Variable intron/exon structure in the oligochaete lombricine kinase gene.

Lombricine kinase is an annelid enzyme that belongs to the phosphagen kinase family of which creatine kinase and arginine kinase are the typical representatives. The enzymes play important roles in the cellular energy metabolism of animals. Biochemical, physiological and molecular information with respect to lombricine kinase is limited compared to other phosphagen kinases. This study presents data on the cDNA sequences of lombricine kinase from two smaller oligochaetes, Enchytraeus sp. and Stylaria sp. The deduced amino acid sequences are analyzed and compared with other selected phosphagen kinases. The intron/exon structure of the lombricine kinase gene was determined for these two species as well as two additional oligochaetes, Lumbriculus variegatus and Tubifex tubifex, and compared with available data for annelid phosphagen kinases. The data indicate the existence of a variable organization of the proposed 8-intron/9-exon gene structure. The results provide further insights in the evolution and position of these enzymes within the phosphagen kinase family.

Effects of the HIV-1 protein Tat on myocardial function and response to endotoxin.

HIV-1 infection has been associated with cardiomyopathy in a subset of patients. In order to determine whether HIV-1 alters myocardial function or the myocardial response to stress, transgenic mice that express the HIV-1 protein Tat were used. Heart function was assessed using the isolated working heart preparation. Response to infection was assessed by measuring heart function at various times after endotoxin administration. Since cytokines are implicated in myocardial dysfunction, plasma tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6) and myocardial mRNA and protein levels of TNF-alpha and IL-6 were determined. Tat by itself did not cause myocardial dysfunction; however, 4 h after endotoxin, myocardial function was more severely compromised in the Tat mice than in control mice. Plasma TNF-alpha levels were elevated at 2 h and higher in the control group but myocardial levels were similar in the two groups. Plasma IL-6 was increased but myocardial levels were different only at 24 h at which time myocardial function was no longer depressed. Tat expression, by itself, did not impair intrinsic myocardial function but did increase myocardial injury induced by endotoxin. Although cytokines are associated with dysfunction, TNF-alpha and IL-6 were probably not responsible for the exaggerated dysfunction in Tat mice receiving endotoxin.

cDNA identification, comparison and phylogenetic aspects of lombricine kinase from two oligochaete species.

Creatine kinase and arginine kinase are the typical representatives of an eight-member phosphagen kinase family, which play important roles in the cellular energy metabolism of animals. The phylum Annelida underwent a series of evolutionary processes that resulted in rapid divergence and radiation of these enzymes, producing the greatest diversity of the phosphagen kinases within this phylum. Lombricine kinase (EC 2.7.3.5) is one of such enzymes and sequence information is rather limited compared to other phosphagen kinases. This study presents data on the cDNA sequences of lombricine kinase from two oligochaete species, the California blackworm (Lumbriculus variegatus) and the sludge worm (Tubifex tubifex). The deduced amino acid sequences are analyzed and compared with other selected phosphagen kinases, including two additional lombricine kinase sequences extracted from DNA databases and provide further insights in the evolution and position of these enzymes within the phosphagen kinase family. The data confirms the presence of a deleted region within the flexible loop (the GS region) of all six examined lombricine kinases. A phylogenetic analysis of these six lombricine kinases clearly positions the enzymes together in a small subcluster within the larger creatine kinase (EC 2.7.3.2) clade.

Identification of a cytoplasmic manganese superoxide dismutase (cMnSOD) in the red swamp crawfish, Procambarus clarkii: cDNA cloning and tissue expression.

A cytoplasmic manganese superoxide dismutase (cMnSOD) cDNA was cloned from the hepatopancreas of the red swamp crawfish, Procambarus clarkii. An initial cDNA fragment was identified by using degenerate primers, and the complete sequence was obtained by using RACE methodology. The full sequence comprises 1140 bp, with an open reading frame of 858 bp encoding a protein of 286 amino acids. Sequence analysis showed that this protein is highly homologous to previously obtained crustacean cMnSODs. Phylogenetic analysis clusters it with all known cMnSODs and in a group distinct from mitochondrial MnSODs. cMnSOD transcripts were detected in the gills, tail muscle, green glands, and hepatopancreas. The data provide additional evidence for the hypothesis that cMnSOD replaced CuZnSOD in crustaceans that use haemocyanin as the respiratory pigment.

The promoter for the gene encoding the catalytic subunit of rat glucose-6-phosphatase contains two distinct glucose-responsive regions.

Glucose homeostasis requires the proper expression and regulation of the catalytic subunit of glucose-6-phosphatase (G-6-Pase), which hydrolyzes glucose 6-phosphate to glucose in glucose-producing tissues. Glucose induces the expression of G-6-Pase at the transcriptional and posttranscriptional levels by unknown mechanisms. To better understand this metabolic regulation, we mapped the cis-regulatory elements conferring glucose responsiveness to the rat G-6-Pase gene promoter in glucose-responsive cell lines. The full-length (-4078/+64) promoter conferred a moderate glucose response to a reporter construct in HL1C rat hepatoma cells, which was dependent on coexpression of glucokinase. The same construct provided a robust glucose response in 832/13 INS-1 rat insulinoma cells, which are not glucogenic. Glucose also strongly increased endogenous G-6-Pase mRNA levels in 832/13 cells and in rat pancreatic islets, although the induced levels from islets were still markedly lower than in untreated primary hepatocytes. A distal promoter region was glucose responsive in 832/13 cells and contained a carbohydrate response element with two E-boxes separated by five base pairs. Carbohydrate response element-binding protein bound this region in a glucose-dependent manner in situ. A second, proximal promoter region was glucose responsive in both 832/13 and HL1C cells, with a hepatocyte nuclear factor 1 binding site and two cAMP response elements required for glucose responsiveness. Expression of dominant-negative versions of both cAMP response element-binding protein and CAAT/enhancer-binding protein blocked the glucose response of the proximal region in a dose-dependent manner. We conclude that multiple, distinct cis-regulatory promoter elements are involved in the glucose response of the rat G-6-Pase gene.