A membrane-proximal tyrosine-based signal mediates internalization of the HIV-1 envelope glycoprotein via interaction with the AP-2 clathrin adaptor

The envelope glycoprotein (Env) of human immunodeficiency virus, type 1 (HIV-1) undergoes rapid internalization after its transport to the cell surface. Env internalization is dependent upon information contained within the cytosolic domain of the protein. Here, we report that the cytosolic domain of Env binds specifically to the medium chain, mu 2, of the clathrin-associated protein complex AP-2, as well as to the complete AP-2 complex. The Env cytosolic domain contains two highly conserved tyrosine-based motifs (Y712SPL and Y768HRL), both of which are capable of binding to mu 2 when presented as short peptides. However, only the membrane-proximal motif Y712SPL binds to mu 2 and is required for internalization in the context of the whole cytosolic domain of Env. A glycine residue (Gly711) adjacent to the Y712SPL motif is also important for binding to mu 2/AP-2 and internalization. These observations suggest that the accessibility of the membrane-proximal GY712SPL to mu 2/AP-2 determines its function as a signal for recruitment of HIV-1 Env into clathrin-coated pits and its ensuing internalization.

The highly conserved C-terminal dileucine motif in the cytosolic domain of the human immunodeficiency virus type 1 envelope glycoprotein is critical for its association with the AP-1 clathrin adaptor [correction of adapter]

Short amino acid sequences in the cytosolic domains of transmembrane proteins are recognized by specialized adaptor [corrected] proteins which are part of coated vesicles utilized to transport membrane proteins between the trans-Golgi network (TGN) and the plasma membrane (forward and backward). Previously, we and others reported that the membrane-proximal tyrosine residues Y712 (human immunodeficiency virus [HIV]) and Y721 (simian immunodeficiency virus [SIV]) in the envelope glycoprotein (Env) of the primate lentiviruses are crucial for the association of Env with clathrin-associated adaptor [corrected] complex AP-2. The same tyrosine-based endocytosis motifs in the cytosolic domains (EnvCD) of transmembrane gp41 of HIV type 1 (HIV-1) and SIV, respectively, were also shown to modulate the interaction with TGN- and endosome-based clathrin-associated complex AP-1. Our findings suggested that EnvCD binding to AP-1, unlike the association of EnvCD with AP-2, is dependent largely on residues other than Y712 and Y721. Here, we tested if motifs downstream of Y712 affect HIV-1 EnvCD-AP-1 binding and Env trafficking. Mutational analysis revealed that the C-terminal leucine-based motif in Env was crucial for the recruitment of AP-1 in vitro and in Env-expressing cells. In addition to affecting Env-AP-1 association, mutations at the C terminus of Env also altered the subcellular localization of Env, suggesting that proper post-Golgi routing of Env depends on its recruitment of AP-1. Finally, the C-terminal dileucine was shown to assist the membrane-proximal Y712 motif in restricting the cell surface expression of Env.

Relationships between CD4 independence, neutralization sensitivity, and exposure of a CD4-induced epitope in a human immunodeficiency virus type 1 envelope protein

A CD4-independent version of the X4 human immunodeficiency virus type 1 (HIV-1) HXBc2 envelope (Env) protein, termed 8x, mediates infection of CD4-negative, CXCR4-positive cells, binds directly to CXCR4 in the absence of CD4 due to constitutive exposure of a conserved coreceptor binding site in the gp120 subunit, and is more sensitive to antibody-mediated neutralization. To study the relationships between CD4 independence, neutralization sensitivity, and exposure of CD4-induced epitopes associated with the coreceptor binding site, we generated a large panel of Env mutants and chimeras between 8x and its CD4-dependent parent, HXBc2. We found that a frameshift mutation just proximal to the gp41 cytoplasmic domain in 8x Env was necessary but not sufficient for CD4 independence and led to increased exposure of the coreceptor binding site. In the presence of this altered cytoplasmic domain, single amino acid changes in either the 8x V3 (V320I) or V4/C4 (N386K) regions imparted CD4 independence, with other changes playing a modulatory role. The N386K mutation resulted in loss of an N-linked glycosylation site, but additional mutagenesis showed that it was the presence of a lysine rather than loss of the glycosylation site that contributed to CD4 independence. However, loss of the glycosylation site alone was sufficient to render Env neutralization sensitive, providing additional evidence that carbohydrate structures shield important neutralization determinants. Exposure of the CD4-induced epitope recognized by monoclonal antibody 17b and which overlaps the coreceptor binding site was highly sensitive to an R298K mutation at the base of the V3 loop and was often but not always associated with CD4 independence. Finally, while not all neutralization-sensitive Envs were CD4 independent, all CD4-independent Envs exhibited enhanced sensitivity to neutralization by HIV-1-positive human sera, indicating that the humoral immune response can exert strong selective pressure against the CD4-independent phenotype in vivo. Whether this can be used to advantage in designing more effective immunogens remains to be seen.

Differential effects of TNF and LTalpha in the host defense against M. bovis BCG

Signaling via TNF receptor type 1 (TNFR1) was shown to be crucial in host defense against the intracellular pathogens L. monocytogenes, M. tuberculosis and M. bovis. To investigate the function of TNF and LTalpha in host defense against M. bovis, mice double deficient for TNF and LTalpha (TNF / LTalpha (- / -)), TNF / LTalpha (- / -) mice complemented with a murine LTalpha transgene (TNF(- / -)) and LTalpha (- / -) mice were infected with BCG and the ensuing pathology was investigated. Control mice showed a normal host defense with early clearance of bacteria. The granulomatous reaction in the liver was accompanied by recruitment of activated macrophages characterized by their acid phosphatase positivity and differentiation into epithelioid cells as well as a coordinated expression of proinflammatory transcripts. In contrast, TNF / LTalpha (- / -) mice showed no comparable recruitment of activated macrophages in the liver. Furthermore, these mice showed extensive necrotic pulmonary lesions with massive growth of acid fast bacilli. Reintroduction of LTalpha as a transgene into TNF / LTalpha (- / -) mice prolonged survival but did not restore resistance to BCG. This, at least partially protective role of LTalpha was further supported by data demonstrating that LTalpha -deficient mice as well were susceptible to BCG infection. In contrast to the deleterious effect of TNF / LTalpha deficiency in BCG infection, BCG-infected TNF / LTalpha (- / -) mice were tolerant to LPS-induced shock. These results demonstrate that TNF as well as LTalpha are involved in murine host defense against BCG and that absence of TNF / LTalpha protects BCG-infected mice from LPS mediated shock.

Long-term results in patients treated with posterior instrumentation and fusion for degenerative scoliosis of the lumbar spine

The authors report a homogeneously investigated and surgically treated series of 40 patients with degenerative scoliosis of the lumbar spine. The series included 22 females and 18 males with a mean age of 62.8 years. The clinical presentation, the diagnostic work-up, the indication for surgery, the surgical techniques and results are reported. Final evaluation was possible in 30 patients at a mean period of observation of 59.5 months. Following a very precise diagnostic and therapeutic protocol excellent, good and satisfactory surgical results were obtained in 13 (43.3%), 16 (53.3%) and 1 (3.3%) patients, respectively. While scoliosis was converted from a mean preoperative Cobb angle of 18.7 degrees to 7.6 degrees mean pre-operative lumbar lordosis was slightly augmented from 37 degrees to 41.5 degrees. The results suggest that maintainance or correction of lumbar lordosis is more important than the conversion of the scoliotic deformity which is probably treated sufficiently by partial correction and stabilization. Observation over time indicates that the degenerative cascade evolves despite internal fixation and fusion in the majority of the patients until a stable state is reached. This stable state is probably rather the result of ankylosis of the facet joints than the effect of posterolateral fusion.

Width-dependent continuous growth of atomically thin quantum nanoribbons from nanoalloy seeds in chalcogen vapor

Nanoribbons (NRs) of atomic layer transition metal dichalcogenides (TMDs) can boost the rapidly emerging field of quantum materials owing to their width-dependent phases and electronic properties. However, the controllable downscaling of width by direct growth and the underlying mechanism remain elusive. Here, we demonstrate the vapor-liquid-solid growth of single crystal of single layer NRs of a series of TMDs (MeX2: Me = Mo, W; X = S, Se) under chalcogen vapor atmosphere, seeded by pre-deposited and respective transition metal-alloyed nanoparticles that also control the NR width. We find linear dependence of growth rate on supersaturation, known as a criterion for continues growth mechanism, which decreases with decreasing of NR width driven by the Gibbs-Thomson effect. The NRs show width-dependent photoluminescence and strain-induced quantum emission signatures with up to ≈ 90% purity of single photons. We propose the path and underlying mechanism for width-controllable growth of TMD NRs for applications in quantum optoelectronics.

[Clinical picture and diagnosis of bee-venom allergy. A comparison between skin tests and RAST determinations]

Of a group of 53 anamnestically assured bee venom allergies 81.1% positive skin tests (bee whole body extract) as well as 79% positive RAST (bee venom) could be proven. A statistical connection between skin test and clinic reaction degree, as well as between "RAST-clinic reaction degree" and "skin test--RAST" could not be found. The agreement between skin test and RAST results was of 71.7%, the positive correlation of 66%. The problem of the diagnosis and the therapy of allergy to hymenopteren stings is briefly described.

A multifunctional test mixture for chiral cyclodextrin GC columns

Gas chromatography (GC) is a powerful tool in the separation science of chiral analytes. The development of a new chiral test mixture for cyclodextrin (CD) coated GC columns allows comparing, choosing and identifying most suitable columns for a given separation challenge. This test mixture contains 12 enantiomer pairs of a broad range of functional groups and it is the first mixture suitable for all types of modified cyclodextrin capillary columns. Column changes can be observed and system performance can be monitored by means of this test mixture, which is therefore a base for reliable results. Furthermore, this publication is thought to be a start-up aid for chiral GC.

[Determination of the IgE serum level: RIST or PRIST? Results of a ring test in Switzerland]

Serum IgE concentrations, determined by two commercial kits (Phadebas RIST and PRIST) in 93 adult controls resulted in a geometrical mean value of 47 (RIST) and 35 U/ml (PRIST) respectively within a + 2 SD value of 195 and 331 U/ml respectively. The difference between the separated random samples is statistically significant (t = 3.79; p less than 1%), but the correlation is still fairly satisfactory (r = 0.79). In the lower regions the IgE values with RIST are as a rule a little higher than with the PRIST method. Surprisingly, one patient showed an extremely low IgE value (7 U/ml) with PRIST, but a considerably higher one (530 U/ml) with RIST. Such marked differences are found occasionally in the literature: heterophile antibodies against bovine gammaglobulin are regarded as responsible for the interference in the Sephadex system of RIST. As the reproducibility of the IgE determinations with the PRIST method is excellent (the correlation coefficient for two PRIST determinations was r = 0.93), and as PRIST allows much lower IgE estimates, this procedure should be given preference, particularly in pediatric patients. On the other hand, RIST must be used for the determination of extremely high values, as for instance in patients with severe atopic dermatitis or with parasitic infestations. In fact they can no longer be exactly evaluated by PRIST. Quality control of IgE serum determinations among twelve randomly chosen laboratories in Switzerland in 5 patients was satisfactory, with one exception. In the case of extremely high values, however, only a few laboratories try to determine the exact value. Indications of more than 500 U/ml were considered sufficient, with actual values amounting to 12,500 U/ml. It is also advisable to standardize the serum dilutions, the use of reference serum and the price. Finally, the indications for IgE determination are discussed. It is considered to have an important bearing on the differential diagnosis and prognosis of atopic diseases in infants and children.

Socio-economically deprived families’ routes to family-based addiction prevention services

Background

Families living in poor socio-economic circumstances, already confronted with social and health inequalities, are often not reached by family-based addiction prevention programmes. Besides quantitative models and health literacy approaches, qualitative research is lacking that could shed light on the exact circumstances and processes that lead to hindered addiction prevention service uptake by these families. Drawing on the concept of 'candidacy', we aimed to reconstruct how socio-economically deprived parents and their (pre-)adolescent children in German-speaking Switzerland identify their candidacy for family-based addiction prevention services.

Methods

Following grounded theory, we collected and analysed data in an iterative-cyclical manner using theoretical sampling and theoretical coding techniques. Sixteen families with children aged 10-14 years were interviewed in depth (parent/s and one child separately). All but one family lived below the at-risk-of poverty threshold.

Results

Families' modes of recognising and handling problems in everyday life were found to be core phenomena that structure the process towards (non-)identification of candidacy for family-based addiction prevention services. Further, thematic relevance of addiction prevention, past experience with offers, integration in systems of assistance (social welfare, etc.), strategies to protect the family, and parents' search movements for support were important for families' identification of candidacy.

Conclusions

Socio-economically deprived families are not a homogeneous group. They differ in modes of problem construction and handling in everyday life; this differently opens up or closes routes to family-based addiction prevention services. Policy and practice should build on a bundle of diverse strategies for outreach to these vulnerable families.

Key messages

Our qualitative study adds scientific knowledge to a better understanding of socio-economically deprived families’ complex routes to family-based addiction prevention services. Results provide evidence that policy and practice should build on a bundle of diverse strategies to reach these vulnerable families. Equity in access to services can thus be improved.