Performance of mouse neural stem cells as a screening reagent: Characterization of PAC1 activity in medium-throughput functional assays

The self-renewal and phenotypic properties of neural stem cells make them an abundant and more physiologically relevant alternative to recombinant cell lines for drug screens to identify ligands acting at neural targets. Here, the authors use high-throughput phenotypic and signaling assays to test the ability of neural stem cells isolated from postnatal mouse hippocam-pus (mNSCs) to deliver high-content and physiologically relevant data on native peptide receptor activity. The authors find that mNSCs express PAC1 but not the related. VPAC1 and VPAC2 receptors. PACl promotes both the proliferation of mNSCs and their differentiation into neuronal-like cells. In addition, the authors show that PAC1 stimulates markedly dif-ferent extracellular signal-regulated kinase signals in mNSCs than in recombinant CHO-PACl cells and is able to couple to Ca²⁺elevation only in CHO-PACl cells. These data suggest that G-protein coupling in CHO-PACl cells is nonphysiological, which may affect the ligand binding properties of the receptor and thus distort the results of a screen by increasing numbers of false positives/negatives. This work reinforces the emerging pharmacological theory that recombinant cell lines are often inappropriate models of natively expressing primary cells, and the authors conclude that mNSCs are a viable and relevant physiological alternative for use in high-throughput drug screens.