As a conserved cell signaling scheme, a large repertoire of surface receptors transduce diverse extracellular signals into a small set of intracellular 2nd messengers, which trigger enzyme cascades that regulate excitability, transmitter release, metabolism, neurite motility and gene expression (Alberts et al., 2014) (Figure 5A). Superimposed upon these conserved 2nd messenger cascades, different cell types deploy a large set of regulatory signaling proteins to control the spatiotemporal dynamics of each signal transduction pathway to achieve appropriate responses. We discovered that whereas most kinase cascades and signal proteins are broadly expressed, a small set of regulatory protein families in the calcium, cyclic nucleotide and small GTPase pathways are highly differential among PCPs and may tailor specific signal transduction properties (Figure 5A).
