Sphingolipid biosynthetic inhibitor L-Cycloserine prevents oxidative-stress-mediated death in an in vitro model of photoreceptor-derived 661W cells

Oxidative stress plays a pivotal role in the pathogenesis of several neurodegenerative diseases. Retinal degeneration causes irreversible death of photoreceptor cells, ultimately leading to vision loss. Under oxidative stress, the synthesis of bioactive sphingolipid ceramide increases, triggering apoptosis in photoreceptor cells and leading to their death. This study investigates the effect of L-Cycloserine, a small molecule inhibitor of ceramide biosynthesis, on sphingolipid metabolism and the protection of photoreceptor-derived 661W cells from oxidative stress. The results demonstrate that treatment with L-Cycloserine, an inhibitor of Serine palmitoyl transferase (SPT), markedly decreases bioactive ceramide and associated sphingolipids in 661W cells. A nontoxic dose of L-Cycloserine can provide substantial protection of 661W cells against H2O2-induced oxidative stress by reversing the increase in ceramide level observed under oxidative stress conditions. Analysis of various antioxidant, apoptotic and sphingolipid pathway genes and proteins also confirms the ability of L-Cycloserine to modulate these pathways. Our findings elucidate the generation of sphingolipid mediators of cell death in retinal cells under oxidative stress and the potential of L-Cycloserine as a therapeutic candidate for targeting ceramide-induced degenerative diseases by inhibiting SPT. The promising therapeutic prospect identified in our findings lays the groundwork for further validation in in-vivo and preclinical models of retinal degeneration.

Mouse Model of Nitrogen Mustard Ocular Surface Injury Characterization and Sphingolipid Signaling

Vesicating chemicals like sulfur mustard (SM) or nitrogen mustard (NM) can cause devastating damage to the eyes, skin, and lungs. Eyes, being the most sensitive, have complicated pathologies that can manifest immediately after exposure (acute) and last for years (chronic). No FDA-approved drug is available to be used as medical counter measures (MCMs) against such injuries. Understanding the pathological mechanisms in acute and chronic response of the eye is essential for developing effective MCMs. Here, we report the clinical and histopathological characterization of a mouse model of NM-induced ocular surface injury (entire surface) developed by treating the eye with 2% (w/v) NM solution for 5 min. Unlike the existing models of specific injury, our model showed severe ocular inflammation, including the eyelids, structural deformity of the corneal epithelium and stroma, and diminished visual and retinal functions. We also observed alterations of the inflammatory markers and their expression at different phases of the injury, along with an activation of acidic sphingomyelinase (aSMase), causing an increase in bioactive sphingolipid ceramide and a reduction in sphingomyelin levels. This novel ocular surface mouse model recapitulated the injuries reported in human, rabbit, and murine SM or NM injury models. NM exposure of the entire ocular surface in mice, which is similar to accidental or deliberate exposure in humans, showed severe ocular inflammation and caused irreversible alterations to the corneal structure and significant vision loss. It also showed an intricate interplay between inflammatory markers over the injury period and alteration in sphingolipid homeostasis in the early acute phase.

Birdlife, a tourist attraction for the southern portion of Bacalar Lagoon, Quintana Roo, Mexico

The Bacalar Lagoon (BL) in Quintana Roo, Mexico; is an area of high interest due to its tourist potential. However, the changes in landuse patterns, urbanization, extensive cattle ranching and rapidly expanding agriculture, have generated negative impacts on areas of adjacent plan communities and wildlife habitats. The objective of this study has to evaluate the level of vegetation conservation in the southern portion of the BL through the avifauna present in sites with contrasting degrees of conservation. Additionally, change "and their habitat preference(s) in the different communities" to and their habitat use preferences in the different communities. To evaluate the level of conservation of the BL, field visits and botanical collections were carried out to identify species. For the counting and identification of birds, monthly surveys were made through coastal tours along the cenote Xul-ha in 2.5 km transects. Four transects were established: two for sites characterized as semi-conserved and two with disturbed sites. A total richness of 40 taxa was observed, which corresponds to 8.1% of the Quintana Roo avifauna and 32% to wetland birds (125 species). The species accumulation curves indicated that semi-conserved and disturbed sites tend to reach asymptotes and with a coverage percentage greater than 90%. In terms of diversity and community structure, no significant differences were observed. However, the semi-conserved and disturbed sites each have 11 unique species and share 18 species. The LB has an intermediate diversity of bird species compared to studies at the Mexican level, the habitat is important for the conservation of birdlife; as it functions as a reservoir of diversity. Strategies has been suggested that promote sustainable tourism, support the restoration of natural vegetation; and facilitate the economic development of the region.

Potentiation of Sphingolipids and TGF-β in the human corneal stroma reveals intricate signaling pathway crosstalks

Corneal haze brought on by fibrosis due to insult can lead to partial or complete vision loss. Currently, corneal transplantation is the gold standard for treating severe corneal fibrosis, which comes with the risk of rejection and the issue of donor tissue shortages. Sphingolipids (SPLs) are known to be associated with fibrosis in various tissues and organs, including the cornea. We previously reported that SPLs are tightly related to Transforming Growth Factor β (TGF-β) signaling and corneal fibrogenesis. This study aimed to elucidate the interplay of SPLs, specifically sphingosine-1-phosphate (S1P) signaling, and its' interactions with TGF-β signaling through detailed analyses of the corresponding downstream signaling targets in the context of corneal fibrosis, in vitro. Healthy human corneal fibroblasts (HCFs) were isolated, plated on polycarbonate membranes, and stimulated with a stable Vitamin C derivative. The 3D constructs were treated with either 5 μM sphingosine-1-phosphate (S1P), 5 μM SPHK I₂ (I₂; inhibitor of sphingosine kinase 1, one of the two enzymes responsible for generating S1P in mammalian cells), 0.1 ng/mL TGF-β1, or 0.1 ng/mL TGF-β3. Cultures with control medium-only served as controls. All 3D constructs were examined for protein expression of fibrotic markers, SPLs, TGF-βs, and relevant downstream signaling pathways. This data revealed no significant changes in any LTBP (latent TGF-β binding proteins) expression when stimulated with S1P or I₂. However, LTBP1 was significantly upregulated via stimulation of TGF-β1 and TGF-β3, whereas LTBP2 was significantly upregulated only with TGF-β3 stimulation. Significant downregulation of TGF-β receptor II (TGF-βRII) following S1P stimulation but significant upregulation following I₂ stimulation was observed. Following TGF-β1, S1P, and I₂ stimulation, phospho-SMAD2 (pSMAD2) was significantly downregulated. Furthermore, I₂ stimulation led to significant downregulation of SMAD4. Adhesion/proliferation/transcription regulation targets, SRC, FAK, and pERK 1/2 were all significantly downregulated by exogenous S1P, whereas I₂ only significantly downregulated FAK. Exogenous TGF-β3 caused significant upregulation of AKT. Interestingly, both I₂ and TGF-β3 caused significant downregulation of JNK expression. Lastly, TGF-β1 led to significant upregulation of sphingosine kinase 1 (SphK1) and sphingosine-1-phosphate receptor 3 (S1PR3), whereas TGF-β3 caused significant upregulation of only SphK1. Together with previously published work from our group and others, S1P inhibition exhibits great potential as an efficacious anti-fibrotic modality in human corneal stromal ECM. The current findings shed further light on a very complex and rather incompletely investigated mechanism, and cement the intricate crosstalk between SPLs and TGF-β in corneal fibrogenesis. Future studies will dictate the potential of utilizing SPLs/TGF-β signaling modulators as novel therapeutics in corneal fibrosis.

Ablation of Sphingosine Kinase 1 Protects Cornea from Neovascularization in a Mouse Corneal Injury Model

The purpose of this study was to investigate the role of sphingosine kinase 1 (SphK1), which generates sphingosine-1-phosphate (S1P), in corneal neovascularization (NV). Wild-type (WT) and Sphk1 knockout (Sphk1^−/−) mice received corneal alkali-burn treatment to induce corneal NV by placing a 2 mm round piece of Whatman No. 1 filter paper soaked in 1N NaOH on the center of the cornea for 20 s. Corneal sphingolipid species were extracted and identified using liquid chromatography/mass spectrometry (LC/MS). The total number of tip cells and those positive for ethynyl deoxy uridine (EdU) were quantified. Immunocytochemistry was done to examine whether pericytes were present on newly forming blood vessels. Cytokine signaling and angiogenic markers were compared between the two groups using multiplex assays. Data were analyzed using appropriate statistical tests. Here, we show that ablation of SphK1 can significantly reduce NV invasion in the cornea following injury. Corneal sphingolipid analysis showed that total levels of ceramides, monohexosyl ceramides (HexCer), and sphingomyelin were significantly elevated in Sphk^−/− corneas compared to WT corneas, with a comparable level of sphingosine among the two genotypes. The numbers of total and proliferating endothelial tip cells were also lower in the Sphk1^−/− corneas following injury. This study underscores the role of S1P in post-injury corneal NV and raises further questions about the roles played by ceramide, HexCer, and sphingomyelin in regulating corneal NV. Further studies are needed to unravel the role played by bioactive sphingolipids in maintenance of corneal transparency and clear vision.

A multi-scale agent-based model for avascular tumour growth

In this paper, we have developed a multi-scale, lattice-free, agent based model of avascular tumour growth in epithelial tissue. The model integrates different events to identify the underlying diversity within intracellular, cellular, and extracellular layer dynamics. The model considers every cell as an agent. A cellular agent may proliferate, spawns two identical daughter agents, or it may be transformed into other phenotypes during its life time depending on its internal proteins' activity as well as its external microenvironment. In this context, a simplified age-structured cell cycle model is adopted from the existing literature. The model considers that the intracellular events are regulated by p27 gene expression. In this model, p27 protein controls the overall tumour growth dynamics. Moreover, p27 is controlled by the external oxygen and nutrients that are modelled with the reaction-diffusion equations. The model also considers several biophysical forces which directly effect on the tumour growth dynamics. This modelling framework offers biologically realistic outcomes and also covers important criteria of the hallmarks of cancer which include oxygen and nutrient consumptions, micro-environmental heterogeneity, tumour cell proliferation by avoiding growth suppressor signals, replication of tumour cells at an abnormally faster rate, and resistance of apoptosis. The avascular tumour growth model is validated with immunohistochemistry and histopathology data. The outcome of the proposed model is very close to the range of the patient data, which concludes that the model is capable enough to mimic these complex biophysical phenomena.

Sphingolipids as critical players in retinal physiology and pathology

Sphingolipids have emerged as bioactive lipids involved in the regulation of many physiological and pathological processes. In the retina, they have been established to participate in numerous processes, such as neuronal survival and death, proliferation and migration of neuronal and vascular cells, inflammation, and neovascularization. Dysregulation of sphingolipids is therefore crucial in the onset and progression of retinal diseases. This review examines the involvement of sphingolipids in retinal physiology and diseases. Ceramide (Cer) has emerged as a common mediator of inflammation and death of neuronal and retinal pigment epithelium cells in animal models of retinopathies such as glaucoma, age-related macular degeneration (AMD), and retinitis pigmentosa. Sphingosine-1-phosphate (S1P) has opposite roles, preventing photoreceptor and ganglion cell degeneration but also promoting inflammation, fibrosis, and neovascularization in AMD, glaucoma, and pro-fibrotic disorders. Alterations in Cer, S1P, and ceramide 1-phosphate may also contribute to uveitis. Notably, use of inhibitors that either prevent Cer increase or modulate S1P signaling, such as Myriocin, desipramine, and Fingolimod (FTY720), preserves neuronal viability and retinal function. These findings underscore the relevance of alterations in the sphingolipid metabolic network in the etiology of multiple retinopathies and highlight the potential of modulating their metabolism for the design of novel therapeutic approaches.

Role of ceramides in the pathogenesis of diabetes mellitus and its complications

Diabetes mellitus (DM) is a systemic metabolic disease that affects 463 million adults worldwide and is a leading cause of cardiovascular disease, blindness, nephropathy, peripheral neuropathy, and lower-limb amputation. Lipids have long been recognized as contributors to the pathogenesis and pathophysiology of DM and its complications, but recent discoveries have highlighted ceramides, a class of bioactive sphingolipids with cell signaling and second messenger capabilities, as particularly important contributors to insulin resistance and the underlying mechanisms of DM complications. Besides their association with insulin resistance and pathophysiology of type 2 diabetes, evidence is emerging that certain species of ceramides are mediators of cellular mechanisms involved in the initiation and progression of microvascular and macrovascular complications of DM. Advances in our understanding of these associations provide unique opportunities for exploring ceramide species as potential novel therapeutic targets and biomarkers. This review discusses the links between ceramides and the pathogenesis of DM and diabetic complications and identifies opportunities for novel discoveries and applications.

Avascular tumour growth models based on anomalous diffusion

In this study, we model avascular tumour growth in epithelial tissue. This can help us to understand that how an avascular tumour interacts with its microenvironment and what type of physical changes can be observed within the tumour spheroid before angiogenesis. This understanding is likely to assist in the development of better diagnostics, improved therapies, and prognostics. In biological systems, most of the diffusive processes are through cellular membranes which are porous in nature. Due to its porous nature, diffusion in biological systems are heterogeneous. The fractional diffusion equation is well suited to model heterogeneous biological systems, though most of the early studies did not use this fact. They described tumour growth with simple diffusion-based model. We have developed a spherical model based on simple diffusion initially, and then the model is upgraded with fractional diffusion equations to express the anomalous nature of biological system. In this study, two types of fractional models are developed: one of fixed order and the other of variable order. The memory formalism technique is also included in these anomalous diffusion models. These three models are investigated from phenomenological point view by measuring some parameters for characterizing avascular tumour growth over time. Tumour microenvironment is very complex in nature due to several concurrent molecular mechanisms. Diffusion with memory (fixed as well as variable) formation may be an oversimplified technique, and does not reflect the detailed view of the tumour microenvironment. However, it is found that all the models offer realistic and insightful information of the tumour microenvironment at the macroscopic level, and approximate well the physical phenomena. Also, it is observed that the anomalous diffusion based models offer a closer description to clinical facts than the simple model. As the simulation parameters get modified due to different biochemical and biophysical processes, the robustness of the model is determined. It is found that the anomalous diffusion models are moderately sensitive to the parameters.

Abstract 4361: Role of Rab GTPases and endosomal adaptor proteins in oncogenic RAS induced formation of perinuclear signaling complexes (PSCs)

Oncogenic RAS signaling leads to neoplastic transformation in immortalized cells and oncogene induced senescence in primary cells. Our laboratory has found that in both primary and immortalized cells oncogenic RAS induces constitutive perinuclear re-localization of p-ERK, CK2, and the MAPK scaffolding protein, KSR1. KSR1 binds to p-ERK and CK2, forming assemblies that we call “perinuclear signaling complexes” (PSCs). We observe PSCs in all cancer cell lines tested and in KRasG12V-driven mouse lung tumors, indicating that PSC formation is an important and integral characteristic of tumor cells. Our results show that KSR1 is essential for PSCs, as RNAi-mediated depletion of KSR1 or knockout of KSR1 disrupted their formation. We also demonstrated a key role for endosomal trafficking in this localized RAS signaling, as pharmacological inhibition of endocytosis prevented PSC formation. Furthermore, Rab11A, a Rab GTPase involved in trafficking of recycling endosomes, is required for establishment of PSCs and co-localizes with a pool of cellular CK2 and KSR1, but not p-ERK. Moreover, Rab11A knockdown caused decreased proliferation and survival of A549 cells (human KRAS mutant non-small cell lung adenocarcinoma). Our results demonstrate that there may be at least two classes of PSC-containing endosomes, p-ERK bound endosomes and CK2 bound endosomes. We are currently attempting to identify Rab GTPases that may differentiate these two kinds of PSC containing endosomes. Jongsma et al. (Cell, 2016) have shown that endosomes associated with the ubiquitin adaptor proteins EPS15, Tollip or TAXBP1 localize to the perinuclear region via the signaling adaptor, SQSTM1 (p62), which is tethered to the ER. We found that Tollip knockdown in A549 cells disrupted the CK2 bound endosomes but not p-ERK bound endosomes. Tollip knockdown also decreased cell proliferation and cell survival, while increasing apoptosis and autophagy. Whether other adaptor proteins are involved in RAS-mediated PSC formation remains to be determined. Growth factors (GF) also transiently induced PSCs in normal cells with delayed kinetics (4-6 hr). Our findings indicate that transformed cells sustain this novel late phase of GF signaling, localizing RAS pathway kinases to a nuclear-proximal compartment to drive tumorigenesis. We propose that PSCs are hallmarks of cancer cells and may represent useful biomarkers for cancer diagnosis and therapeutic responses.

Citation Format: Srikanta Basu, Sandip K. Basu, Jacqueline Salotti, Peter F. Johnson. Role of Rab GTPases and endosomal adaptor proteins in oncogenic RAS induced formation of perinuclear signaling complexes (PSCs) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4361.

A RAS-CaMKKβ-AMPKα2 pathway promotes senescence by licensing post-translational activation of C/EBPβ through a novel 3'UTR mechanism

Oncogene-induced senescence (OIS) is an intrinsic tumor suppression mechanism that requires the p53 and RB pathways and post-translational activation of C/EBPβ through the RAS-ERK cascade. We previously reported that in transformed/proliferating cells, C/EBPβ activation is inhibited by G/U-rich elements (GREs) in its 3′UTR. This mechanism, termed “3′UTR regulation of protein activity” (UPA), maintains C/EBPβ in a low-activity state in tumor cells and thus facilitates senescence bypass. Here we show that C/EBPβ UPA is overridden by AMPK signaling. AMPK activators decrease cytoplasmic levels of the GRE binding protein HuR, which is a key UPA component. Reduced cytoplasmic HuR disrupts 3′UTR-mediated trafficking of Cebpb transcripts to the peripheral cytoplasm – a fundamental feature of UPA – thereby stimulating C/EBPβ activation and growth arrest. In primary cells, oncogenic RAS triggers a Ca⁺⁺-CaMKKβ-AMPKα2-HuR pathway, independent of AMPKα1, that is essential for C/EBPβ activation and OIS. This axis is disrupted in cancer cells through down-regulation of AMPKα2 and CaMKKβ. Thus, CaMKKβ-AMPKα2 signaling constitutes a key tumor suppressor pathway that activates a novel UPA-cancelling mechanism to unmask the cytostatic and pro-senescence functions of C/EBPβ.

Oncogenic RAS-Induced Perinuclear Signaling Complexes Requiring KSR1 Regulate Signal Transmission to Downstream Targets

The precise characteristics that distinguish normal and oncogenic RAS signaling remain obscure. Here, we show that oncogenic RAS and BRAF induce perinuclear relocalization of several RAS pathway proteins, including the kinases CK2 and p-ERK1/2 and the signaling scaffold KSR1. This spatial reorganization requires endocytosis, the kinase activities of MEK-ERK and CK2, and the presence of KSR1. CK2α colocalizes with KSR1 and Rab11, a marker of recycling endosomes, whereas p-ERK associates predominantly with a distinct KSR1-positive endosomal population. Notably, these perinuclear signaling complexes (PSC) are present in tumor cell lines, mouse lung tumors, and mouse embryonic fibroblasts undergoing RAS-induced senescence. PSCs are also transiently induced by growth factors (GF) in nontransformed cells with delayed kinetics (4-6 hours), establishing a novel late phase of GF signaling that appears to be constitutively activated in tumor cells. PSCs provide an essential platform for RAS-induced phosphorylation and activation of the prosenescence transcription factor C/EBPβ in primary MEFs undergoing senescence. Conversely, in tumor cells, C/EBPβ activation is suppressed by 3'UTR-mediated localization of Cebpb transcripts to a peripheral cytoplasmic domain distinct from the PSC region. Collectively, our findings indicate that sustained PSC formation is a critical feature of oncogenic RAS/BRAF signaling in cancer cells that controls signal transmission to downstream targets by regulating selective access of effector kinases to substrates such as C/EBPβ.Significance: In addressing the long-standing question of the difference between normal and oncogenic RAS pathway signaling, this study shows that oncogenic RAS specifically triggers constitutive endocytosis-dependent movement of effector kinases to a perinuclear region, thereby creating connections to unique downstream targets such as the core prosenescence and the inflammatory regulatory transcription factor C/EBPβ. Cancer Res; 78(4); 891-908. ©2017 AACR.

Identification of senescent cell surface targetable protein DPP4

Kim et al. show that DPP4 (dipeptidyl peptidase 4) was selectively expressed on the surface of senescent human diploid fibroblasts and that this enabled their preferential elimination.

Senescent cell accumulation in aging tissues is linked to age-associated diseases and declining function, prompting efforts to eliminate them. Mass spectrometry analysis revealed that DPP4 (dipeptidyl peptidase 4) was selectively expressed on the surface of senescent, but not proliferating, human diploid fibroblasts. Importantly, the differential presence of DPP4 allowed flow cytometry-mediated isolation of senescent cells using anti-DPP4 antibodies. Moreover, antibody-dependent cell-mediated cytotoxicity (ADCC) assays revealed that the cell surface DPP4 preferentially sensitized senescent, but not dividing, fibroblasts to cytotoxicity by natural killer cells. In sum, the selective expression of DPP4 on the surface of senescent cells enables their preferential elimination.

Mesenchymal stromal cells derived from acute myeloid leukemia bone marrow exhibit aberrant cytogenetics and cytokine elaboration

Bone marrow-derived mesenchymal stromal cells (BM-MSCs) play a fundamental role in the BM microenvironment (BME) and abnormalities of these cells may contribute to acute myeloid leukemia (AML) pathogenesis. The aim of the study was to characterize the cytokine and gene expression profile, immunophenotype and cytogenetics of BM-MSCs from AML patients compared to normal BM-MSCs from healthy donors. AML BM-MSCs showed decreased monocyte chemoattractant protein-1 levels compared to normal BM-MSCs. AML BM-MSCs expressed similar β1 integrin, CD44, CD73, CD90 and E-cadherin compared to normal BM-MSCs. Cytogenetic analysis revealed chromosomal aberrations in AML BM-MSCs, some overlapping with and others distinct from their corresponding AML blasts. No significant difference in gene expression was detected between AML BM-MSCs compared to normal BM-MSCs; however, comparing the differences between AML and MSCs from AML patients with the differences between normal hematopoietic cells and normal MSCs by Ingenuity pathway analysis showed key distinctions of the AML setting: (1) upstream gene regulation by transforming growth factor beta 1, tumor necrosis factor, tissue transglutaminase 2, CCAAT/enhancer binding protein alpha and SWItch/Sucrose NonFermentable related, matrix associated, actin dependent regulator of chromatin, subfamily a, member 4; (2) integrin and interleukin 8 signaling as overrepresented canonical pathways; and (3) upregulation of transcription factors FBJ murine osteosarcoma viral oncogene homolog and v-myb avian myeloblastosis viral oncogene homolog. Thus, phenotypic abnormalities of AML BM-MSCs highlight a dysfunctional BME that may impact AML survival and proliferation.

Abstract A11: Oncogenic Ras signaling involves sustained perinuclear localization of the effector kinases p-ERK1/2 and CK2 via KSR-1 and endosomal trafficking

In primary cells oncogenic Ras can induce cellular senescence, an important tumor suppression mechanism that must be bypassed in tumor cells. Oncogene-induced senescence is regulated in part by the transcription factor C/EBPβ, which is post-translationally activated by Ras signaling. We previously reported that C/EBPβ activation by H-RasV12 is suppressed in immortalized and transformed cells by a novel 3'UTR-dependent mechanism termed 3'UTR regulation of protein activity, or UPA. UPA acts by restricting the Cebpb mRNA to a peripheral cytoplasmic region, which is spatially distinct from a perinuclear compartment containing the C/EBPβ-activating kinase, p-ERK1/2. UPA can thereby block C/EBPβ phosphorylation/activation and suppress its pro-senescence functions in tumor cells. Here we identify CK2 as another C/EBPβ kinase that undergoes perinuclear relocalization in RasV12-expressing cells. Accordingly, CK2-mediated phosphorylation of C/EBPβ was inhibited by the Cebpb 3'UTR in tumor cells but not primary cells. The MAPK signaling scaffold KSR-1 and endocytic trafficking were both required for RasV12-induced activation of C/EBPβ and perinuclear targeting of p-ERK and CK2. CK2 co-localized and interacted with KSR-1 and Rab11 (a marker of recycling endosomes), while p-ERK appeared to be associated with a different endosomal population. RasV12 expression led to sustained perinuclear localization of p-ERK and CK2 in both transformed and senescent cells. In contrast, growth factors (GFs) only transiently induced this response, which occurred with delayed kinetics (4-6 hr) coinciding with transitory activation of C/EBPβ. Our results indicate that oncogenic Ras signaling involves constitutive activation of the delayed GF signaling phase, characterized by restriction of the effector kinases p-ERK and CK2 to perinuclear endosomes. In this compartment they can access critical targets such as C/EBPβ in a UPA-regulated manner to promote either transformation or senescence.

Citation Format: Sook Lee, Sandip K. Basu, Vijay Walia, Deborah K. Morrison, Peter F. Johnson. Oncogenic Ras signaling involves sustained perinuclear localization of the effector kinases p-ERK1/2 and CK2 via KSR-1 and endosomal trafficking. [abstract]. In: Proceedings of the AACR Special Conference on RAS Oncogenes: From Biology to Therapy; Feb 24-27, 2014; Lake Buena Vista, FL. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(12 Suppl):Abstract nr A11. doi: 10.1158/1557-3125.RASONC14-A11

Abdominal cocoon

Background The abdominal cocoon syndrome was first described as a rare condition where part of or the whole small bowel is encased within a fibrous membrane. Idiopathic sclerosing encapsulating peritonitis (or abdominal cocoon) is a rare cause of small bowel obstruction, especially in adult population. Diagnosis is usually incidental at laparotomy. But preoperative diagnosis can be made. Case presentation This report is of a 27-year-old Bangladeshi male who presented with increasing abdominal pain and features of subacute intestinal obstruction. He had a history appendicectomy 2 months back through grid iron incision in a peripheral hospital. Pre-operative work-up did not reveal a sac like structure encasing small intestinal loops. At computed tomography of the abdomen and pelvis, a huge cystic structure was seen encasing loops of small bowel. At laparotomy, a fibrous capsule was revealed, in which small bowel loops were encased, with the presence of interloop adhesions. A diagnosis of primary abdominal cocoon was established and extensive adhesiolysis was performed. The patient had an uneventful recovery and follow-up. No evidence of Kochs noted in the abdomen or on histopathology of tissue sent for examination. Conclusion Abdominal cocoon is a rare cause of small bowel obstruction, but should be suspected especially in cases with attacks of non strangulating obstruction in the same individual. A high index of clinical suspicion may be generated by the recurrent character of small bowel obstruction. Clinicians must rigorously pursue a preoperative diagnosis. The overall prognosis is satisfactory. DOI: http://dx.doi.org/10.3329/pulse.v5i2.20269 Pulse Vol.5 July 2011 p.61-64

Haemangioma of the nasal bone

A 16 year-old female presented for her cosmetic deformity with a slowly progressing swelling of insidious onset on the upper part of the bridge of the nose slightly towards the left side for 3 year duration. Clinical & radiological examination revealed an intra-osseous tumor of nasal bone. Histopathologically the tumor was a cavernous haemangioma of nasal bone. A follow up study upto 13-year showed no recurrence. A detailed search of world literature is carried out with clinical history & history of trauma. It could that nasal bone haemangioma is separate disease entity. The patients usually seek advise for their cosmetic deformity & sometime for nasal bleeding.

An arrow in the nasal cavity, ethmoid and nasopharynx

A penetrating foreign body (Metallic arrow) involving the ethmoidal air cells nose and nasopharynx is being reported.

Play safe with safety pins

Three cases of Safety pins in the aerodigestive tract have been presented here with a brief review of litereture.

Proximate Composition and Functional Properties of Mushroom Flours from Ganoderma spp., Omphalotus olearius (DC.) Sing. and Hebeloma mesophaeum (Pers.) Quél. Used in Nasarawa State, Nigeria

The proximate composition and functional properties of three edible mushroom (Ganoderma spp., Omphalotus olearius (DC.) Sing. and Hebeloma mesophaeum (Pers.) Quél.) flours used in Nasarawa state, Nigaria were investigated using standard analytical techniques. The samples contained crude protein in the range of 18.5% in Omphalotus olearius to 21.5% in Ganoderma spp. Crude fat varied with values ranging from 6.9% in Ganoderma spp. to 8.7% in Omphalotus olearius. Other proximate composition values were in the following ranges: moisture content 10.0 - 11.1%, ash 7.3 - 8.3%, crude fibre 2.8 - 3.5% and carbohydrate (by difference) 50.3 - 50.9%. The range values of functional properties were: foaming capacity 101.8 - 131.5%, foaming stability 51.0 - 54.0%, water absorption capacity 260.0 - 390.0%, oil absorption capacity 450 - 480%, oil emulsion capacity 57.3 - 61.0mLg- 1, least gelation concentration 12.0 - 14.0% and bulk density 230.0 - 410.0gmL-1. The results showed that these nutrient rich mushroom flours under investigation may prove useful in the formulation of different food products where foaming, emulsification, retention of flavour and palatability as well as gel formation are required.

Foreign body in ENT--general practitioner's duty

Foreign body in ENT region is an age-old problem. Introduction of foreign body in ear, nose and throat is specially seen in children. There are many types of foreign body seen in the ear, nose and throat. They can aspirate into larynx, trachea and bronchus. How to manage the removal of foreign body in ear, nose and throat had been discussed in a nutshell. General practitioners should be skilled enough to remove foreign body with their limited resources and they should know when to send the cases to an ENT specialist or to a hospital.

Manufacturing techniques and excipients used during the design of biodegradable polymer-based microspheres containing therapeutic peptide/protein for parenteral controlled drug delivery

In the last couple of decades, use of biodegradable polymer-based microspheres has been recognized as an interesting and promising approach for parenteral controlled delivery of therapeutic peptide/protein, including antigens. The main objectives of this review are (i) to update the current state of art of manufacturing of peptide/protein-loaded microspheres through both conventional and newer microencapsulation techniques, and (ii) to bring into focus the various possible instability problems, and the investigated mechanistic ways to obviate the instability problems of peptide/protein drug during microspheres preparation as well as its release from the microspheres. The solubilization, stabilization, and preservation enhancing excipients that are used in peptide/protein-loaded microspheres are briefly overviewed.

Mycobacterium tuberculosis 6-kDa early secreted antigenic target (ESAT-6) protein downregulates lipopolysaccharide induced c-myc expression by modulating the extracellular signal regulated kinases 1/2

Background

Mycobacterium tuberculosis (Mtb) causes death of 2–3 million people every year. The persistence of the pathogenic mycobacteria inside the macrophage occurs through modulation of host cell signaling which allows them, unlike the other non-pathogenic species, to survive inside the host. The secretory proteins of M. tuberculosis have gained attention in recent years both as vaccine candidates and diagnostic tools; they target the immune system and trigger a putatively protective response; however, they may also be involved in the clinical symptoms of the disease.

Results

Our studies showed that RD-1-encoded secretory protein ESAT-6 is involved in modulation of the mitogen-activated protein (MAP) kinase-signaling pathway inside the macrophage. ESAT-6 induced phosphorylation of extracellular signal-regulated kinases 1/2 (ERK1/2) in the cytoplasm but not in the nucleus, which normally is the case for MAP kinases. ESAT-6 also antagonized LPS-induced ERK1/2 phosphorylation in the nucleus. Stimulation of cells by ESAT-6 along with sodium orthovanadate (a tyrosine phosphatase inhibitor) restored phosphorylation of ERK1/2 in the nucleus, suggesting active dephosphorylation of ERK1/2 by some putative phosphatase(s) in the nucleus. Further, ESAT-6 was found to down regulate the expression of LPS-inducible gene c-myc in an ERK1/2-dependent manner.

Conclusion

This study showed the effect of secretory proteins of M. tuberculosis in the modulation of macrophage signaling pathways particularly ERK1/2 MAP kinase pathway. This modulation appears to be achieved by limiting the ERK1/2 activation in the nucleus which ultimately affects the macrophage gene expression. This could be a mechanism by which secretory proteins of Mtb might modulate gene expression inside the macrophages.

Mycobacterium tuberculosis secretory proteins CFP‐10, ESAT‐6 and the CFP10:ESAT6 complex inhibit lipopolysaccharide‐induced NF‐κB transactivation by downregulation of reactive oxidative species (ROS) production

Mycobacterium tuberculosis (Mtb) causes death of 2-3 million people annually and is considered one of the most successful intracellular pathogens to persist inside the host macrophage. Recent studies have implicated the role of RD-1 region of Mtb genome in the mycobacterial pathogenesis. The role of RD-1-encoded secretory proteins of Mtb in modulation of macrophage function has not been investigated in detail. Here we show that RD-1 encoded two major secretory proteins, namely, culture filtrate protein-10 kDa (CFP-10) and early secreted antigenic target-6 kDa (ESAT-6), and their 1:1 CFP-10:ESAT6 complex inhibit production of reactive oxidative species (ROS) in RAW264.7 cells. These proteins also downregulated the bacterial lipopolysaccharide (LPS)-induced ROS production, which, in turn, downregulated LPS-induced nuclear factor-kappaB (NF-kappaB) p65 DNA-binding activity, as well as inhibited the NF-kappaB-dependent reporter gene (chloramphenicol acetyl transferase) expression in the treated macrophages. Moreover, addition of N-acetyl cysteine, which is a scavenger of ROS, also inhibited LPS-induced reporter gene expression by scavenging the ROS, thereby preventing NF-kappaB transactivation. These studies indicate that the secretory proteins CFP-10, ESAT-6 and the CFP10:ESAT6 complex of Mtb can inhibit LPS-induced NF-kappaB-dependent gene expression via downregulation of ROS production.

Merkel cell carcinoma: a case report

Merkel cell carcinoma is an uncommon, highly malignant, primary cutaneous neuroendocrine tumour mostly occurring as a solitary nodule on the head or on the extremities. It has high recurrence rate. We hereby report a case of Merkel cell carcinoma in a young woman.

Mycobacterium tuberculosis secreted antigen (MTSA-10) modulates macrophage function by redox regulation of phosphatases

Macrophages are the primary host cells for Mycobacterium tuberculosis (Mtb). Although macrophages can mount a strong inflammatory response to dispose of invading microbial pathogens, the immune dysfunction of the Mtb-infected macrophage constitutes the hallmark of mycobacterial pathogenesis. A 10-kDa, Mtb secretory antigen (MTSA-10), encoded by ORF Rv3874, is one of the predominant members of the 'region of difference 1' locus of Mtb genome that has been strongly implicated in mycobacterial virulence. In this study, we investigated the possible role of MTSA-10 in modulating the macrophage dysfunction in a mouse macrophage cell line J774.1. We found that recombinant MTSA-10 caused extensive protein dephosphorylation in J774.1 cells as revealed by two-dimensional gel electrophoresis analysis. We also observed that MTSA-10 treatment downregulated the reactive oxygen species levels in the cells leading to activation of cellular protein phosphatases putatively responsible for the dephosphorylation phenomenon. This implied a direct role of MTSA-10 in the disruption of host cell signaling, resulting in downregulation of transcription of several genes essential for macrophage function.

Tumoral calcinosis--clinicopathological study of five cases

Five cases of tumoral calcinosis were studied during the period of January-february 1999 in MIMER medical college, Talegaon, a rural place 35kms. from Pune. All the Five patients were females residing in nonendemic area for Dracunculosis. They were from 5th-6th decade. They were otherwise healthy and had normal serum calcium and phosphorus levels and no eosinophilia. All had large, hard subcutaneous lump around hip joint. The skin overlying the swelling was normal. Histologically all cases showed similar morphology, the lesions were composed of large and small deposits of calcium. The foreign-body giant cell reaction was seen in two cases. There were no eosinophils and lymphocytes. On multiple sectioning none of the cases revealed any evidence of dead or living parasite. Old and recent necrosis was absent. These cases are presented since the condition is comparatively rare and it appeared in crops in our Institute.

Role of grommet in otitis media with effusion: A necessity or nuisance? A comparative study

Otitis media with effusion is one of the commonest otological problems in paediatric age group. The condition occurs in childhood as overt or covert hearing loss presenting as an educational or behavioural problem. As there is widespread controversy regarding its precise aetiology, natural history and pathogenesis a treatment dilemma still persists. The main goal of this study is to compare the efficacy of different modalities of medical and surgical treatment designed for this condition and analysis of the results statistical.

IL-6 and IL-12 specifically regulate the expression of Rab5 and Rab7 via distinct signaling pathways

Recent studies have shown that phagosome maturation depends on the balance between pro-inflammatory and anti-inflammatory cytokines, indicating that cytokine modulates phagosome maturation. However, the mechanism of cytokine-mediated modulation of intracellular trafficking remains to be elucidated. Here, we have shown that treatment of macrophages with IL-6 specifically induce the expression of Rab5 through the activation of extracellular signal-regulated kinase, whereas IL-12 exclusively upregulate the expression of Rab7 through the activation of p38 MAPK. We have cloned the 5'-flanking regions of the rab5c or rab7 into the promoterless reporter vector. Our results have shown that cells transfected with rab5c chimera are transactivated by IL-6, and IL-12 specifically transactivates cells containing rab7 chimera. Moreover, our results also show that IL-12 induces lysosomal transport, whereas IL-6 stimulates the fusion between early compartments in macrophages and accordingly modulates Salmonella trafficking and survival in macrophages. This is the first demonstration showing that cytokine differentially regulates endocytic trafficking by controlling the expression of appropriate Rab GTPase, and provides insight into the mechanism of cytokine-mediated regulation of intracellular trafficking.

Binding of diclofenac sodium with bovine serum albumin at different temperatures, pH and ionic strengths

The study was designed to examine the binding of diclofenac sodium with bovine serum albumin (BSA) at different temperatures (20 degrees, 30 degrees and 40 degrees C), pH (6.4, 7.4 and 8.4) and ionic strengths (micro = 0.1, 0.2 and 0.3) by means of equilibrium dialysis method. The concentration of diclofenac sodium was maintained at wider range from 15 to 900 micromole/l and BSA concentration was maintained at 61.5 micromole/l. The data obtained were interpreted by nonlinear regression method using Graphpad prism software. The analysis showed that the interaction between diclofenac sodium with BSA results in two-site saturable binding. A decrease in association constant was observed with increasing temperature. The average standard free energy change (deltaGdegrees) value was -7.07 (site I) and -4.2 (site II) Kcal/mol. The standard enthalpy change (deltaHdegrees) and the standard entropy change (deltaSdegrees) were -7.8 Kcal/mole, -2.35 cal/mole (site I) and -7.4 Kcal/mole, -10.5 cal/mole (site II), respectively. The negative enthalpy change suggested the binding between diclofenac sodium and the binding sites of BSA were spontaneous and exothermic. The negative value of deltaHdegrees and deltaSdegrees indicated hydrogen bonding and van der Waal's force was the major mechanism for diclofenac sodium and BSA interaction. Increase in pH and ionic strength also caused decrease in association constant of diclofenac sodium and BSA binding.

Acute toxicity and diuretic studies of Rungia repens aerial parts in rats

Ethanolic extract of Rungia repens aerials parts (300 and 600 mg/kg p.o) showed diuretic activity in rats. The acute toxicity, orally evaluated in mice, was found to be higher than 3000 mg/kg.

Effect of sulfidogenic and methanogenic inhibitors on reductive dehalogenation of 2-chlorophenol

The potential for reductive dehalogenation of 2-CP in anaerobic batch cultures of fresh-water digested sludge under sulfidogenic and methanogenic conditions was investigated in the presence or absence of respective inhibitors: molybdate and BESA at various concentrations (0 to 10 mM). Triplicate cultures (50% vol/vol) were set-up under an atmosphere of 20% CO2 and 80% N2 in 160 ml serum bottles using anaerobic digester sludge and a mineral medium containing 0.1% yeast extract. The dehalogenation of 2-CP, as well as methanogenesis, occurred at the same rate in the presence or absence of sulphate. Sulphate reduction did not inhibit 2-CP degrading populations. The presence of BESA--a known inhibitor of methane producers partially inhibited methanogenesis and slowed 2-CP dehalogenation at even 1 mM concentration with phenol and acetate accumulation in the cultures. The accumulation was proportional to the increase in concentration of BESA in the system. Molybdate on the other hand completely inhibited both sulphate reduction and 2-CP dehalogenation at a concentration of 10 mM. The dehalogenation of 2-CP continued in the presence of 1 mM molybdate even after the cessation of sulphate reduction indicating that sulphate-reducing bacteria were not directly involved in the dehalogenation of 2-CP in this study. Inhibition of 2-CP dehalogenation and sulphate reduction along with accumulation of propionate at 10 mM molybdate in the cultures strongly suggests that the dehalogenation of 2-CP was more directly linked to syntrophic activity of the mixed culture compared to sulphate reduction.

Deaf child--a general practitioner's responsibility

The power of a child's speaking language never develops if he is deaf. Deafness persists if it is not detected early. Childhood deafness is either congenital or acquired. At birth, doctors or attendants can detect deafness by arousing the baby with sudden loud noise. At 4 months onwards mothers and doctors can detect deafness. The baby at this age can turn its head or eyes towards the source of the sound. By 12 months to 2 years of age it is very difficult to detect deafness. By the age of 3 years children again become co-operative and it becomes easier to detect deafness. Children should always be screened for deafness while being admitted to nursery classes. In school going age ie, 5 years onwards loss of tests can be employed to detect deafness. If a child is suspected be deaf, a general practitioner's responsibility is to refer him to an ENT specialist earlier. Any child whose mother believes her child is deaf should be given due attention. Otitis media with effusion, enlarged adenoid, chronic suppurative otitis media, recurrent otitis media are some diseases to be carefully looked into by the general practitioners. Now-a-days cochlear implantation surgery is gaining popularity to give hearing to deaf child. Moreover regular screening for deafness should be included school heath programme.

Hemoglobin receptor in Leishmania is a hexokinase located in the flagellar pocket

Hb endocytosis in Leishmania is mediated through a 46-kDa protein located in the flagellar pocket. To understand the nature of the Hb receptor (HbR), we have purified the 46-kDa protein to homogeneity from Leishmania promastigote membrane. Purified HbR specifically binds Hb. The gene for HbR was cloned, and sequence analysis of the full-length HbR gene indicates the presence of hexokinase (HK) signature sequences, ATP-binding domain, and PTS-II motif. Four lines of evidence indicate that HbR in Leishmania is a hexokinase: 1) the recombinant HbR binds Hb, and the Hb-binding domain resides in the N terminus of the protein; 2) recombinant proteins and cell lysate prepared from HbR-overexpressing Leishmania promastigotes show enhanced HK activity in comparison with untransfected cells; 3) immunolocalization studies using antibodies against the N-terminal fragment (Ld-HbR-DeltaC) of Ld-HbR indicate that this protein is located in the flagellar pocket of Leishmania; and 4) binding and uptake of (125)I-Hb by Leishmania is significantly inhibited by anti-Ld-HbR-DeltaC antibody and Ld-HbR-DeltaC, respectively. Taken together, these results indicate that HK present in the flagellar pocket of Leishmania is involved in Hb endocytosis.

Rab5-mediated endosome-endosome fusion regulates hemoglobin endocytosis in Leishmania donovani

To understand the trafficking of endocytosed hemoglobin (Hb) in Leishmania, we investigated the characteristics of in vitro fusion between endosomes containing biotinylated Hb (BHb) and avidin-horseradish peroxidase (AHRP). We showed that early endosome fusion in Leishmania is temperature and cytosol dependent and is inhibited by ATP depletion, ATPgammaS, GTPgammaS and N-ethylmaleimide treatment. The Rab5 homolog from Leishmania donovani, LdRab5, was cloned and expressed. Our results showed that homotypic fusion between the early endosomes in Leishmania is Rab5 dependent. Early endosomes containing BHb fused efficiently with late endosomes in a process regulated by Rab7, whereas no fusion between early and late endosomes was detected using fluid phase markers. Pre-treatment of early endosomes containing BHb with monoclonal antibody specific for the C-terminus of the Hb receptor (HbR) or the addition of the C-terminal cytoplasmic fragment of the HbR specifically inhibited the fusion with late endosomes, suggesting that signal(s) mediated through the HbR cytoplasmic tail promotes the fusion of early endosomes containing Hb with late endosomes.

Intracellular delivery of drugs to macrophages

Toxic side effects which often complicate successful therapy in a number of diseases possibly arise due to the fact that at therapeutically effective concentrations the non-target cells in the body are also exposed to the cytotoxic effects of the drugs. Minimization of such adverse reactions might be feasible through drug delivery modalities that would reduce the uptake of the drugs by non-target cells and selectively deliver the drug only to the target cells (and/or intracellular sites) at relatively low extracellular concentrations. The current generic approach to site-specific drug delivery consists of attaching the therapeutic agent to a carrier recognized only by the cells where the pharmacological action is desired. Two types of recognition elements on the surface of target cells are being exploited for this purpose, viz., (i) antigens capable of generating specific, non-cross reactive antibodies, and (ii) receptors on the cell surface capable of efficient transport of the ligands. In general, incomplete specificity for the target cells and poor internalization of antibody-drug conjugates still limit the usefulness of antibodies for site-specific drug delivery applications necessitating exploration of alternatives. The alternate possibility is to exploit the exquisite cell type specificity and high efficiency of endocytosis of macromolecules mediated by specific receptors present on the surface of target cells for delivering drugs. A large number of infectious, metabolic, and neoplastic diseases are associated with macrophages leading to morbidities and mortalities to millions of people worldwide, thus an appropriate design of a drug delivery system to macrophages will be of tremendous help.

Mason diabetes--report of a family

A 48-year-old Hindu housewife was presented with increased appetite, thirst, frequency of micturition, weakness, cramps in the legs, tingling in the fingers, decline in bladder-bowel control and dimness of vision. She was a patient of diabetes. On investigations and history, she was diagnosed as a case of type 2 diabetes transmitted in three generations as an autosomal dominant trait.

Diverting intracellular trafficking of Salmonella to the lysosome through activation of the late endocytic Rab7 by intracellular delivery of muramyl dipeptide

Previously, we showed that live Salmonella-containing phagosomes (LSP) recruit early acting Rab5 and promote fusion with early endosomes, thus avoiding transport to the lysosomes. Therefore, live Salmonella survive in a specialized compartment. Here we show that scavenger-receptor-mediated intracellular delivery of muramyl dipeptide (MDP) to macrophages leads to efficient killing of Salmonella both in vitro and in vivo. To understand the intracellular trafficking modulation of Salmonella by delivery of MDP, we investigated the levels of endocytic Rab proteins, which are the major regulators of vesicular transport. Western blot analysis reveals reduced Rab5 and enhanced Rab7 content in the maleylated bovine serum albumin-MDP (MBSA-MDP)-treated cells. The reduced content of Rab5 in the treated cells and on phagosomes inhibits the fusion of Salmonella-containing phagosomes with early endosomes, and the enhanced Rab7 content in these cells facilitated targeting of LSP to lysosomes, which contain cathepsin D and vacuolar ATPase, for killing. In vitro reconstitution of lysosomal transport demonstrated that a reduced content of Rab5 and an enhanced level of Rab7 in MBSA-MDP-treated cells is primarily responsible for targeting Salmonella to lysosomes. Intracellular delivery of MDP thus offers a general strategy against macrophage-associated infections caused by intracellular pathogens that survive in the host cell by resisting transport to lysosomes.

Scavenger receptor-specific allergen delivery elicits IFN-gamma-dominated immunity and directs established TH2-dominated responses to a nonallergic phenotype

BACKGROUND

Immunotherapeutic approaches to allergy consist of reliably changing allergen-specific T(H)2 immunity associated with secretion of IL-4, IL-5, and IL-13, along with IgE antibodies in atopic individuals to T(H)1 immunity. Our earlier data show that targeting of protein antigens to antigen-presenting cells (APCs), such as macrophages, by means of scavenger receptors (SRs) results in a pronounced T(H)1 immunity. Here we demonstrate a novel experimental approach for the conversion of T(H)2 immunity to T(H)1 immunity by using SR delivery of allergens.

OBJECTIVES

We sought to show that targeting of allergens by means of SRs to APCs triggers T(H)1 immunity and that an established T(H)2 immunity to the Der p 1-immunodominant peptide 111-139 (p1, 111-139) can be modulated to a nonallergic T(H)1 phenotype.

METHODS

Analysis of the T cell-derived cytokines IL-4, IL-5, IL-13, and IFN-gamma in response to p1, 111-139 in C57BL/6 mice 7 to 42 days after immunization, measurement of specific antibody responses, eosinophilic infiltrate, and skin hypersensitivity in response to allergen challenge constitute the parameters of in vivo immunity.

RESULTS

We show that p1, 111-139, when delivered to APCs by means of SR, elicits a T(H)1-dominant immunity. If it is delivered to APCs either after chemical coupling to SR ligands or by means of mere coadsorption on alum in the presence of an SR ligand, the established T(H)2 immunity can be modified to T(H)1 immunity.

CONCLUSIONS

SR-mediated delivery of allergens has immunotherapeutic potential that may be usable in atopic individuals.

A novel gene encoding a 54 kDa polypeptide is essential for butane utilization by Pseudomonas sp. IMT37

Twenty-three propane- and butane-utilizing bacteria were isolated from soil samples collected from oilfields. Three of them have been identified as Rhodococcus sp. IMT35, Pseudomonas sp. IMT37 and Pseudomonas sp. MT40. SDS-PAGE analysis of the membrane of Rhodococcus sp. IMT35 revealed the presence of at least four polypeptides induced by propane. Polyclonal antibody raised against a 58 kDa polypeptide from Rhodococcus sp. IMT35 specifically detected bacteria which were actively utilizing propane or butane. Immunoscreening of a genomic library in lambdagt11 with this antibody resulted in isolation of a clone containing a 4.9 kb EcoRI genomic DNA fragment. This 4.9 kb DNA fragment was found to hybridize specifically with organisms which could grow on propane or butane. This fragment could therefore be used as a probe for detection of such bacteria. A 2.3 kb fragment having an ORF encoding a polypeptide of 54 kDa was identified by screening a genomic library of Pseudomonas sp. IMT37 with this 4.9 kb EcoRI fragment. The sequence of the ORF (designated orf54) was found to be novel. Primer extension and S1 nuclease mapping showed that transcription of the ORF starts at base 283 and it had sequences upstream similar to that of a Pseudomonas promoter (-12, -24 type). Disruption of the ORF by a kanamycin ('kan') cassette prevented the organism from growing on any alkane but did not affect its ability to utilize the respective alkanols and acids, indicating that alcohol dehydrogenase and subsequent steps in the pathway remained unaltered. The mutants had no detectable level of butane monooxygenase activity. Therefore, the product of this gene plays a crucial role in the first step of the pathway and is an essential component of monooxygenase. The findings imply that this bacterium either employs a common genetic and metabolic route or at least shares the product of this gene for utilization of many alkanes.