Limited HIV Infection of Central Memory and Stem Cell Memory CD4+ T Cells Is Associated with Lack of Progression in Viremic Individuals

A rare subset of HIV-infected individuals, designated viremic non-progressors (VNP), remain asymptomatic and maintain normal levels of CD4+ T-cells despite persistently high viremia. To identify mechanisms potentially responsible for the VNP phenotype, we compared VNPs (average >9 years of HIV infection) to HIV-infected individuals who have similar CD4+ T-cell counts and viral load, but who are likely to progress if left untreated (“putative progressors”, PP), thus avoiding the confounding effect of differences related to substantial CD4+ T cell depletion. We found that VNPs, compared to PPs, had preserved levels of CD4+ stem cell memory cells (T_SCM (p<0.0001), which was associated with decreased HIV infection of these cells in VNPs (r = −0.649, p = 0.019). In addition, VNPs had decreased HIV infection in CD4+ central memory (T_CM) cells (p = 0.035), and the total number of T_CM cells was associated with increased proliferation of memory CD4+ T cells (r = 0.733, p = 0.01). Our results suggest that, in HIV-infected VNPs, decreased infection of CD4+ T_CM and T_SCM, cells are involved in preservation of CD4+ T cell homeostasis and lack of disease progression despite high viremia.     

Absence of cross-presenting cells in the salivary gland and viral immune evasion confine cytomegalovirus immune control to effector CD4 T cells

Horizontal transmission of cytomegaloviruses (CMV) occurs via prolonged excretion from mucosal surfaces. We used murine CMV (MCMV) infection to investigate the mechanisms of immune control in secretory organs. CD4 T cells were crucial to cease MCMV replication in the salivary gland (SG) via direct secretion of IFNγ that initiated antiviral signaling on non-hematopoietic cells. In contrast, CD4 T cell helper functions for CD8 T cells or B cells were dispensable. Despite SG-resident MCMV-specific CD8 T cells being able to produce IFNγ, the absence of MHC class I molecules on infected acinar glandular epithelial cells due to viral immune evasion, and the paucity of cross-presenting antigen presenting cells (APCs) prevented their local activation. Thus, local activation of MCMV-specific T cells is confined to the CD4 subset due to exclusive presentation of MCMV-derived antigens by MHC class II molecules on bystander APCs, resulting in IFNγ secretion interfering with viral replication in cells of non-hematopoietic origin.     

Distinct Role of Pyk2 in Mediating Thromboxane Generation Downstream of Both G12/13 and Integrin αIIbβ3 in Platelets

Proline-rich tyrosine kinase 2 (Pyk2) is activated by various agonists in platelets. We evaluated the signaling mechanism and the functional role of Pyk2 in platelets by using pharmacological inhibitors and Pyk2-deficient platelets. We found that platelet aggregation and secretion in response to 2-methylthio-ADP (2-MeSADP) and AYPGKF were diminished in the presence of Pyk2 inhibitors or in Pyk2-deficient platelets, suggesting that Pyk2 plays a positive regulatory role in platelet functional responses. It has been shown that ADP-, but not thrombin-induced thromboxane (TxA₂) generation depends on integrin signaling. Unlike ADP, thrombin activates G_12/13 pathways, and G_12/13 pathways can substitute for integrin signaling for TxA₂ generation. We found that Pyk2 was activated downstream of both G_12/13 and integrin-mediated pathways, and both 2-MeSADP- and AYPGKF-induced TxA₂ generation was significantly diminished in Pyk2-deficient platelets. In addition, TxA₂ generation induced by co-stimulation of G_i and G_z pathways, which is dependent on integrin signaling, was inhibited by blocking Pyk2. Furthermore, inhibition of 2-MeSADP-induced TxA₂ generation by fibrinogen receptor antagonist was not rescued by co-stimulation of G_12/13 pathways in the presence of Pyk2 inhibitor. We conclude that Pyk2 is a common signaling effector downstream of both G_12/13 and integrin αIIbβ3 signaling, which contributes to thromboxane generation.     

Arylglycine derivatives as potent transient receptor potential melastatin 8 (TRPM8) antagonists

A series of arylglycine-based analogs was synthesized and tested for TRPM8 antagonism in a cell-based functional assay. Following structure–activity relationship studies in vitro, a number of compounds were identified as potent TRPM8 antagonists and were subsequently evaluated in an in vivo pharmacodynamic assay of icilin-induced ‘wet-dog’ shaking in which compound 12 was fully effective. TRPM8 antagonists of the type described here may be useful in treating pain conditions wherein cold hypersensitivity is a dominant feature.     

Cytokinin promotes flowering of Arabidopsis via transcriptional activation of the FT paralogue TSF

Cytokinins are involved in many aspects of plant growth and development, and physiological evidence also indicates that they have a role in floral transition. In order to integrate these phytohormones into the current knowledge of genetically defined molecular pathways to flowering, we performed exogenous treatments of adult wild type and mutant Arabidopsis plants, and analysed the expression of candidate genes. We used a hydroponic system that enables synchronous growth and flowering of Arabidopsis, and allows the precise application of chemicals to the roots for defined periods of time. We show that the application of N⁶‐benzylaminopurine (BAP) promotes flowering of plants grown in non‐inductive short days. The response to cytokinin treatment does not require FLOWERING LOCUS T (FT), but activates its paralogue TWIN SISTER OF FT (TSF), as well as FD, which encodes a partner protein of TSF, and the downstream gene SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1). Treatment of selected mutants confirmed that TSF and SOC1 are necessary for the flowering response to BAP, whereas the activation cascade might partially act independently of FD. These experiments provide a mechanistic basis for the role of cytokinins in flowering, and demonstrate that the redundant genes FT and TSF are differently regulated by distinct floral‐inducing signals.     

Behavioral correlates of extra-pair copulation in Indri indri

Active pursuit of extra-pair mating has been reported for Indri indri, the socially monogamous largest living lemur. This study, conducted in a mountain rainforest in eastern Madagascar, presents the first evidence for extra-pair mating of indri and discusses the alternative mating strategy and alteration of the social, territorial, spatial, and vocal behavior of the adult female of a group of wild indris. Further studies may investigate whether extra-pair copulation is an attempt to breed with a partner of superior quality and thus lead to extra-pair paternity. If so, it could potentially play a role in maintaining genetic variability within a population.     

SNX12 role in endosome membrane transport

In this paper, we investigated the role of sorting nexin 12 (SNX12) in the endocytic pathway. SNX12 is a member of the PX domain-containing sorting nexin family and shares high homology with SNX3, which plays a central role in the formation of intralumenal vesicles within multivesicular endosomes. We found that SNX12 is expressed at very low levels compared to SNX3. SNX12 is primarily associated with early endosomes and this endosomal localization depends on the binding to 3-phosphoinositides. We find that overexpression of SNX12 prevents the detachment (or maturation) of multivesicular endosomes from early endosomes. This in turn inhibits the degradative pathway from early to late endosomes/lysosomes, much like SNX3 overexpression, without affecting endocytosis, recycling and retrograde transport. In addition, while previous studies showed that Hrs knockdown prevents EGF receptor sorting into multivesicular endosomes, we find that overexpression of SNX12 restores the sorting process in an Hrs knockdown background. Altogether, our data show that despite lower expression level, SNX12 shares redundant functions with SNX3 in the biogenesis of multivesicular endosomes.     

Targeting of the small GTPase Rap2b, but not Rap1b, to lipid rafts is promoted by palmitoylation at Cys176 and Cys177 and is required for efficient protein activation in human platelets

Rap1b and Rap2b are the only members of the Rap family of GTPases expressed in circulating human platelets. Rap1b is involved in the inside-out activation of integrins, while the role of Rap2b is still poorly understood. In this work, we investigated the localization of Rap proteins to specific microdomains of plasma membrane called lipid rafts, implicated in signal transduction. We found that Rap1b was not associated to lipid rafts in resting platelets, and did not translocate to these microdomains in stimulated cells. By contrast, about 20% of Rap2b constitutively associated to lipid rafts, and this percentage did not increase upon platelet stimulation. Rap2b interaction with lipid rafts also occurred in transfected HEK293T cell. Upon metabolic labelling with [(3)H]palmitate, incorporation of the label into Rap2b was observed. Palmitoylation of Rap2b did not occur when Cys176 or Cys177 were mutated to serine, or when the C-terminal CAAX motif was deleted. Contrary to CAAX deletion, Cys176 and Cys177 substitution did not alter the membrane localization of Rap2b, however, relocation of the mutants within lipid rafts was completely prevented. In intact platelets, disruption of Rap2b interaction with lipid rafts obtained by cholesterol depletion caused a significant inhibition of aggregation. Importantly, agonist-induced activation of Rap2b was concomitantly severely impaired. These results demonstrate that Rap2b, but not the more abundant Rap1b, is associated to lipid rafts in human platelets. This interaction is supported by palmitoylation of Rap2b, and is important for a complete agonist-induced activation of this GTPase.     

Sexually dimorphic phrase organization in the song of the indris (Indri indri)

Animal acoustic communication often takes the form of complex sequences, composed of multiple distinct acoustic units, which can vary in their degree of stereotypy. Studies of sequence variation may contribute to our understanding of the structural flexibility of primates' songs, which can provide essential ecological and behavioral information about variability at the individual, population, and specific level and provide insights into the mechanisms and drivers responsible for the evolutionary change of communicative traits. Several methods have been used for investigating different levels of structural information and sequence similarity in acoustic displays. We studied intra and interindividual variation in the song structuring of a singing primate, the indri (Indri indri), which inhabits the montane rain forests of Madagascar. Indri groups emit duets and choruses in which they combine long notes, short single units, and phrases consisting of a variable number of units (from two to six) with slightly descending frequency. Males' and females' contributions to the song differ in the temporal and frequency structure of song units and repertoire size. We calculated the similarity of phrase organization across different individual contributions using the Levenshtein distance, a logic distance that expressed the minimum cost to convert a sequence into another and can measure differences between two sequences of data. We then analyzed the degree of similarity within and between individuals and found that: (a) the phrase structure of songs varied between reproductive males and females: female structuring of the song showed a higher number of phrases if compared to males; (b) male contributions to the song were overall more similar to those of other males than were female contributions to the song of other females; (c) male contributions were more stereotyped than female contributions, which showed greater individual flexibility. The picture emerging from phrase combinatorics in the indris is in agreement with previous findings of rhythmic features and song repertoire size of the indris, which also suggested that female songs are potentially less stereotyped than those of males.