MicroRNAs modulate immunological and inflammatory responses in Holstein cattle naturally infected with Mycobacterium avium subsp. paratuberculosis.

MicroRNAs (miRNAs) regulate the post-transcriptional expression of genes by binding to their target mRNAs. In this study, whole miRNA sequencing was used to compare the expression of miRNAs in ileocecal valve (ICV) and peripheral blood (PB) samples of cows with focal or diffuse paratuberculosis (PTB)-associated lesions in gut tissues versus (vs) control cows without lesions. Among the eight miRNAs differentially expressed in the PB samples from cows with diffuse lesions vs controls, three (miR-19a, miR-144, miR32) were also down-regulated in cows with diffuse vs focal lesions. In the ICV samples, we identified a total of 4, 5, and 18 miRNAs differentially expressed in cows with focal lesions vs controls, diffuse lesions vs controls, and diffuse vs focal lesions, respectively. The differential expression of five microRNAs (miR-19a, miR-144, miR-2425-3p, miR-139, miR-101) was confirmed by RT-qPCR. Next, mRNA target prediction was performed for each differentially expressed miRNA. A functional analysis using the predicted gene targets revealed a significant enrichment of the RNA polymerase and MAPK signaling pathways in the comparison of cows with focal vs no lesions and with diffuse vs focal lesions, respectively. The identified miRNAs could be used for the development of novel diagnostic and therapeutical tools for PTB control.

Population structure of OXA-48-producing Klebsiella pneumoniae ST405 isolates during a hospital outbreak characterised by genomic typing.

OBJECTIVES: The aim of this study was to investigate the structure of a broad and sustained hospital outbreak of OXA-48-producing Klebsiella pneumoniae (KpO48) belonging to sequence type 405 (ST405). METHODS: Whole-genome sequencing and comparison of ten ST405 KpO48 isolates obtained from clinical samples in our hospital was performed. Using stringent criteria, 36 single nucleotide polymorphisms (SNPs) were detected (range 0-21 in pairwise comparisons), and allele-specific PCR was used to call the SNPs among a larger set of isolates. RESULTS: Several haplotypes were identified within the population. The haplotypes did not show a spatial structure, but a temporal evolution of sequential haplotype replacements was observed. CONCLUSIONS: The dispersed spatial distribution suggests a reservoir formed by a large pool of colonised patients, and the temporal replacement pattern suggests that the sustained outbreak was composed of several small outbreaks that appeared and rapidly dispersed to several units.

ALCAM/CD166 adhesive function is regulated by the tetraspanin CD9.

ALCAM/CD166 is a member of the immunoglobulin superfamily of cell adhesion molecules (Ig-CAMs) which mediates intercellular adhesion through either homophilic (ALCAM-ALCAM) or heterophilic (ALCAM-CD6) interactions. ALCAM-mediated adhesion is crucial in different physiological and pathological phenomena, with particular relevance in leukocyte extravasation, stabilization of the immunological synapse, T cell activation and proliferation and tumor growth and metastasis. Although the functional implications of ALCAM in these processes is well established, the mechanisms regulating its adhesive capacity remain obscure. Using confocal microscopy colocalization, and biochemical and functional analyses, we found that ALCAM directly associates with the tetraspanin CD9 on the leukocyte surface in protein complexes that also include the metalloproteinase ADAM17/TACE. The functional relevance of these interactions is evidenced by the CD9-induced upregulation of both homophilic and heterophilic ALCAM interactions, as reflected by increased ALCAM-mediated cell adhesion and T cell migration, activation and proliferation. The enhancement of ALCAM function induced by CD9 is mediated by a dual mechanism involving (1) augmented clustering of ALCAM molecules, and (2) upregulation of ALCAM surface expression due to inhibition of ADAM17 sheddase activity.

The sheddase activity of ADAM17/TACE is regulated by the tetraspanin CD9.

ADAM17/TACE is a metalloproteinase responsible for the shedding of the proinflammatory cytokine TNF-α and many other cell surface proteins involved in development, cell adhesion, migration, differentiation, and proliferation. Despite the important biological function of ADAM17, the mechanisms of regulation of its metalloproteinase activity remain largely unknown. We report here that the tetraspanin CD9 and ADAM17 partially co-localize on the surface of endothelial and monocytic cells. In situ proximity ligation, co-immunoprecipitation, crosslinking, and pull-down experiments collectively demonstrate a direct association between these molecules. Functional studies reveal that treatment with CD9-specific antibodies or neoexpression of CD9 exert negative regulatory effects on ADAM17 sheddase activity. Conversely, CD9 silencing increased the activity of ADAM17 against its substrates TNF-α and ICAM-1. Taken together, our results show that CD9 associates with ADAM17 and, through this interaction, negatively regulates the sheddase activity of ADAM17.

The tetraspanin CD9 inhibits the proliferation and tumorigenicity of human colon carcinoma cells.

The implication of the tetraspanin CD9 in cancer has received much recent attention and an inverse correlation between CD9 expression and the metastatic potential and cancer survival rate has been established for different tumor types. In contrast to the well-established role of CD9 in metastasis, very little is known about the involvement of this tetraspanin in the process of development of primary tumors. In the present study, we present evidence on the implication of CD9 in colon carcinoma tumorigenesis. We report here that ectopic expression of CD9 in colon carcinoma cells results in enhanced integrin-dependent adhesion and inhibition of cell growth. Consistently with these effects, treatment of these cells with anti-CD9-specific antibodies resulted in (i) increased beta1 integrin-mediated cell adhesion through a mechanism involving clustering of integrin molecules rather than altered affinity; (ii) induction of morphological changes characterized by the acquisition of an elongated cell phenotype; (iii) inhibition of cell proliferation with no significant effect on cell survival; (iv) increased expression of membrane TNF-alpha, and finally (v) inhibition of the in vivo tumorigenic capacity in nude mice. In addition, through the use of selective blockers of TNF-alpha, we have demonstrated that this cytokine partly mediates the antiproliferative effects of CD9. These results clearly establish for the first time a role for CD9 in the tumorigenic process.

Activation pathways of alpha4beta1 integrin leading to distinct T-cell cytoskeleton reorganization, Rac1 regulation and Pyk2 phosphorylation.

Alpha4beta1 integrin is highly expressed in lymphocytes and is essential in hematopoiesis, extravasation, and the inflammatory response. Alpha4beta1 can be activated by intracellular signals elicited upon T-cell activation by phorbol esters, CD3 crosslinking, or certain chemokine/receptor interactions (inside-out activation). Divalent cations or certain anti-beta1 mAbs (i.e., TS2/16) can also bind and activate integrins directly (outside-in activation). In both cases, activation results in increased adhesion and/or affinity for ligands. It is not known if these various stimuli produce the same or different post-adhesion events. To address this, we have studied the cytoskeleton organization and intracellular signaling following activation of 41 in Jurkat cells and in human T-lymphoblasts. Treatment with Mn2+, alpha-CD3 mAb or the chemokine SDF-1alpha followed by attachment to the fibronectin fragment H89 or the endothelial molecule VCAM-1 (alpha4beta1 ligands), resulted in cell polarization and migration. In contrast, activation with PMA or TS2/16 induced cell spreading and strong adherence. Video microscopy and Transwell analyses confirmed these results, which correlated with different resistance to detachment under flow. Activation of the small GTPase RhoA or transfection with the constitutively active mutants V14RhoA or V12Rac1, abolished the alpha4beta1-induced cell polarization but did not affect cell spreading. Moreover, Rac1 activity was distinctly modulated by agents that induce a polarized or spread phenotype. The tyrosine kinase Pyk2 was highly phosphorylated upon induction of cell polarity but not during cell spreading. These results reveal novel properties of alpha4beta1 integrin, namely the ability to trigger two types of T-cell cytoskeletal response with different signaling requirements.

Endothelial tetraspanin microdomains regulate leukocyte firm adhesion during extravasation.

Tetraspanins associate with several transmembrane proteins forming microdomains involved in intercellular adhesion and migration. Here, we show that endothelial tetraspanins relocalize to the contact site with transmigrating leukocytes and associate laterally with both intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). Alteration of endothelial tetraspanin microdomains by CD9-large extracellular loop (LEL)-glutathione S-transferase (GST) peptides or CD9/CD151 siRNA oligonucleotides interfered with ICAM-1 and VCAM-1 function, preventing lymphocyte transendothelial migration and increasing lymphocyte detachment under shear flow. Heterotypic intercellular adhesion mediated by VCAM-1 or ICAM-1 was augmented when expressed exogenously in the appropriate tetraspanin environment. Therefore, tetraspanin microdomains have a crucial role in the proper adhesive function of ICAM-1 and VCAM-1 during leukocyte adhesion and transendothelial migration.

A functionally relevant conformational epitope on the CD9 tetraspanin depends on the association with activated beta1 integrin.

Tetraspanins associate on the cell membrane with several transmembrane proteins, including members of the integrin superfamily. The tetraspanin CD9 has been implicated in cell motility, metastasis, and sperm-egg fusion. In this study we characterize the first CD9 conformation-dependent epitope (detected by monoclonal antibody (mAb) PAINS-13) whose expression depends on changes in the activation state of associated beta(1) integrins. MAb PAINS-13 precipitates CD9 under conditions that preserve the association of this tetraspanin with integrins, but not under conditions that disrupt these interactions. Induction of activation of beta(1) integrins by temperature, divalent cation Mn(2+), or mAb TS2/16 correlated with enhanced expression of the PAINS-13 epitope on a variety of cells. Through the use of different K562 myeloid leukemia transfectant cells expressing specific members of the beta(1) integrin subfamily we show that the expression of the PAINS-13 epitope depends on CD9 association with alpha(6)beta(1) integrin. The mAb PAINS-13 reactivity has been mapped to the CD9 region comprising residues 112-154 in the NH(2) half of the large extracellular loop. Also, we show that the CD9 conformation recognized by mAb PAINS-13 is functionally relevant in beta(1) integrin-mediated cellular processes including wound healing migration, tubular morphogenesis, cell adhesion and spreading and in signal transduction involving phosphatidylinositol 3-kinase activation.