An overlooked connection: serotonergic mediation of estrogen-related physiology and pathology

BACKGROUND: In humans, serotonin has typically been investigated as a neurotransmitter. However, serotonin also functions as a hormone across animal phyla, including those lacking an organized central nervous system. This hormonal action allows serotonin to have physiological consequences in systems outside the central nervous system. Fluctuations in estrogen levels over the lifespan and during ovarian cycles cause predictable changes in serotonin systems in female mammals. DISCUSSION: We hypothesize that some of the physiological effects attributed to estrogen may be a consequence of estrogen-related changes in serotonin efficacy and receptor distribution. Here, we integrate data from endocrinology, molecular biology, neuroscience, and epidemiology to propose that serotonin may mediate the effects of estrogen. In the central nervous system, estrogen influences pain transmission, headache, dizziness, nausea, and depression, all of which are known to be a consequence of serotonergic signaling. Outside of the central nervous system, estrogen produces changes in bone density, vascular function, and immune cell self-recognition and activation that are consistent with serotonin's effects. For breast cancer risk, our hypothesis predicts heretofore unexplained observations of the opposing effects of obesity pre- and post-menopause and the increase following treatment with hormone replacement therapy using medroxyprogesterone. SUMMARY: Serotonergic mediation of estrogen has important clinical implications and warrants further evaluation

A modular data and control system to improve sensitivity, selectivity, speed of analysis, ease of use, and transient duration in an external source FTICR-MS

We present here a new Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) controller designed and constructed to meet the growing need for increased speed, memory, and ease of use. The system realizes these goals via the first published application of fast PXI bus technology and by employing a graphical user interface (GUI) for control of all aspects of ion production, delivery, containment, manipulation of internal and kinetic energies, and measurement in an external source instrument. Additionally, new hardware for monitoring and control of these aspects and for processing extended datasets both to and from the instrument have been implemented.\u3cbr/\u3e\u3cbr/\u3eThe modular nature of the control hardware makes the instrument platform, in this case a modified external source 7T FTICR-MS, irrelevant. The GUI consists of two separate modules; one provides a temporal representation of the pulses, voltages (rf and dc), and dc heater currents that control all aspects of the experiment while the other provides complex data analysis capabilities and design of excitation waveforms. Real-time monitoring of the transient signal is available in this module as well as near real-time monitoring of the resulting mass spectrum (using a truncated dataset). A PXI bus with 40 digital to analog converters (DAC) and 64 digital (TTL) sources drive the source, optics, and trapping functions of the instrument as well as the other peripheral hardware. Acquisition is realized using a VME bus with a TTL triggered program resident on an embedded processor to minimize dead time. The acquisition system is equipped with 192 MB memory for both excitation and detection waveforms with FIFO buffering to provide full rate bandwidth of 10 MHz, and four digital down converters (DDCs) to enable mixing of heterodyne signals for narrow band measurements completes the ensemble.\u3cbr/\u3

Mastering the canonical loop of serine protease inhibitors: Enhancing potency by optimising the internal hydrogen bond network

Background Canonical serine protease inhibitors commonly bind to their targets through a rigid loop stabilised by an internal hydrogen bond network and disulfide bond(s). The smallest of these is sunflower trypsin inhibitor (SFTI-1), a potent and broad-range protease inhibitor. Recently, we re-engineered the contact β-sheet of SFTI-1 to produce a selective inhibitor of kallikrein-related peptidase 4 (KLK4), a protease associated with prostate cancer progression. However, modifications in the binding loop to achieve specificity may compromise structural rigidity and prevent re-engineered inhibitors from reaching optimal binding affinity. Methodology/Principal Findings In this study, the effect of amino acid substitutions on the internal hydrogen bonding network of SFTI were investigated using an in silico screen of inhibitor variants in complex with KLK4 or trypsin. Substitutions favouring internal hydrogen bond formation directly correlated with increased potency of inhibition in vitro. This produced a second generation inhibitor (SFTI-FCQR Asn14) which displayed both a 125-fold increased capacity to inhibit KLK4 (Ki = 0.0386±0.0060 nM) and enhanced selectivity over off-target serine proteases. Further, SFTI-FCQR Asn14 was stable in cell culture and bioavailable in mice when administered by intraperitoneal perfusion. Conclusion/Significance These findings highlight the importance of conserving structural rigidity of the binding loop in addition to optimising protease/inhibitor contacts when re-engineering canonical serine protease inhibitors