Are Filopodia Privileged Signaling Structures in Migrating Cells?

Area of Science:

• Cell Biology
• Biophysics

Background:

• Filopodia are actin-rich cell protrusions involved in sensing the microenvironment.
• Their small size challenges the study of dynamic signaling processes within them.

Purpose of the Study:

• To investigate the signaling capacity of filopodia by quantifying molecular densities.
• To develop methods for analyzing biosensor data in confined filopodial structures.

Main Methods:

• Utilized total internal reflection fluorescence microscopy on migrating fibroblasts.
• Coexpressed plasma membrane or AktPH domain biosensor with cytosolic volume markers.
• Developed a method to estimate filopodial radii and correct for geometric effects in biosensor data.

Main Results:

• Filopodia exhibit higher densities of 3' phosphoinositides compared to the adjacent cell periphery.
• Quantified molecular abundance within filopodia using geometric correction.

Conclusions:

• The findings support the hypothesis that filopodia are sites of active local signal transduction.
• Filopodial signaling is influenced by localized concentrations of signaling molecules like phosphoinositides.