Peptidyl-prolyl cis-trans isomerase A participates in the selenium transport into the rat brain

Selenium, an essential micronutrient, plays vital roles in the brain. Selenoprotein P (SELENOP), a major plasma selenoprotein, is thought to transport selenium to the brain. However, Selenop-knockout mice fed a diet containing an adequate amount of selenium shows no objective neurological dysfunction which is observed in the selenium-deficient diet-fed Selenop-knockout mice. This fact indicated that selenium from low-mass selenium-source compounds can be transported by SELENOP-independent alternative pathways to the brain. In this study, to obtain the basic information about the SELENOP-independent transport pathways, we performed ex vivo experiments in which the rat brain cell membrane fraction was analyzed to find selenium-binding and/or -interactive proteins using its reactive metabolic intermediate, selenotrisulfide (STS), and MALDI TOF-mass spectrometry. Several membrane proteins with the cysteine (C) thiol were found to be reactive with STS through the thiol-exchange reaction. One of the C-containing proteins in the brain cell membrane fraction was identified as peptidyl-prolyl cis-trans isomerase (PPIase) A from tryptic fragmentation experiments and database search. Among the 4 C residues in rat PPIase A, 21st C was proved to react with STS by assessment using C mutated recombinant proteins. PPIase A is ubiquitously expressed and also associates with a variety of biologically important events such as immunomodulation, intracellular signaling, transcriptional regulation and protein trafficking. Consequently, PPIase A was thought to participate in the selenium transport into the rat brain.

The role of PP5 and PP2C in cardiac health and disease

Protein phosphatases are important, for example, as functional antagonists of β-adrenergic stimulation of the mammalian heart. While β-adrenergic stimulations increase the phosphorylation state of regulatory proteins and therefore force of contraction in the heart, these phosphorylations are reversed and thus force is reduced by the activity of protein phosphatases. In this context the role of PP5 and PP2C is starting to unravel. They do not belong to the same family of phosphatases with regard to sequence homology, many similarities with regard to location, activation by lipids and putative substrates have been worked out over the years. We also suggest which pathways for regulation of PP5 and/or PP2C described in other tissues and not yet in the heart might be useful to look for in cardiac tissue. Both phosphatases might play a role in signal transduction of sarcolemmal receptors in the heart. Expression of PP5 and PP2C can be increased by extracellular stimuli in the heart. Because PP5 is overexpressed in failing animal and human hearts, and because overexpression of PP5 or PP2C leads to cardiac hypertrophy and KO of PP5 leads to cardiac hypotrophy, one might argue for a role of PP5 and PP2C in heart failure. Because PP5 and PP2C can reduce, at least in vitro, the phosphorylation state of proteins thought to be relevant for cardiac arrhythmias, a role of these phosphatases for cardiac arrhythmias is also probable. Thus, PP5 and PP2C might be druggable targets to treat important cardiac diseases like heart failure, cardiac hypertrophy and cardiac arrhythmias.

Endogenous opiates and behavior: 2010

This paper is the thirty-third consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2010 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration (Section 16); and immunological responses (Section 17).