Cloning and functional analysis of goat SWEET1

SWEETs are a recently discovered class of sugar transporters that mediate glucose uptake in the intestine and mammary glands. Our objectives were to clone goat SWEET1 and conduct a functional analysis of its effect on glucose efflux in goat mammary gland epithelial cells. We cloned and sequenced the goat SWEET1 gene from goat mammary glands, then conducted an analysis of the structure of goat SWEET1, including a prediction of the transmembrane helices and potential N-glycosylation sites. To investigate the biological function of goat SWEET1, we also generated goat SWEET1-transfected goat mammary gland epithelial cells using the eukaryotic expression vector pcDNA3.1-gSWEET1. Goat SWEET1 overexpression can reduce glucose absorption in mammary gland epithelial cells with increasing expression of GLUT1, GLUT4, and GLUT12, which may be attributed to glucose efflux arising from the leading role played by goat SWEET1. This study will improve our understanding of the glucose balance in mammary glands and the level of glucose in milk.