CCK1 and 2 receptors are expressed in immortalized rat brain neuroblasts: intracellular signals after cholecystokinin stimulation.

Cholecystokinin (CCK) is one of the most abundant neuropeptides in the central nervous system (CNS) where it promotes important functions by activation of receptors CCK1 and CCK2. Our aim was to investigate CCK receptors expression and their downstream intracellular signaling in immortalized rat brain neuroblasts. Results show that CCK1 and CCK2 receptor mRNAs and CCK2 receptor protein are expressed in neuroblasts. CCK incubation of neuroblasts leads to stimulation in a time-dependent manner of several signaling pathways, such as tyrosine phosphorylation of adaptor proteins paxillin and p130(Cas), phosphorylation of p44/p42 ERKs as well as PKB (Ser473). Moreover, CCK-8 stimulates the DNA-binding activity of the transcription factor AP-1. The CCK2 receptor agonist gastrin stimulates ERK1/2 phosphorylation in a comparable degree as CCK does. ERK1/2 phosphorylation activated by CCK-8 was markedly inhibited by the CCK2 receptor antagonist CR2945. Incubation for 48 h with CCK-8 increases neuroblasts viability in a similar degree as EGF. In summary, our data clearly identify CCK1 and CCK2 receptor mRNAs and CCK2 receptor protein in brain neuroblasts and show that incubation with CCK promotes cell proliferation and activates the phosphorylation of survival transduction pathways. Stimulation of ERK1/2 phosphorylation by CCK is mainly mediated by the CCK2 receptor. Moreover, this work might provide a novel model of proliferating neuronal cells to further study the biochemical mechanisms by which the neuropeptide CCK exerts its actions in the CNS.