Coordination of Pathways in Metazoans: An Integrated Framework

There are hundreds, if not thousands, of pathways in a unicellular prokaryotic organism, and all these pathways will have to be controlled, regulated, and coordinated to ensure their proper functioning. As organisms evolve from unicellular eukaryotic organisms to multicellular organisms such as the metazoans, more pathways have evolved to support more diverse biological functions. As a result, fine-tuned control, regulation, and coordination of these pathways becomes an immensely complex and demanding task. Yet, consistent with Darwin’s insight that “nature is prodigal in variety, though niggard in innovation,” nature has produced only a few master coordination hubs for these pathways. Moreover, multicellular organisms such as metazoans have evolved two broader means for coordinating various pathways: cross-talk and communication. Cross-talk operates via having shared components and links between intracellular pathways whereas communication operates via transmitting intercellular signals such as hormones and other ligands with membrane receptors and downstream intracellular signal transductions pathways. Our framework points to a more complex network-based approach for understanding biological pathways and the consequences of their disruption, escape, and malfunction such as cancer, aging, and other diseases.