Functional Analyse of GLUT1 and GLUT12 in Glucose Uptake in Goat Mammary Gland Epithelial Cells

Abstract

Glucose transport, mediated by glucose transporters, is necessary for mammary gland development and lactation. GLUT1 and GLUT12 could both be expressed in the pregnant and lactating mammary gland to participate in the glucose uptake process. In this study, the goat GLUT1 and GLUT12 genes were cloned from Saanen dairy goats and transfected into goat mammary gland epithelial cells to assess their biological functions and distributions. The results showed that both goat GLUT1 and GLUT12 had 12 predicted membrane-spanning helices. Goat GLUT1 and GLUT12 each influenced the mRNA expression of the other transporter and increased the glucose consumption and lactose yield in GLUT1- and GLUT12-transfected goat mammary gland epithelial cells, respectively. The overexpression of GLUT1 or GLUT12 also increased the expression of amino acid transporters SLC1A5, SLC3A2 and SLC7A5 and affected genes expressions in GMGE cells. Using immunofluorescence staining, GLUT1 was detected throughout the cytoplasm and localized to the Golgi apparatus around the nuclear membrane, whereas GLUT12 was mainly distributed in the perinuclear region and cytoplasm. This study contributes to the understanding of how GLUT1 and GLUT12 cooperate in the incorporation of nutrient uptake into mammary gland epithelial cells and the promotion of milk synthesis in the goat mammary gland during lactation.

Biosynthesis of milk fat, protein, and lactose: roles of transcriptional and posttranscriptional regulation

“…The importance of glucose transporters in mammary is supported by a study where it was demonstrated that overexpression of SLC2A1 and SLC2A12 genes in goat mammary epithelial cells increases uptake of glucose. However, an increase in lactose synthesis was observed only in conjunction with an overexpression of SLC2A1 (248). This finding supports the prominent role of GLUT1 in lactose synthesis, likely by importing glucose into the Golgi, as demonstrated in lactating rat (157).…”

“…Relevant data support the existence of a positive interaction between glucose transport and availability of AA for milk protein synthesis. In the same study, the overexpression of GLUT proteins also increased expression of milk protein-related genes (248). The increase in expression of mTOR-related AA transporters SLC3A2 and SLC7A5 by overexpression of SLC2A12 provides support for a reciprocal regulatory connection of GLUT proteins with mTOR (76).…”

“…Goat mammary epithelial cells overexpressing SLC2A1 or SLC2A12, which are glucose transporter genes, had significant or numerically greater expression of SLC1A5, SLC3A2, and SLC7A5 coding for AA transporters (248). Relevant data support the existence of a positive interaction between glucose transport and availability of AA for milk protein synthesis.…”

Advances on Research in Protein-Enriched Cow’s Milk: A Review from Omics Perspective

“…Accumulating evidences have shown a cross talk between AA transporters and glucose. For example, when glucose transporter genes SLC2A1 or SLC2A12 are overexpressed in goat mammary epithelial cells, expression levels of SLC3A2, SLC1A5, and SLC7A5 genes coding for AA transporters are increased [66], supporting a positive correlation between glucose transport and AA availability for milk protein synthesis. In the same study, overexpression of glucose transporter GLUT increased the expression of milk protein-related genes [66].…”

“…For example, when glucose transporter genes SLC2A1 or SLC2A12 are overexpressed in goat mammary epithelial cells, expression levels of SLC3A2, SLC1A5, and SLC7A5 genes coding for AA transporters are increased [66], supporting a positive correlation between glucose transport and AA availability for milk protein synthesis. In the same study, overexpression of glucose transporter GLUT increased the expression of milk protein-related genes [66]. Increased expression of mTOR-related AA transporters such as SLC3A2 and SLC7A5 by overexpressing SLC2A12 glucose transporter provides evidence for regulatory connection of glucose transporter GLUT proteins with mTOR.…”