Involvement of penaeidins in defense reactions of the shrimp Litopenaeus stylirostris to a pathogenic vibrio

The present study reports for the first time the involvement of an antimicrobial peptide in the defense reactions of a shrimp infected by a pathogenic Vibrio, Vibrio penaeicida. New members of the penaeidin family were characterized in the shrimp Litopenaeus stylirostris by RT-PCR and RACE-PCR from hemocyte total RNAs, and by mass spectrometry detection and immunolocalization of mature peptides in shrimp hemocytes. In infected shrimps, bacteria and penaeidin distribution colocalized in the gills and the lymphoid organ that represented the main infected sites. Moreover, the shrimp immune response to infection involved massive hemocyte recruitment to infection sites where released penaeidin may participate in the isolation and elimination of the bacteria, We show that the ability of the shrimps to circumvent shrimp infections is closely related to a recovery phase based on the hematopoietic process.Received 25 November 2003; received after revision 8 January 2004; accepted 21 January 2004     

Identification of swelling-activated Cl<Superscript>-</Superscript> current in rabbit cardiac Purkinje cells

The presence and functional role of the swelling-activated Cl^- current (I_Cl(swell)) in rabbit cardiac Purkinje cells was examined using patch-clamp methodology. Extracellular hypotonicity (210 or 135 mOsm) activated an outwardly rectifying, time-independent current with a reversal potential close to the calculated Cl^- equilibrium potential (E_Cl). The magnitude of this current was related to tonicity of the superfusate. The current was blocked by 0.5 mM 4,4-diisothiocyanostilbene-2,2-disulfonic acid (DIDS). These features are comparable to those of I_Cl(swell) found in sinoatrial nodal, atrial, and ventricular myocytes. I_Cl(swell) activation at 210 and 135 mOsm depolarized the resting membrane potential with 6 and 10 mV and shortened the action potential by 18 and 33%, respectively. DIDS partially reversed I_Cl(swell)-induced action potential changes. We conclude that I_Cl(swell) is present in Purkinje cells and its activation leads to action potential shortening and resting membrane potential depolarization, both of which can promote the development of reentrant arrhythmias.Received 20 January 2004; received after revision 17 February 2004; accepted 25 February 2004     

Oxygen intervention in the regulation of gene expression: the photosynthetic bacterial paradigm

The means by which oxygen intervenes in gene expression has been examined in considerable detail in the metabolically versatile bacterium Rhodobacter sphaeroides. Three regulatory systems are now known in this organism, which are used singly and in combination to modulate genes in response to changing oxygen availability. The outcome of these regulatory events is that the molecular machinery is present for the cell to obtain energy by means that are best suited to prevailing conditions, while at the same time maintaining cellular redox balance. Here, we explore the dangers associated with molecular oxygen relative to the various metabolisms used by R. sphaeroides, and then present the most recent findings regarding the features and operation of each of the three regulatory systems which collectively mediate oxygen control in this organism.Received 26 June 2003; received after revision 30 July 2003; accepted 8 August 2003     

What’s new in the renin-angiotensin system?

Activation of the type 1 angiotensin II receptor (AT(1)R) is associated with the aetiology of left ventricular hypertrophy, although the exact intracellular signalling mechanism(s) remain unclear. Transactivation of the epidermal growth factor receptor (EGFR) has emerged as a central mechanism by which the G protein-coupled AT(1)R, which lacks intrinsic tyrosine kinase activity, can stimulate the mitogen-activated protein kinase signalling pathways thought to mediate cardiac hypertrophy. Current studies support a model whereby AT(1)R-dependent transactivation of EGFRs on cardiomyocytes involves stimulation of membrane-bound metalloproteases, which in turn cleave EGFR ligands such as heparin-binding EGF from a plasma membrane-associated precursor. Numerous aspects of the 'triple membrane-passing signalling' paradigm of AT(1)R-induced EGFR transactivation remain to be characterised, including the identity of the specific metalloproteases involved, the intracellular mechanism for their activation and the exact EGFR subtypes required. Here we examine how 'hijacking' of the EGFR might explain the ability of the AT(1)R to elicit the temporally and qualitatively diverse responses characteristic of the hypertrophic phenotype, and discuss the ramifications of delineating these pathways for the development of new therapeutic strategies to combat cardiac hypertrophy.     

What’s new in the renin-angiotensin system?

The angiotensin AT(4) receptor was originally defined as the specific, high-affinity binding site for the hexapeptide angiotensin IV (Ang IV). Subsequently, the peptide LVV-hemorphin 7 was also demonstrated to be a bioactive ligand of the AT(4) receptor. Central administration of Ang IV, its analogues or LVV-hemorphin 7 markedly enhance learning and memory in normal rodents and reverse memory deficits observed in animal models of amnesia. The AT(4) receptor has a broad distribution and is found in a range of tissues, including the adrenal gland, kidney, lung and heart. In the kidney Ang IV increases renal cortical blood flow and decreases Na(+) transport in isolated renal proximal tubules. The AT(4) receptor has recently been identified as the transmembrane enzyme, insulin-regulated membrane aminopeptidase (IRAP). IRAP is a type II integral membrane spanning protein belonging to the M1 family of aminopeptidases and is predominantly found in GLUT4 vesicles in insulin-responsive cells. Three hypotheses for the memory-potentiating effects of the AT(4) receptor/IRAP ligands, Ang IV and LVV-hemorphin 7, are proposed: (i) acting as potent inhibitors of IRAP, they may prolong the action of endogenous promnestic peptides; (ii) they may modulate glucose uptake by modulating trafficking of GLUT4; (iii) IRAP may act as a receptor, transducing the signal initiated by ligand binding to its C-terminal domain to the intracellular domain that interacts with several cytoplasmic proteins.     

Oncogenic protein tyrosine kinases

Signals through Kit receptor tyrosine kinase are essential for development of erythrocytes, melanocytes, germ cells, mast cells and interstitial cells of Cajal (ICCs). Mice and rats with a double gene dose of loss-of-function mutations of Kit show depletion of these cells. Although human homozygotes with loss-of-function mutations of Kit have not been reported, gain-of-function mutations of Kit result in development of tumors from mast cells, germ cells and ICCs in humans. The ICC tumors are called gastrointestinal stromal tumors (GISTs), and GISTs are a good target for the Kit inhibitor imatinib mesylate. The interrelationship between the type of Kit gain-of-function mutations and the therapeutic effect of imatinib mesylate has been well characterized in GISTs. Kit is interesting from both a biological and clinical view-point.     

Gelsolin superfamily proteins: key regulators of cellular functions

Cytoskeletal rearrangement occurs in a variety of cellular processes and involves a wide spectrum of proteins. Among these, the gelsolin superfamily proteins control actin organization by severing filaments, capping filament ends and nucleating actin assembly [1]. Gelsolin is the founding member of this family, which now contains at least another six members: villin, adseverin, capG, advillin, supervillin and flightless I. In addition to their respective role in actin filament remodeling, these proteins have some specific and apparently non-overlapping particular roles in several cellular processes, including cell motility, control of apoptosis and regulation of phagocytosis (summarized in table 1). Evidence suggests that proteins belonging to the gelsolin superfamily may be involved in other processes, including gene expression regulation. This review will focus on some of the known functions of the gelsolin superfamily proteins, thus providing a basis for reflection on other possible and as yet incompletely understood roles for these proteins.     

Snake venom thrombin-like enzymes: from reptilase to now

The snake venom thrombin-like enzymes (SVTLEs) comprise a number of serine proteases functionally and structurally related to thrombin. Until recently, only nine complete sequences of this subgroup of the serine protease family were known. Over the past 5 years, the primary structure of several SVTLEs has been characterized, and now this family includes several members. Of particular interest is their possible use in pathologies such as thrombosis. The aim of the present review is to summarize the state of the art concerning the evolutionary, structural and biological features of the SVTLEs.Received 16 August 2003; received after revision 26 September 2003; accepted 1 October 2003     

Polarization of immunity induced by direct injection of naked sequence-stabilized mRNA vaccines

In the context of developing a safe genetic vaccination strategy we tested and studied globin-stabilized mRNA-based vaccination in mice. This vaccination strategy has the advantages of genetic vaccination (easy production, adaptability to any disease and inexpensive storage when lyophilized), but not the drawbacks of DNA vaccination (long-term uncontrolled expression of a transgene, possibility of integration into the host genome and possible induction of anti-DNA antibodies). We report here that injection of naked -globin untranslated region (UTR)-stabilized mRNA coding for -galactosidase is followed by detectable translation in vivo. In addition, we show that such a vaccination strategy primes a T helper 2 (Th2) type of response which can be enhanced and shifted to a Th1-type immune response by application of recombinant granulocyte/macrophage colony-stimulating factor 1 day after mRNA injection. Our data demonstrate that the administration of globin UTR-stabilized mRNA is a versatile vaccination strategy that can be manipulated to fit the requirement of antiviral, antibacterial or antitumor immunity.Received 14 June 2004; received after revision 19 July 2004; accepted 9 August 2004     

Alternative splicing of Bcl-2-related genes: functional consequences and potential therapeutic applications

Apoptosis is a morphologically distinct form of cell death. It is executed and regulated by several groups of proteins. Bcl-2 family proteins are the main regulators of the apoptotic process acting either to inhibit or promote it. More than 20 members of the family have been identified so far and most have two or more isoforms. Alternative splicing is one of the major mechanisms providing proteomic complexity and functional diversification of the Bcl-2 family proteins. Pro- and anti-apoptotic Bcl-2 family members should function in harmony for the regulation of the apoptosis machinery, and their relative levels are critical for cell fate. Any mechanism breaking down this harmony by changing the relative levels of these antagonistic proteins could contribute to many diseases, including cancer and neurodegenerative disorders. Recent studies have shown that manipulation of the alternative splicing mechanisms could provide an opportunity to restore the proper balance of these regulator proteins. This review summarises current knowledge on the alternative splicing products of Bcl-2-related genes and modulation of splicing mechanisms as a potential therapeutic approach.Received 5 January 2004; received after revision 31 March 2004; accepted 6 April 2004