Regulation of Polyamine Transport by Chmp1 in Drosophila Melanogaster

Polyamines are small organic cations that are essential for a number of biological processes such as cell proliferation and cell cycle progression. High concentrations of polyamines are often associated with diseases like cancer (Paz et al.). While the metabolism of polyamines has been well studied (Schneider and Wendisch), the mechanisms by which polyamines are transported are poorly understood. Previous research has described lung carcinoma cells (H157), which are devoid of polyamine transport activity (Shao et al.). It has been hypothesized that these cells exhibit high expression of Chmp1. Chmp1 has been shown to be involved in vesicular trafficking, which makes Chmp1 a valid potential player in the polyamine transport system (PTS) (Howard et al.). Drosophila melanogaster larvae were used in these experiments because the overexpression of Chmp1 in tissue culture was unsuccessful. In these studies, imaginal discs from wild type (WT) and Chmp1 overexpressing (o/e) larvae were harvested and incubated for 18 hours at 25°C in the presence or absence of 1μg/mL 20-hydroxyecdysone (hydroxy) as it is known that discs develop in the presence of hydroxy and not in its absence (Wang, et al). In order to study whether Chmp1 overexpression regulates polyamine transport, a cytotoxic drug known to enter cells via the PTS, Ant44 (a generous gift from Dr. Otto Phanstiel) was added to the leg imaginal discs. It was proposed that if Chmp1 o/e down-regulates the PTS, then the addition of Ant44 would not inhibit leg development because it cannot enter the cell through the polyamine transporter. Polyamine rescue experiments were also performed in the presence of hydroxy and difluoromethylornithine (DFMO), an inhibitor of polyamine metabolism, to study whether the addition of different polyamines could rescue development of imaginal leg discs in Chmp1 o/e flies. It was proposed that if Chmp1 o/e down-regulates the PTS, then adding polyamines in the presence of hydroxy and DFMO would decrease leg development in Chmp1 o/e flies. If Chmp1 is found to be a down-regulator of the PTS, this may provide insight into the underlying mechanisms that are involved in polyamine transport. A better understanding of the players involved in the PTS could provide a vital target for cancer drug development (Nowotarski et al.).