Glucose transport in amastigotes and promastigotes of Leishmania mexicana mexicana

Burchmore, R.J.S. and Hart, D.T. (1995) Glucose transport in amastigotes and promastigotes of Leishmania mexicana mexicana. Molecular and Biochemical Parasitology, 74(1), pp. 77-86. (doi: 10.1016/0166-6851(95)02485-9) (PMID:8719247)

Abstract

Promastigotes and amastigotes of Leishmania mexicana mexicana transported 2-deoxy-d-glucose (2-DOG) by a saturable process with a Km of 24 ± 3 μM and Vmax of 2.21 nmol min−1 (mg protein)−1 for the promastigote and a Km of 29 ± 8 μM and Vmax of 0.13 nmol min−1 (mg protein)−1 for the amastigote stage. Amastigotes incorporated 2-DOG maximally at pH 5.0, while for promastigotes the optimum was at pH 7.0. Mid-log phase promastigotes were found to accumulate 2-DOG via a stereospecific carrier-mediated process which was competitively inhibited by d-glucose and d-mannose but not l-glucose. Transport was dependent upon temperature, with a Q10 in promastigotes of 1.83 and an optimum rate at 35°C (±4°C) with an activation energy of 50.12 kJ mol−1. Stationary phase promastigotes accumulated 2-DOG at approximately twice the rate of mid-log phase promastigotes. Cytochalasin B, forskolin and phloretin were all found to inhibit human erythrocyte 2-DOG uptake but only cytochalasin B was found significantly to inhibit promastigote 2-DOG uptake. Interestingly, leishmanial 2-DOG uptake was inhibited by a series of membrane potential antagonists including the ionophore monensin, the H+ATPase inhibitor N,N′-dicyclohexylcarbodiimide (DCCD) and uncoupling agent carbonylcyanide-4-(triflouromethoxy) phenylhydrazone (FCCP), as well as, the tricyclic drugs chlomipramine and imipramine, but was insensitive to the Na+/K+ ATPase inhibitor ouabain and the antitrypanosomal drugs Pentostam and Suramin. We therefore conclude that there are significant structural and mechanistic differences between the d-glucose uptake systems of Leishmania and the mammalian host to merit the inclusion of glucose transporters as putative targets for rational drug design.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Burchmore, Dr Richard
• Authors: Burchmore, R.J.S., and Hart, D.T.
• College/School: College of Medical Veterinary and Life Sciences > School of Infection & Immunity
• Journal Name: Molecular and Biochemical Parasitology
• Publisher: Elsevier BV
• ISSN: 0166-6851
• ISSN (Online): 1872-9428
• Published Online: 06 April 2000