Kayano et al. (1988) screened a human fetal skeletal muscle cDNA library using low-stringency conditions to identify clones
that cross-hybridize with a hepatoma-derived glucose transporter cDNA. The predicted amino acid sequence indicates that this protein possesses 12 potential
membrane-spanning domains.The mRNA encoding this protein was present in
most if not all tissues, although the amounts varied widely.
Gould and Holman (1993) provided a review of the glucose transporter family, referred to GLUT3 as the brain-type
glucose transporter. It appears that high GLUT3 protein expression is confined generally to tissues that exhibit a high glucose
demand, such as brain and nerve.
General function
Channel/transport protein
Comment
Cellular localization
Plasma membrane
Comment
Ovarian function
Ovulation
Comment
Kol et al characterizes the rat ovary as a site of hormonally dependent glucose transporter (Glut) expression, and explores
the potential role of interleukin (IL)-1, a putative intermediary in the ovulatory process, in this regard. Molecular probing
throughout a simulated estrous cycle revealed a significant surge in ovarian Glut3 (but not Glut1) expression at the time of
ovulation. Treatment of cultured whole ovarian dispersates from immature rats with IL-1beta resulted in upregulation of the
relative abundance of the Glut1 (4.5-fold) and Glut3 (3.5-fold) proteins as determined by Western blot analysis. Other
members of the Glut family (i.e., Gluts 2, 4, and 5) remained undetectable. The ability of IL-1 to upregulate Glut1 and Glut3
transcripts proved time-, dose-, nitric oxide-, and protein biosynthesis-dependent but glucose independent. Other ovarian
agonists (i.e., TNF alpha, IGF-I, interferon-gamma, and insulin) were without effect. Taken together,
the mammalian ovary is a site of cyclically determined Glut1 and Glut3 expression.
Expression regulated by
Growth Factors/ cytokines, interleukin-1
Comment
Ovarian localization
Theca
Comment
Zhou J, et al 2000 reported that GLUT3 was expressed in thecal cells surrounding growing follicles and was not
appreciably different in Igf1 null compared with wild type ovaries.
Follicle stages
Antral, Preovulatory, Corpus luteum
Comment
Gene expression of glucose transporter (GLUT) 1, 3 and 4 in bovine follicle and corpus luteum Nishimoto H, et al .
Glucose is the main energy substrate in the bovine ovary, and a sufficient supply of it is necessary to sustain the ovarian activity. Glucose cannot permeate the plasma membrane, and its uptake is mediated by a number of glucose transporters (GLUT). In the present study, we investigated the gene expression of GLUT1, 3 and 4 in the bovine follicle and corpus luteum (CL). Ovaries were obtained from Holstein x Japanese Black F1 heifers. Granulosa cells and theca interna layers were harvested from follicles classified into five categories by their physiologic status: follicular size (>/= 8.5 mm: dominant; < 8.5 mm: subordinate), ratio of estradiol (E(2)) to progesterone in follicular fluid (>/= 1: E(2) active;<1: E(2) inactive), and stage of estrous cycle (luteal phase, follicular phase). CL were also classified by the stage of estrous cycle. Expression levels of GLUT1, 3 and 4 mRNA were quantified by a real-time PCR. The mRNA for GLUT1 and 3 were detected in the bovine follicle and CL at comparable levels to those in classic GLUT-expressing organs such as brain and heart. Much lower but appreciable levels of GLUT4 were also detected in these tissues. The gene expression of these GLUT showed tissue- and stage-specific patterns. Despite considerable differences in physiologic conditions, similar levels of GLUT1, 3 and 4 mRNA were expressed in subordinate follicles as well as dominant E(2)-active follicles in both luteal and follicular phases, whereas a notable increase in the gene expression of these GLUT was observed in dominant E(2)-inactive follicles undergoing the atretic process. In these follicles, highly significant negative correlations were observed between the concentrations of glucose in follicular fluid and the levels of GLUT1 and 3 mRNA in granulosa cells, implying that the local glucose environment affects glucose uptake of follicles. These results indicate that GLUT1 and 3 act as major transporters of glucose while GLUT4 may play a supporting role in the bovine follicle and CL.