Alternative splicing generates two lactate dehydrogenase subunits differentially expressed during hypoxia via HIF-1 in the shrimp Litopenaeus vannamei

The glucose transporter 1 -GLUT1- from the white shrimp Litopenaeus vannamei is up-regulated during hypoxia

“…In hepatopancreas, GLUT1 activity can be directed to glucose movement out of the cell since it is a glycogen storage organ [60] and can export glucose to other tissues, this is supported by early results where LDHvan1 or LDHvan2 mRNA did not change at 1 h of hypoxia [7]. On the other hand, in gills, glucose may be mainly utilized in anaerobic glycolysis since both LDHvan1 mRNA levels and LDH enzymatic activity are triggered by hypoxia with concomitant lactate accumulation [5,7].…”

“…The GLUT1 regulation by hypoxia has not been reported in crustaceans but, it is well known that in L. vannamei hypoxia induces a shift from aerobic to anaerobic metabolism with lactate accumulation [3][4][5]. Furthermore our group found that in hypoxic conditions, the expression of hexokinase (HK) [6] and lactate dehydrogenase 1 (LDHvan1) [7] are induced in gills. These results suggest that the anaerobic glycolysis pathway is accelerated and therefore, the cells need for glucose also increases, thus, our results agree with the higher expression of GLUT1 after 3 h of hypoxia in both, gills and hepatopancreas (Fig.…”

“…This can give rise to multiple related proteins by alternative splicing, additionally introns have crucial functions in transcription initiation, transcription elongation, transcription termination, polyadenylation, nuclear export and mRNA stability (for review see [49] ). Introns are important for genome evolution and is very interesting that the LvGLUT1 gene has the same number of introns as its homolog in human, which is also the case for the shrimp lactate dehydrogenase gene [7], while other genes have significantly less introns in shrimp compared to human, as the shrimp catalase gene with four introns compared to 12 in humans [50]. As mentioned above, GLUT are highly conserved proteins and this can be related to the presence of high number of introns [51], moreover the number of introns appear to be also related to the length of the protein [52].…”

“…Two pairs of primers designed from the cDNA were used to obtain the first gene sequences, SLCf4/SLCr3 (Table 1) and generated a 1654 pb and SLCf5/SLCf4Rv (Table 1) generated a 866 pb fragments from genomic DNA previously isolated [7]. All PCR products were purified, cloned and sequenced as above.…”

“…In response to these fluctuations in environmental oxygen, shrimp metabolism quickly shifts from aerobic to anaerobic to obtain energy as shown by the rapid increase of lactate and glucose concentrations in different tissues [3][4][5]. Furthermore, hypoxia increases the expression and activity of glycolytic enzymes [6,7] suggesting that the anaerobic glycolysis pathway is accelerated. If anaerobic glycolysis is accelerated, then the cells must have an adequate supply of glucose, probably by increasing either the activity or the quantity of GLUT proteins as occurs in mammalian cells where GLUT1 mRNA and protein were stimulated by hypoxia in neonatal rat brain [8] and in mammary epithelial cells [9].…”