GSK3beta (Phospho-Ser9) ELISA Kit

An imbalance in dopamine-mediated neurotransmission is a hallmark physiological feature of neuropsychiatric disorders, such as schizophrenia. Recent evidence demonstrates that dopamine D-2 receptors, which are the main target of antipsychotics, modulate the activity of the protein kinase Akt, which is known to be downregulated in the brain of patients with schizophrenia. Akt has an important role in the regulation of cellular processes that are critical for neurodevelopment, including gene transcription, cell proliferation, and neuronal migration. Thus, it is possible that during brain development, altered Akt-dependent dopamine signaling itself may lead to defects in neural circuit formation. Here, we used a zebrafish model to assess the direct impact of altered dopamine signaling on brain development and larval motor behavior. We demonstrate that D-2 receptor activation acutely suppresses Akt activity by decreasing the level of pAkt(Thr308) in the larval zebrafish brain. This D-2-dependent reduction in Akt activity negatively regulates larval movement and is distinct from a D-1-dependent pathway with opposing affects on motor behavior. In addition, we show that D-2-dependent suppression of Akt activity causes a late onset change in GSK3b activity, a known downstream target of Akt signaling. Finally, altered D-2 receptor signaling, or direct inhibition of Akt activity, causes a significant decrease in the size of the GABAergic neuron population throughout most of the brain. Our observations suggest that D-2 receptor signaling suppresses Akt-GSK3b activity, which regulates GABAergic neuron development and motor behavior.

Background: The beta-amyloid precursor protein (APP) and the related beta-amyloid precursor-like proteins (APLPs) undergo complex proteolytic processing giving rise to several fragments. Whereas it is well established that A beta accumulation is a central trigger for Alzheimer's disease, the physiological role of APP family members and their diverse proteolytic products is still largely unknown. The secreted APPs alpha ectodomain has been shown to be involved in neuroprotection and synaptic plasticity. The gamma-secretase-generated APP intracellular domain (AICD) functions as a transcriptional regulator in heterologous reporter assays although its role for endogenous gene regulation has remained controversial. Results: To gain further insight into the molecular changes associated with knockout phenotypes and to elucidate the physiological functions of APP family members including their proposed role as transcriptional regulators, we performed DNA microarray transcriptome profiling of prefrontal cortex of adult wild-type (WT), APP knockout (APP(-/-)), APLP2 knockout (APLP2(-/-)) and APPsa knockin mice (APP(alpha/alpha)) expressing solely the secreted APPs alpha ectodomain. Biological pathways affected by the lack of APP family members included neurogenesis, transcription, and kinase activity. Comparative analysis of transcriptome changes between mutant and wild-type mice, followed by qPCR validation, identified co-regulated gene sets. Interestingly, these included heat shock proteins and plasticity-related genes that were both down-regulated in knockout cortices. In contrast, we failed to detect significant differences in expression of previously proposed AICD target genes including Bace1, Kai1, Gsk3b, p53, Tip60, and Vglut2. Only Egfr was slightly up-regulated in APLP2(-/-) mice. Comparison of APP(-/-) and APP(alpha/alpha) with wildtype mice revealed a high proportion of co-regulated genes indicating an important role of the C-terminus for cellular signaling. Finally, comparison of APLP2(-/-) on different genetic backgrounds revealed that background-related transcriptome changes may dominate over changes due to the knockout of a single gene. Conclusion: Shared transcriptome profiles corroborated closely related physiological functions of APP family members in the adult central nervous system. As expression of proposed AICD target genes was not altered in adult cortex, this may indicate that these genes are not affected by lack of APP under resting conditions or only in a small subset of cells.