Asymmetric modulation of a catecholamine-regulated protein in the rat brain, following quinpirole administration

Cloning, characterization, and functional studies of a human 40-kDa catecholamine-regulated protein: implications in central nervous system disorders

Catecholamine-regulated proteins (CRPs) have been shown to bind dopamine and other structurally related catecholamines; in particular, the 40-kDa CRP (CRP40) protein has been previously cloned and functionally characterized. To determine putative human homologs, BLAST analysis using the bovine CRP40 sequence identified a human established sequence tag (EST) with significant homology (accession #BQ224193). Using this EST, we cloned a recombinant human brain CRP40-like protein, which possessed chaperone activity. Radiolabeled dopamine binding studies with recombinant human CRP40 protein demonstrated the ability of this protein to bind dopamine with low affinity and high capacity. The full-length human CRP40 nucleotide sequence was elucidated (accession #DQ480334) with RNA ligase-mediated rapid amplification of complementary DNA ends polymerase chain reaction, while Northern blot hybridization suggested that human CRP40 is an alternative splice variant of the 70-kDa mitochondrial heat shock protein, mortalin. Human SH-SY5Y neuroblastoma cells treated with the antipsychotic drug, haloperidol, exhibited a significant increase in CRP40 messenger RNA expression compared to untreated control cells, while other dopamine agonists/antagonists also altered CRP40 expression and immunolocalization. In conclusion, these results show that we have cloned a splice variant of mortalin with a novel catecholamine binding function and that this chaperone-like protein may be neuroprotective in dopamine-related central nervous system disorders.

Differential modulation of a 40 kDa catecholamine regulated protein in the core and shell subcompartments of the nucleus accumbens following chronic quinpirole and haloperidol administration in the rat

Past reports have shown dopamine (DA) D2/D3 receptor agonist quinpirole (QNP) and the DA D2 receptor antagonist, haloperidol (HAL) display a significant increase in expression of catecholamine regulated protein (CRP40) in the nucleus accumbens (NAcc) and the striatum, respectively. The present study investigated the in vivo effects of QNP and HAL on CRP40 protein levels within the core and shell subcompartments of the NAcc. As significant homology exists between CRP40 and Hsp70/Hsc70, parallel studies with inducible Hsp70 and constitutive Hsc70 were conducted to establish the specificity with respect to QNP on Hsp70 and CRP40. Results demonstrated that CRP40 protein was significantly expressed in the shell relative to the core region of NAcc following chronic QNP (+16.28%+/-0.42%, P<0.05) and CRP40 protein was significantly expressed in the core vs. the shell following chronic HAL (+36.02%+/-0.75%, P<0.05). There was no significant change in Hsp70 protein levels following chronic QNP or HAL administration. The results demonstrated selective modulation of CRP40 within NAcc by QNP and HAL treatment, without affecting Hsp70.

Altered quinpirole-induced local cerebral glucose utilization in anterior cortical regions in rats after sensitization to quinpirole

Dopaminergic psychostimulants produce behavioral responses of greater magnitude with repeated, intermittent administration, than a single, acute dose, a phenomenon known as "sensitization." Most studies of sensitization have focused on the "motive circuit"; however, some additional anterior cortical regions also appear to be affected. In this study, alterations in regional neuronal activity in anterior cortical brain areas produced by quinpirole, a D(2)/D(3) agonist, were assessed on the basis of local cerebral glucose utilization (LCGU) using the [(14)C]-2-deoxyglucose (2-DG) method. Adult, male Long-Evans rats (180-200 g, n = 7-9/group) were subjected to ten injections of quinpirole (0.5 mg/kg, s.c.) administered every third day; controls and drug-naive rats received saline. Locomotor activity was quantitated after injections one and ten to confirm sensitization. The 2-DG procedure was initiated 60 min after an 11th injection in freely moving rats. LCGU was determined in 11 anterior cortical brain regions by quantitative autoradiography. In drug-naive rats, quinpirole decreased LCGU in the cingulate cortex-area 3 (-16%) and infralimbic cortex (-16%). In sensitized rats, quinpirole decreased LCGU in the cingulate cortex-area 1 (-19%), frontal cortex-area 3 (-19%), lateral orbital cortex (-18%), medial/ventral orbital cortex (-17%), and parietal cortex (-17%) as well as in the cingulate cortex-area 3 (-19%) and infralimbic cortex (-20%); (all P < 0.05 v. control). This suggests that decreased neuronal activity in the cingulate cortex-area 1, frontal cortex-area 3, lateral orbital cortex, medial/ventral orbital cortex, and parietal cortex, in addition to altered activity in the motive circuit, may underlie the augmented behavioral response to quinpirole in sensitized animals.

Heat shock protein 12A shows reduced expression in the prefrontal cortex of subjects with schizophrenia

BACKGROUND

Deoxyribonucleic acid microarray analyses of dorsolateral prefrontal cortex (DLPFC) area 9 from 10 matched pairs of schizophrenic and control subjects revealed a consistent and significant decrease (p = .001; mean log2 signal difference = -.58) in transcript expression for a gene clone KIAA0417. This database entry has been recently annotated as two highly homologous members of a heat-shock protein family (HSPA12A and HSPA12B).

METHODS

We followed up our initial results by in situ hybridization in subjects with schizophrenia, major depression, and a chronic haloperidol-treated nonhuman primate model. Furthermore, we investigated the distribution of HSPA12A and HSPA12B transcripts across the human and nonhuman primate brain.

RESULTS

We found that HSPA12A (but not HSPA12B) is highly expressed in the human brain and shows a neuron- and region-specific transcript distribution, with strongest expression in the frontal and occipital cortical regions. HSPA12A messenger ribonucleic acid was significantly reduced (p < .01; mean log2 optical density difference = -.84) across subjects with schizophrenia but not in the DLPFC of subjects with major depression or in monkeys chronically treated with haloperidol.

CONCLUSIONS

The data are consistent with metabolic alterations in schizophrenia, reflected in selective changes in the expression of certain genes encoding proteins involved in cellular metabolism or metabolic responsiveness.