Effect of prostaglandins on tyrosylprotein sulfotransferase activity in rat submandibular salivary glands

Molecular characterization of novel sulfotransferases from the tick, Ixodes scapularis

Background

Ixodes scapularis, commonly known as the blacklegged or deer tick, is the main vector of Lyme disease in the United States. Recent progress in transcriptome research has uncovered hundreds of different proteins expressed in the salivary glands of hard ticks, the majority of which have no known function, and include many novel protein families. We recently identified transcripts coding for two putative cytosolic sulfotransferases in these ticks which recognized phenolic monoamines as their substrates. In this current study, we characterize the genetic expression of these two cytosolic sulfotransferases throughout the tick life cycle as well as the enzymatic properties of the corresponding recombinant proteins. Interestingly, the resultant recombinant proteins showed sulfotransferase activity against both neurotransmitters dopamine and octopamine.

Results

The two sulfotransferase genes were coded as Ixosc SULT 1 & 2 and corresponding proteins were referred as Ixosc Sult 1 and 2. Using gene-specific primers, the sulfotransferase transcripts were detected throughout the blacklegged tick life cycle, including eggs, larvae, nymphs, adult salivary glands and adult midgut. Notably, the mRNA and protein levels were altered upon feeding during both the larval and nymphal life stages. Quantitative PCR results confirm that Ixosc SULT1 was statistically increased upon blood feeding while Ixosc SULT 2 was decreased. This altered expression led us to further characterize the function of these proteins in the Ixodid tick. The sulfotransferase genes were cloned and expressed in a bacterial expression system, and purified recombinant proteins Ixosc Sult 1(R) and 2(R) showed sulfotransferase activity against neurotransmitters dopamine and octopamine as well as the common sulfotransferase substrate p-nitrophenol. Thus, dopamine- or octopamine-sulfonation may be involved in altering the biological signal for salivary secretion in I. scapularis.

Conclusions

Collectively, these results suggest that a function of Ixosc Sult 1 and Sult 2 in Ixodid tick salivary glands may include inactivation of the salivation signal via sulfonation of dopamine or octopamine.

Premastication: the second arm of infant and young child feeding for health and survival?

Premastication of foods for infants was a crucial behavioural adaptation to neoteny that ensured nutritional adequacy during the period of complementary feeding throughout the course of human evolution until recent times.While the paps and gruels of agricultural systems provided an alternative and modern food technology appears to make it unnecessary, we argue that, in addition to its role in nutrition, premastication also played a crucial role in supporting infant health. Its abandonment, particularly in poor communities, has placed children at increased risk of inadequate nutrition and decreased ability to confront infections associated with the introduction of complementary foods.We present two empirical studies. Section I is a cross-cultural study of the ethnographic literature in order to estimate prevalence in non-Western societies.One-third of ethnographies in the worldwide sample with data on infant feeding report premastication. Section II presents the results of a qualitative study in China, conducted in order to provide data on the likelihood that this percent is incorrect due to under-reporting.The finding that 63% of Chinese university students received premasticated food as infants, whereas none of eight ethnographic studies performed in Han China identified premastication in their reports, provides support for the conclusion that the cross-cultural study grossly underestimates its prevalence in non-Western societies. Section III is a discussion of potential benefits and risks of infant exposure to maternal saliva.We conclude with the argument for a concerted research effort to determine whether premastication can solve not only the 'weanling dilemma' in poor countries but also some of the health problems among the better-off.

Thyrotropin and iodide regulate sulfate concentration in thyroid cells. Relationship to thyroglobulin sulfation

Thyroglobulin (Tg), the thyroid hormone precursor, is sulfated both on tyrosines and on carbohydrates. We showed recently that sulfated tyrosines were involved in thyroid hormone synthesis. Moreover, we also reported that Tg sulfation is downregulated by thyrotropin (TSH), especially on tyrosines. This control may occur at each step in the sulfation process. In this paper, we studied the regulation of the concentration of cytosolic inorganic sulfate, the first substrate, in porcine thyroid cells stimulated by TSH with or without iodide. The amounts of cytosolic sulfate and the cytosolic volumes measured showed that the sulfate concentration depends only on cytosolic volume changes in response to TSH and iodide treatment. After the cells were labelled with [35S]-sulfate, the specific radioactivity (SRA) of cytosolic sulfate was determined. When cells were treated with only TSH, the concentration and SRA of cytosolic sulfate decreased by 30%, and by about 15% when cells were incubated with both TSH and iodide. TSH decreased more conspicuously the rate of [35S]-sulfate incorporation into Tg (by 57% without iodide, by 43% with iodide) than the concentration and SRA of cytosolic sulfate, while iodide altered these parameters to the same extent (15%). These findings suggest that TSH regulates other steps in the sulfation process, such as specific substrate and enzyme levels, while iodide controls mainly the sulfate concentration.Key words: cytosolic inorganic sulfate measurement, capillary electrophoresis, intracellular sulfate concentration, thyroglobulin sulfation, primary culture thyroid cells.