The retrieval function of the KDEL receptor requires PKA phosphorylation of its C-terminus

The KDEL receptor is a Golgi/intermediate compartment-located integral membrane protein that carries out the retrieval of escaped ER proteins bearing a C-terminal KDEL sequence. This occurs throughout retrograde traffic mediated by COPI-coated transport carriers. The role of the C-terminal cytoplasmic domain of the KDEL receptor in this process has been investigated. Deletion of this domain did not affect receptor subcellular localization although cells expressing this truncated form of the receptor failed to retain KDEL ligands intracellularly. Permeabilized cells incubated with ATP and GTP exhibited tubular processes-mediated redistribution from the Golgi area to the ER of the wild-type receptor, whereas the truncated form lacking the C-terminal domain remained concentrated in the Golgi. As revealed with a peptide-binding assay, this domain did not interact with both coatomer and ARF-GAP unless serine 209 was mutated to aspartic acid. In contrast, alanine replacement of serine 209 inhibited coatomer/ARF-GAP recruitment, receptor redistribution into the ER, and intracellular retention of KDEL ligands. Serine 209 was phosphorylated by both cytosolic and recombinant protein kinase A (PKA) catalytic subunit. Inhibition of endogenous PKA activity with H89 blocked Golgi-ER transport of the native receptor but did not affect redistribution to the ER of a mutated form bearing aspartic acid at position 209. We conclude that PKA phosphorylation of serine 209 is required for the retrograde transport of the KDEL receptor from the Golgi complex to the ER from which the retrieval of proteins bearing the KDEL signal depends.     

Specific IgE induced by Kudoa sp. (Myxosporea: Multivalvulida) antigens in BALB/c mice

The majority of Kudoa species infect the somatic muscle of fish establishing cysts. As there is no effective method to detect infected fish without destroying them, these parasited fish reach the consumer. We have developed this work to determine whether this parasite contains antigenic compounds capable of provoking an immune response in laboratory animals, in order to consider the possible immunopathological effects in man by the ingestion of Kudoa infected fish. BALB/c mice were injected by the subcutaneous route with the following extracts suspended in aluminium hydroxide: Group 1 (black Kudoa sp. pseudocyst extract), group 2 (white Kudoa sp. pseudocyst extract). Specific IgE levels were measured by ELISA. IgE detected in both groups 1 and 2 showed the possible allergenic nature of some of the components of the parasitic extracts.     

Longitudinal Study on the Natural Infection of Biomphalaria straminea and B. glabrata by Schistosoma mansoni in an Endemic Area of Schistosomiasis in Pernambuco,Brazil

The abundance of snail hosts and the rates of infection with Schistosoma mansoni were monitored monthly for four years in two representative localities subjected to repeated chemotherapy of infected persons. Snail abundance varied from 1.0 to 4.4 collected per person/minute/station for Biomphalaria straminea and from 0.1 to 7.0 for B. glabrata. Infection rates of snails in nature varied from 0% to 15% for the former and from 0% to 70% for the latter species. Human infection increased from 35.5% to 61.9% in the locality occupied by B. straminea, and decreased from 40.3% to 20.8% in that occupied by B. glabrata. No relationship could be detected between human infection and the snail variables. Despite seasonal variations, natural infection persisted throughout the monitoring period in both snail species. It reached remarkably high levels in B. straminea when compared to those obtained by other authors probably because of differences in methodology. It is recommended that longitudinal studies should be carried out focally and periodically to avoid underestimating the prevalence of schistosome infection in snails.     

Adhesion of B cell lines to endothelial cells from human lymphoid tissue modulates tyrosine phosphorylation and endothelial cell activation

Through the production of cytokines and growth factors the endothelium of secondary lymphoid organs plays a crucial role in controlling lymphocyte migration to the lymphoid microenvironment, an essential step in the initiation of the immune response. Here we demonstrate that direct contact of B cell lines with tonsil-derived human endothelial cells resulted in changes in the phosphorylation state of endothelial cells, causing their functional activation. We found a rapid (<15-s) and transient dephosphorylation, followed by a rapid rephosphorylation of tyrosine residues of the focal adhesion kinase, paxillin, and ERK2. Maximal rephosphorylation occurred after 15-30 min of B cell contact. Preincubation of lymphoid B cells with an adhesion-blocking Ab directed against alpha(4)beta(1) integrin abrogated adhesion-mediated changes of endothelial cell tyrosine phosphorylation, suggesting that cell contact was essential. Similar patterns of tyrosine phosphorylation, but with slightly different kinetics were induced after cross-linking of beta(1) integrin or CD40 on endothelial cells. Functional activation of endothelial cells by B cell adhesion was confirmed by the production of IL-6, IL-8, monocyte chemoattractant protein-1, M-CSF, and macrophage inflammatory protein-1beta mRNA. However, direct cross-linking of beta(1) integrin and CD40 failed to accomplish the same functional activation. These data indicate that direct contact of lymphoid B cells with the endothelium from lymphoid tissue induce endothelial cell signaling, resulting in chemokine and cytokine production. This phenomenon may provide a mechanism for the remodeling of the endothelium from lymphoid tissues, thus contributing to the free migration of lymphocytes and other cells into the lymphoid organs.     

Genome sequence of Shigella flexneri 2a: insights into pathogenicity through comparison with genomes of Escherichia coli K12 and O157

We have sequenced the genome of Shigella flexneri serotype 2a, the most prevalent species and serotype that causes bacillary dysentery or shigellosis in man. The whole genome is composed of a 4 607 203 bp chromosome and a 221 618 bp virulence plasmid, designated pCP301. While the plasmid shows minor divergence from that sequenced in serotype 5a, striking characteristics of the chromosome have been revealed. The S.flexneri chromosome has, astonishingly, 314 IS elements, more than 7-fold over those possessed by its close relatives, the non-pathogenic K12 strain and enterohemorrhagic O157:H7 strain of Escherichia coli. There are 13 translocations and inversions compared with the E.coli sequences, all involve a segment larger than 5 kb, and most are associated with deletions or acquired DNA sequences, of which several are likely to be bacteriophage-transmitted pathogenicity islands. Furthermore, S.flexneri, resembling another human-restricted enteric pathogen, Salmonella typhi, also has hundreds of pseudogenes compared with the E.coli strains. All of these could be subjected to investigations towards novel preventative and treatment strategies against shigellosis.     

Ethical Implications of Pharmacogenetics – Do Slippery Slope Arguments Matter?

Pharmacogenetics is a rapidly expanding area of research exploring the relationship between inter-individual genetic variation and drug response, with the goal of developing genetically optimised therapies. Slippery slope arguments claim that a particular action should be rejected (or supported) because it might be the first step onto a slippery slope leading to undesirable (or desirable) consequences. In this article, several slippery slope arguments relevant to the context of pharmacogenetics are evaluated under consideration of underlying reasons for their popularity. The author concludes that although the examined arguments are unconvincing as slippery slope arguments, they do matter in this context. While positive slippery slope arguments serve as a driving force to fuel the development of pharmacogenetics, their negative counterparts play an important role to sensitise policy makers and the public to potential problems.