Costimulation induced phosphorylation of L-plastin facilitates surface transport of the T cell activation molecules CD69 and CD25

Rearrangements in the actin cytoskeleton play a pivotal role for costimulation-induced formation of the immunological synapse and T cell activation. Yet, little is known about the actin-binding proteins that link costimulation to rearrangements in the actin cytoskeleton. Here we demonstrate that phosphorylation of the actin bundling protein L-plastin in response to costimulation through TCR/CD3 plus CD2 or CD28, respectively, is important for the activation of human peripheral blood T lymphocytes (PBT). Mass spectrometry and site-directed mutagenesis revealed that Ser5 represents the only phospho-acceptor site of L-plastin in PBT. Wild-type L-plastin (wt-LPL) and a non-phosphorylatable 5A-L-plastin (5A-LPL) equally relocalized to the immunological synapse between PBT and APC. Yet importantly, cells expressing 5A-LPL showed a significantly lower expression of the T cell activation molecules CD25 and CD69 on the cell surface than cells expressing wt-LPL. This effect is due to a failure in the transport of CD25 and CD69 to the cell surface since the total amount of these proteins within the cells remained unchanged. In conclusion, phosphorylation of the actin bundling protein L-plastin represents a so-far-unknown mechanism by which costimulation controls the transport of activation receptors to the T cell surface.     

Transforming a hospital nursing research fellowship into an evidence-based practice fellowship

An established hospital-based nursing research fellowship program was transformed into an evidence-based practice fellowship despite its previous high satisfaction ratings from nursing leaders and nurse fellow participants. The faculty for the fellowship program determined that the long-term outcomes of the research program were insufficient in light of the hospital resources committed to the fellowship program. An evidence-based practice approach was then created in anticipation that greater short-term and more sustained longer-term benefits for the hospital would be realized. The transformation of the fellowship and the short-term outcomes are described.     

Book Review

Performance Breakthroughs for Adolescents With Learning Disabilities or ADD. G. Markel & J. Greenbaum.     

Characterization of Renal Toxicity in Mice Administered the Marine Biotoxin Domoic Acid

Domoic acid (DA), an excitatory amino acid produced by diatoms belonging to the genus Pseudo-nitzschia, is a glutamate analog responsible for the neurologic condition referred to as amnesic shellfish poisoning. To date, the renal effects of DA have been underappreciated, although renal filtration is the primary route of systemic elimination and the kidney expresses ionotropic glutamate receptors. To characterize the renal effects of DA, we administered either a neurotoxic dose of DA or doses below the recognized limit of toxicity to adult Sv128/Black Swiss mice. DA preferentially accumulated in the kidney and elicited marked renal vascular and tubular damage consistent with acute tubular necrosis, apoptosis, and renal tubular cell desquamation, with toxic vacuolization and mitochondrial swelling as hallmarks of the cellular damage. Doses≥0.1 mg/kg DA elevated the renal injury biomarkers kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin, and doses≥0.005 mg/kg induced the early response genes c-fos and junb. Coadministration of DA with the broad spectrum excitatory amino acid antagonist kynurenic acid inhibited induction of c-fos, junb, and neutrophil gelatinase-associated lipocalin. These findings suggest that the kidney may be susceptible to excitotoxic agonists, and renal effects should be considered when examining glutamate receptor activation. Additionally, these results indicate that DA is a potent nephrotoxicant, and potential renal toxicity may require consideration when determining safe levels for human exposure.Domoic acid (DA), a water-soluble, heat-stable tricarboxylic acid produced by diatoms belonging to the genus Pseudo-nitzschia, is responsible for a condition known as amnesic shellfish poisoning in humans.^1–4 Shellfish, such as clams and mussels, and fish that accumulate DA serve as vectors of exposure to various species of birds and aquatic mammals in addition to humans.^5,6 Initially recognized as a human toxicant when more than 100 people became ill after eating contaminated mussels in eastern Canada in 1987, DA poisoning was defined by the occurrence of gastrointestinal or neurologic symptoms ranging from abdominal cramps and headache to more severe cases of memory loss, seizures, coma, and even death.^2,4 Increased awareness and governmental regulation, which set a limit of 20 μg DA/g in shellfish tissue, has reduced the incidence of DA toxicity in humans since the 1987 outbreak. However, there is concern that exposure will increase because of the growing presence of toxic diatom-producing algal blooms, which are often attributed to human factors, such as pollution, shipping, and global warming, leading to greater nutrient availability, greater distribution of algal species, and longer growth periods.^7–14 Although the overt gastrointestinal and neurologic manifestations have defined the disease, emerging evidence from animal and human studies support previously unrecognized threats and novel toxicologic syndromes caused by subclinical toxicity from acute and chronic DA exposures, which may ultimately challenge the adequacy of the current acceptable limit.^15–18DA is a potent activator of kainate receptors (KRs) as well as a subpopulation of α-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid receptors (AMPARs).¹⁹ The toxic response produced by DA is a coordinated effort, which involves initial activation of KR and AMPAR by DA and secondary activation of N-methyl-D-aspartate receptors (NMDARs) by glutamate, and it is associated with an influx of Ca²⁺ across the plasma membrane, inflammation, neuronal cell injury and death, and neurobehavioral alterations.^19–22 Although they are extensively characterized in the central nervous system, glutamate receptors are also expressed at peripheral sites and have been shown to exhibit toxicity in multiple tissues, including the kidney, where NMDARs contribute to organ damage in models of ischemia-reperfusion injury and gentamicin nephrotoxicity.^23–26 There is limited information about the effects of DA on the kidney; however, oral dosing in coho salmon has shown that the kidney is a primary site of DA accumulation in this species, and studies in rodents have shown that renal excretion is the exclusive route of systemic DA elimination.^27,28 Examination of sea lions after DA poisoning has also revealed some evidence of interstitial nephritis, renal edema, and elevated BUN, although the exact cause of these findings cannot be definitively attributed to DA toxicity.^29,30 Furthermore, sea lions with acute DA toxicosis seem to have an elevated hematocrit,³¹ suggesting that water reabsorption or red blood cell production could be affected, both of which are functions of the kidney. Despite this circumstantial evidence, a detailed examination of the renal response to DA administration has not been fully explored. The purpose of the current study was to characterize the acute renal effects of DA at doses that produce neurotoxicity and neurobehavioral changes (1.0–2.5 mg/kg) as well as several lower doses (0.0005–0.5 mg/kg), which are considered below the limit of toxicity.