Elafin and its precursor trappin-2 still inhibit neutrophil serine proteinases when they are covalently bound to extracellular matrix proteins by tissue transglutaminase

Multifaceted roles of human elafin and secretory leukocyte proteinase inhibitor (SLPI), two serine protease inhibitors of the chelonianin family

Elafin and SLPI are low-molecular weight proteins that were first identified as protease inhibitors in mucous fluids including lung secretions, where they help control excessive proteolysis due to neutrophil serine proteases (elastase, proteinase 3 and cathepsin G). Elafin and SLPI are structurally related in that both have a fold with a four-disulfide core or whey acidic protein (WAP) domain responsible for inhibiting proteases. Elafin is derived from a precursor, trappin-2 or pre-elafin, by proteolysis. Trappin-2, which is itself a protease inhibitor, has a unique N-terminal domain that enables it to become cross-linked to extracellular matrix proteins by transglutaminase(s). SLPI and elafin/trappin-2 are attractive candidates as therapeutic molecules for inhibiting neutrophil serine proteases in inflammatory lung diseases. Hence, they have become the WAP proteins most studied over the last decade. This review focuses on recent findings revealing that SLPI and elafin/trappin-2 have many biological functions as diverse as anti-bacterial, anti-fungal, anti-viral, anti-inflammatory and immuno-modulatory functions, in addition to their well-recognized role as protease inhibitors.

Roles of transglutaminases in cardiac and vascular diseases

All transglutaminases share the common enzymatic activity of transamidation, or the cross-linking of glutamine and lysine residues to form N epsilon (gamma-glutamyl) lysyl isopeptide bonds. The plasma proenzyme factor XIII is responsible for stabilizing the fibrin clot against physical and fibrinolytic disruption. Another member of the transglutaminase family, tissue transglutaminase or TG2 is abundantly expressed in cardiomyocytes, vascular cells and macrophages. The transglutaminases have a variety of functions independent of their transamidating activity. For example, TG2 binds and hydrolyzes GTP, thereby fostering signal transduction by several G protein coupled receptors. Accumulating evidence points to novel roles for factor XIII and TG2 in cardiovascular biology including: (a) modulating platelet activity, (b) regulating glucose control, (c) contributing to the development of hypertension, (d) influencing the progression of atherosclerosis, (e) regulating vascular permeability and angiogenesis (f) and contributing to myocardial signaling, contractile activity and ischemia/reperfusion injury. In this review, we summarize the cardiovascular biology of two members of the family of transglutaminases, Factor XIII and TG2.

Accumulation of elafin in actinic elastosis of sun-damaged skin: elafin binds to elastin and prevents elastolytic degradation

Elafin has a primary structure with two functional domains; a transglutaminase substrate domain at the N-terminus and a protease inhibitor domain at the C-terminus. Elafin expression has so far been reported only for epithelial tissues. Accumulation of elafin was immunohistochemically detected in the actinic elastosis of sun-damaged skin. Exposure of normal skin to UVA induced elafin expression that colocalized with elastic fibers. Incubation of synthetic transglutaminase substrate domain of elafin and elastin molecules in the presence of tissue transglutaminase in vitro resulted in the formation of a higher molecular complex on SDS-PAGE. Elafin expression was not detected in normal cultured skin fibroblasts, but was induced by UVA irradiation at both messenger RNA and protein levels. When radiolabeled insoluble elastin was incubated with recombinant full-length elafin and tissue transglutaminase, insoluble elastin became more resistant to neutrophil elastase digestion. These results indicate that (1) dermal fibroblasts potentially express elafin on UV irradiation, (2) UV-mediated elafin interacts with elastin, and (3) the elafin-elastin complex protects elastic fibers from elastolytic degradation, leading to the accumulation of elastic fibers in the actinic elastosis of sun-damaged skin. The transglutaminase substrate moiety of elafin plays an important role in anchoring elafin at its proper sites of action during UV-induced aging processes.

Survey of the year 2005 commercial optical biosensor literature

We identified 1113 articles (103 reviews, 1010 primary research articles) published in 2005 that describe experiments performed using commercially available optical biosensors. While this number of publications is impressive, we find that the quality of the biosensor work in these articles is often pretty poor. It is a little disappointing that there appears to be only a small set of researchers who know how to properly perform, analyze, and present biosensor data. To help focus the field, we spotlight work published by 10 research groups that exemplify the quality of data one should expect to see from a biosensor experiment. Also, in an effort to raise awareness of the common problems in the biosensor field, we provide side-by-side examples of good and bad data sets from the 2005 literature.