Polarized sphingolipid transport from the subapical compartment changes during cell polarity development

Area of Science:

• Cell Biology
• Membrane Trafficking
• Cell Polarity

Background:

• The subapical compartment (SAC) is crucial for polarized transport of proteins and lipids in cells.
• HepG2 cells utilize the SAC for sorting sphingomyelin and glucosylceramide.
• Understanding the regulation of SAC-mediated transport is key to cell polarity.

Purpose of the Study:

• To investigate the role of protein kinase A (PKA) in regulating polarity development within the SAC.
• To identify and characterize the specific membrane transport pathways involved in establishing cell polarity.
• To differentiate PKA-regulated pathways from other apical transport routes within the SAC.

Main Methods:

• Utilized fluorescent lipid analogues (sphingomyelin, glucosylceramide) to track trafficking within HepG2 cells.
• Investigated the role of endogenous protein kinase A (PKA) activation in regulating membrane transport.
• Differentiated distinct transport pathways based on their trafficking routes and regulation.

Main Results:

• Polarity development is regulated by transient PKA activation.
• A specific membrane transport pathway, marked by sphingomyelin trafficking, is activated from the SAC to the apical membrane.
• This PKA-regulated pathway is distinct from the apical recycling pathway and switches directionality to the basolateral side upon reaching optimal polarity.

Conclusions:

• Transient PKA activation is a key regulator of subapical compartment (SAC) function in establishing cell polarity.
• A novel PKA-dependent sphingomyelin transport pathway from the SAC to the apical membrane has been identified.
• This pathway exhibits dynamic directional switching, contributing to the maintenance of cell polarity.