Tracking Cellular Signaling by Fluorescence Microscopy

In this video the activity of a signaling pathway regulating efferocytosis – the engulfment and destruction of apoptotic (dying) cells by phagocytes such as macrophages – is monitored by fluorescent microscopy.

These macrophages are expressing synthetic genes which mark the plasma membrane of the cell in red (PM-RFP), and the signaling lipid PI(3)P in green (FYVE-GFP). These cells are engulfing small beads coated in a lipid mixture which mimics dying cells (*). Efferocytosed apoptotic cells are engulfed into a vacuole derived from the plasma membrane – visible in this video as the red ring around the efferocytosed beads. Activity of the signaling lipid on the efferosome can be observed as the appearance and disappearance of a green ring around the efferocytosed beads.

While this example tracks PI(3)P signaling, other signaling pathways and cellular responses can be investigated by expressing genes, or using dyes, which report the activity of these other pathways.