Gene expression, cellular localization, and enzymatic activity of diacylglycerol kinase isozymes in rat ovary and placenta

Identification of Lipids and Cytokines in Plasma and Follicular Fluid before and after Follicle-Stimulating Hormone Stimulation as Potential Markers for Follicular Maturation in Cattle

The process of follicle maturation leading to ovulation is a key milestone in female fertility. It is known that circulating lipids and cytokines play a role in the follicle's ability to go through follicular maturation and the ovulatory processes. However, the specific mechanisms are not well understood. We posit that dysregulation of granulosa cells influences the ovarian environment, which tries to adapt by changing released lipids and cytokines to achieve follicular maturation. Eleven non-lactating adult females underwent estrus synchronization with two injections of PGF2α 14 days apart. Daily blood samples were collected for 28 days to monitor steroid hormone production after the second injection. To understand the potential impacts of lipids and cytokines during ovulation, a low-dose FSH stimulation (FSHLow) was performed after resynchronization of cows, and daily blood samples were collected for 14 days to monitor steroid hormone production until ovariectomies. The lipidomic analysis demonstrated increased circulating diacylglycerides and triacylglycerides during the mid-luteal phase and after FSHLow treatment. Cholesteryl esters decreased in circulation but increased in follicular fluid (FF) after FSHLow. Increased circulating concentrations of TNFα and reduced CXCL9 were observed in response to FSHLow. Therefore, specific circulating lipids and cytokines may serve as markers of normal follicle maturation.

mRNA expression of diacylglycerol kinase isoforms in insulin-sensitive tissues: effects of obesity and insulin resistance

Diacylglycerol kinase (DGK) isoforms regulate signal transduction and lipid metabolism. DGKδ deficiency leads to hyperglycemia, peripheral insulin resistance, and metabolic inflexibility. Thus, dysregulation of other DGK isoforms may play a role in metabolic dysfunction. We investigated DGK isoform mRNA expression in extensor digitorum longus (EDL) and soleus muscle, liver as well as subcutaneous and epididymal adipose tissue in C57BL/6J mice and obese and insulin-resistant ob/ob mice. All DGK isoforms, except for DGKκ, were detectable, although with varying mRNA expression. Liver DGK expression was generally lowest, with several isoforms undetectable. In soleus muscle, subcutaneous and epididymal adipose tissue, DGKδ was the most abundant isoform. In EDL muscle, DGKα and DGKζ were the most abundant isoforms. In liver, DGKζ was the most abundant isoform. Comparing obese insulin-resistant ob/ob mice to lean C57BL/6J mice, DGKβ, DGKι, and DGKθ were increased and DGKε expression was decreased in EDL muscle, while DGKβ, DGKη and DGKθ were decreased and DGKδ and DGKι were increased in soleus muscle. In liver, DGKδ and DGKζ expression was increased in ob/ob mice. DGKη was increased in subcutaneous fat, while DGKζ was increased and DGKβ, DGKδ, DGKη and DGKε were decreased in epididymal fat from ob/ob mice. In both adipose tissue depots, DGKα and DGKγ were decreased and DGKι was increased in ob/ob mice. In conclusion, DGK mRNA expression is altered in an isoform- and tissue-dependent manner in obese insulin-resistant ob/ob mice. DGK isoforms likely have divergent functional roles in distinct tissues, which may contribute to metabolic dysfunction.

Enzymatic activity and gene expression of diacylglycerol kinase isozymes in developing retina of rats

Photoreceptors contain highly specialized structures for phototransduction, which is mediated by rhodopsins and heterotrimeric G-proteins. The signal is transmitted through the cGMP cascade, which controls cGMP-gated cation channels in mammals, while in flies it is operated by phosphoinositide (PI) cascade through a second messenger diacylglycerol (DG), which engenders the opening of Ca2+ channels. Recent studies suggest that PI-related signaling cascade is also involved in the phototransduction in mammalian retina. This study examined whether one PI-related enzyme, diacylglycerol kinase (DGK), which is regarded as a regulator of the DG signal through its metabolism, is expressed in mammalian retina. Enzymatic assay, Northern blot and RT-PCR analyses, and in situ hybridization histochemistry were performed to assess the expression profile of DGK isozymes and their cellular localization. In rat retina DGKε, DGKζ, and DGKι are the dominant species with distinct patterns of expression. At the cellular level, DGKε is the only one detected intensely in the photoreceptor layer, although DGKι and DGKζ are observed in bipolar and ganglion cell layers. These results suggest that each DGK isozyme plays a different role in the signal transduction in distinct cell types and that DGKε is a candidate involved in the photoreceptor PI signaling machinery.

Identification of GAS-dependent interferon-sensitive target genes whose transcription is STAT2-dependent but ISGF3-independent

Signal transducer and activator of transcription 2 (STAT2) is best known as a critical transactivator component of the interferon-stimulated gene factor 3 (ISGF3) complex that drives the expression of many interferon (IFN)-inducible genes. However, STAT2 is also involved in DNA binding in non-ISGF3 transcriptional complexes. We used a DNA microarray to survey the expression of genes regulated by IFN-inducible, STAT2-dependent DNA binding, and compared the cDNAs of IFN-treated cells overexpressing intact STAT2 to those of IFN-treated cells overexpressing mutated STAT2 lacking the DNA binding domain. The IFN-inducible expression of genes known to be regulated by ISGF3 was similar in both cases. However, a subset of IFN-inducible genes was identified whose expression was decreased in cells expressing the mutated STAT2. Importantly, these genes all contained gamma-activated sequence (GAS)-like elements in their 5' flanking sequences. Our data reveal the existence of a collection of GAS-regulated target genes whose expression is IFN-inducible and independent of ISGF3 but highly dependent on the STAT2 DNA binding domain. This report is the first analysis of the contribution of the STAT2 DNA binding domain to IFN responses on a global basis, and shows that STAT2 is required for the IFN-inducible activation of the full spectrum of GAS target genes.

Gene expression and localization of diacylglycerol kinase isozymes in the rat spinal cord and dorsal root ganglia

The dorsal root ganglion (DRG) and dorsal horn of the spinal cord are areas through which primary afferent information passes enroute to the brain. Previous studies have reported that, during normal neuronal activity, the regional distribution of a second messenger, diacylglycerol (DG), which is derived from phosphoinositide turnover, is diverse in these areas. However, the way that DG is regulated in these organs remains unknown. The present study was performed to investigate mRNA expression and protein localization of DG kinase (DGK) isozymes, which play a central role in DG metabolism. Gene expression for DGK isozymes was detected with variable regional distributions and intensities in the spinal cord. Among the isozymes, most intense signals were found for DGKzeta and DGKiota in the DRG. By immunohistochemical analysis, DGKzeta immunoreactivity was detected heterogeneously in the nucleus and cytoplasm of small DRG neurons with variable levels of distribution, whereas it was detected exclusively in the cytoplasm of large neurons. On the other hand, DGKiota immunoreactivity was distributed solely in the cytoplasm of most of the DRG neurons. Double-immunofluorescent imaging of these isozymes showed that they coexisted in a large population of DRG neurons at distinct subcellular sites, i.e., DGKzeta in the nucleus and DGKiota in the cytoplasm. Thus, DGK isozymes may have different functional roles at distinct subcellular sites. Furthermore, the heterogeneous subcellular localization of DGKzeta between the nucleus and cytoplasm implies the possible translocation of this isozyme in small DRG neurons under various conditions.