Biomedical subjects

L R Bevilaqua

Publications and source records attributed to L R Bevilaqua.

8 recordsLinked to original sources

PubMed2005

Memory consolidation induces N-methyl-D-aspartic acid-receptor- and Ca2+/calmodulin-dependent protein kinase II-dependent modifications in alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor properties.

The N-methyl-D-aspartic acid (NMDA) receptor-dependent activation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) is necessary for induction of the long-term potentiation of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor-mediated responses in the CA1 region of the hippocampus, a putative model for learning and memory. We analyzed the interplay among NMDA receptor, CaMKII and AMPA receptor during consolidation of the memory for an inhibitory avoidance learning task in the rat. Bilateral intra-CA1 infusion of the NMDA receptor antagonist D-(-)-2-amino-5-phosphonopentanoic acid (AP5) or of the CaMKII inhibitor 2-[N-(2-hydroxyethyl)]-N-(4-methoxybenzenesulfonyl)] amino-N-(4-chlorocinnamyl)-N-methylbenzylamine) (KN-93) immediately after step-down inhibitory avoidance training hindered memory consolidation. Learning of the avoidance response induced the NMDA receptor-dependent translocation of alphaCaMKII to a postsynaptic density-enriched fraction isolated from dorsal CA1 and the autophosphorylation of this kinase at Thr-286. Step-down inhibitory avoidance training increased the quantity of GluR1 and GluR2/3 AMPA receptor subunits and the phosphorylation of GluR1 at Ser-831 but not at Ser-845 in CA1 postsynaptic densities. The intra-CA1 infusion of KN-93 and AP5 blocked the increases in GluR1 and GluR2/3 levels and the phosphorylation of GluR1 brought on by step-down inhibitory avoidance training. Our data suggest that step-down inhibitory avoidance learning promotes the learning-specific and NMDA receptor-dependent activation of CaMKII in the CA1 region of the dorsal hippocampus and that this activation is necessary for phosphorylation and translocation of AMPA receptor to the postsynaptic densities, similarly to what happens during long-term potentiation.

2-Amino-5-phosphonovalerate↗

PubMed2001

Phosphorylation of Ser(19) alters the conformation of tyrosine hydroxylase to increase the rate of phosphorylation of Ser(40).

The effect of phosphorylation on the shape of tyrosine hydroxylase (TH) was studied directly using gel filtration and indirectly using electrospray ionization mass spectrometry. Phosphorylation of Ser(19) and Ser(40) produced a TH molecule with a more open conformation than the non-phosphorylated form. The conformational effect of Ser(19) phosphorylation is less pronounced than that of the Ser(40) phosphorylation. The effect of Ser(19) and Ser(40) phosphorylation appears to be additive. Binding of dopamine produced a more compact form when compared with the non-dopamine-bound TH. The interdependence of Ser(19) and Ser(40) phosphorylation was probed using electrospray ionization mass spectrometry. The rate constants for the phosphorylation of Ser(19) and Ser(40) were determined by electrospray ionization mass spectrometry using a consecutive reaction model. The rate constant for the phosphorylation of Ser(40) is approximately 2- to 3-fold higher if Ser(19) is already phosphorylated. These results suggest that phosphorylation of Ser(19) alters the conformation of tyrosine hydroxylase to allow increased accessibility of Ser(40) to kinases.

Calcium-Calmodulin-Dependent Protein Kinase Type 2↗

PubMed2001

Angiotensin II promotes the phosphorylation of cyclic AMP-responsive element binding protein (CREB) at Ser133 through an ERK1/2-dependent mechanism.

In cells from the adrenal medulla, angiotensin II (AII) regulates both the activity and mRNA levels of catecholamine biosynthetic enzymes whose expression is thought to be under the control of cAMP-responsive element (CRE) binding protein (CREB). In this study, we evaluated the effect of AII stimulation on CREB phosphorylation at Ser133 (pCREB) in bovine adrenal chromaffin cells (BACC). We found that AII produces a rapid and AII type-1 receptor (AT1)-dependent increase in pCREB levels, which is blocked by the MEK1/2 inhibitor U0126 but not by H-89, SB203580 or KN-93, suggesting that it is mediated by the extracellular-regulated protein kinases 1 and 2 (ERK1/2) and not by cAMP-dependent protein kinase (PKA), p38 mitogen-activated protein kinase (p38MAPK) or Ca(2+)/calmodulin-dependent protein kinases (CaMKs) dependent pathways. Gel-shift experiments showed that the increase in pCREB levels is accompanied by an ERK1/2-dependent upregulation of CRE-binding activity. We also found that AII promotes a rapid and reversible increase in the activity of the non-receptor tyrosine kinase Src and that the inhibition of this enzyme completely blocks the AII-induced phosphorylation of ERK1/2, the CREB kinase (p90)RSK and CREB. Our data support the hypothesis that in BACC, AII upregulates CREB functionality through a mechanism that requires Src-mediated activation of ERK 1/2 and (p90)RSK.

Adrenal Medulla↗

PubMed2000

Learning-associated activation of nuclear MAPK, CREB and Elk-1, along with Fos production, in the rat hippocampus after a one-trial avoidance learning: abolition by NMDA receptor blockade.

It is widely accepted that the formation of long-term memory (LTM) requires neuronal gene expression, protein synthesis and the remodeling of synaptic contacts. From mollusk to mammals, the cAMP/PKA/CREB signaling pathway has been shown to play a pivotal role in the establishment of LTM. More recently, the MAPK cascade has been also involved in memory processing. Here, we provide evidence for the participation of hippocampal PKA/CREB and MAPK/Elk-1 pathways, via activation of NMDA receptors, in memory formation of a one-trial avoidance learning in rats. Learning of this task is associated with an activation of p44 and p42 MAPKs, CREB and Elk-1, along with an increase in the levels of the catalytic subunit of PKA and Fos protein in nuclear-enriched hippocampal fractions. These changes were blocked by the immediate posttraining intra-hippocampal infusion of APV, a selective blocker of glutamate NMDA receptors, which renders the animals amnesic for this task. Moreover, no changes were found in control-shocked animals. Thus, inhibitory avoidance training in the rat is associated with an increase in the protein product of an IEG, c-fos, which occurs concomitantly with the activation of nuclear MAPK, CREB and Elk-1. NMDA receptors appear to be a necessary upstream step for the activation of these intracellular cascades during learning.

2-Amino-5-phosphonovalerate↗

PubMed2000

Rapid and transient learning-associated increase in NMDA NR1 subunit in the rat hippocampus.

Several lines of evidence indicate that glutamate NMDA receptors are critically involved in long-term potentiation (LTP) and in certain forms of learning. It was previously demonstrated that memory formation of an inhibitory avoidance task in chick is specifically associated with an increase in the density of NMDA receptor in selected brain regions. Here we report on the effect of a one trial inhibitory avoidance training in rats, a hippocampal-dependent learning task, on the levels of different subunits of the glutamate NMDA receptor in synaptic plasma membranes (SPM) isolated from the hippocampus. Training rats on a one trial inhibitory avoidance task results in a rapid, transient and selective increase (+33%, p < 0.05) in NMDA NRI subunit expression in hippocampal SPM of rats sacrificed 30 min posttraining. No changes were observed at 0 or 120 min after training or in shocked animals in comparison to naive control rats. In addition, no training-associated increase in the levels of NMDA NR2A and NR2B or AMPA GluR 2/3 subunits was observed at any timepoint tested. In conclusion, the present findings support the hypothesis that alterations in expression of synaptic NMDA NR1 subunits in the hippocampus are specifically associated with memory formation of an inhibitory avoidance task and strongly suggest that hippocampal NMDA receptors are crucially involved in the neural mechanisms underlying certain forms of learning.

Animals↗

PubMed1999

Experience-dependent increase in cAMP-responsive element binding protein in synaptic and nonsynaptic mitochondria of the rat hippocampus.

Cyclic AMP-responsive element binding protein (CREB) plays a pivotal role in the formation of long-term memory in Drosophila, Aplysia, mice and rats. Recently, we were able to demonstrate that CREB and its serine 133 phosphorylated form p-CREB are localized in synaptic and nonsynaptic mitochondria of the rat brain. Here we report on the effect of a one-trial inhibitory avoidance training procedure on mitochondrial CREB from the rat hippocampus. This aversively motivated training task is associated with a time-dependent increase (34-35%) in both p-CREB and CREB immunoreactivities detected in synaptic mitochondria of the hippocampus. In nonsynaptic mitochondria, p-CREB levels increased in both trained and shocked animals. In addition to CREB, two CRE-element binding repressors, CREB-2 and CREM-1, were also detected in purified brain mitochondria. No changes were observed in CREB-2 and CREM-1 immunoreactivities in hippocampal synaptic mitochondria after an inhibitory avoidance training. Taken together the present findings represent the first evidence showing that brain mitochondrial CREB may participate in plasticity-dependent changes associated with a behavioural training procedure.

Animals↗

PubMed1999

Cyclic AMP-responsive element binding protein in brain mitochondria.

Cyclic AMP-responsive element binding protein (CREB) is critically involved in many important brain functions, including the formation of long-term memory. CREB is the best characterized member of a family of transcription factors (CREB/ATF family) recognized to be important nuclear targets for intracellular signal transduction systems. Here we show, by using different approaches, that CREB is unexpectedly localized to mitochondria of the rat brain. Controlled subcellular fractionation of hippocampus and cerebral cortex showed that both synaptic and nonsynaptic mitochondria exhibited immunoreactivity to the phosphorylated form of CREB (pCREB). Moreover, CREB extracted from synaptic mitochondria is able to be phosphorylated by the catalytic subunit of protein kinase A and dephosphorylated by protein phosphatase 1 or 2B. DNA mobility shift assays showed the presence of binding activity to the calcium-cyclic AMP-responsive element in mitochondrial extracts from hippocampus; this binding complex was specifically supershifted by an anti-CREB antibody. Immunoelectron microscopic analysis of hippocampal subcellular fractions revealed that pCREB immunoreactivity is localized in close association with the inner mitochondrial membrane. These results, together with recent findings describing the presence and phosphorylation of CREB in developing dendrites, suggest that CREB may participate in different mechanisms involved in the communication between extracellular signals and the expression of genes.

Animals↗

PubMed1995

Beta-globin gene cluster haplotype distribution in five Brazilian Indian tribes.

Haplotypes derived from five polymorphic restriction sites in the beta-globin gene cluster were investigated in 139 individuals from five different Brazilian Indian tribes by the polymerase chain reaction (PCR). Eight haplotypes were identified. Haplotypes 2 ((+)----) and 6 (-)++(-)+) were the most frequent and were common to all tribes. Their prevalences ranged from 60% to 93% and from 3% to 18%, respectively. Average heterozygosity measured by the Gini-Simpson index is markedly reduced among these Brazilian Indians when compared with Europeans (56%), but much less (8%) in relation to Asiatics, suggesting the absence of an important bottleneck effect in the early colonization of South America. The coefficient of gene differentiation (GST') was estimated as 0.082 among six Brazilian Indian tribes, but when only three Tupi-Mondé-speaking tribes were considered, this estimate was reduced to 0.030.

Base Sequence↗