Small molecule drug screening in Drosophila identifies the 5HT2A receptor as a feeding modulation target

Abstract

Dysregulation of eating behavior can lead to obesity, which affects 10% of the adult population worldwide and accounts for nearly 3 million deaths every year. Despite this burden on society, we currently lack effective pharmacological treatment options to regulate appetite. We used Drosophila melanogaster larvae to develop a high-throughput whole organism screen for drugs that modulate food intake. In a screen of 3630 small molecules, we identified the serotonin (5-hydroxytryptamine or 5-HT) receptor antagonist metitepine as a potent anorectic drug. Using cell-based assays we show that metitepine is an antagonist of all five Drosophila 5-HT receptors. We screened fly mutants for each of these receptors and found that serotonin receptor 5-HT2A is the sole molecular target for feeding inhibition by metitepine. These results highlight the conservation of molecular mechanisms controlling appetite and provide a method for unbiased whole-organism drug screens to identify novel drugs and molecular pathways modulating food intake.

Identified Serotonin-Releasing Neurons Induce Behavioral Quiescence and Suppress Mating inDrosophila

“…In the superior lateral protocerebrum region, these neurons might be modulated by PMPV1 neurons, ultimately regulating courtship behavior. We find feeding behavior also to be affected by thermogenetically activating a large proportion of 5-HT neurons, in accordance with pharmacological findings (Gasque et al, 2013), but not by those PMPV cluster neurons that we isolated. Because our approach to identify neurons is based on monitoring locomotor activity, it might be that feedingregulating 5-HT neurons are not directly associated with locomotor behavior.…”

“…Although insect behavior does not bear similarly complex psychological implications, Drosophila's behavioral repertoire is rich and, in many aspects, dependent on proper 5-HT signaling. In larval or adult Drosophila, 5-HT has been shown to affect feeding behavior (Neckameyer, 2010;Gasque et al, 2013), courtship behavior (Becnel et al, 2011), aggression (Dierick andGreenspan, 2007;Alekseyenko et al, 2010Alekseyenko et al, , 2014, and memory formation (Sitaraman et al, 2008(Sitaraman et al, , 2012Lee et al, 2011). Understanding this complexity is made difficult by both the widespread arborizations of 5-HT neurons and the relatively large number of 5-HT receptor genes (i.e., at least 14 in mammals) (Hannon and Hoyer, 2008) and five in Drosophila (Blenau and Thamm, 2011).…”

“…Understanding this complexity is made difficult by both the widespread arborizations of 5-HT neurons and the relatively large number of 5-HT receptor genes (i.e., at least 14 in mammals) (Hannon and Hoyer, 2008) and five in Drosophila (Blenau and Thamm, 2011). Our knowledge about the behavioral and physiological roles of 5-HT in both Drosophila and mammals derives mainly from studies using brain-wide, global manipulations of 5-HT or its target (e.g., by pharmacological or genetic block of its synthesis) (Dierick and Greenspan, 2007;Sitaraman et al, 2008;Neckameyer, 2010;Lee et al, 2011;Sadaf et al, 2012), or by pharmacological or genetic impairment of 5-HT receptors (Yuan et al, 2005(Yuan et al, , 2006Nichols, 2007;Becnel et al, 2011;Gasque et al, 2013), as well as by manipulating 5-HT reuptake through transporters (Silva et al, 2014). However, in recent years, the development of elaborate techniques to selectively dissect neuronal circuits in a cell-specific manner in model systems like Drosophila has advanced strongly (Venken et al, 2011), paving the way for the attribution of more precise roles to subpopulations of distinct, identifiable neurons.…”

Big Lessons from Tiny Flies:<em> Drosophila Melanogaster </em>as a Model to Explore Dysfunction of Dopaminergic and Serotonergic Neurotransmitter Systems

“…1B, represented as red spheres). Drosophila expresses five G protein-coupled serotonin receptors, Gi/Go-coupled the 5HT-R1A and -1B, the Gq-coupled -5HT-R2A and -2B and the Gs-coupled 5HT-R7 [98][99][100][101][102].…”

Serotonin and the search for the anatomical substrate of aggression

“…Not surprisingly, therefore, silencing of 5HT1B receptor-expressing neurons with Kir 2.1 28 or activating them with the dTrpA1 channel (data not shown) had no effects on male aggression. Members of the 5HT2 category (5HT2A and the recently discovered close homologue 5HT2B 29 ) reportedly regulate larval heart rate 30 , and larval feeding behavior also is regulated by 5HT2A receptors 29 . The brain distribution of 5HT2B receptors has not been determined, but 5HT2A 31 , 5HT1A 32 and 5HT7 33 receptor subtypes are expressed in many neuropil regions where they mediate various behaviors in Drosophila.…”