Biology subjects

Kartvelishvily, E.

Publications and source records attributed to Kartvelishvily, E..

4 recordsLinked to original sources

bioRxiv2020

Hyaluronan-NK cell Interaction Controls the Primary Vascular Barrier during Early Pregnancy

Successful implantation is associated with a unique spatial pattern of vascular remodeling, characterized by profound peripheral neo-vascularization surrounding a peri-embryo avascular niche. We hypothesized that hyaluronan controls the formation of the unique vascular pattern encompassing the embryo. This hypothesis was evaluated by genetic modification of hyaluronan metabolism specifically targeted to embryonic trophoblast cells. The outcome of altered hyaluronan deposition on uterine vascular remodeling and post-implantation development were analyzed by MRI, detailed histological examinations, and RNA-sequencing of uterine NK cells. Our experiments revealed that eliminating the anti-angiogenic hyaluronan, led to elevated expression of MMP-9, VEGF-A and its receptor VEGFR-2, accompanied by reduced recruitment of uterine NK cells. Further local decrease in VEGFR-3 resulted in impaired formation of vascular sinuous folds, ectopic angiogenesis and dysfunctional uterine NK cells. Conversely, enhanced deposition of hyaluronan caused the expansion of the maternal-embryo barrier, leading to an increased diffusion distance and aborted implantation. These results demonstrate a pivotal role for hyaluronan in successful pregnancy by fine-tuning the peri-embryo avascular niche and maternal vascular morphogenesis.

developmental biology↗

bioRxiv2020

A novel calcium-concentrating compartment drives biofilm formation and persistent infections

In nature, bacteria reside in biofilms - multicellular differentiated communities held together by extracellular matrix. In this work, we identified a novel subpopulation essential for biofilm formation - mineral-forming cells. This subpopulation contains an intracellular calcium-accumulating niche, in which the formation of a calcium carbonate mineral is initiated. As the biofilm colony develops, this mineral grows in a controlled manner, forming a functional macrostructure that serves the entire community. The molecular mechanisms promoting calcite scaffold formation were conserved between three distant phyla - the Gram-positive Bacillus subtilis, Gram-negative Pseudomonas aeruginosa and the actinobacterium Mycobacterium abscessus. Biofilm development of all three species was similarly impaired by inhibition of calcium uptake and carbonate accumulation. Moreover, chemical inhibition and mutations targeting mineralization both significantly reduced the attachment of P. aeruginosa to the lung, as well as the subsequent damage inflicted by biofilms to lung tissues, and restored their sensitivity to antibiotics. The evolutionary conserved cellular pathway controlling the fundamental feature of biofilm development uncovered in this work offers novel druggable targets for antibiotics to combat otherwise untreatable biofilm infections.

microbiology↗

bioRxiv2019

ERM-Dependent Assembly of T-Cell Receptor Signaling and Co-stimulatory Molecules on Microvilli Prior to Activation

SummaryT-cell surfaces are covered with microvilli, actin-rich and flexible protrusions. We use super-resolution microscopy to show that [≥]90% T-cell receptor (TCR) complex molecules TCR{beta} and TCR{zeta}, as well as the co-receptor CD4 and the co-stimulatory molecule CD2 reside on microvilli of human T cells. Furthermore, TCR proximal signaling molecules involved in the initial stages of the immune response, such as the protein tyrosine kinase Lck and the key adaptor molecule LAT, are also enriched on microvilli. Notably, phosphorylated proteins of the ERM (ezrin, radixin, moesin) family colocalize with these heterodimers as well as with actin filaments within the microvilli of resting T cells. This finding implies a role for one or more phosphorylated ERMs in linking the TCR complex to the actin cytoskeleton within microvilli. Indeed, expression of a dominant-negative ezrin fragment effectively redistributes TCR molecules over the whole T cell surface. Our results establish microvilli as key signaling hubs, in which the TCR complex and its proximal signaling molecules and adaptors are pre-assembled prior to activation in an ERM-dependent manner. The preformed positioning of these actin-binding TCR assemblies on individual microvilli can facilitate the local transmission of TCR signals seconds after TCR occupancy and impacts the slower subsequent events that lead to the assembly of immunological synapses.

immunology↗

bioRxiv2018

Bacterial virulence against an oceanic bloom-forming phytoplankter is mediated by algal DMSP

Emiliania huxleyi is a bloom forming microalga that impacts the global sulfur cycle by producing large amounts of dimethylsulfoniopropionate (DMSP) and its volatile metabolic product dimethyl sulfide (DMS). Top-down regulation of E. huxleyi blooms is attributed to viruses and grazers, however, the possible involvement of algicidal bacteria in bloom demise is still elusive. We isolated from a North Atlantic E. huxleyi bloom a Roseobacter strain, Sulfitobacter D7, which exhibited algicidal effects against E. huxleyi upon co-culturing. Both the alga and the bacterium were found to co-occur during a natural E. huxleyi bloom, therefore establishing this host-pathogen system as an attractive, ecologically relevant model for studying alga-bacterium interaction in the oceans. During interaction, Sulfitobacter D7 consumed and metabolized algal DMSP to produce high amounts of methanethiol, an alternative product of DMSP catabolism. We revealed a unique strain-specific response, in which E. huxleyi strains that exuded higher amounts of DMSP were more susceptible to Sulfitobacter D7 infection. Intriguingly, exogenous application of DMSP enhanced bacterial virulence and induced susceptibility in a resistant algal strain to the bacterial pathogen. This DMSP-dependent pathogenicity was highly specific as compared to supplementation of propionate and glycerol. We propose a novel function for DMSP, in addition to its central role in mutualistic interactions, as a mediator of bacterial virulence that may regulate E. huxleyi blooms.

microbiology↗