Core microscope and standard DAPI/FITC/TRITC filter sets.

Learn more about lysosome markers

References

  1. Cooper GM (2000). The Cell: A Molecular Approach. 2nd edition. Sunderland (MA): Sinauer Associates.Lysosomes.
  2. Xu H and Ren Dejian (2016). Annu Rev Physiol. 77:57-80. PMID: 25668017.
  3. Tang T, Yang Zy, Wang D, et al. (2020). Cell and Biosci. 10(1):131. PMID: 33292489.

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