Biomedical subjects

Joan Sallés

Publications and source records attributed to Joan Sallés.

4 recordsLinked to original sources

PubMed2006

Levels of G-protein alpha q/11 subunits and of phospholipase C-beta(1-4), -gamma, and -delta1 isoforms in postmortem human brain caudate and cortical membranes: potential functional implications.

The levels of expression of G-protein alpha(q/11) (Galpha(q/11)) subunits and PLC-beta(1-4), -gamma, and -delta(1) isoforms were quantified by Western blot analysis in order to establish their contribution to the patterns of PLC functioning reported here. Quantitative measurements of the levels of Galpha(q/11) subunits in each region were obtained by comparison with known amounts of Escherichia coli expressed recombinant Galpha(q) subunits. Quantitative analysis indicated that Galpha(q/11) subunits are abundant polypeptides in human brain, with values ranging from about 1200 ng/mg in cerebral cortex to close to 900 ng/mg of membrane protein in caudate. In cerebral cortical membranes, the PLC-beta(1) isoform was more abundant than in caudate membranes. The highest levels of PLC-beta(2) expression were detected in caudate membranes. PLC-beta(3) was little expressed, and there were no significant differences in the relative values between both brain regions. Finally, the levels of the PLC-beta(4) isoform were significantly lower in caudate than in cortical membranes. It is concluded that although most of these data represent relative, not absolute, measures of protein levels within these regions, they contribute nonetheless to the significant differences observed in signaling capacities through the PLC system in both human brain regions.

Adult↗

PubMed2006

Transmembrane signaling through phospholipase C-beta in the developing human prefrontal cortex.

To investigate changes in muscarinic receptor-stimulated phospholipase C-beta (PLC-beta) activity during brain development, we examined the functional coupling of each of the three major protein components of the phosphoinositide system (M1, M3, and M5 muscarinic receptor subtypes; Gq/11 proteins; PLC-beta1-4 isoforms) in membrane preparations from post-mortem human prefrontal cerebral cortex collected at several stages of prenatal and postnatal development. In human prenatal brain membranes, PLC was found to be present and could be activated by calcium, but the ability of guanosine-5'-o-3 thiotriphosphate (GTPgammaS) or carbachol (in the presence of GTPgammaS) to modulate prenatal PLC-beta was significantly weaker than that associated with postnatal PLC-beta. Western blot analysis revealed that the levels of Galphaq/11 did not change significantly during development. In contrast, dramatically higher levels of expression of PLC-beta1-4 isoforms and of M1, M3, and M5 muscarinic receptors were detected in the child vs. the fetal brain, a finding that might underlie the observed increased activity of PLC. Thus, inositol phosphate production may be more efficiently regulated by altering the amount of effectors (PLC-beta1-4) and receptors (M1,3,5 subtypes) than by altering the level of Galphaq/11 subunits. These results demonstrate that different PLC isoforms are expressed in the prefrontal cortex of the developing human brain in an age-specific manner, suggesting specific roles not only in synaptic transmission but also in the differentiation and maturation of neurons in the developing brain.

Actins↗

PubMed2004

Differential postmortem delay effect on agonist-mediated phospholipase Cbeta activity in human cortical crude and synaptosomal brain membranes.

The phosphoinositide signal transduction system, and particularly, phospholipase Cbeta isozymes, are relevant in the etiopathogeny of human neuropsychiatric pathologies such as depression. Stimulation of phospholipase Cbeta activity by muscarinic receptors and G proteins was determined in crude and synaptosomal membrane preparations from nine postmortem human frontal cortices (postmortem delay range 8 to 50 h). Thus, the phospholipase Cbeta activity was determined by measuring the hydrolysis of exogenous [3H]-phosphatidylinositol 4,5-bisphosphate. There was a postmortem delay-mediated decrease in the PIP2 hydrolysis irrespective of the membrane preparation used (P < 0.05). Moreover, there were statistically significant differences for exponential decay curve parameters (K factor and Span) of PLCbeta activity induced by agonist-mediated activation between crude and synaptosomal membrane preparations. These results show that the postsynaptic component of the PLCbeta activity is more sensible to the postmortem delay effect.

Adult↗

PubMed2002

Design, synthesis and pharmacological evaluation of 5-hydroxytryptamine(1a) receptor ligands to explore the three-dimensional structure of the receptor.

In this work, we evaluate the structural differences of transmembrane helix 3 in rhodopsin and the 5-hydroxytryptamine 1A (5-HT1A) receptor caused by their different amino acid sequence. Molecular dynamics simulations of helix 3 in the 5-HT1A receptor tends to bend toward helix 5, in sharp contrast to helix 3 in rhodopsin, which is properly located within the position observed in the crystal structure. The relocation of the central helix 3 in the helical bundle facilitates the experimentally derived interactions between the neurotransmitters and the Asp residue in helix 3 and the Ser/Thr residues in helix 5. The different amino acid sequence that forms helix 3 in rhodopsin (basically the conserved Gly(3.36)Glu(3.37) motif in the opsin family) and the 5-HT1A receptor (the conserved Cys(3.36)Thr(3.37) motif in the neurotransmitter family) produces these structural divergences. These structural differences were experimentally checked by designing and testing ligands that contain comparable functional groups but at different interatomic distance. We have estimated the position of helix 3 relative to the other helices by systematically changing the distance between the functional groups of the ligands (1 and 2) that interact with the residues in the receptor. Thus, ligand 1 optimally interacts with a model of the 5-HT1A receptor that matches rhodopsin template, whereas ligand 2 optimally interacts with a model that possesses the proposed conformation of helix 3. The lack of affinity of 1 (K(i) > 10,000 nM) and the high affinity of 2 (K(i) = 24 nM) for the 5-HT1A receptor binding sites, provide experimental support to the proposed structural divergences of helix 3 between the 5-HT1A receptor and rhodopsin.

Amino Acids↗