Tapeworms absorb and consume large quantities of glucose through
their syncytial tegument, storing the excess as
glycogen. Although some studies on the metabolism of glucose in several
tapeworms are available, the proteins that mediate
its uptake and distribution in their tissue have not been identified. We
describe the isolation and characterization of cDNA
clones encoding 2 facilitated diffusion glucose transporters (TGTP1 and
TGTP2) from Taenia solium, the causal agent
of human and porcine cysticercosis. Radio-isotope labelled hexose uptake
mediated by TGTP1 expressed in Xenopus
oocytes is inhibited by the natural stereoisomers d-glucose and
d-mannose but not by l-glucose. Transport by TGTP1
is sensitive to classical inhibitors of facilitated diffusion such as phloretin
and cytochalasin B, and insensitive to ouabain.
TGTP2 did not function in Xenopus oocytes. Localization studies
using specific anti-TGTP1 and anti-TGTP2 antibodies
show that TGTP1 is abundant in a number of structures underlying the tegument
in adult parasites and larvae, whereas
TGTP2 appears to be localized only on the tegumentary surface of the larvae
and is not detected in adults.
Functional Characterization of DEAD-Box RNA Helicases in Arabidopsis thaliana under Abiotic Stress Conditions
