Phospho-eNOS Ser-1176 is associated with the nucleoli and the Golgi complex in C6 rat glioma cells

Histone deacetylases 2 and 9 are coexpressed and nuclear localized in human molar odontoblasts in vivo

Histone deacetylases (HDACs) are components of nuclear multiprotein complexes that deacetylate histones and perform important roles in repression of transcription.Using specific rabbit mAbs, we analyzed by immune histochemistry and confocal immunofluorescence analysis the expression and subcellular localization of HDAC1–4 and HDAC9 in sections of adult human third molars. HDAC2 and HDAC9 were expressed in some pulpal cells and strongly expressed in the majority of mature odontoblasts.In contrast, only weak expression of HDAC1, HDAC3 and HDAC4 was observed. Confocal immunofluorescence analysis together with the DNA stain DRAQ5 revealed that HDAC2 and HDAC9 were coexpressed within the odontoblast nucleus, but localized to distinct subnuclear structures.In contrast to the current point of view, HDAC2 is strongly expressed in a terminally differentiated cell type.Our results imply that class I and II HDACs are involved in the transcriptional regulation of human odontoblasts in vivo.

Identification and functional characterization of phosphorylation sites on GTP cyclohydrolase I

OBJECTIVE

The posttranslational regulation of GTP cyclohydrolase I (GCH-1), the rate-limiting enzyme for tetrahydrobiopterin (BH4) synthesis, remains elusive. Here, we identified specific phosphorylation sites on GCH-1 and characterized the function of these sites.

METHODS AND RESULTS

Mass spectrometry studies showed overexpressed rat GCH-1 was phosphorylated at serine (S) 51, S167, and threonine (T) 231 in HEK293 cells, whereas a computational analysis of GCH-1 revealed 8 potential phosphorylation sites (S51, S72, T85, T91, T103, S130, S167 and T231). GCH-1 activity and BH4 were significantly decreased in cells transfected with the phospho-defective mutants (S72A, T85A, T91A, T103A, or S130A) and increased in cells transfected with the T231A mutant. BH4 and BH2 were increased in cells transfected with S51E, S72E, T85E, T91E, T103D, or T130D mutants, but decreased in cells transfected with the T231D mutant, whereas cells transfected with the S167A or the S167E mutant had increased BH2. Additionally, cells transfected with the T231A mutant had reduced GCH-1 nuclear localization and nuclear GCH-1 activity.

CONCLUSIONS

Our data suggest GCH-1 activity is regulated either positively by phosphorylation S51, S72, T85, T91, T103, and S130, or negatively at T231. Such information might be useful in designing new therapies aiming at improving BH4 bioavailability.

Nuclear angiotensin II type 2 (AT2) receptors are functionally linked to nitric oxide production

Expression of nuclear angiotensin II type 1 (AT(1)) receptors in rat kidney provides further support for the concept of an intracellular renin-angiotensin system. Thus we examined the cellular distribution of renal ANG II receptors in sheep to determine the existence and functional roles of intracellular ANG receptors in higher order species. Receptor binding was performed using the nonselective ANG II antagonist (125)I-[Sar(1),Thr(8)]-ANG II ((125)I-sarthran) with the AT(1) antagonist losartan (LOS) or the AT(2) antagonist PD123319 (PD) in isolated nuclei (NUC) and plasma membrane (PM) fractions obtained by differential centrifugation or density gradient separation. In both fetal and adult sheep kidney, PD competed for the majority of cortical NUC (> or =70%) and PM (> or =80%) sites while LOS competition predominated in medullary NUC (> or =75%) and PM (> or =70%). Immunodetection with an AT(2) antibody revealed a single approximately 42-kDa band in both NUC and PM extracts, suggesting a mature molecular form of the NUC receptor. Autoradiography for receptor subtypes localized AT(2) in the tubulointerstitium, AT(1) in the medulla and vasa recta, and both AT(1) and AT(2) in glomeruli. Loading of NUC with the fluorescent nitric oxide (NO) detector DAF showed increased NO production with ANG II (1 nM), which was abolished by PD and N-nitro-l-arginine methyl ester, but not LOS. Our studies demonstrate ANG II receptor subtypes are differentially expressed in ovine kidney, while nuclear AT(2) receptors are functionally linked to NO production. These findings provide further evidence of a functional intracellular renin-angiotensin system within the kidney, which may represent a therapeutic target for the regulation of blood pressure.

Time-dependent Activation of ERK1/2 in Nerve Terminals of the Dentin-Pulp Complex following Bradykinin Treatment

The extracellular signal-regulated kinases 1 and 2 (ERK1/2) have been implicated in the inflammation-dependent sensitization of nociceptors, and the inflammatory mediator bradykinin (BK) led to a reduced threshold in the nociceptor terminals, activating intracellular signaling by phosphorylating receptors and ion channels. The effects of BK on the non-transcriptional modulation of the ERK1/2 in the peripheral nociceptor terminals, including in nerve endings of the dentin-pulp complex, are unknown. The time-dependent effects of BK (10−7 M) on the ERK1/2 phosphorylation in nerve terminals of the dentin-pulp complex were investigated by quantitative and double immunolabeling with organ bath experiments. In nerve terminals, total and p-ERK1/2 were detected. In comparison with the controls, the numbers of p-ERK1/2-positive nerve endings increased after 1 and 3 min and decreased after 10 min of BK treatment. Analysis of the data indicates that BK induces phosphorylation-mediated local activation of ERK1/2 in nerve terminals modulating nociception in the dentin-pulp complex.