Hemopoietic cell survival is regulated by exogenous concentrations of GM-CSF. The selective activation of the Ser⁵⁸⁵/14-3-3/PI-3 kinase survival-only pathway is triggered by low pM concentrations of GM-CSF (left). The alternative survival and proliferation pathway triggered by higher concentrations of GM-CSF is dependent on the dodecamer assembly and involves the Jak/STAT, Ras/mitogen-activated protein kinase, and PI-3 kinase pathways (right). The key receptor-proximal events that initiate these signaling pathways are the mutually exclusive phosphorylation of Ser⁵⁸⁵ and of Tyr⁵⁷⁷ of βc.