CiteULike: Author Pellissier

Modifying ligand-induced and constitutive signaling of the human 5-HT4 receptor.

WC Chang — 2008-07-03T00:55:33-00:00

PLoS ONE, Vol. 2, No. 12. (2007)

G protein-coupled receptors (GPCRs) signal through a limited number of G-protein pathways and play crucial roles in many biological processes. Studies of their in vivo functions have been hampered by the molecular and functional diversity of GPCRs and the paucity of ligands with specific signaling effects. To better compare the effects of activating different G-protein signaling pathways through ligand-induced or constitutive signaling, we developed a new series of RASSLs (receptors activated solely by synthetic ligands) that activate different G-protein signaling pathways. These RASSLs are based on the human 5-HT(4b) receptor, a GPCR with high constitutive G(s) signaling and strong ligand-induced G-protein activation of the G(s) and G(s/q) pathways. The first receptor in this series, 5-HT(4)-D(100)A or Rs1 (RASSL serotonin 1), is not activated by its endogenous agonist, serotonin, but is selectively activated by the small synthetic molecules GR113808, GR125487, and RO110-0235. All agonists potently induced G(s) signaling, but only a few (e.g., zacopride) also induced signaling via the G(q) pathway. Zacopride-induced G(q) signaling was enhanced by replacing the C-terminus of Rs1 with the C-terminus of the human 5-HT(2C) receptor. Additional point mutations (D(66)A and D(66)N) blocked constitutive G(s) signaling and lowered ligand-induced G(q) signaling. Replacing the third intracellular loop of Rs1 with that of human 5-HT(1A) conferred ligand-mediated G(i) signaling. This G(i)-coupled RASSL, Rs1.3, exhibited no measurable signaling to the G(s) or G(q) pathway. These findings show that the signaling repertoire of Rs1 can be expanded and controlled by receptor engineering and drug selection.

[Acute Weston Hurst necrotizing hemorrhagic leukoencephalitis]

A Donnet — 2008-05-23T14:23:06-00:00

Revue neurologique, Vol. 152, No. 12. (December 1996), pp. 748-751.

The clinical and pathological findings of a 43-year-old woman, diagnosed as having acute hemorrhagic leukoencephalitis at postmortem examination, are presented. The acute hemorrhagic leukoencephalitis affects mainly young adults and is the most fulminant from of demyelinating disease. It is frequently preceded by a respiratory infection. Diagnosis is facilitated by CT scanning and MRI, which reveal the massive lesion in the cerebral white matter. Many cases terminate fatally in 2 or 4 days, but in others survival is longer. The pathological findings are distinctive.

Measuring the Kinetics of Biomolecular Recognition with Magnetic Colloids

Cohen Tannoudji — 2008-05-07T23:01:32-00:00

Physical Review Letters, Vol. 100, No. 10. (2008)

We introduce a general methodology based on magnetic colloids to study the recognition kinetics of tethered biomolecules. Access to the full kinetics of the reaction is provided by an explicit measure of the time evolution of the reactant densities. Binding between a single ligand and its complementary receptor is here limited by the colloidal rotational diffusion. It occurs within a binding distance that can be extracted by a reaction-diffusion theory that properly accounts for the rotational Brownian dynamics. Our reaction geometry allows us to probe a large diversity of bioadhesive molecules and tethers, thus providing a quantitative guidance for designing more efficient reactive biomimetic surfaces, as required for diagnostic, therapeutic, and tissue engineering techniques.

5-HT4 Receptor Activation of the ERK Pathway Depends on Src Activation but Not on G Protein or beta-Arrestin Signaling.

Gael Barthet — 2007-04-07T14:12:30-00:00

Mol Biol Cell (21 March 2007)

Monitoring Editor: J. Silvio Gutkind The 5-HT4 receptors have recently emerged as key modulators of learning, memory and cognitive processes. In neurons, 5-HT4Rs activate cAMP production and PKA, however, nothing is known about their ability to activate another key signaling pathway involved in learning and memory: the ERK pathway. Here, we show that 5-HT4R-stimulation, in primary neurons, produced a potent but transient activation of the ERK pathway. Surprisingly, this activation was mostly PKA-independent. Similarly, using pharmacological, genetic and molecular tools, we also observed that 5-HT4Rs in HEK293 cells, activated the ERK pathway in a Gs/cAMP/PKA-independent manner. We also demonstrated that other classical G proteins (Gq/Gi/Go) and associated downstream messengers were not implicated in the 5-HT4R-activated ERK pathway. The 5-HT4R-mediated ERK activation appeared to be dependent on Src tyrosine kinase and yet totally independent of beta-arrestin. Immunocytofluorescence revealed that p-ERK activation by 5-HT4R was restrained to the plasma membrane, whereas p-Src colocalized with the receptor and carried on even after endocytosis. This phenomenon may result from a tight interaction between 5-HT4R and p-Src detected by coimmunoprecipitation. Finally, we confirmed that the main route by which 5-HT4Rs activate ERKs in neurons was Src-dependent. Thus, in addition to classical cAMP/PKA signaling pathways, 5-HT4Rs may use ERK pathways to control memory process.

Release of guanylin immunoreactivity from the isolated vascularly perfused rat colon.

F Moro — 2006-06-26T12:25:46-00:00

Endocrinology, Vol. 141, No. 7. (July 2000), pp. 2594-2599.

The intestinal peptide guanylin regulates the electrolyte/water transport in the intestinal epithelium. The aim of the present study was to investigate the mechanisms that modulate its secretion in the isolated vascularly perfused rat colon by using a specific guanylin RIA. Intraarterial infusion of bethanechol (10(-4) M) or bombesin (10(-7) M) elicited a significant 6-fold increase in the release of guanylin immunoreactivity (G-IR) in the lumen. Bombesin-stimulated G-IR secretion was strongly reduced by tetrodotoxin, whereas atropine had no effect. VIP (10(-7) M) induced a moderate release of G-IR, whereas substance P, calcitonin gene-related peptide, peptide YY, somatostatin, and neurotensin were without effect. Dimethyl-PGE2 (1.4 x 10(-5) M) or interleukin-1beta (2.5 x 10(-10) M) induced a 3-fold increase in G-IR in the lumen, whereas the degranulator compound bromolasalocid did not stimulate guanylin secretion. Forskolin (10(-5) M) or sodium nitroprusside (10(-4)-10(-3) M) induced a significant release of G-IR. In contrast, PMA (10(-7) M) or ionophore A23187 (10(-6) M) did not modify basal secretion of G-IR. Upon stimulation of guanylin release with bombesin or bethanechol, an increase in G-IR in the portal effluent was also detected. The release of G-IR in the portal effluent was 40-fold lower than that of G-IR into the luminal perfusate. Additionally, analysis with gel chromatography revealed that the immunoreactive material released in the lumen or in the portal effluent coeluted with the 15-amino acid peptide originally isolated from rat intestine. In conclusion, the present data suggest that the enteric nervous system and immune cells may modulate guanylin release from the rat colon. The release of guanylin in the lumen and portal effluent suggests that this peptide may exert both luminal/paracrine and hormonal effects.

[Continuous administration of mivacurium for short procedures. Delayed onset and recovery from neuromuscular blockade]

D Pellissier — 2005-06-29T16:21:30-00:00

Ann Fr Anesth Reanim, Vol. 14, No. 6. (1995), pp. 467-471.

OBJECTIVE: To assess the delays of onset and spontaneous recovery from neuromuscular block produced by mivacurium administered by continuous infusion for short procedure requiring a deep relaxation. STUDY DESIGN: Prospective open non comparative study. PATIENTS: Twenty-nine class ASA I and II adults undergoing a stomatological procedure of short duration were included in the study. METHOD: General anaesthesia was obtained with a continuous infusion of propofol, supplemented with alfentanil and N2O-O2 mixture. Neuromuscular blockade, assessed with electromyography of the adductor pollicis muscle, was obtained with mivacurium (150 micrograms.kg-1). After restoration of 5% of neuromuscular transmission, mivacurium was administered by continuous infusion in order to maintain a blockade between 91 and 99%. RESULTS: The delay for decreasing twitch height by 95% was 2.9 +/- 1.0 min. The mean dose for maintenance of blockade was 10.9 +/- 1.5 micrograms.kg-1.min-1. The delay of spontaneous recovery from blockade was 10.2 min, 16.6 min and 21.3 min for obtaining 25, 75 and 95% twitchs respectively. The delay for the twitch increase from 25 to 75% was 6.6 min. DISCUSSION: Mivacurium in continuous infusion provides rapidly a deep and stable neuromuscular blockade followed by a rapid spontaneous restoration of neuromuscular transmission in patients with normal pseudocholinesterases.