Actin Labeling

Actin is one of the most abundant proteins found in cells, and actin filaments can be readily labeled using fluorescent forms of a naturally occurring protein called phalloidin.

Learn about labeled phalloidin and its utility in imaging studies to provide context for other labeled targets.

Actin, a protein found in every eukaryotic cell, exists as both monomers and polymers and can be found in many different tertiary forms. Actin plays a variety of roles in cytoskeletal structural support, cell motility, cellular junctions, muscle contraction, and cellular signaling. Given its wide-ranging and diverse roles, it’s not surprising that it is one of the most abundant proteins found in cells. Actin can be labeled with a fluorophore very easily when the monomers form a certain type of microfilament, referred to as F-actin. Phalloidin, a molecule isolated from death cap mushrooms, binds F-actin microfilaments very tightly and with high specificity and—unlike many primary antibodies against actin—does not bind other forms of actin. When phalloidin is conjugated to a fluorophore, it becomes a very useful tool for cell biologists who are using fluorescence microscopy to study their cells. Labeling F-actin can help show the overall shape and structure of the cell and provide context for other fluorescent labels.

Figure 2. After fixing, permeabilizing, and blocking, BPAE cells were labeled with ActinRed reagent (TRITC-conjugated phalloidin that labels F-actin), and nuclei were labeled with NucBlue Fixed reagent (a form of DAPI).

Figure 3. Live HeLa cells were stained with CellMask Green Actin Tracking Stain, MitoTracker Orange Stain, and Hoechst 34580 dye for 30 minutes at 37°C. The sample was imaged on an EVOS M7000 Imaging System using a 40X objective.