No abstract

STriatal Enriched protein tyrosine Phosphatase (STEP) is a brain-specific protein that is thought to play a role in synaptic plasticity. This hypothesis is based on previous findings demonstrating a role for STEP in the regulation of the extracellular signal-regulated kinase1/2 (ERK1/2). We have now generated a STEP knockout mouse and investigated the effect of knocking out STEP in the regulation of ERK1/2 activity. Here, we show that the STEP knockout mice are viable and fertile and have no detectable cytoarchitectural abnormalities in the brain. The homozygous knockout mice lack the expression of all STEP isoforms, whereas the heterozygous mice have reduced STEP protein levels when compared with the wild-type mice. The STEP knockout mice show enhanced phosphorylation of ERK1/2 in the striatum, CA2 region of the hippocampus, as well as central and lateral nuclei of the amygdala. In addition, the cultured neurons from KO mice showed significantly higher levels of pERK1/2 following synaptic stimulation when compared with wild-type controls. These data demonstrate more conclusively the role of STEP in the regulation of ERK1/2 activity.

Deficits in the basal ganglia pathways modulating cortical motor activity underlie both Parkinson disease (PD) and Huntington disease (HD). Phosphodiesterase 10A (PDE10A) is enriched in the striatum, and animal data suggest that it is a key regulator of this circuitry. Here, we report on germline PDE10A mutations in eight individuals from two families affected by a hyperkinetic movement disorder due to homozygous mutations c.320A>G (p.Tyr107Cys) and c.346G>C (p.Ala116Pro). Both mutations lead to a reduction in PDE10A levels in recombinant cellular systems, and critically, positron-emission-tomography (PET) studies with a specific PDE10A ligand confirmed that the p.Tyr107Cys variant also reduced striatal PDE10A levels in one of the affected individuals. A knock-in mouse model carrying the homologous p.Tyr97Cys variant had decreased striatal PDE10A and also displayed motor abnormalities. Striatal preparations from this animal had an impaired capacity to degrade cyclic adenosine monophosphate (cAMP) and a blunted pharmacological response to PDE10A inhibitors. These observations highlight the critical role of PDE10A in motor control across species.

No abstract

A genetic algorithms (GA) based strategy is described for the identification or optimization of active leads. This approach does not require the synthesis and evaluation of huge libraries. Instead it involves iterative generations of smaller sample sets, which are assayed, and the “experimentally” determined biological response is used as an input for GA to rapidly find better leads. The GA described here has been applied to the identification of potent and selective stromelysin substrates from a combinatorial-based population of 206 or 64 000 000 possible hexapeptides. Using GA, we have synthesized less then 300 unique immobilized peptides in a total of five generations to achieve this end. The results show that each successive generation provided better and unique substrates. An additional strategy of utilizing the knowledge gained in each generation in a spin-off SAR activity is described here. Sequences from the first generations were evaluated for stromelysin and collagenase activity to identify stromelysin-selective substrates. GlyProSerThr-TyrThr with Tyr as the P1‘ residue is such an example. A number of peptides replacing Tyr with unusual monomers were synthesized and evaluated as stromelysin substrates. This led to the identification of Ser(OBn) as the best and most selective P1‘ residue for stromelysin.