Lysosomal PIP₃ revealed by genetically encoded lipid biosensors

Area of Science:

• Cell Biology
• Molecular Signaling
• Lipid Biochemistry

Background:

• 3-Phosphoinositides (3-PIs), including PIP3 and PI(3,4)P2, are vital lipid second messengers in the PI3K/Akt pathway.
• This pathway regulates cell growth and is often dysregulated in cancer.
• The precise localization of 3-PIs within cellular membranes beyond the plasma membrane is not fully understood.

Purpose of the Study:

• To investigate the spatial distribution and regulation of specific 3-PIs in cellular membranes.
• To develop and utilize novel biosensors for precise detection of PIP3 and PI(3,4)P2.

Main Methods:

• Development of genetically encodable biosensors selective for PIP3 or PI(3,4)P2.
• Microscopy and biochemical assays to track lipid localization and dynamics.
• Investigating the role of endocytosis in 3-PI trafficking.

Main Results:

• PIP3 was found to accumulate significantly at the lysosome upon growth factor stimulation.
• Contrary to the established view, PIP3 is not exclusively localized to the plasma membrane.
• Lysosomal PIP3 originates from the plasma membrane and its internalization depends on dynamin-dependent endocytosis.

Conclusions:

• PIP3 exhibits dynamic trafficking via endocytosis to access subcellular compartments like lysosomes.
• This spatial regulation allows PIP3 to influence signaling pathways in a compartment-specific manner.
• The findings challenge the conventional understanding of PIP3 localization and highlight its broader role in cellular signaling.