The tyrosine phosphatase STEP: implications in schizophrenia and the molecular mechanism underlying antipsychotic medications.

Glutamatergic signaling through N-methyl-D-aspartate receptors (NMDARs) is required for synaptic plasticity. Disruptions in glutamatergic signaling are proposed to contribute to the behavioral and cognitive deficits observed in schizophrenia (SZ). One possible source of compromised glutamatergic function in SZ is decreased surface expression of GluN2B-containing NMDARs. STEP(61) is a brain-enriched protein tyrosine phosphatase that dephosphorylates a regulatory tyrosine on GluN2B, thereby promoting its internalization. Here, we report that STEP(61) levels are significantly higher in the postmortem anterior cingulate cortex and dorsolateral prefrontal cortex of SZ patients, as well as in mice treated with the psychotomimetics MK-801 and phencyclidine (PCP). Accumulation of STEP(61) after MK-801 treatment is due to a disruption in the ubiquitin proteasome system that normally degrades STEP(61). STEP knockout mice are less sensitive to both the locomotor and cognitive effects of acute and chronic administration of PCP, supporting the functional relevance of increased STEP(61) levels in SZ. In addition, chronic treatment of mice with both typical and atypical antipsychotic medications results in a protein kinase A-mediated phosphorylation and inactivation of STEP(61) and, consequently, increased surface expression of GluN1/GluN2B receptors. Taken together, our findings suggest that STEP(61) accumulation may contribute to the pathophysiology of SZ. Moreover, we show a mechanistic link between neuroleptic treatment, STEP(61) inactivation and increased surface expression of NMDARs, consistent with the glutamate hypothesis of SZ.

Antimicrobial activity of synthetic bornyl benzoates against Trypanosoma cruzi.

We report here for the first time the in vitro effects of (1S,2R,4S)-1,7,7-trimethyl-bicyclo[2·2·1]heptan-2-yl-3',4',5'-trimethoxy benzoate (1) and (1S,2R,4S)-1,7,7-trimethyl-bicyclo[2·2·1]heptan-2-yl benzoate (2) on the growth and ultrastructure of Trypanosoma cruzi. These two synthetic compounds exerted an antiproliferative effect on the epimastigote forms of the parasite. The ICs(50/72h) of two synthetic L-bornyl benzoates, 1 and 2, was 10·1 and 12·8 µg/ml, respectively. Both compounds were more selective against epimastigotes than HEp-2 cells. Ultrastructural analysis revealed intense cytoplasmic vacuolization and the appearance of cytoplasmic materials surrounded by membranes. The treatment of peritoneal macrophages with compounds 1 and 2 caused a significant decrease in the number of T. cruzi-infected cells. L-Bornyl benzoate derivatives may serve as a potential source for the development of more effective and safer chemotherapeutic agents against T. cruzi infections.

Effects of estradiol upon the thymus and lymphoid organs of immature female rats.

PIP: The purpose of this study was to determine if large amounts of estrogenic hormones produced by the placenta could play a role in the development of the lymphoid tissue changes of pregnancy. 40 immature female rats were used. The group was divided into 4 lots of 10 animals each. The first group was castrated. The second group was castrated and given 1.5 mg of estradiol valerianate every fifth day to a total of 4.5 mg. The third group was castrated and injected with peanut oil only, the vehicle used for the estradiol. The fourth, a control group, was untreated. All animals were killed on Day 19. Spleens, genital organs, thymus glands, and mediastinal lumph nodes were removed, weighed and prepared for histologic examination. Thymus glands showed involution. The genital organs were well developed in the group receiving estradiol, but showed involution in other castrated animals. Histological examination of the thymus of animals receiving estradiol showed signs of lymphatic depletion. Spleens, lymph nodes, and adrenals appeared normal. It was concluded that estradiol, and possible other estrogenic hormones, might be of importance in the mechanisms of the immune response. This could apply to the Rh immunization of the pregnant female to her fetus.^ieng