generation-identification-gm-csf-derived-alveolar-like-macrophages

Generation and Identification of GM-CSF Derived Alveolar-like Macrophages and Dendritic Cells From Mouse Bone Marrow

Macrophages and dendritic cells (DCs) are innate immune cells found in tissues and lymphoid organs that play a key role in the defense against pathogens. ...

University of British Columbia

Rhodococcus sp. strain RHA1, a potent polychlorinated-biphenyl (PCB)-degrading strain, contains three linear plasmids ranging in size from 330 to 1,100 kb. As part of a genome sequencing project, we report here the complete sequence and characterization of the smallest and least-well-characterized of the RHA1 plasmids, pRHL3. The plasmid is an actinomycete invertron, containing large terminal inverted repeats with a tightly associated protein and a predicted open reading frame (ORF) that is similar to that of a mycobacterial rep gene. The pRHL3 plasmid has 300 putative genes, almost 21% of which are predicted to have a catabolic function. Most of these are organized into three clusters. One of the catabolic clusters was predicted to include limonene degradation genes. Consistent with this prediction, RHA1 grew on limonene, carveol, or carvone as the sole carbon source. The plasmid carries three cytochrome P450-encoding (CYP) genes, a finding consistent with the high number of CYP genes found in other actinomycetes. Two of the CYP genes appear to belong to novel families; the third belongs to CYP family 116 but appears to belong to a novel class based on the predicted domain structure of its reductase. Analyses indicate that pRHL3 also contains four putative "genomic islands" (likely to have been acquired by horizontal transfer), insertion sequence elements, 19 transposase genes, and a duplication that spans two ORFs. One of the genomic islands appears to encode resistance to heavy metals. The plasmid does not appear to contain any housekeeping genes. However, each of the three catabolic clusters contains related genes that appear to be involved in glucose metabolism.

Functional characterization of a catabolic plasmid from polychlorinated- biphenyl-degrading Rhodococcus sp. strain RHA1.

Genomic and proteomic approaches were used to investigate phthalate and benzoate catabolism in Rhodococcus sp. strain RHA1, a polychlorinated biphenyl-degrading actinomycete. Sequence analyses identified genes involved in the catabolism of benzoate (ben) and phthalate (pad), the uptake of phthalate (pat), and two branches of the beta-ketoadipate pathway (catRABC and pcaJIHGBLFR). The regulatory and structural ben genes are separated by genes encoding a cytochrome P450. The pad and pat genes are contained on a catabolic island that is duplicated on plasmids pRHL1 and pRHL2 and includes predicted terephthalate catabolic genes (tpa). Proteomic analyses demonstrated that the beta-ketoadipate pathway is functionally convergent. Specifically, the pad and pat gene products were only detected in phthalate-grown cells. Similarly, the ben and cat gene products were only detected in benzoate-grown cells. However, pca-encoded enzymes were present under both growth conditions. Activity assays for key enzymes confirmed these results. Disruption of pcaL, which encodes a fusion enzyme, abolished growth on phthalate. In contrast, after a lag phase, growth of the mutant on benzoate was similar to that of the wild type. Proteomic analyses revealed 20 proteins in the mutant that were not detected in wild-type cells during growth on benzoate, including a CatD homolog that apparently compensated for loss of PcaL. Analysis of completed bacterial genomes indicates that the convergent beta-ketoadipate pathway and some aspects of its genetic organization are characteristic of rhodococci and related actinomycetes. In contrast, the high redundancy of catabolic pathways and enzymes appears to be unique to RHA1 and may increase its potential to adapt to new carbon sources.

Catabolism of benzoate and phthalate in Rhodococcus sp. strain RHA1: redundancies and convergence.

Rhodococcus sp. RHA1 (RHA1) is a potent polychlorinated biphenyl-degrading soil actinomycete that catabolizes a wide range of compounds and represents a genus of considerable industrial interest. RHA1 has one of the largest bacterial genomes sequenced to date, comprising 9,702,737 bp (67% G+C) arranged in a linear chromosome and three linear plasmids. A targeted insertion methodology was developed to determine the telomeric sequences. RHA1's 9,145 predicted protein-encoding genes are exceptionally rich in oxygenases (203) and ligases (192). Many of the oxygenases occur in the numerous pathways predicted to degrade aromatic compounds (30) or steroids (4). RHA1 also contains 24 nonribosomal peptide synthase genes, six of which exceed 25 kbp, and seven polyketide synthase genes, providing evidence that rhodococci harbor an extensive secondary metabolism. Among sequenced genomes, RHA1 is most similar to those of nocardial and mycobacterial strains. The genome contains few recent gene duplications. Moreover, three different analyses indicate that RHA1 has acquired fewer genes by recent horizontal transfer than most bacteria characterized to date and far fewer than Burkholderia xenovorans LB400, whose genome size and catabolic versatility rival those of RHA1. RHA1 and LB400 thus appear to demonstrate that ecologically similar bacteria can evolve large genomes by different means. Overall, RHA1 appears to have evolved to simultaneously catabolize a diverse range of plant-derived compounds in an O(2)-rich environment. In addition to establishing RHA1 as an important model for studying actinomycete physiology, this study provides critical insights that facilitate the exploitation of these industrially important microorganisms.

The complete genome of Rhodococcus sp. RHA1 provides insights into a catabolic powerhouse.

Mycothiol (1d-myo-inosityl 2-[N-acetyl-L-cysteinyl]amido-2-deoxy-alpha-D-glucopyranoside) is an important microbial thiol present only in actinomycetes. Rhodococcus jostii RHA1 degrades a wide range of xenobiotics, including polychlorinated biphenyls, nitriles and N-nitrosodimethylamine. Analyses revealed that this strain produces two thiols, mycothiol and ergothioneine, found in the other actinomycetes. A mycothiol ligase mutant strain of R. jostii RHA1 deficient in the production of mycothiol was constructed. This mutant has a number of interesting characteristics: (a) it overproduces the intermediate glucosamine-inositol (1-O-(2-amino-1-deoxy-alpha-D-glucopyranosyl)-D-myo-inositol); (b) it is deficient in the biochemical degradation of a number of xenobiotics metabolized by the parent strain; (c) it shows increased susceptibility to a number of antibiotics; and (d) it shows unusual growth characteristics, exhibiting a long lag phase before normal exponential growth. The diverse phenotypes of the mutant indicate the utility of R. jostii RHA1 as a model for deciphering the various functions of mycothiol.

Characterization of a mycothiol ligase mutant of Rhodococcus jostii RHA1.

CD44 is expressed on T cells where its ability to bind hyaluronan is tightly regulated. Here, we investigated when T cells bind hyaluronan during an immune response. We found that naïve, murine T cells do not bind fluoresceinated hyaluronan but are induced to bind upon antigen-induced T-cell activation in vitro and in vivo. Hyaluronan binding occurred on proliferating T cells and the percentage of hyaluronan-binding cells correlated with the strength of the activation stimulus. A small percentage of hyaluronan-binding cells persisted after in vitro activation and had a memory phenotype (CD122(+) CD44(hi)). This hyaluronan-binding population increased after culture with IL-7 or IL-15 and proliferated more rapidly than nonbinding cells. In vivo, approximately 20-30% of antigen-specific OT-I CD8(+) memory T cells in the spleen and BM bound hyaluronan. Hyaluronan binding identified memory cells that proliferated faster in IL-7 and IL-15, and enriched for CD62L(+) central memory cells. In vivo homeostatic proliferation induced hyaluronan binding on a small percentage of the most rapidly dividing cells after several cell divisions. This study demonstrates that hyaluronan binding is induced upon antigen-induced T-cell activation and occurs on a percentage of the most proliferative activated and memory T cells.

Hyaluronan binding identifies the most proliferative activated and memory T cells.

Rhodococcus jostii RHA1, a catabolically diverse soil actinomycete, is highly resistant to long-term nutrient starvation. After 2 years of carbon starvation, 10% of the bacterial culture remained viable. To study the molecular basis of such resistance, we monitored the abundance of about 1,600 cytosolic proteins during a 2-week period of carbon source (benzoate) starvation. Hierarchical cluster analysis elucidated 17 major protein clusters and showed that most changes occurred during transition to stationary phase. We identified 196 proteins. A decrease in benzoate catabolic enzymes correlated with benzoate depletion, as did induction of catabolism of alternative substrates, both endogenous (lipids, carbohydrates, and proteins) and exogenous. Thus, we detected a transient 5-fold abundance increase for phthalate, phthalate ester, biphenyl, and ethyl benzene catabolic enzymes, which coincided with at least 4-fold increases in phthalate and biphenyl catabolic activities. Stationary-phase cells demonstrated an ∼250-fold increase in carbon monoxide dehydrogenase (CODH) concurrent with a 130-fold increase in CODH activity, suggesting a switch to CO or CO(2) utilization. We observed two phases of stress response: an initial response occurred during the transition to stationary phase, and a second response occurred after the cells had attained stationary phase. Although SigG synthesis was induced during starvation, a ΔsigG deletion mutant showed only minor changes in cell survival. Stationary-phase cells underwent reductive cell division. The extreme capacity of RHA1 to survive starvation does not appear to involve novel mechanisms; rather, it seems to be due to the coordinated combination of earlier-described mechanisms.

Proteomic analysis of survival of Rhodococcus jostii RHA1 during carbon starvation.

WhiB-like (Wbl) proteins are well known for their diverse roles in actinobacterial morphogenesis, cell division, virulence, primary and secondary metabolism, and intrinsic antibiotic resistance. Gene disruption experiments showed that three different Actinobacteria (Mycobacterium smegmatis, Streptomyces lividans, and Rhodococcus jostii) each exhibited a different whiB7-dependent resistance profile. Heterologous expression of whiB7 genes showed these resistance profiles reflected the host's repertoire of endogenous whiB7-dependent genes. Transcriptional activation of two resistance genes in the whiB7 regulon, tap (a multidrug transporter) and erm(37) (a ribosomal methyltransferase), required interaction of WhiB7 with their promoters. Furthermore, heterologous expression of tap genes isolated from Mycobacterium species demonstrated that divergencies in drug specificity of homologous structural proteins contribute to the variation of WhiB7-dependent drug resistance. WhiB7 has a specific tryptophan/glycine-rich region and four conserved cysteine residues; it also has a peptide sequence (AT-hook) at its C terminus that binds AT-rich DNA sequence motifs upstream of the promoters it activates. Targeted mutagenesis showed that these motifs were required to provide antibiotic resistance in vivo. Anaerobically purified WhiB7 from S. lividans was dimeric and contained 2.1 ± 0.3 and 2.2 ± 0.3 mol of iron and sulfur, respectively, per protomer (consistent with the presence of a 2Fe-2S cluster). However, the properties of the dimer's absorption spectrum were most consistent with the presence of an oxygen-labile 4Fe-4S cluster, suggesting 50% occupancy. These data provide the first insights into WhiB7 iron-sulfur clusters as they exist in vivo, a major unresolved issue in studies of Wbl proteins.

WhiB7, an Fe-S-dependent transcription factor that activates species-specific repertoires of drug resistance determinants in actinobacteria.

Although classical dendritic cells (DCs) arise from distinct progenitors in the bone marrow, the origin of inflammatory DCs and the distinction between monocyte-derived DCs and macrophages is less clear. In vitro culture of mouse bone marrow cells with GM-CSF is a well-established method to generate DCs, but GM-CSF has also been used to generate bone marrow-derived macrophages. In this article, we identify a distinct subpopulation of cells within the GM-CSF bone marrow-derived DC culture based on their ability to bind hyaluronan (HA), a major component of the extracellular matrix and ligand for CD44. HA identified a morphologically distinct subpopulation of cells within the immature DC population (CD11c(+) MHC II(mid/low)) that were CCR5(+)/CCR7(-) and proliferated in response to GM-CSF, but, unlike immature DCs, did not develop into mature DCs expressing CCR7 and high levels of MHC II, even after stimulation with LPS. The majority of these cells produced TNF-α in response to LPS but were unable to activate naive T cells, whereas the majority of mature DCs produced IL-12 and activated naive T cells. This HA binding population shared many characteristics with alveolar macrophages and was retained in the alveolar space after lung instillation even after LPS stimulation, whereas the MHC II(high) mature DCs were found in the draining lymph node. Thus, HA binding in combination with MHC II expression can be used to identify alveolar-like macrophages from GM-CSF-treated bone marrow cultures, which provides a useful in vitro model to study alveolar macrophages.

Manisha Dosanjh

Microbiology and Immunology

University of British Columbia

Generation and Identification of GM-CSF Derived Alveolar-like Macrophages and Dendritic Cells From Mouse Bone Marrow