Superresolution Microscopy Reveals Distinct Phosphoinositide Subdomains Within the Cilia Transition Zone

Area of Science:

• Cell Biology
• Molecular Biology
• Microscopy

Background:

• Primary cilia are microtubule-based organelles crucial for cellular signaling.
• Phosphoinositides (PI) are key signaling lipids regulating cellular events.
• PI signaling and turnover occur in primary cilia, but their precise localization is unknown.

Purpose of the Study:

• To precisely map the localization of phosphoinositides within primary cilia.
• To investigate the localization of the phosphoinositide-metabolizing enzyme INPP5E.

Main Methods:

• Superresolution microscopy (2D stimulated emission depletion microscopy).
• Live cell imaging.
• Optimized fixation and permeabilization protocols.

Main Results:

• PI(3,4,5)P3 and PI(4,5)P2 were localized to distinct ring-shaped subdomains at the inner transition zone membrane.
• PI(3,4,5)P3 subdomain was more distal than PI(4,5)P2 subdomain.
• INPP5E was found concentrated at the cilia base, within the transition zone, in a ring-shaped domain.

Conclusions:

• This study provides a superresolution map of phosphoinositides within the primary cilia transition zone.
• INPP5E localizes to the transition zone membrane, where it can regulate local phosphoinositide metabolism.
• These findings elucidate the spatial organization of lipid signaling at the primary cilia transition zone.