124 research outputs found
Premio Sapienza Ricerca, sezione Under 40, per la ricerca di eccellenza intitolata “Permeabilità al Ca2+ dei recettori nicotinici dell’acetilcolina”, svolta nel quinquennio 2004-2008.
No full textIl Prof. Sergio Fucile, del Dipartimento di Fisiologia e Farmacologia della Sapienza, studia i canali ionici, proteine che permettono il passaggio di correnti elettriche attraverso le membrane cellulari e sono coinvolti nei meccanismi di trasporto dell’informazione nei sistemi biologici. La nicotina attiva dei canali in grado di far entrare ioni calcio nelle cellule e di influenzare numerosi processi alla base di varie patologie neurologiche, fra le quali le sindromi miasteniche, l’epilessia e la sclerosi laterale amiotrofica
Le tecniche teatrali sono in grado di influenzare positivamente il cervello umano?
No full textThe special issue of the journal «Biblioteca Teatrale», devoted to the subject of “Theatre as Enriched Environment”, is the result of an international conference held at Sapienza University of Rome in June 2015. In a multidisciplinary perspective (human and social sciences, cognitive and medical sciences), the contributions are experience proofs, and theoretical and methodological reflections about the value and the role that theatre can get in certain situations of uneasiness and deprivation. Essay: Laura Maggi, Sergio Fucile, “Are Theatrical Techniques Able to Positively Influence Human Brain?
The distribution of charged amino acid residues and the Ca(2+) permeability of nicotinic acetylcholine receptors: a predictive model
No full textNicotinic acetylcholine receptors (nAChRs) are cation-selective ligand-gated ion channels exhibiting variable Ca(2+) permeability depending on their subunit composition. The Ca(2+) permeability is a crucial functional parameter to understand the physiological role of nAChRs, in particular considering their ability to modulate Ca(2+)-dependent processes such as neurotransmitter release. The rings of extracellular and intracellular charged amino acid residues adjacent to the pore-lining TM2 transmembrane segment have been shown to play a key role in the cation selectivity of these receptor channels, but to date a quantitative relationship between these structural determinants and the Ca(2+) permeability of nAChRs is lacking. In the last years the Ca(2+) permeability of several nAChR subtypes has been experimentally evaluated, in terms of fractional Ca(2+) current (Pf, i.e., the percentage of the total current carried by Ca(2+) ions). In the present study, the available Pf-values of nAChRs are used to build a simplified modular model describing the contribution of the charged residues in defined regions flanking TM2 to the selectivity filter controlling Ca(2+) influx. This model allows to predict the currently unknown Pf-values of existing nAChRs, as well as the hypothetical Ca(2+) permeability of subunit combinations not able to assemble into functional receptors. In particular, basing on the amino acid sequences, a Pf > 50% would be associated with homomeric nAChRs composed by different α subunits, excluding α7, α9, and α10. Furthermore, according to the model, human α7β2 receptors should have Pf-values ranging from 3.6% (4:1 ratio) to 0.1% (1:4 ratio), much lower than the 11.4% of homomeric α7 nAChR. These results help to understand the evolution and the function of the large diversity of the nicotinic receptor family
Ca2+ permeability of nicotinic acetylcholine receptors
No full textNicotinic acetylcholine receptors (nAChRs) are expressed in muscle cells and neurons, as well as in an increasing number of other cell types. The nAChR channels are permeable to cations, including Ca2+. Ca2+ entry through nAChR channels has been shown to modulate several Ca2+-dependent cellular processes, such as neurotransmitter release, synaptic plasticity, and cell motility. The value of Ca2+ permeability associated to a particular nAChR subtype thus represents an important indication for its physiological role. This review summarizes the quantitative data on Ca2+ permeability obtained from several nAChR subtypes in native and heterologous systems. Different experimental approaches are compared, and the structural determinants of Ca2+ permeability are discussed. (C) 2003 Elsevier Ltd. All rights reserved
About a new method to measure fractional Ca2+ currents through ligand-gated ion channels
No full text[No abstract available
Calcium influx through muscle nAChR-channels: one route, multiple roles
No full textAlthough Ca2+ influx through muscle nAChR-channels has been described over the past 40 years, its functions remain still poorly understood. In this review we suggest possible roles of Ca2+ entry at all stages of muscle development, summarizing the evidence present in literature. nAChRs are expressed in myoblasts prior to fusion, and can be activated in the absence of an ACh-releasing nerve terminal, with Ca2+ influx likely contributing to regulate cell fusion. Upon establishment of nerve-muscle contact, Ca2+ influx contributes to orchestrate the signaling required for the correct formation of the neuromuscular junction. Finally, in the mature synapse, Ca2+ entry through postsynaptic nAChR-channels - highly Ca2+ permeable, in particular in humans - acts on K+ and Na+ channels to shape endplate excitability. However, when genetic defects cause excessive channel activation, Ca2+ influx becomes toxic and causes endplate myopathy. Throughout the review, we highlight how Ricardo Miledi has contributed to construct this whole body of knowledge, from the initial description of Ca2+ permeability of endplate nAChR channels, to the rationale for the treatment of endplate excitotoxic damage under pathological conditions. This article belongs to the special issue on SI: Miledi ́s contributions
Nicotinic AChR in Congenital Myasthenic Syndromes
No full textAbout 20 % of the identified cases of congenital myasthenic syndromes are due to defects causing
overstimulation of endplate ACh receptors, with consequent excessive Ca2+ entry, endplate structural
damage, and impairment of the neuromuscular transmission. Overstimulation arises from extended
dwelling of ACh in the synaptic cleft because of absence of acetylcholine esterase or from prolonged
activation of “slow-channel” mutant ACh receptors. The high Ca2+ permeability of human endplate ACh
receptor, recently described likely predisposes to excitotoxic damage. The good knowledge of ACh
receptor function has allowed molecular understanding of the defects introduced in channel kinetics and
Ca2+ permeability by slow-channel mutations and the design of efficient therapeutic strategies. These
forms of congenital myasthenic syndrome are treated by limiting ACh-induced cation entry, thus
preventing endplate degeneration. Several molecules of wide clinical use, such as fluoxetine and quinidine,
but also verapamil and salbutamol modulate AChR kinetics and ion selectivity and may be used to lower
ACh-evoked responses in these patients. In this contribution we summarize the main findings in the field
5-HT3 Receptors in Rat Dorsal Root Ganglion Neurons: Ca(2+) Entry and Modulation of Neurotransmitter Release
No full textRat dorsal root ganglion (DRG) neurons express 5-hydroxytryptamine receptors (5-HT3Rs). To elucidate their physiological role in the modulation of sensory signaling, we aimed to quantify their functional expression in newborn and adult rat DRG neurons, as well as their ability to modulate the Ca(2+)-dependent neurotransmitter release, by means of electrophysiological techniques combined with fluorescence-based Ca(2+) imaging. The selective 5-HT3R agonist mCPBG (10 μM) elicited whole-cell currents in 92.5% of adult DRG neurons with a significantly higher density current than in responding newborn cells (52.2%), suggesting an increasing serotoninergic modulation on primary afferent cells during development. Briefly, 5-HT3Rs expressed by adult DRG neurons are permeable to Ca(2+) ions, with a measured fractional Ca(2+) current (i.e., the percentage of total current carried by Ca(2+) ions, Pf) of 1.0%, similar to the value measured for the human heteromeric 5-HT3(A/B) receptor (P(f) = 1.1%), but lower than that of the human homomeric 5-HT3(A) receptor (P(f) = 3.5%). mCPBG applied to co-cultures of newborn DRG and spinal neurons significantly increased the miniature excitatory postsynaptic currents (mEPSCs) frequency in a subset of recorded spinal neurons, even in the presence of Cd(2+), a voltage-activated Ca(2+) channel blocker. Considered together, our findings indicate that the Ca(2+) influx through heteromeric 5-HT3Rs is sufficient to increase the spontaneous neurotransmitter release from DRG to spinal neurons
Cholinergic stimulation of human microcytoma cell line H69.
No full textExperiments were addressed to investigate the mechanisms by which cholinergic stimulation is coupled to the enhancement of proliferation of small cell lung cancer cells H69. Muscarinic stimulation triggers the release of cytosolic Ca2+ and of inositol(1,4,5) trisphosphate with comparable time courses. The presence of alpha-bungarotoxin or the absence of Ca2+ in external medium suppresses enhancement of clonal growth induced by brief applications of nicotine. Here we suggest that Ca2+ mobilization represents a trigger for the enhancement of small cell lung cancer cell proliferation upon cholinergic stimulation
Ca2+ permeability of human heteromeric nAChRs expressed by transfection in human cells
No full textThe Ca2+ permeability of the human heteromeric 34, 42 and 44 neuronal nicotinic acetylcholine receptors (nAChRs) was estimated by measuring the fractional Ca2+ current (Pf) flowing through the ligand-activated receptor-channels. Simultaneous recordings of transmembrane currents and fluorescence transients, using the whole-cell patch-clamp technique combined with fura-2 fluorescence microscopy, were performed in transiently transfected human cells. The human 42 nAChR showed a Pf value of 2.6%, while the human 34 nAChR showed a similar Pf value
of 2.7%. Conversely, 44 nAChR exhibited a Pf value (1.5%) significantly smaller than those of both 42 and 34 nAChRs. In test experiments performed in HEK 293 cells stably expressing rat GluR1AMPA receptor subunit,we repeated the determination of Pf, whose value (3.2%) has previously been reported by others using the same fluorescent dye; and we found a very similar Pf value (3.5%). In further test experiments, we found that Pf values of chick 34 (4.4%) and 44 (2.1%) matched those previously reported by us using confocal fluorescence microscopy. Thus, our findings
are consistent with those elsewhere reported even using different experimental procedures, giving a strong support to the following sequence of Ca2+ permeability: h-34 > h-42 > h-44
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