Molecular cloning and functional characterization of Cryptobia salmositica scaffold 107 as a glucose transporter

초록

Cryptobia salmositica belonging to the order Kinetoplastida is a haemoflagellated pathogen of salmonid fishes on the west coast of Notrh America. This protoxoans can be identified in skin, gill and blood. It is distinguished from other flagellates by the presence of a DNA-containing compartment of their mitochondrion called a kinetoplast. The parasite is normally transmitted by the blood sucking leech Pisciola salmositica. On the west coast of North America it cause cryptobiosis in economically important fishes such as salmon or rainbow trout. To clarify the nutrient metabolism the glucose transporter was cloned and characterized. The scaffold 107 from whole gene database was focused as glucose transporter named CSGT1. The CSGT1 gene was isolated from total RNA of cultured Cryptobia salmositica using reverse transcription-polymerase chain reaction method. For the characterization of transport function, the Xenopus laevis oocyte expression system was employed. The CSGT1 consists of 1545 base pairs that encode a 515 amino acid residue protein. The hydropathy analysis suggested that CSGT1 possesses 10 putative membrane-spanning domains. The CSGT1 transport tritium labeled deoxyglucose (about 3.5 folds) with time-dependent manner and without sodium ion dependency. The CSGT1 showed uniport properties by efflux experiment. The concentration dependency showed saturable uptakes following Michaelis-Menten equation with 340 nM of Km value and 90.8 pmol/oocyte/hr of Vmax value. From the results, CSGT1 may become a target of the developing new therapeutic agent for crytobiosis.