Polyamine transport is mediated by both endocytic and solute carrier transport mechanisms in the gastrointestinal tract

Abstract

The polyamines spermidine and spermine, and their precursor putrescine, are required for cell growth and cellular functions. The high levels of tissue polyamines are implicated in carcinogenesis. The major sources of exogenous polyamines are diet and intestinal luminal bacteria in gastrointestinal (GI) tissues. Both endocytic and solute carrier-dependent mechanisms have been described for polyamine uptake. Knocking down of caveolin-1 protein increased polyamine uptake in colon cancer-derived HCT116 cells. Dietary supplied putrescine was accumulated in GI tissues and liver in caveolin-1 knockout mice more than wild-type mice. Knocking out of nitric oxide synthase (NOS2), which has been implicated in the release of exogenous polyamines from internalized vesicles, abolished the accumulation of dietary putrescine in GI tissues. Under conditions of reduced endogenous tissue putrescine contents, caused by treatment with the polyamine synthesis inhibitor difluoromethylornithine (DFMO), small intestinal and colonic mucosal polyamine contents increased with dietary putrescine levels, even in mice lacking NOS2. Knocking down the solute carrier transporter SLC3A2 in HCT116-derived Hkh2 cells reduced the accumulation of exogenous putrescine and total polyamine contents in DFMO treated cells, relative to non-DFMO-treated cells. These data demonstrate that exogenous putrescine is transported into GI tissues by caveolin-1-and NOS2-dependent mechanisms, but that the solute carrier transporter SLC3A2 can function bidirectionally to import putrescine under conditions of low tissue polyamines.caveolin-1; NOS2; SLC3A2; gastrointestinal tissue POLYAMINES ARE SMALL ORGANIC compounds that have two or more amino groups and are found in almost all organisms (6, 13). The major polyamines found in cells are spermidine and spermine, and their precursor putrescine. Among these, putrescine and spermidine are essential factors for cell growth (4). Polyamines can bind to anions such as DNA, RNA, and ATP and can thereby regulate their functions (9). The major sources of exogenous polyamines come from diet and luminal bacteria (11). An antibiotic treatment to remove microbial flora activity (7) or polyamine-free diet (15) increased the polyamine-depleting effect of the polyamine biosynthetic enzyme inhibitor difluoromethylornithine (DFMO). These results indicate that transport makes a significant contribution to cellular polyamine levels.We have identified the amino acid transporter SLC3A2 as a polyamine export protein in colon cancer-derived cells (24). SLC3A2 associated with the polyamine catabolic enzyme spermidine/spermine N 1 -acetyltransferase, SAT1, and catalyzed the export of acetylated polyamines by the polyamine/ arginine exchange reaction. As for polyamine uptake, we have reported that polyamine uptake was mediated by caveolaedependent endocytosis in colon cancer-derived cells (16).Caveolae are flask-shaped invaginations of plasma membrane with a diameter of 50 -100 nm. They have been implicated in endocytosis and signal transductions...

Sensitivity of cloned muscle, heart and neuronal voltage-gated sodium channels to block by polyamines

“…21 Estimated levels of extracellular PAs in plasma and inflamed tissues range from mM to mM. 33 Evidence for a functional role of extracellular PAs include: vesicular release of PAs by depolarization of brain slices, 4 transport of exogenous PAs from dietary intake and gut bacteria sources into gastrointestinal cells, 5 external block and activation of GluR channels, [25][26][27][28] activation of the TRPV1 capsaicin receptor channel in peripheral sensory neurons, 33 and gating shift of Ca V channel current.…”

“…36 A prolonged 30 min exposure of transfected HEK293 cells to 1 mM extracellular spermidine or spermine suppresses the time course of recovery from inward rectification in the whole-cell mode (Fig. 5), suggesting that slow cellular uptake of PAs by endocytosis or transport proteins 5,6 may be a physiological mechanism of Na V channel modulation. The fact that cytoplasmic PAs block outward Na V current in a voltage-dependent manner 39 indicates that PAs are likely to bind within the Na + conduction pathway accessible from the intracellular side of the channel.…”

“…3 Membrane transport of PAs involves both endocytotic uptake and solute carrier mechanisms although specific PA transport proteins have not been conclusively identified in mammals. [3][4][5][6] In mammalian brains, PAs are taken up by glial cells and presynaptic terminals, accumulated in synaptic vesicles, and have been proposed to function as neuromodulators. 4 Alteration of PA metabolism has been recently implicated in human Parkinson disease.…”

Evaluation of Difluoromethylornithine for the Chemoprevention of Barrett's Esophagus and Mucosal Dysplasia

“…We observed a partial rebound in putrescine levels at 12 months, but levels remained approximately 50% below those found at baseline. Putrescine is the most prevalent dietary polyamine (44) and is the preferred substrate for the polyamine transport system (45). A study in patients with prior colorectal adenomas found that putrescine levels rebounded in normal rectal mucosa after 12 months of continuous low-dose DMFO (500 mg/d), suggesting an adaptive response to prolonged ODC suppression with a compensatory cellular uptake of diet-or bacteria-derived putrescine (46).…”

Recent Advances in Bacterial Polyamine Transport Systems

“…However, the transport system for polyamines in bacteria through transporters is different from that of animals through endocytosis (Uemura et al 2010 ). Some bacteria and most animals use ornithine decarboxylase for polyamine biosynthesis.…”