Iris Depaz

Expression of hNP22 Is Altered in the Frontal Cortex and Hippocampus of the Alcoholic Human Brain

BACKGROUND Human neuronal protein (hNP22) is a gene with elevated messenger RNA expression in the prefrontal cortex of the human alcoholic brain. hNP22 has high homology with a rat protein (rNP22). These proteins also share homology with a number of cytoskeleton-interacting proteins. METHODS A rabbit polyclonal antibody to an 18-amino acid epitope was produced for use in Western and immunohistochemical analysis. Samples from the human frontal and motor cortices were used for Western blots (n = 10), whereas a different group of frontal cortex and hippocampal samples were obtained for immunohistochemistry (n = 12). RESULTS The hNP22 antibody detected a single protein in both rat and human brain. Western blots revealed a significant increase in hNP22 protein levels in the frontal cortex but not the motor cortex of alcoholic cases. Immunohistochemical studies confirmed the increased hNP22 protein expression in all cortical layers. This is consistent with results previously obtained using Northern analysis. Immunohistochemical analysis also revealed a significant increase of hNP22 immunoreactivity in the CA3 and CA4 but not other regions of the hippocampus. CONCLUSIONS It is possible that this protein may play a role in the morphological or plastic changes observed after chronic alcohol exposure and withdrawal, either as a cytoskeleton-interacting protein or as a signaling molecule.

Changes in neuronal protein 22 expression and cytoskeletal association in the alcohol‐dependent and withdrawn rat brain

The action of alcohol on neuronal pathways has been an issue of increasing research focus, with numerous findings contradicting the previously accepted idea that its effect is nonspecific. The human NP22 (hNP22) gene was revealed by its elevated expression in the frontal cortex of the human alcoholic. The sequences of hNP22 and the rat orthologue rNP22 contain a number of domains consistent with those of cytoskeletal‐interacting proteins. Localization of rNP22 is restricted to the cytoplasm and processes of neurons and it colocalizes with elements of the microfilament and microtubule matrices including filamentous actin (F‐actin), α‐tubulin, tau, and microtubule‐associated protein 2 (MAP2). Withdrawal of Wistar rats after alcohol dependence induced by alcohol vapor produced elevated levels of rNP22 mRNA and protein in the cortex, CA2, and dentate gyrus regions of the hippocampus. In contrast, there was decreased rNP22 expression in the striatum after chronic ethanol exposure. Chronic ethanol exposure did not markedly alter rNP22 colocalization with F‐actin, α‐tubulin, or MAP2, although colocalization at the periphery of the neuronal soma with F‐actin was observed only after chronic ethanol exposure and withdrawal. Rat NP22 colocalization with MAP2 was reduced during withdrawal, whereas association with α‐tubulin and actin was maintained. These findings suggest that the effect of chronic ethanol exposure and withdrawal on rNP22 expression is region selective. Rat NP22 may affect microtubule or microfilament function, thereby regulating the neuroplastic changes associated with the development of alcohol dependence and physical withdrawal.

Expression of human neuronal protein 22, a novel cytoskeleton-associated protein, was decreased in the anterior cingulate cortex of schizophrenia

Human neuronal protein 22 (hNP22) is a novel neuron-specific protein featuring numerous motifs previously described in cytoskeleton-associating and signaling proteins. Because previous studies have supported abnormalities in neuronal cytoarchitecture and/or development in the schizophrenia brain, we examined the expression of hNP22 in the anterior cingulate cortex, the hippocampus and the prefrontal cortex of schizophrenic and normal control postmortem brains using high-sensitive immunohistochemistry. Seven schizophrenic and seven age- and sex-matched control brains were examined. The ratio of hNP22-immunopositive cells/total cells was significantly reduced in layer V (p=.020) and layer VI (p=.022) of the anterior cingulate cortex of schizophrenic brain compared with controls. In contrast, there were no significant changes observed in the hippocampus and the prefrontal cortex. These results suggest that altered expression of hNP22 may be associated with modifications in neuronal cytoarchitecture leading to dysregulation of neural signal transduction in the anterior cingulate cortex of the schizophrenia brain.

Using Peer Teaching to Support Co-Operative Learning in Undergraduate Pharmacology.

Abstract We report findings from the second phase of a study of co-operative, group-based assessment in Pharmacology for second-year undergraduates at The University of Queensland, Australia. Students (n = 285) enrolled in the 2006 Bachelor of Science degree program completed a group-based assessment task (weighted 10% of their course). Blended teaching strategies and the task design were modified to support group formation and peer teaching. A Jigsaw teaching strategy was adopted to support a co-operative learning task in which groups created and submitted a Notice of Intent (NOI) or mini grant proposal based on the topic of Drug Dependence. Assessment was 7% from the NOI and 3% from an individual quiz. In post-assessment surveys, students reported more favourable attitudes towards assessment in which group members received the same marks than in a pre-teaching survey. Findings from the post-task assessment survey were that most students worked co-operatively around assessment. Most students reported that peer teaching help them to complete their assignment and their individual quiz (3%) more than working in “expert panels” or group-based writing. Overall marks were high: the mean ± sd for the group-based NOI was 80 ± 13% and for the averaged quiz marks, 73 ± 13%. The need for more detailed study of group dynamics is recommended.

The novel cytoskeleton-associated protein Neuronal protein 22: Elevated expression in the developing rat brain

Neuronal development and process targeting is mediated by proteins of the cytoskeleton. However, the signaling pathways underlying these mechanisms are complex and have not yet been fully elucidated. Neuronal protein 22 (NP22) has been identified as a cytoskeleton-associated protein. It colocalizes with microtubules and actin, the two major components of the cytoskeleton. It contains numerous signaling motifs and induces process formation in non-neuronal cells. Expression of rat NP22 (rNP22) rises incrementally at specific time points during brain development, with the greatest elevation occurring during synaptogenesis in the rat brain. Its neuronal localization is primarily at the plasma membrane of the soma in the embryonic brain and progresses into homogeneous expression in the postnatal rat brain. Data suggest that NP22 may play a role in mediating the molecular events governing development of the neuronal architecture. Furthermore, its sustained expression in postnatal brain implies a function in the maintenance of neuronal morphology.

Chronic ethanol has region-selective effects on Egr-1 and Egr-3 DNA-binding activity and protein expression in the rat brain.

This study focused on the DNA-binding activity and protein expression of the transcription factors Egr-1 and Egr-3 in the rat brain cortex and hippocampus after chronic or acute ethanol exposure. DNA-binding activity was reduced in both regions after chronic ethanol exposure and was restored to the level of the pair-fed group at 16 h of withdrawal. Cortical Egr-1 protein levels were not altered by chronic ethanol exposure but increased 16 h after withdrawal, thus mirroring DNA-binding activity. In contrast, Egr-3 protein levels did not undergo any change. There was no change in the level of either protein in the hippocampus. Immunohistochemistry revealed a region-selective change in immunopositive cells in the cortex and hippocampus. Finally, an acute bolus dose of ethanol did not affect Egr DNA-binding activity and ethanol treatment did not alter the DNA-binding activity or protein levels of the transcription factor Sp1. These observations suggest that chronic exposure to ethanol has region-selective effects on the DNA-binding activity and protein expression of Egr-1 and Egr-3 transcription factors in the rat brain. These changes occur after prolonged ethanol exposure and may thus reflect neuroadaptive changes associated with physical dependency and withdrawal. These effects are also transcription factor-selective. Clearly, protein expression is not the sole mediator of the changes in DNA-binding activity and chronic ethanol exposure must have effects on modulatory agents of Egr DNA-binding activity.

Differential Expression of Cytochrome P450 Enzymes from the CYP2C Subfamily in the Human Brain

Cytochrome P450 enzymes from the CYP2C subfamily play a prominent role in the metabolic clearance of many drugs. CYP2C enzymes have also been implicated in the metabolism of arachidonic acid to vasoactive epoxyeicosatrienoic acids. CYP2C8, CYP2C9, and CYP2C19 are expressed in the adult liver at significant levels; however, the expression of CYP2C enzymes in extrahepatic tissues such as the brain is less well characterized. Form-specific antibodies to CYP2C9 and CYP2C19 were prepared by affinity purification of antibodies raised to unique peptides. CYP2C9 and CYP2C19 were located in microsomal fractions of all five human brain regions examined, namely the frontal cortex, hippocampus, basal ganglia, amygdala, and cerebellum. Both CYP2C9 and CYP2C19 were detected predominantly within the neuronal soma but with expression extending down axons and dendrites in certain regions. Finally, a comparison of cortex samples from alcoholics and age-matched controls suggested that CYP2C9 expression was increased in alcoholics.

Differential Expression of Human Cytochrome P450 Enzymes from the CYP3A Subfamily in the Brains of Alcoholic Subjects and Drug-Free Controls

Cytochrome P450 enzymes are responsible for the metabolism of most commonly used drugs. Among these enzymes, CYP3A forms mediate the clearance of around 40–50% of drugs and may also play roles in the biotransformation of endogenous compounds. CYP3A forms are expressed both in the liver and extrahepatically. However, little is known about the expression of CYP3A proteins in specific regions of the human brain. In this study, form-selective antibodies raised to CYP3A4 and CYP3A5 were used to characterize the expression of these forms in the human brain. Both CYP3A4 and CYP3A5 immunoreactivity were found to varying extents in the microsomal fractions of cortex, hippocampus, basal ganglia, amygdala, and cerebellum. However, only CYP3A4 expression was observed in the mitochondrial fractions of these brain regions. N-terminal sequencing confirmed the principal antigen detected by the anti-CYP3A4 antibody in cortical microsomes to be CYP3A4. Immunohistochemical analysis revealed that CYP3A4 and CYP3A5 expression was primarily localized in the soma and axonal hillock of neurons and varied according to cell type and cell layer within brain regions. Finally, analysis of the frontal cortex of chronic alcohol abusers revealed elevated expression of CYP3A4 in microsomal but not mitochondrial fractions; CYP3A5 expression was unchanged. The site-specific expression of CYP3A4 and CYP3A5 in the human brain may have implications for the role of these enzymes in both normal brain physiology and the response to drugs.

Membrane integration of recombinant human P450 forms.

Amino terminal sequence modification of cytochrome P450 enzymes is often necessary to achieve expression in bacteria. The aim of this study was to examine the effect of such modifications on membrane integration and P450 activity. Forms that retained substantial N-terminal hydrophobic sequences remained unaffected by treatments to remove peripheral membrane proteins and were released only by detergent. Truncated P450s 2A13, 2C9 (δ3–20), 2C19 (δ3–20), 2D6 (DB11) and 2E1 remained principally membrane-bound, but some P450 was found in the soluble fraction and could be partially extracted by alkaline and high salt treatments. The subcellular localization of P450s 2C9 and 2C19 assessed by fluorescence microscopy mirrored the distribution between subcellular fractions. The MALLLAVFL modified forms of P450 2C9 YFP, P450 2C18 YFP and P450 2C19 YFP were found primarily at the periphery of the cells, whereas the truncated forms of P450 2C9 (δ3–20) YFP and 2C19 (δ3–20) YFP were observed at the periphery as well as inside the cells. N-terminal variants of P450s 2C9 and 2C19 showed altered kinetics towards form-selective substrates. Rates of diclofenac 4´-hydroxylation by P450 2C9 and luciferin H-EGE metabolism by P450 2C19 were higher for the MALLLAVFL-modified forms compared with the (δ3–20) truncated forms despite supplementation of truncated form incubations with additional reductase. Thus, N-terminal sequence modifications changed the degree of membrane integration, potentially affecting subcellular localization, interactions with redox partners, and hence enzymatic activity.

Neuronal protein 22 colocalises with both the microtubule and microfilament cytoskeleton in neurite-like processes.

The expression of human neuronal protein 22 (hNP22) is up-regulated in the superior frontal cortex of chronic alcoholics. hNP22 shares significant homology with a number of proteins implicated in bundling of actin filaments. In addition, it contains domains similar to those found in microtubule-associated proteins. We investigated the ability of hNP22 to induce cytoskeletal changes by overexpression in Chinese hamster ovary cells. Overexpression of hNP22 resulted in process formation in these cells that increased upon treatment with cytochalasin D, an actin depolymerising agent. Transfection of mutant hNP22 containing either a deletion of the putative actin-binding domain or deletion of a consensus protein kinase C (PKC) phosphorylation site (Ser-180) failed to induce process formation. In contrast, a mutation to mimic persistent PKC phosphorylation resulted in a cellular morphology similar to that seen in wild-type hNP22 transfections. This observation suggests that hNP22 requires phosphorylation at Ser-180 by PKC to induce cytoskeletal rearrangements. hNP22 was also observed to colocalise with actin and tubulin in processes of transfected cells. An hNP22-specific antibody specifically immunoprecipitated a complex including tubulin from human brain indicating that hNP22 binds directly to microtubules. Taken together, this data suggests that NP22 is part of a signaling complex that associates with cytoskeletal elements to regulate neuronal morphology.