Tegumental Glucose Permeability in Male and Female Schistosoma mansoni

Abstract

Tegumental hexose transporters have been kinetically characterized in mated and separated male and female Schistosoma mansoni 8-12 wk postinfection. Significant gender-specific differences in Km and Vmax were observed. In mated males, the estimated constants (mean +/- SE) were: Km = 0.63 +/- 0.31 mM, Vmax = 0.93 +/- 0.44 nmol/mg worm water/min, and the Kd = 0.25 +/- 0.09 microliter/mg worm water/min. In mated females the kinetics were: Km = 0.99 +/- 0.40 mM, Vmax = 1.22 +/- 0.42 nmol/mg worm water/min, and Kd = 0.60 +/- 0.14 microliter/mg worm water/min. The influx of 2-deoxy-D-glucose and 3-O-methylglucose has been similarly characterized; these analogs share the same glucose transporter in male and female schistosomes. 2-Deoxy-D-glucose has a higher affinity, and 3-O-methylglucose a lower affinity, than does glucose. Because mated male schistosomes supply glucose to female partners, similarities between the free glucose concentration of the male and the affinity of the transporter determined for mated female schistosomes suggest that male-to-female transfer may be a potentially rate-limiting step in glucose utilization by the female. Permeability x surface are (PS) products and Vmax/Km ratios were significantly elevated in mated schistosomes, suggesting that the transporter is primarily localized to the dorsal surface of the male. Gender- and mating-specific analyses of PS products indicate that tegumental permeability to glucose is significantly increased in mated schistosomes, and compares very favorably to that of the host liver.

Immunolocalization of aSchistosoma mansonifacilitated diffusion glucose transporter to the basal, but not the apical, membranes of the surface syncytium

“…There is some evidence of energy-dependent glucose transport within schistosomes (Uglem & Read, 1975) although it is difficult to explain why the parasite would require an energy driven process to take glucose into the tegument from the glucose-rich serum that bathes the worm. In fact, several reports indicate that, under these physiological conditions, glucose is absorbed through the tegument (Fripp, 1967;Rogers & Bueding, 1975) and occurs primarily by facilitated diffusion (Isseroff, Bonta & Levy, 1972;Uglem & Read, 1975;Cornford et al 1988). Thus, the system most analogous to glucose uptake by schistosomes is probably the mammalian blood brain barrier where a single facilitated glucose transporter (GLUT1) moves glucose across both membranes.…”

Metabolite movement across the schistosome surface

“…Glucose is one metabolite that is copiously consumed; adult Schistosoma mansoni are reported to import across their teguments their dry weight in glucose every 5 h (Bueding, 1950) and at a rate three times higher than the glucose uptake by the mucosal border of the rabbit ileum (Gomme & Albrechtsen, 1988). Uptake is not an active process but is via facilitated diffusion (Isseroff et al , 1972; Uglem & Read, 1975; Cornford et al , 1988). These observations suggested that facilitated-diffusion glucose transporter proteins (GTPs) are localized within the schistosome tegument.…”

Sexual Preferences in Nutrient Utilization Regulate Oxygen Consumption and Reactive Oxygen Species Generation in Schistosoma mansoni: Potential Implications for Parasite Redox Biology

“…Schistosoma parasites are dioecious, with two genetically defined and dimorphic sexes [ 76 – 78 ], and these differences can be extended to worm energy and redox metabolism [ 47 , 52 , 57 ]. For example, glutamate, aspartate, and alanine uptake were reportedly higher in males [ 52 , 57 ], while no apparent gender trend was observed in glucose uptake [ 47 , 52 , 79 – 81 ]. Also, the rates of glucose, glutamate, and alanine oxidation were higher in males of both S .…”