Atypical PI3Ks coordinate chemotaxis, signaling dynamics, and multicellular development in Dictyostelium

Area of Science:

• Cell Biology
• Molecular Biology
• Developmental Biology

Background:

• Phosphoinositide 3-kinase (PI3K) signaling is crucial for cellular processes like protrusion, polarity, and development in Dictyostelium discoideum.
• Canonical Class I PI3Ks and PI(3,4,5)P3 production do not fully explain all PI3K-dependent pathways, including Ras activity attenuation, PI(3,4)P2 polarity, cAMP relay, and development coordination.

Purpose of the Study:

• To identify and characterize atypical PI3K-family enzymes in Dictyostelium discoideum.
• To elucidate the distinct roles of these atypical PI3Ks in regulating cellular signaling and multicellular development.

Main Methods:

• Genetic analysis of atypical PI3K mutants (pikF⁻, pikG⁻, pikH⁻).
• Observation of cellular behaviors including chemotaxis, actin dynamics, and cAMP signaling.
• Utilizing kinase-dead rescue experiments to confirm enzyme function.
• Employing PI(3,4)P2 biosensors to monitor phosphoinositide dynamics.

Main Results:

• PikF constrains Ras-phosphoinositide-actin signaling, affecting chemotactic precision and development.
• PikG is essential for endogenous cAMP oscillations, polarity, and multicellular aggregation.
• PikH primarily supports efficient phagocytic uptake.
• Conserved catalytic lysines are vital for the developmental and uptake functions of these PI3Ks.

Conclusions:

• Atypical PI3Ks (PikF, PikG, PikH) represent functionally distinct regulators in Dictyostelium discoideum.
• These enzymes diversify the PI3K signaling toolkit, separating key processes into distinct kinase-dependent modules.
• The findings provide a new framework for understanding PI3K-mediated regulation of cellular functions and development.