Pharmacological Properties of Chromobacterium violaceum Violacein at the Human Serotonin 2C Receptor

Serotonin (5‐HT), a neurotransmitter, plays a role in many physiological responses by binding to 16 receptor subtypes. The 5‐HT 2C receptor subtype is a 7‐transmembrane, G protein‐coupled receptor (GPCR) that is involved in neuronal excitability, spatial learning, mood, and appetite. The microorganism Chromobacterium violaceum produces a purple pigment, violacein, which can be extracted from liquid cultures. Violacein has antibiotic, antileishmanial, antiviral and antitumoral effects in various cancer cell lines. Violacein is similar in structure to 5‐HT, however, no one has ever reported the activity of violacein at 5‐HT receptors. To investigate the effect of violacein on 5‐HT 2C receptor trafficking, Human Embryonic Kidney (HEK) 293 cells expressing fluorescently‐tagged 5‐HT 2C receptor were treated with 5‐HT, violacein, water or vehicle, fixed and visualized with fluorescent microscopy. Violacein treatment did not cause receptor internalization. Given our recent discovery that the 5‐HT 2C receptor can activate the JAK/STAT pathway, we examined if violacein could impact this activation. HEK 293 cells expressing 5‐HT 2C receptor were treated with violacein or pretreated with violacein followed by incubation with 5‐HT. Phosphorylation states of JAK2 and STAT3 were examined by immunoblotting. Preliminary data suggests that violacein may hinder activation of STAT3 but further study is required. We will also investigate the effect of violacein on G‐protein activation by measuring phosphoinositide hydrolysis. Affinity for violacein to the 5‐HT 2C receptor will be investigated by competition binding. Support or Funding Information Department of Education Title III HBGI Grant No. P031B141010