Butyrate increases intracellular calcium levels and enhances growth hormone release from rat anterior pituitary cells via the G-protein-coupled receptors GPR41 and 43

Butyrate is a short-chain fatty acid (SCFA) closely related to the ketone body ß-hydroxybutyrate (BHB), which is considered to be the major energy substrate during prolonged exercise or starvation. During fasting, serum growth hormone (GH) rises concomitantly with the accumulation of BHB and butyrate. Interactions between GH, ketone bodies and SCFA during the metabolic adaptation to fasting have been poorly investigated to date. In this study, we examined the effect of butyrate, an endogenous agonist for the two G-protein-coupled receptors (GPCR), GPR41 and 43, on non-stimulated and GH-releasing hormone (GHRH)-stimulated hGH secretion. Furthermore, we investigated the potential role of GPR41 and 43 on the generation of butyrate-induced intracellular Ca2+ signal and its ultimate impact on hGH secretion. To study this, wt-hGH was transfected into a rat pituitary tumour cell line stably expressing the human GHRH receptor. Treatment with butyrate promoted hGH synthesis and improved basal and GHRH-induced hGH-secretion. By acting through GPR41 and 43, butyrate enhanced intracellular free cytosolic Ca2+. Gene-specific silencing of these receptors led to a partial inhibition of the butyrate-induced intracellular Ca2+ rise resulting in a decrease of hGH secretion. This study suggests that butyrate is a metabolic intermediary, which contributes to the secretion and, therefore, to the metabolic actions of GH during fasting.

Mitochondrial protein import receptors in Kinetoplastids reveal convergent evolution over large phylogenetic distances

Mitochondrial protein import is essential for all eukaryotes and mediated by hetero-oligomeric protein translocases thought to be conserved within all eukaryotes. We have identified and analysed the function and architecture of the non-conventional outer membrane (OM) protein translocase in the early diverging eukaryote Trypanosoma brucei. It consists of six subunits that show no obvious homology to translocase components of other species. Two subunits are import receptors that have a unique topology and unique protein domains and thus evolved independently of the prototype receptors ​Tom20 and ​Tom70. Our study suggests that protein import receptors were recruited to the core of the OM translocase after the divergence of the major eukaryotic supergroups. Moreover, it links the evolutionary history of mitochondrial protein import receptors to the origin of the eukaryotic supergroups.

Elevated temperature differentially affects virulence, VirB protein accumulation, and T-pilus formation in different Agrobacterium tumefaciens and Agrobacterium vitis strains.

That gene transfer to plant cells is a temperature-sensitive process has been known for more than 50 years. Previous work indicated that this sensitivity results from the inability to assemble a functional T pilus required for T-DNA and protein transfer to recipient cells. The studies reported here extend these observations and more clearly define the molecular basis of this assembly and transfer defect. T-pilus assembly and virulence protein accumulation were monitored in Agrobacterium tumefaciens strain C58 at different temperatures ranging from 20 degrees C to growth-inhibitory 37 degrees C. Incubation at 28 degrees C but not at 26 degrees C strongly inhibited extracellular assembly of the major T-pilus component VirB2 as well as of pilus-associated protein VirB5, and the highest amounts of T pili were detected at 20 degrees C. Analysis of temperature effects on the cell-bound virulence machinery revealed three classes of virulence proteins. Whereas class I proteins (VirB2, VirB7, VirB9, and VirB10) were readily detected at 28 degrees C, class II proteins (VirB1, VirB4, VirB5, VirB6, VirB8, VirB11, VirD2, and VirE2) were only detected after cell growth below 26 degrees C. Significant levels of class III proteins (VirB3 and VirD4) were only detected at 20 degrees C and not at higher temperatures. Shift of virulence-induced agrobacteria from 20 to 28 or 37 degrees C had no immediate effect on cell-bound T pili or on stability of most virulence proteins. However, the temperature shift caused a rapid decrease in the amount of cell-bound VirB3 and VirD4, and VirB4 and VirB11 levels decreased next. To assess whether destabilization of virulence proteins constitutes a general phenomenon, levels of virulence proteins and of extracellular T pili were monitored in different A. tumefaciens and Agrobacterium vitis strains grown at 20 and 28 degrees C. Levels of many virulence proteins were strongly reduced at 28 degrees C compared to 20 degrees C, and T-pilus assembly did not occur in all strains except "temperature-resistant" Ach5 and Chry5. Virulence protein levels correlated well with bacterial virulence at elevated temperature, suggesting that degradation of a limited set of virulence proteins accounts for the temperature sensitivity of gene transfer to plants.

PreImplantation Factor bolsters neuroprotection via modulating Protein Kinase A and Protein Kinase C signaling

A synthetic peptide (sPIF) analogous to the mammalian embryo-derived PreImplantation Factor (PIF) enables neuroprotection in rodent models of experimental autoimmune encephalomyelitis and perinatal brain injury. The protective effects have been attributed, in part, to sPIF's ability to inhibit the biogenesis of microRNA let-7, which is released from injured cells during central nervous system (CNS) damage and induces neuronal death. Here, we uncover another novel mechanism of sPIF-mediated neuroprotection. Using a clinically relevant rat newborn brain injury model, we demonstrate that sPIF, when subcutaneously administrated, is able to reduce cell death, reverse neuronal loss and restore proper cortical architecture. We show, both in vivo and in vitro, that sPIF activates cyclic AMP dependent protein kinase (PKA) and calcium-dependent protein kinase (PKC) signaling, leading to increased phosphorylation of major neuroprotective substrates GAP-43, BAD and CREB. Phosphorylated CREB in turn facilitates expression of Gap43, Bdnf and Bcl2 known to have important roles in regulating neuronal growth, survival and remodeling. As is the case in sPIF-mediated let-7 repression, we provide evidence that sPIF-mediated PKA/PKC activation is dependent on TLR4 expression. Thus, we propose that sPIF imparts neuroprotection via multiple mechanisms at multiple levels downstream of TLR4. Given the recent FDA fast-track approval of sPIF for clinical trials, its potential clinical application for treating other CNS diseases can be envisioned.

Activating enhancer binding protein 2 epsilon (AP-2ε)-deficient mice exhibit increased matrix metalloproteinase 13 expression and progressive osteoarthritis development.

INTRODUCTION The transcription factor activating enhancer binding protein 2 epsilon (AP-2ε) was recently shown to be expressed during chondrogenesis as well as in articular chondrocytes of humans and mice. Furthermore, expression of AP-2ε was found to be upregulated in affected cartilage of patients with osteoarthritis (OA). Despite these findings, adult mice deficient for AP-2ε (Tfap2e(-/-)) do not exhibit an obviously abnormal cartilaginous phenotype. We therefore analyzed embryogenesis of Tfap2e(-/-) mice to elucidate potential transient abnormalities that provide information on the influence of AP-2ε on skeletal development. In a second part, we aimed to define potential influences of AP-2ε on articular cartilage function and gene expression, as well as on OA progression, in adult mice. METHODS Murine embryonic development was accessed via in situ hybridization, measurement of skeletal parameters and micromass differentiation of mesenchymal cells. To reveal discrepancies in articular cartilage of adult wild-type (WT) and Tfap2e(-/-) mice, light and electron microscopy, in vitro culture of cartilage explants, and quantification of gene expression via real-time PCR were performed. OA was induced via surgical destabilization of the medial meniscus in both genotypes, and disease progression was monitored on histological and molecular levels. RESULTS Only minor differences between WT and embryos deficient for AP-2ε were observed, suggesting that redundancy mechanisms effectively compensate for the loss of AP-2ε during skeletal development. Surprisingly, though, we found matrix metalloproteinase 13 (Mmp13), a major mediator of cartilage destruction, to be significantly upregulated in articular cartilage of adult Tfap2e(-/-) mice. This finding was further confirmed by increased Mmp13 activity and extracellular matrix degradation in Tfap2e(-/-) cartilage explants. OA progression was significantly enhanced in the Tfap2e(-/-) mice, which provided evidence for in vivo relevance. This finding is most likely attributable to the increased basal Mmp13 expression level in Tfap2e(-/-) articular chondrocytes that results in a significantly higher total Mmp13 expression rate during OA as compared with the WT. CONCLUSIONS We reveal a novel role of AP-2ε in the regulation of gene expression in articular chondrocytes, as well as in OA development, through modulation of Mmp13 expression and activity.

Incremental value of heart-type fatty acid-binding protein in suspected acute myocardial infarction early after symptom onset.

BACKGROUND The early diagnosis of acute myocardial infarction (AMI) very soon after symptom onset remains a major clinical challenge, even when using high-sensitivity cardiac troponin (hs-cTnT). METHODS AND RESULTS We investigated the incremental value of heart-type fatty acid-binding protein (hFABP) in a pre-specified subgroup analysis of patients presenting with suspected AMI within 1 h of symptom onset to the emergency department (ED) in a multicentre study. HFABP was measured in a blinded fashion. Two independent cardiologists using all available clinical information, including hs-cTnT, adjudicated the final diagnosis. Overall, 1411 patients were enrolled, of whom 105 patients presented within 1 h of symptom onset. Of these, 34 patients (32.4%) had AMI. The diagnostic accuracy as quantified by the area under the receiver-operating characteristics curve (AUC) of hFABP was high (0.84 (95% CI 0.74-0.94)). However, the additional use of hFABP only marginally increased the diagnostic accuracy of hs-cTnT (AUC 0.88 (95% CI 0.81-0.94) for hs-cTnT alone to 0.90 (95% CI 0.83-0.98) for the combination; p=ns). After the exclusion of 18 AMI patients with ST-segment elevation, similar results were obtained. Among the 16 AMI patients without ST-segment elevation, six had normal hs-cTnT at presentation. Of these, hFABP was elevated in two (33.3%) patients. CONCLUSIONS hFABP does not seem to significantly improve the early diagnostic accuracy of hs-cTnT in the important subgroup of patients with suspected AMI presenting to the ED very early after symptom onset.

Antibodies against major histocompatibility complex class II antigens directly inhibit the growth of T cells infected with Theileria parva without affecting their state of activation

We have analyzed the effect of antibodies (Abs) directed against major histocompatibility complex (MHC) class II Abs on the proliferation of Theileria parva-infected (Tpi) T cells. Anti-MHC class II Abs exert a direct effect on Tpi T cells causing an acute block in their proliferation. The inhibition does not involve apoptosis and is also entirely reversible. The rapid arrest of DNA synthesis caused by anti-MHC class II Abs is not due to interference with the state of activation of the T cells since the transcriptional activator NF-kappa B remains activated in arrested cells. In addition, interleukin 2 (IL-2), IL-2R, and c-myc gene expression are also unaffected. By analyzing the cell-cycle phase distribution of inhibited cells, it could be shown that cells in all phases of the cell cycle are inhibited. The signal transduction pathway that results in inhibition was shown to be independent of protein kinase C and extracellular Ca2+. Tyrosine kinase inhibitors, however, partly reduced the level of inhibition and, conversely, phosphatase inhibitors enhanced it. The possible relevance of this phenomenon in other systems is discussed.

Immunisation with live attenuated Salmonella dublin expressing a sporozoite protein confers partial protection against Theileria parva

Cattle immunised with a recombinant form of p67, the major surface antigen of Theileria parva sporozoites, have been shown to be protected against parasite challenge. In an attempt to simplify the immunisation procedure live attenuated Salmonella strains expressing p67 have been constructed and used to induce anti-p67 immune responses in cattle. All animals immunised with these strains developed strong antibody responses to p67. Specific T cell responses could be detected in the majority of immunised cattle. Challenge with T. parva sporozoites revealed a significant level of protection in immunised calves compared to naive control animals or animals inoculated with non-recombinant attenuated Salmonella.

INVESTIGATIONS ON THE INTRACELLULAR LOCALIZATION OF PHOSPHATIDYLSERINE SYNTHASE FROM ESCHERICHIA COLI

Phosphatidylserine synthase catalyzes the committed step in the synthesis of the major lipid of Escherichia coli, phosphatidylethanolamine, and may be involved in regulating the balance of the zwitterionic and anionic phospholipids in the membrane. Unlike the other enzymes involved in the biosynthesis of phospholipids in E. coli, phosphatidylserine synthase is not membrane associated but seems to have a high affinity for the ribosomal fraction of cells broken by various methods. Investigations on the enzyme in cell free extracts using glycerol gradient centrifugation revealed that the binding of the synthase to ribosomes may be prevented by the presence of highly basic compounds such as spermidine and by the presence of detergent-lipid substrate micelles under assay conditions. Thus phosphatidylserine synthase may not be ribosome associated under physiological conditions but associated with its membrane bound substrate (Louie and Dowhan (1980) J. Biol. Chem. 255, 1124).^ In addition homogeneous enzyme shows many of the properties of a membrane associated protein. It binds nonionic detergent such as Triton X-100, which is also required during purification of the enzyme. Optimal catalytic activity is also dependent on micelle or surface bound substrate. Phosphatidylserine synthase has been synthesized in vitro using a coupled transcription-translation system dependent on the presence of the cloned structural gene. The translation product was found to preferentially associate with the ribosomal fraction even in the presence of added E. coli membranes. Preferential membrane binding could be induced if the membranes were supplemented with the lipid substrate CDP-diacylglycerol. Similar effects were obtained with the acidic lipids phosphatidylglycerol and cardiolipin. On the other hand the zwitterionic lipid phosphatidylethanolamine and the lipid product phosphatidylserine did not cause any detectable membrane association. These results are consistent with the enzyme recognizing membrane bound substrate (Carman and Dowhan (1979) J. Biol. Chem. 254, 8391) and with the lipid charge influencing membrane interaction.^ Phosphatidylserine synthase is at a branch point in lipid metabolism, which may determine the distribution of the zwitterionic and anionic phospholipids in the membrane. The results obtained here indicate phosphatidylserine synthase may play a significant role in membrane lipid biosynthesis by maintaining charge balance of the E. coli membrane. In determining the localization of phosphatidylserine synthase in vitro one may have a better understanding of its function and control in vivo and may also have a better understanding of its role in membrane assembly.^

Loss of activator protein-2alpha results in overexpression of the thrombin receptor and correlates with the malignant phenotype of human melanoma

Increasing evidence demonstrates that the thrombin receptor (protease activated receptor-1, PAR-1) plays a major role in tumor invasion and contributes to the metastatic phenotype of human melanoma. We demonstrate that the metastatic potential of human melanoma cells correlates with overexpression of PAR-1. The promoter of the PAR-1 gene contains multiple putative AP-2 and Sp1 consensus elements. We provide evidence that an inverse correlation exists between the expression of AP-2 and the expression of PAR-1 in human melanoma cells. Re-expression of AP-2 in WM266-4 melanoma cells (AP-2 negative) resulted in decreased mRNA and protein expression of PAR-1 and significantly reduced the tumor potential in nude mice. ChIP analysis of the PAR-1 promoter regions bp −365 to −329 (complex 1) and bp −206 to −180 (complex 2) demonstrates that in metastatic cells Sp1 is predominantly binding to the PAR-1 promoter, while in nonmetastatic cells AP-2 is bound. In vitro analysis of complex 1 demonstrates that AP-2 and Sp1 bind to this region in a mutually exclusive manner. Transfection experiments with full-length and progressive deletions of the PAR-1 promoter luciferase constructs demonstrated that metastatic cells had increased promoter activity compared to low and nonmetastatic melanoma cells. Our data shows that exogenous AP-2 expression decreased promoter activity, while transient expression of Sp1 further activated expression of the reporter gene. Mutational analysis of complex 1 within PAR-1 luciferase constructs further demonstrates that the regulation of PAR-1 is mediated through interactions with AP-2 and Sp1. Moreover, loss of AP-2 in metastatic cells alters the AP-2 to Sp1 ratio and DNA-binding activity resulting in overexpression of PAR-1. In addition, we evaluated the expression of AP-2 and PAR-1 utilizing a tissue microarray of 93 melanocytic lesions spanning from benign nevi to melanoma metastasis. We report loss of AP-2 expression in malignant tumors compared to benign tissue while PAR-1 was expressed more often in metastatic melanoma cells than in benign melanocytes. We propose that loss of AP-2 results in increased expression of PAR-1, which in turn results in upregulation of gene products that contribute to the metastatic phenotype of melanoma. ^

Targeting dysregulated nuclear proteins androgen receptor and enhancer of zeste homolog 2: Clinical implication and mechanism underline

Cancer is the most devastating disease that has tremendous impacts on public health. Many efforts have been devoted to fighting cancer through either translational or basic researches for years. Nowadays, it emerges the importance to converge these two research directions and complement to each other for battling with cancer. Thus, our study aims at both translational and basic research directions. The first goal of our study is focus on translational research to search for new agents targeting prevention and therapy of advanced prostate cancer. Hormone refractory prostate cancer is incurable and lethal. Androgen receptor (AR) mediates androgen's effect not only on the tumor initiation but also plays the major role in the relapse transition of prostate cancer. Here we demonstrate that emodin, a natural compound, can directly target AR to suppress prostate cancer cell growth in vitro and prolong the survival of C3(1)/SV40 transgenic mice in vivo. Emodin treatment resulted in repressing androgen-dependent transactivation of AR by inhibiting AR nuclear translocation. Emodin decreased the association of AR and heat shock protein 90 and increased the association of AR and MDM2, which in turn, induces AR degradation through a proteasome-mediated pathway in a ligand independent manner. Our work indicates a new mechanism for the emodin-mediated anticancer effect and justifies further investigation of emodin as a therapeutic and preventive agent for prostate cancer. The second goal of our study is try to elucidate the fundamental tumor biology of cancer progression then provide the rationale to develop more efficient therapeutic strategy. Enhancer of zeste homologue 2 (EZH2) plays an important role in many biological processes through its intrinsic methyltransferase activity to trimethylate lysine 27 in histone H3. Although overexpression of EZH2 has been shown to be involved in cancer progression, the detailed mechanisms are elusive. Here, we show that Akt phosphorylates EZH2 at serine 21 and suppresses its methyltransferase activity by impeding the binding to its substrate histone H3, resulting in a decrease of lysine 27 trimethylation and derepression of silenced genes, thus promotes cell proliferation and tumorigenicity. Our results also show that histone methylation is not permanent but regulated in a dynamic manner and that the Akt signaling pathway is involved in the regulation of this epigenetic modification through phosphorylation of EZH2, thus contributing to oncogenic processes. ^

Insulin-like growth factor binding protein 2 (IGFBP2) promotes glioma development and progression

Overexpression of insulin-like growth factor binding protein 2 (IGFBP2) is associated with progression and poor survival in many types of human cancer (such as prostate, ovarian, adrenocortical, breast, colorectal carcinomas, leukemia, and high-grade gliomas). We therefore hypothesize that IGFBP2 is a key regulator of tumor progression. We tested our hypothesis in gliomas using the somatic gene transfer RCAS-tva mouse model system, which permits the introduction of specific genes into specific, cell lineages, in this case glial cells (RCAS: Replication competent avian sarcomavirus, tv-a: avian RCAS virus receptor). Mice are transgenic and harbor the tv-a receptor under the control of a glial-specific promoter and study genes are cloned into the RCAS vector for post-natal intracranial delivery. For these experiments, the study genes were IGFBP2, platelet-derived growth factor B (PDGFB), K-Ras, Akt, and IIp45 (invasion inhibitory protein 45 kDa; known to bind and block IGFBP2 activity), which were delivered separately and in combination. Our results show that PDGFB signaling leads exclusively to the formation of low-grade (WHO grade II) oligodendrogliomas. PDGFB delivered in combination with IGFBP2 results in the formation of anaplastic oligodendrogliomas (WHO grade III), which are characterized by increased cellularity, vascular proliferation, small regions of necrosis, increased mitotic activity, and increased activation of the Akt pathway. IIp45 injected in combination with PDGFB and IGFBP2 ablates IGFBP2-induced tumor progression, which results in formation of low-grade oligodendrogliomas, and an overall reduction in tumor incidence. K-Ras expression was required to form astrocytomas with either IGFBP2 or Akt, indicating the activation of two separate pathways is necessary for gliomagenesis. In ex vivo experiments, blockade of Akt by an inhibitor led to decreased viability of cells co-expressing IGFBP2 versus PDGFB expression alone. This study provides definitive evidence, for the first time, that: (1) IGFBP2 plays a role in activation of the Akt pathway, (2) IGFBP2 collaborates with K-Ras or PDGFB in the development and progression of two major types of glioma, and (3) IGFBP2-induced tumor progression can be ablated by IIp45 or by specific inhibition of the Akt pathway. ^

The role of AKT-mediated phosphorylation in suppression of MAD1 and the development of new approach in protein complex detection

MAX dimerization protein 1 (MAD1) is a basic-helix-loop-helix transcription factors that recruits transcription repressor such as HDAC to suppress target genes transcription. It antagonizes to MYC because the promoter binding sites for MYC are usually also serve as the binding sites for MAD1 so they compete for it. However, the mechanism of the switch between MYC and MAD1 in turning on and off of genes' transcription is obscure. In this study, we demonstrated that AKT-mediated MAD1 phosphorylation inhibits MAD1 transcription repression function. The association between MAD1 and its target genes' promoter is reduced after been phosphorylated by AKT; therefore, consequently, allows MYC to occupy the binding site and activates transcription. Mutation of such phosphorylation site abrogates the inhibition from AKT. In addition, functional assays demonstrated that AKT suppressed MAD1-mediated transcription repression of its target genes hTERT and ODC. Cell cycle and cell growth were also been released from inhibition by MAD1 in the presents of AKT. Taken together, our study suggests that MAD1 is a novel substrate of AKT and AKT-mediated MAD1 phosphorylation inhibits MAD1function; therefore, activates MAD1 target genes expression. ^ Furthermore, analysis of protein-protein interaction is indispensable for current molecular biology research, but multiplex protein dynamics in cells is too complicated to be analyzed by using existing biochemical methods. To overcome the disadvantage, we have developed a single molecule level detection system with nanofluidic chip. Single molecule was analyzed based on their fluorescent profile and their profiles were plotted into 2 dimensional time co-incident photon burst diagram (2DTP). From this 2DTP, protein complexes were characterized. These results demonstrate that the nanochannel protein detection system is a promising tool for future molecular biology. ^

Increased geranylgeranylated K-Ras contributes to antineoplastic effects of farnesyltransferase inhibitors.

The Ras family of small GTPases (N-, H-, and K-Ras) is a group of important signaling mediators. Ras is frequently activated in some cancers, while others maintain low level activity to achieve optimal cell growth. In cells with endogenously low levels of active Ras, increasing Ras signaling through the ERK and p38 MAPK pathways can cause growth arrest or cell death. Ras requires prenylation – the addition of a 15-carbon (farnesyl) or 20-carbon (geranylgeranyl) group – to keep the protein anchored into membranes for effective signaling. N- and K-Ras can be alternatively geranylgeranylated (GG’d) if farnesylation is inhibited but are preferentially farnesylated. Small molecule inhibitors of farnesyltransferase (FTIs) have been developed as a means to alter Ras signaling. Our initial studies with FTIs in malignant and non-malignant cells revealed FTI-induced cell cycle arrest, reduced proliferation, and increased Ras signaling. These findings led us to the hypothesis that FTI induced increased GG’d Ras. We further hypothesized that the specific effects of FTI on cell cycle and growth result from increased signal strength of GG’d Ras. Our results did show that increase in GG’d K-Ras in particular results in reduced cell viability and cell cycle arrest. Genetically engineered constructs capable of only one type of prenylation confirmed that GG’d K-Ras recapitulated the effect of FTI in 293T cells. In tumor cell lines ERK and p38 MAPK pathways were both strongly activated in response to FTI, indicating the increased activity of GG’d K-Ras results in antiproliferative signals specifically through these pathways. These results collectively indicate FTI increases active GG’d K-Ras which activates ERK and p38 MAPKs to reduced cell viability and induce cell cycle arrest in malignant cells. This is the first report that identifies increased activity of GG’d K-Ras contributes to antineoplastic effects from FTI by increasing the activity of downstream MAPKs. Our observations suggest increased GG’d K-Ras activity, rather than inhibition of farnesylated Ras, is a major source of the cytostatic and cytotoxic effects of FTI. Our data may allow for determination of which patients would benefit from FTI by excluding tumors or diseases which have strong K-Ras signaling.

INTERACTION OF BACILLUS ANTHRACIS EXOSPORIUM PROTEIN BCLA WITH COMPLEMENT FACTOR H AND SPORE PERSISTENCE IN THE LUNG

Anthrax outbreaks in the United States and Europe and its potential use as a bioweapon have made Bacillus anthracis an interest of study. Anthrax infections are caused by the entry of B. anthracis spores into the host via the respiratory system, the gastrointestinal tract, cuts or wounds in the skin, and injection. Among these four forms, inhalational anthrax has the highest lethality rate and persistence of spores in the lungs of animals following pulmonary exposure has been noted for decades. However, details or mechanisms of spore persistence were not known. In this study, we investigated spore persistence in a mouse model. The results suggest that B. anthracis spores have special properties that promote persistence in the lung, and that there may be multiple mechanisms contributing to spore persistence. Moreover, recent discoveries from our laboratory suggest that spores evolved a sophisticated mechanism to interact with the host complement system. The complement system is a crucial part of the host defense mechanism against foreign microorganisms. Knowledge of the specific interactions that occur between the complement system and B. anthracis was limited. Studies performed in our laboratory have suggested that spores of B. anthracis can target specific proteins, such as Factor H (fH) of the complement system. Spores of B. anthracis are enclosed by an exosporium, which consists of a basal layer surrounded by a nap of hair-like filaments. The major structural component of the filaments is called Bacillus collagen-like protein of anthracis (BclA), which comprises a central collagen-like region and a globular C-terminal domain. BclA is the first point of contact with the innate system of an infected host. In this study, we investigated the molecular details of BclA-fH interaction with respect to the specific binding mechanism and the functional significance of this interaction in a murine model of anthrax infection. We hypothesized that the recruitment of fH to the spore surface by BclA limits the extent of complement activation and promotes pathogen survival and persistence in the infected host. Findings from this study are significant to understanding how to treat post-exposure prophylaxis and improve our knowledge of spores with the host immune system.