Peptide Inhibitors Disrupt the Serotonin 5-HT_2CReceptor Interaction with Phosphatase and Tensin Homolog to Allosterically Modulate Cellular Signaling and Behavior

Abstract

Serotonin (5-hydroxytryptamine; 5-HT) signaling through the 5-HT2C receptor (5-HT2CR) is essential in normal physiology, whereas aberrant 5-HT2CR function is thought to contribute to the pathogenesis of multiple neural disorders. The 5-HT2CR interacts with specific protein partners, but the impact of such interactions on 5-HT2CR function is poorly understood. Here, we report convergent cellular and behavioral data that the interaction between the 5-HT2CR and protein phosphatase and tensin homolog (PTEN) serves as a regulatory mechanism to control 5-HT2CR-mediated biology but not that of the closely homologous 5-HT2AR. A peptide derived from the third intracellular loop of the human 5-HT2CR [3L4F (third loop, fourth fragment)] disrupted the association, allosterically augmented 5-HT2CR-mediated signaling in live cells, and acted as a positive allosteric modulator in rats in vivo. We identified the critical residues within an 8 aa fragment of the 3L4F peptide that maintained efficacy (within the picomolar range) in live cells similar to that of the 3L4F peptide. Last, molecular modeling identified key structural features and potential interaction sites of the active 3L4F peptides against PTEN. These compelling data demonstrate the specificity and importance of this protein assembly in cellular events and behaviors mediated by 5-HT2CR signaling and provide a chemical guidepost to the future development of drug-like peptide or small-molecule inhibitors as neuroprobes to study 5-HT2CR allostery and therapeutics for 5-HT2CR-mediated disorders.

Functional Status of the Serotonin 5-HT2C Receptor (5-HT2CR) Drives Interlocked Phenotypes that Precipitate Relapse-Like Behaviors in Cocaine Dependence

“…The importance of 5-HT 2C R function in the generation of impulsive action is supported by observations that the systemic administration of selective 5-HT 2C R agonists or 5-HT 2C R antagonists decrease and increase impulsive action, respectively (Anastasio et al, 2013a;Cunningham et al, 2012;Fletcher et al, 2011;Winstanley et al, 2004b). These effects reliably match the efficacy and directionality of the effects of these ligands in tasks that measure cocaineseeking Cunningham et al, 2012;Fletcher et al, 2008;Grottick et al, 2001).…”

“…Procedures occurred in standard five-hole nosepoke operant chambers equipped with a houselight, food tray, and an external pellet dispenser capable of delivering 45 mg pellets (Bio-Serv, Frenchtown, NJ) housed within a ventilated and sound-attenuated chamber (MedAssociates, St Albans, VT). The 1-CSRT task methodology has been described previously Anastasio et al, 2013a). In the pre-training stage, rats (n ¼ 176) were habituated to the test chamber and introduced to a nosepoke response for food pellets.…”

“…The total number of responses (premature, correct, incorrect, and omissions) were recorded Anastasio et al, 2013a;Cunningham et al, 2012). Premature responses were used to assess impulsive action.…”

“…The one-choice serial reaction time (1-CSRT) task, a simplified variant of the 5-CSRT task, is rapidly entrained and assesses deficits in behavioral control to appropriately withhold a prepotent response (action restraint) independent from complex visuospatial attentional processes (as in the 5-CSRT task) Anastasio et al, 2013a;Cunningham et al, 2012;Dalley et al, 2002;Robbins, 2002). We tested the hypothesis that impulsive action and cocaine cue reactivity are interlocked constructs; the 1-CSRT task was used to identify impulsive action phenotypes in an outbred rat population before cocaine self-administration and assessment of cue reactivity in the form of lever presses reinforced by a cocaine-associated discrete cue complex during forced abstinence (FA) (Field and Cox, 2008).…”

Roles of PTEN/PI3K/AKT/GSK3? Pathway in Neuron Signaling Involved in Autism

“…Honokiol, a compound in traditional eastern herbal medicines, can chemically diminish the PI3K/AKT signaling by up-regulation of PTEN expression [68]. However, PTEN indirectly promotes 5-HT synthesis and secretion via inhibiting the signaling [69,70]. In addition, there is a crosstalk between PTEN and 5-HT receptor [70].…”