Sequence of Atlantic cod (Gadus morhua) GLUT4, GLUT2 and GPDH:developmental stage expression, tissue expression and relationship to starvation-induced changes in blood glucose

Abstract

SUMMARY cDNAs of putative glucose transporters, GLUT4 and GLUT2, were cloned from Atlantic cod (Gadus morhua). The GLUT4 cDNA encodes a 503 amino acid and the GLUT2 cDNA a 506 amino acid protein. Phylogenetic analysis, amino acid sequence alignment, and tissue distribution support categorizing them as homologues of mammalian GLUT4 and 2. GLUT4 clusters with GLUT4s from fish and other vertebrates. It shows 84% amino acid identity to GLUT4 from coho salmon and brown trout and 65% identity with other vertebrates. It is most highly expressed in heart, strongly expressed in red and white skeletal muscle and present at lower levels in gill, gonad, intestine, and kidney. GLUT2 clusters with GLUT2 from rainbow trout and other vertebrates. It shows 75% amino acid identity with rainbow trout and 62% identity with chicken GLUT2. In Atlantic cod, GLUT2 is most highly expressed in liver with lower levels noted in intestine and kidney. Food deprivation for 2 months was used as a vehicle to monitor GLUT expression at different blood glucose levels. Starvation resulted in a decrease in blood glucose and liver glycogen that recovered following 20 days of re-feeding. GLUT4 expression in heart was decreased with starvation and increased with re-feeding. GLUT4 mRNA level in heart correlated with blood glucose. It is suggested that this relationship is related to insulin responsiveness. GLUT4 expression in white muscle increased with starvation and decreased with re-feeding. It is proposed that this is due to the necessity to maintain high levels of the glucose transporter protein in the face of starvation-associated proteolysis. GLUT2 expression in liver correlated with blood glucose, consistent with higher rates of glucose transport from liver to blood in the fed state than in the food-deprived state. Glycerol-3-phosphate dehydrogenase (GPDH) cDNA was also cloned. It encodes a 351 amino acid protein, which is 73-90% identical to GPDH from numerous other fish species. GPDH is ubiquitously expressed. Expression in heart decreased with starvation and increased with refeeding, whereas expression in liver did not change with starvation. In other studies, gene expression was monitored at nine time points from fertilization of eggs to larval development. GLUT4 is detectable in fertilized eggs and is fully expressed by the halfway to hatching point. GLUT2 is not evident at fertilization, is detectable at halfway to hatching, and fully expressed at hatching. GPDH expression was evident from fertilization.

Expression of rainbow trout glucose transporters GLUT1 and GLUT4 during in vitro muscle cell differentiation and regulation by insulin and IGF-I

“…To date, four members of the family of facilitated glucose transporters (GLUT1-4) have been cloned and identified in different species of teleost fish (7, 20 -22, 27, 35, 44, 45, 49). In particular, GLUT1 and GLUT4 are expressed in fish skeletal muscle (8,12,22,35,43). Functional studies of fish GLUT1 and GLUT4 homologs expressed in Xenopus oocytes have demonstrated that these transporters are indeed able to transport glucose and that they differ in their affinity for glucose, since that for GLUT4 is higher than that for GLUT1, albeit lower than that of their mammalian counterparts (7,43).…”

Molecular cloning and gene expression analysis in aquaculture science: a review focusing on respiration and immune responses in European sea bass (Dicentrarchus labrax)

“…Sea bass GLUT2, like all GLUT isoforms (Mueckler et al 1985) adopt a 12-transmembrane domain structure, with intracellular amino-and carboxyl-termini, an extra cellular loop between the first and second transmembrane segments, and a large intracellular loop between the transmembrane segments 6 and 7. The predicted sea bass GLUT2 amino acid sequence reveals also several functionally important sequence motifs described in all known members of the GLUT protein family (Mueckler et al 1985;Sato and Mueckler 1999;Hall et al 2004Hall et al , 2006.…”

“…In recent years, the four mammalian GLUT homologues belonging to class I also have been identified in fish: GLUT1 in tilapia, rainbow trout, common carp, and Atlantic cod (Wright et al 1998;Teerijoki et al 2000;Hall et al 2004Hall et al , 2006; GLUT2 in rainbow trout and Atlantic cod (Krasnov et al 2001;Hall et al 2006); GLUT3 in grass carp and Atlantic cod (Zhang et al 2003); and GLUT4 in brown trout and Atlantic cod (Planas et al 2000;Hall et al 2006). The presence of mammalian GLUT homologues in fish has kindled an interest in studying their transcriptional regulation, not only because of the importance of glucose uptake in the overall energetic and regulation of carbohydrate metabolism, but also since many fish species face either acute or chronic low oxygen challenges.…”

“…Hall et al (2004Hall et al ( , 2006 described a GLUT1 expressed in at least 10 tissue types of Atlantic cod (G. morhua). The same ubiquitous distribution for GLUT1 was previously found by Teerijoki et al (2000) in rainbow trout (O. mykiss).…”

Efecto del tratamiento con leptina sobre la actividad del sistema glucosensor y la expresión de neuropéptidos implicados en la regulación de la ingesta de alimento en trucha arcoíris (Onchorhynchus mykiss)

“…GLUT2 se ha encontrado en el cerebro de varias especies de peces como el pez zebra (Danio rerio) (Castillo et al, 2009), trucha arco iris (Soengas et al, 2006;Polakof et al, 2007b) y lubina (Dicentrarchus labrax) (Terova et al, 2009). Se ha observado que la expresión de GLUT2 en el cerebro varía con la concentración de glucosa en el plasma de trucha arco iris (Polakof et al, 2007b), pero no en el bacalao (Gadus morhua) (Hall et al, 2006). Además, la expresión de GLUT2 ha sido caracterizada en áreas cerebrales discretas de trucha arco iris (Polakof et al, 2007b).…”