Class I PI 3-kinases: Function and evolution.

Area of Science:

• Cell Biology
• Evolutionary Biology
• Biochemistry

Background:

• Class I phosphoinositide 3-kinases (PI3K) are crucial regulators of fundamental cellular processes in humans, including growth, proliferation, survival, and polarity.
• Activation of PI3Ks by cell surface receptors generates the lipid second messenger phosphatidylinositol (3,4,5)-trisphosphate (PIP3), which controls downstream signaling.
• PIP3 directly modulates the function of numerous effector proteins, forming a complex signaling network.

Purpose of the Study:

• To review the fundamental biology of the PI3K pathway.
• To analyze the evolutionary distribution and origins of PI3K pathway components and their functions across different taxa.
• To provide a phylogenetic framework for understanding human cellular process regulation.

Main Methods:

• Literature review of PI3K pathway biology.
• Phylogenetic analysis of PI3K pathway components, including class I PI3Ks, AKT, and Cytohesins.
• Comparative genomics and functional analysis across metazoa, amoebozoa, and choanoflagellates.

Main Results:

• Class I PI3Ks are broadly distributed across metazoa, amoebozoa, and choanoflagellates, indicating ancient origins in unicellular organisms.
• The PI3K pathway likely evolved in single-celled organisms and was subsequently co-opted for intercellular communication in metazoans.
• Downstream PIP3-binding proteins like AKT and Cytohesins show a similar ancient distribution, while other effectors evolved later.

Conclusions:

• The PI3K pathway has deep evolutionary roots, originating before the emergence of multicellular animals.
• Understanding the evolutionary history of the PI3K pathway provides insights into the conservation and divergence of cellular regulation mechanisms.
• Genomic and functional phylogenies of regulatory systems like the PI3K pathway are essential for deciphering human cellular processes.