Alternative endocytic pathway for immunoglobulin A Fc receptors (CD89) depends on the lack of FcRgamma association and protects against degradation of bound ligand

IgA is the most abundant immunoglobulin in mucosal areas but is only the second most common antibody isotype in serum because it is catabolized faster than IgG. IgA exists in monomeric and polymeric forms that function through receptors expressed on effector cells. Here, we show that IgA Fc receptor(s) (FcalphaR) are expressed with or without the gamma chain on monocytes and neutrophils. gamma-less FcalphaR represent a significant fraction of surface FcalphaR molecules even on cells overexpressing the gamma chain. The FcalphaR-gamma2 association is up-regulated by phorbol esters and interferon-gamma. To characterize gamma-less FcalphaR functionally, we generated mast cell transfectants expressing wild-type human FcalphaR or a receptor with a point mutation (Arg --> Leu at position 209) which was unable to associate with the gamma chain. Mutant gamma-less FcalphaR bound monomeric and polymeric human IgA1 or IgA2 but failed to induce exocytosis after receptor clustering. The two types of transfectant showed similar kinetics of FcalphaR-mediated endocytosis; however, the endocytosis pathways of the two types of receptor differed. Whereas mutant FcalphaR were localized mainly in early endosomes, those containing FcalphaR-gamma2 were found in endo-lysosomal compartments. Mutant gamma-less FcalphaR recycled the internalized IgA toward the cell surface and protected against IgA degradation. Cells expressing the two forms of FcalphaR, associated or unassociated with gamma chains, may thus have differential functions either by degrading IgA antibody complexes or by recycling serum IgA.     

Multiple Kisspeptin Receptors in Early Osteichthyans Provide New Insights into the Evolution of This Receptor Family

Deorphanization of GPR54 receptor a decade ago led to the characterization of the kisspeptin receptor (Kissr) in mammals and the discovery of its major role in the brain control of reproduction. While a single gene encodes for Kissr in eutherian mammals including human, other vertebrates present a variable number of Kissr genes, from none in birds, one or two in teleosts, to three in an amphibian, xenopus. In order to get more insight into the evolution of Kissr gene family, we investigated the presence of Kissr in osteichthyans of key-phylogenetical positions: the coelacanth, a representative of early sarcopterygians, the spotted gar, a non-teleost actinopterygian, and the European eel, a member of an early group of teleosts (elopomorphs). We report the occurrence of three Kissr for the first time in a teleost, the eel. As measured by quantitative RT-PCR, the three eel Kissr were differentially expressed in the brain-pituitary-gonadal axis, and differentially regulated in experimentally matured eels, as compared to prepubertal controls. Subfunctionalisation, as shown by these differences in tissue distribution and regulation, may have represented significant evolutionary constraints for the conservation of multiple Kissr paralogs in this species. Furthermore, we identified four Kissr in both coelacanth and spotted gar genomes, providing the first evidence for the presence of four Kissr in vertebrates. Phylogenetic and syntenic analyses supported the existence of four Kissr paralogs in osteichthyans and allowed to propose a clarified nomenclature of Kissr (Kissr-1 to -4) based on these paralogs. Syntenic analysis suggested that the four Kissr paralogs arose through the two rounds of whole genome duplication (1R and 2R) in early vertebrates, followed by multiple gene loss events in the actinopterygian and sarcopterygian lineages. Due to gene loss there was no impact of the teleost-specific whole genome duplication (3R) on the number of Kissr paralogs in current teleosts.     

Association between coding variability in the LRP gene and the risk of late-onset Alzheimer’s disease

We have sequenced the entire (89 exons) open reading frame of the LRP gene in 12 cases of Alzheimer’s disease (AD) from Northern France. We have found no novel changes but confirm the occurrence of a polymorphism in exon 6 of the gene (A216V). This polymorphism is rare (2.8% of controls) and is in linkage equilibrium with previously reported polymorphisms. The V216 allele is negatively associated with the disease in a large case-controlled series. These data suggest that the LRP receptor may be involved in the pathobiology of AD, but the association that we report here cannot explain the previously reported genetic data implicating the LRP gene in AD. If the LRP gene is a major site of genetic variability leading to AD, there must be other biologically relevant variability in promoter or other regulatory elements of this large gene. Received: 28 December 1998 / Accepted: 1 March 1999     

Focal adhesion kinase regulation by oxidative stress in different cell types

Focal adhesion kinase (FAK) is a tyrosine kinase ubiquitously expressed in cells. It was initially shown to be the initiator of focal adhesion formation in adherent cells, after its binding to integrins which induce its autophosphorylation. However, it can be also activated by a great variety of other stimuli able to act on different intracellular signaling. Reactive oxygen species (ROS), which have been shown to act as external or internal cell stimuli, induce tyrosine phosphorylation of FAK. Its autophosphorylation is followed by a submembranous localization which is crucial for many of the biological roles of FAK, including cell spreading, cell migration, cell proliferation, and prevention of apoptosis. It plays an important role in development of tumor cells, its regulation could be thus a way of impairing cell proliferation in cancer. We describe in this review the structure, activity, and functions of FAK in different cells and how ROS are able, like other stimuli, to induce its phosphorylation and modification of cell morphology and structure. The link between ROS and FAK activation could explain the role of ROS in mediating cell proliferation, cell migration, or apoptosis.     

D-penicillamine-induced autoimmunity in Brown-Norway rats. Similarities with HgCl2-induced autoimmunity

D-penicillamine (DP) has been previously shown to induce an autoimmune disease in Brown-Norway (BN) rats, characterized by a dermatitis, by the production of antinuclear antibodies, by the formation fo circulating immune complexes, and by linear IgG deposits along the glomerular basement membrane. These manifestations are quite similar to those observed in mercuric chloride (HgCl2)-induced autoimmunity. The mechanism of the latter disease has been recently partly elucidated. The aim of this study was to compare DP and HgCl2-induced autoimmunity in BN rats and to compare the mechanisms involved in both situations. A transient increase in the number of spleen cells, affecting B cells and CD4+ T cells, and an increase in serum IgE concentration, previously reported in HgCl2-induced autoimmunity, were observed during DP treatment. Autoreactive anti-class II T cells able to proliferate not only in the presence of autologous B cells but also in the presence of syngeneic normal B cells were found in DP-treated BN rats. Spontaneous regulation occurred, associated with the disappearance of autoreactive T cells. Suppressor CD8+ T cells were not involved in this phenomenon. Mechanisms involved in both the induction and the regulation of DP-induced autoimmunity seem to be quite similar to those reported in HgCl2-induced autoimmunity.     

Moving forward with metronomic chemotherapy: meeting report of the 2nd International Workshop on Metronomic and Anti-Angiogenic Chemotherapy in Paediatric Oncology

Metronomic chemotherapy, which is defined by the frequent, repetitive administration of chemotherapeutic drugs at relatively low doses, and without prolonged drug-free break, is an emerging strategy to fight cancer. Initially thought to act by targeting tumor angiogenesis, additional mechanisms have been recently unveiled, and metronomic chemotherapy is now considered to represent a form of multitargeted therapy. Despite representing a genuine alternative for advanced and/or high-risk cancer therapy, the development of metronomic approaches in pediatric oncology is still in the early stage. The few numbers of large-scale state-of-the-art clinical trials, issues regarding terminology and the limited understanding of the complex and intertwined mechanisms of action of metronomic treatments have limited progress in this important field of research. On March 18 and 19, 2010, the 2nd International Workshop on Metronomic and Anti-Angiogenic Chemotherapy in Paediatric Oncology was held in Marseille, France, and brought together clinicians, basic scientists, physician-scientists, trainees, and students from all around the world. The main aim of this international meeting was to provide a unique forum to 1) reflect on the major advances that have been made in this field of research since its creation, 2) communicate results from the most recent clinical trials and preclinical studies, 3) discuss the current and future challenges of the field, and 4) set forth a solid framework for future collaborative biologic and clinical studies. The present report documents the main preclinical and clinical data that were presented in the keynote and best abstract sessions and delivers the key messages from the meeting.     

Increased adenylate cyclase catalytic activity explains how estrogens "in vivo" promote lipolytic activity in rat white fat cells

Estradiol administration (5 micrograms per day x 4 days) to ovariectomized rats resulted in a 60-70% increase in the maximal lipolytic response of their white adipocytes to isoproterenol, epinephrine, IBMX and forskolin. These altered lipolytic responses were accompanied by parallel changes in the intracellular cyclic AMP levels found in response to 1 mM IBMX alone (+ 106%) or combined with submaximal concentrations of isoproterenol (+205%), epinephrine (+190%) and forskolin (235%). Studies of the adenylate cyclase activity revealed an overall increase in the stimulatory responsiveness of the enzyme (+150 to +200%) after the estradiol-treatment, regardless of the stimulatory agents tested (GTP, GppNHp, fluoride, isoproterenol, ACTH, forskolin). Finally, the finding of a 2-fold enhancement of the Mn2+ (+/- GDP beta S)-stimulated adenylate cyclase activity after the estradiol-treatment strongly suggests that increased activity of the catalytic subunit of this enzyme is the likely mechanism whereby estrogens promote lipolysis in rat fat cells.     

A novel method for predicting transmembrane segments in proteins based on a statistical analysis of the SwissProt database: the PRED-TMR algorithm.

We present a novel method that predicts transmembrane domains in proteins using solely information contained in the sequence itself. The PRED-TMR algorithm described, refines a standard hydrophobicity analysis with a detection of potential termini ('edges', starts and ends) of transmembrane regions. This allows one both to discard highly hydrophobic regions not delimited by clear start and end configurations and to confirm putative transmembrane segments not distinguishable by their hydrophobic composition. The accuracy obtained on a test set of 101 non-homologous transmembrane proteins with reliable topologies compares well with that of other popular existing methods. Only a slight decrease in prediction accuracy was observed when the algorithm was applied to all transmembrane proteins of the SwissProt database (release 35). A WWW server running the PRED-TMR algorithm is available at http://o2.db.uoa. gr/PRED-TMR/