Bryostatins

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Margo G Haygood - One of the best experts on this subject based on the ideXlab platform.

  • Bryostatins biological context and biotechnological prospects
    Current Opinion in Biotechnology, 2010
    Co-Authors: Amaro E Trindadesilva, Grace E Limfong, Koty H Sharp, Margo G Haygood
    Abstract:

    Bryostatins are a family of protein kinase C modulators that have potential applications in biomedicine. Found in miniscule quantities in a small marine invertebrate, lack of supply has hampered their development. In recent years, Bryostatins have been shown to have potent bioactivity in the central nervous system, an uncultivated marine bacterial symbiont has been shown to be the likely natural source of the Bryostatins, the bryostatin biosynthetic genes have been identified and characterized, and bryostatin analogues with promising biological activity have been developed and tested. Challenges in the development of Bryostatins for biomedical and biotechnological application include the cultivation of the bacterial symbiont and heterologous expression of bryostatin biosynthesis genes. Continued exploration of the biology as well as the symbiotic origin of the Bryostatins presents promising opportunities for discovery of additional Bryostatins, and new functions for Bryostatins.

  • localization of candidatus endobugula sertula and the Bryostatins throughout the life cycle of the bryozoan bugula neritina
    The ISME Journal, 2007
    Co-Authors: Koty H Sharp, Seana K Davidson, Margo G Haygood
    Abstract:

    ‘Candidatus Endobugula sertula,’ the uncultivated γ-proteobacterial symbiont of the marine bryozoan Bugula neritina, synthesizes Bryostatins, complex polyketides that render B. neritina larvae unpalatable to predators. Although the symbiosis is well described, little is known about the locations of ‘E. sertula’ or the Bryostatins throughout larval settlement, metamorphosis and early development. In this study, we simultaneously localized ‘E. sertula’ and the Bryostatins in multiple stages of the B. neritina life cycle, using a novel bryostatin detection method based on its known ability to bind mammalian protein kinase C. Our results suggest that the Bryostatins are deposited onto the exterior of B. neritina larvae during embryonic development, persist on the larval surface throughout metamorphosis and are shed prior to cuticle formation. During metamorphosis, ‘E. sertula’ remains adhered to the larval pallial epithelium and is incorporated into the preancestrula cystid tissue layer, which ultimately develops into a bud and gives rise to the next zooid in the colony. Colocalization of bryostatin signal with aggregates of ‘E. sertula’ in buds of ancestrulae suggested new synthesis of Bryostatins in ancestrulae. In adult B. neritina colonies, symbiont microcolonies were observed in the funicular cords of rhizoids, which likely result in asexual transmission of ‘E. sertula’ to regenerated colonies. Furthermore, bryostatin signal was detected on the surface of the rhizoids of adult B. neritina colonies. Through simultaneous localization of the Bryostatins and the ‘E. sertula,’ we determined how ‘E. sertula’ is transmitted, and identified shifts in bryostatin localization throughout the life cycle of the host B. neritina.

  • evidence for the biosynthesis of Bryostatins by the bacterial symbiont candidatus endobugula sertula of the bryozoan bugula neritina
    Applied and Environmental Microbiology, 2001
    Co-Authors: Margo G Haygood, Seana K Davidson, Scott W Allen, Christine Anderson
    Abstract:

    The marine bryozoan, Bugula neritina, is the source of the Bryostatins, a family of macrocyclic lactones with anticancer activity. Bryostatins have long been suspected to be bacterial products. B. neritina harbors the uncultivated gamma proteobacterial symbiont “Candidatus Endobugula sertula.” In this work several lines of evidence are presented that show that the symbiont is the most likely source of Bryostatins. Bryostatins are complex polyketides similar to bacterial secondary metabolites synthesized by modular type I polyketide synthases (PKS-I). PKS-I gene fragments were cloned from DNA extracted from the B. neritina-“E. sertula” association, and then primers specific to one of these clones, KSa, were shown to amplify the KSa gene specifically and universally from total B. neritina DNA. In addition, a KSa RNA probe was shown to bind specifically to the symbiotic bacteria located in the pallial sinus of the larvae of B. neritina and not to B. neritina cells or to other bacteria. Finally, B. neritina colonies grown in the laboratory were treated with antibiotics to reduce the numbers of bacterial symbionts. Decreased symbiont levels resulted in the reduction of the KSa signal as well as the bryostatin content. These data provide evidence that the symbiont E. sertula has the genetic potential to make Bryostatins and is necessary in full complement for the host bryozoan to produce normal levels of Bryostatins. This study demonstrates that it may be possible to clone bryostatin genes from B. neritina directly and use these to produce Bryostatins in heterologous host bacteria.

  • identification of sibling species of the bryozoan bugula neritina that produce different anticancer Bryostatins and harbor distinct strains of the bacterial symbiont candidatus endobugula sertula
    The Biological Bulletin, 1999
    Co-Authors: Seana K Davidson, Margo G Haygood
    Abstract:

    Although the cosmopolitan marine bryozoan Buga chemotype M lacks Bryostatins with the octa-2,4- dienoate substituent. B. neritina contains a symbiotic y-pro- teobacterium "Cundidutus Endobugula sertula," and it has been proposed that Bryostatins may be synthesized by bac- terial symbionts. In this study, B. neritina populations along the California coast were sampled for genetic variation and bryostatin content. Colonies that differ in chemotype also differ genetically by 8% in the mitochondrial cytochrome c oxidase subunit 1 (CO I) gene; this difference is sufficient to suggest that the chemotypes represent different species. Each species contains a distinct strain of "E. sertula" that differs at four nucleotide sites in the small subunit ribo- somal RNA (SSU rRNA) gene. These results indicate that the chemotypes have a genetic basis rather than an environ- mental cause. Gene sequences from an Atlantic sample matched sequences from the California chemotype M col- onies, suggesting that this type may be cosmopolitan due to transport on boat hulls.

  • Bacterial Symbionts of the Bryostatin-Producing Bryozoan Bugula Neritina
    New Developments in Marine Biotechnology, 1998
    Co-Authors: Margo G Haygood, Seana K Davidson
    Abstract:

    Bugula neritina (Cheilostomata, Cellularoidea) is an arborescent bryozoan with a cosmopolitan distribution in temperate marine waters. Bugula neritina is a subject of current research interest because it is the source of the Bryostatins (Pettit, 1991) a family of cytotoxic macrocyclic lactones, one of which, bryostatin 1, is currently in clinical trials for treatment of cancer (Jayson et al., 1995; Philip et al., 1993; Prendiville et al., 1993). Many bryozoans produce alkaloids (Anthoni et al., 1990) presumably as a chemical defense, but B. neritina is the only bryozoan currently known to produce complex polyketides. Polyketides are compounds typically produced by actinomycetes and fungi, and in at least one case by a proteobacterium (Schupp et al., 1995).

Eric J Thomas - One of the best experts on this subject based on the ideXlab platform.

  • synthesis of vinylic iodides for incorporation into the c17 c27 fragment of Bryostatins
    Tetrahedron, 2017
    Co-Authors: Thomas J Gregson, Eric J Thomas
    Abstract:

    Abstract Vinylic iodides were identified as useful intermediates for the synthesis of the C17-C27 fragment of the Bryostatins with control of the geometry of the exocyclic methoxycarbonylmethylene group. Following literature precedent, the Piers ( E )-stereoselective addition of tributyltin hydride to an alkynoate followed by ester reduction and tin-iodine exchange gave vinylic iodides that could be used to form the C20-C21 bond of the Bryostatins. Chelation controlled addition of lithiated 3-silyloxypropynes to 2-alkoxyaldehydes followed by reductive iodination was used to prepare vinylic iodides that could be used in the complementary assembly of the C21-C22 bond of the Bryostatins. Initial studies of the synthesis of intermediates for metathesis studies using metal catalysed reactions of a vinylic iodide for C21-C22 bond formation were complicated by cyclisation reactions.

  • some limitations of an approach to the assembly of Bryostatins by ring closing metathesis
    Organic and Biomolecular Chemistry, 2017
    Co-Authors: Raphael Dumeunier, Thomas J Gregson, Somhairle Maccormick, Hiroki Omori, Eric J Thomas
    Abstract:

    Preliminary studies into the use of ring-closing metathesis (RCM) in a convergent approach for the total synthesis of Bryostatins are described. An ester that would have provided an advanced intermediate for a synthesis of a 20-deoxybryostatin by a RCM was prepared from an unsaturated acid and alcohol corresponding to the C1–C16 and C17–C27 fragments. However, studies of the formation of the C16–C17 double-bond by RCM were not successful and complex mixtures of products were obtained. To provide an insight into factors that may be involved in hindering RCM in this system, a slightly simplified C1–C16 acid and modified C17–C25 alcohols were prepared and their use for the synthesis of analogues of Bryostatins was investigated. Although only low yields were obtained, it appeared that macrolides analogous to the Bryostatins can be prepared by RCM, using the Grubbs II catalyst, if the precursors lack the two methyl groups at C18. RCM was not observed, however, for substrates in which these methyl groups were present.

  • synthesis of c16 c27 fragments of Bryostatins modified by 20 20 difluorination
    Tetrahedron Letters, 2015
    Co-Authors: Paul R Mears, Eric J Thomas
    Abstract:

    2-Hydroxytetrahydropyrans corresponding to the C16–C27 fragment of Bryostatins which have been difluorinated at C20 (bryostatin numbering) have been synthesised. The fluorine substituents were introduced by difluoroallylation. An (E)-selective Wittig reaction using a stabilised ylide provided the required methoxycarbonylmethylene substituent with excellent stereoselectivity.

  • Synthesis of C16–C27-fragments of Bryostatins modified by 20,20-difluorination
    Tetrahedron Letters, 2015
    Co-Authors: Paul R Mears, Eric J Thomas
    Abstract:

    2-Hydroxytetrahydropyrans corresponding to the C16–C27 fragment of Bryostatins which have been difluorinated at C20 (bryostatin numbering) have been synthesised. The fluorine substituents were introduced by difluoroallylation. An (E)-selective Wittig reaction using a stabilised ylide provided the required methoxycarbonylmethylene substituent with excellent stereoselectivity.

  • Approaches to the total synthesis of biologically active natural products: studies directed towards Bryostatins
    Phytochemistry Reviews, 2010
    Co-Authors: Anthony P. Green, Simon Hardy, Eric J Thomas
    Abstract:

    Progress on a total synthesis of the marine natural products, the Bryostatins, is reviewed. Following studies aimed at the synthesis of the 1,16- and 17,27-fragments, procedures for the assembly of the macrocyclic ring of the Bryostatins were investigated. Although ring-closing metathesis was not found to be useful for the synthesis of Bryostatins with geminal dimethyl groups at C18, the modified Julia reaction was found to be useful for the stereoselective formation of the 16,17-double-bond and led to a synthesis of an advanced macrocyclic intermediate. Several novel synthetic procedures feature in this work.

Peter M. Blumberg - One of the best experts on this subject based on the ideXlab platform.

  • Munc13 Is a Molecular Target of Bryostatin 1.
    Biochemistry, 2019
    Co-Authors: Francisco A. Blanco, Noemi Kedei, Agnes Czikora, Gary A. Mitchell, Satyabrata Pany, Anamitra Ghosh, Peter M. Blumberg
    Abstract:

    Bryostatin 1 is a natural macrolide shown to improve neuronal connections and enhance memory in mice. Its mechanism of action is largely attributed to the modulation of novel and conventional protein kinase Cs (PKCs) by binding to their regulatory C1 domains. Munc13-1 is a C1 domain-containing protein that shares common endogenous and exogenous activators with novel and conventional PKC subtypes. Given the essential role of Munc13-1 in the priming of synaptic vesicles and neuronal transmission overall, we explored the potential interaction between bryostatin 1 and Munc13-1. Our results indicate that in vitro bryostatin 1 binds to both the isolated C1 domain of Munc13-1 (Ki = 8.07 ± 0.90 nM) and the full-length Munc13-1 protein (Ki = 0.45 ± 0.04 nM). Furthermore, confocal microscopy and immunoblot analysis demonstrated that in intact HT22 cells bryostatin 1 mimics the actions of phorbol esters, a previously established class of Munc13-1 activators, and induces plasma membrane translocation of Munc13-1, a h...

  • Biological activity of the bryostatin analog Merle 23 on mouse epidermal cells and mouse skin.
    Molecular Carcinogenesis, 2016
    Co-Authors: Jessica S. Kelsey, Jin-qiu Chen, Michelle A. Herrmann, Mark E. Petersen, Gary E. Keck, Christophe Cataisson, Stuart H. Yuspa, David O. Baumann, Kevin M. Mcgowan, Peter M. Blumberg
    Abstract:

    : Bryostatin 1, a complex macrocyclic lactone, is the subject of multiple clinical trials for cancer chemotherapy. Although bryostatin 1 biochemically functions like the classic mouse skin tumor promoter phorbol 12-myristate 13-acetate (PMA) to bind to and activate protein kinase C, paradoxically, it fails to induce many of the typical phorbol ester responses, including tumor promotion. Intense synthetic efforts are currently underway to develop simplified bryostatin analogs that preserve the critical functional features of bryostatin 1, including its lack of tumor promoting activity. The degree to which bryostatin analogs maintain the unique pattern of biological behavior of bryostatin 1 depends on the specific cellular system and the specific response. Merle 23 is a significantly simplified bryostatin analog that retains bryostatin like activity only to a limited extent. Here, we show that in mouse epidermal cells the activity of Merle 23 was either similar to bryostatin 1 or intermediate between bryostatin 1 and PMA, depending on the specific parameter examined. We then examined the hyperplastic and tumor promoting activity of Merle 23 on mouse skin. Merle 23 showed substantially reduced hyperplasia and was not tumor promoting at a dose comparable to that for PMA. These results suggest that there may be substantial flexibility in the design of bryostatin analogs that retain its lack of tumor promoting activity. © 2016 Wiley Periodicals, Inc.

  • Neristatin 1 provides critical insight into bryostatin 1 structure-function relationships.
    Journal of Natural Products, 2015
    Co-Authors: Noemi Kedei, George R. Pettit, Cherry L. Herald, Matthew B. Kraft, Gary E. Keck, Noeleen Melody, Peter M. Blumberg
    Abstract:

    Bryostatin 1, a complex macrocyclic lactone isolated from Bugula neritina, has been the subject of multiple clinical trials for cancer. Although it functions as an activator of protein kinase C (PKC) in vitro, bryostatin 1 paradoxically antagonizes most responses to the prototypical PKC activator, the phorbol esters. The bottom half of the bryostatin 1 structure has been shown to be sufficient to confer binding to PKC. In contrast, we have previously shown that the top half of the bryostatin 1 structure is necessary for its unique biological behavior to antagonize phorbol ester responses. Neristatin 1 comprises a top half similar to that of bryostatin 1 together with a distinct bottom half that confers PKC binding. We report here that neristatin 1 is bryostatin 1-like, not phorbol ester-like, in its biological activity on U937 promyelocytic leukemia cells. We conclude that the top half of the bryostatin 1 structure is largely sufficient for bryostatin 1-like activity, provided the molecule also possesses ...

  • Abstract 2454: Comparison of the activity of the bryostatin derivative Merle 23 with that of bryostatin 1 and phorbol ester in mouse epidermal cells.
    Cancer Research, 2013
    Co-Authors: Jessica S. Kelsey, Noemi Kedei, Mark E. Petersen, Gary E. Keck, Christophe Cataisson, Stuart H. Yuspa, Peter M. Blumberg
    Abstract:

    Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Tumor promoting phorbol esters, such as PMA, are potent activators of the PKC pathway. The Bryostatins, marine natural products, activate PKCs similarly to phorbol esters but paradoxically inhibit most phorbol ester responses, including skin tumor promotion. Because of this inhibitory activity on the PKC pathway, bryostatin 1 has been the subject of extensive clinical trials. Serious impediments to clinical development, however, have been the scarcity of natural supplies coupled with great structural complexity, making synthesis problematic. Recent synthetic advances are now yielding simplified structural derivatives. Here, we compare the behavior of the bryostatin derivative Merle 23 with that of bryostatin 1 and phorbol 12-myristate 13-acetate (PMA) in mouse epidermal cells. While having similar binding activity on PKC as does bryostatin 1, Merle 23 behaves like PMA rather than like bryostatin 1 in U937 human leukemia cells but conversely behaves more like bryostatin 1 in the human prostate cancer cell line LNCaP. As a first step in assessing whether Merle 23 possesses or lacks skin tumor promoting activity, its activity in mouse primary keratinocyte cultures was assessed. PMA induces a prominent, prolonged morphological response in keratinocytes. Bryostatin 1 induces a similar initial response, which is however very transient. The morphological response to Merle 23 is more prolonged than for bryostatin 1 but much shorter than for PMA. For initial activation of PKCδ or induction of ERK1/2 phosphorylation, all three ligands show similar activity. By 24 hrs, however, bryostatin 1 is much more potent for down regulation of PKCα, whereas Merle 23 and PMA are similar. For PKCδ, bryostatin 1 at higher concentrations protects PKCδ from down regulation whereas Merle 23 does not. Transcriptional responses of various inflammation genes were monitored by qPCR. PMA causes the greatest increase in transcript levels for all genes investigated. In many cases bryostatin 1 induces a smaller response and the response to Merle 23 generally resembles that of bryostatin 1. While these studies are ongoing, they suggest that Merle 23 largely behaves like bryostatin 1 in the mouse epidermal cells. Our findings emphasize the important role of cellular context in determining the pattern of behavior of Merle 23. An important implication is that different cellular environments reveal different structure activity relations for bryostatin 1-like behavior. Finally, our studies raise the possibility that Merle 23, which is significantly simplified relative to bryostatin 1 in its upper two rings, may be non-promoting, at least in the mouse skin tumor promotion system. Citation Format: Jessica Kelsey, Noemi Kedei, Christophe Cataisson, Mark Petersen, Stuart Yuspa, Gary Keck, Peter Blumberg. Comparison of the activity of the bryostatin derivative Merle 23 with that of bryostatin 1 and phorbol ester in mouse epidermal cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2454. doi:10.1158/1538-7445.AM2013-2454

  • Comparison of transcriptional response to phorbol ester, bryostatin 1, and bryostatin analogs in LNCaP and U937 cancer cell lines provides insight into their differential mechanism of action.
    Biochemical Pharmacology, 2012
    Co-Authors: Noemi Kedei, Andrea Telek, Aleksandra M. Michalowski, Matthew B. Kraft, Wei Li, Yam B. Poudel, Arnab Rudra, Mark E. Petersen, Gary E. Keck, Peter M. Blumberg
    Abstract:

    Abstract Bryostatin 1, like the phorbol esters, binds to and activates protein kinase C (PKC) but paradoxically antagonizes many but not all phorbol ester responses. Previously, we have compared patterns of biological response to bryostatin 1, phorbol ester, and the bryostatin 1 derivative Merle 23 in two human cancer cell lines, LNCaP and U937. Bryostatin 1 fails to induce a typical phorbol ester biological response in either cell line, whereas Merle 23 resembles phorbol ester in the U937 cells and bryostatin 1 in the LNCaP cells. Here, we have compared the pattern of their transcriptional response in both cell lines. We examined by qPCR the transcriptional response as a function of dose and time for a series of genes regulated by PKCs. In both cell lines bryostatin 1 differed primarily from phorbol ester in having a shorter duration of transcriptional modulation. This was not due to bryostatin 1 instability, since bryostatin 1 suppressed the phorbol ester response. In both cell lines Merle 23 induced a pattern of transcription largely like that of phorbol ester although with a modest reduction at later times in the LNCaP cells, suggesting that the difference in biological response of the two cell lines to Merle 23 lies downstream of this transcriptional regulation. For a series of Bryostatins and analogs which ranged from bryostatin 1-like to phorbol ester-like in activity on the U937 cells, the duration of transcriptional response correlated with the pattern of biological activity, suggesting that this may provide a robust platform for structure activity analysis.

Seana K Davidson - One of the best experts on this subject based on the ideXlab platform.

  • localization of candidatus endobugula sertula and the Bryostatins throughout the life cycle of the bryozoan bugula neritina
    The ISME Journal, 2007
    Co-Authors: Koty H Sharp, Seana K Davidson, Margo G Haygood
    Abstract:

    ‘Candidatus Endobugula sertula,’ the uncultivated γ-proteobacterial symbiont of the marine bryozoan Bugula neritina, synthesizes Bryostatins, complex polyketides that render B. neritina larvae unpalatable to predators. Although the symbiosis is well described, little is known about the locations of ‘E. sertula’ or the Bryostatins throughout larval settlement, metamorphosis and early development. In this study, we simultaneously localized ‘E. sertula’ and the Bryostatins in multiple stages of the B. neritina life cycle, using a novel bryostatin detection method based on its known ability to bind mammalian protein kinase C. Our results suggest that the Bryostatins are deposited onto the exterior of B. neritina larvae during embryonic development, persist on the larval surface throughout metamorphosis and are shed prior to cuticle formation. During metamorphosis, ‘E. sertula’ remains adhered to the larval pallial epithelium and is incorporated into the preancestrula cystid tissue layer, which ultimately develops into a bud and gives rise to the next zooid in the colony. Colocalization of bryostatin signal with aggregates of ‘E. sertula’ in buds of ancestrulae suggested new synthesis of Bryostatins in ancestrulae. In adult B. neritina colonies, symbiont microcolonies were observed in the funicular cords of rhizoids, which likely result in asexual transmission of ‘E. sertula’ to regenerated colonies. Furthermore, bryostatin signal was detected on the surface of the rhizoids of adult B. neritina colonies. Through simultaneous localization of the Bryostatins and the ‘E. sertula,’ we determined how ‘E. sertula’ is transmitted, and identified shifts in bryostatin localization throughout the life cycle of the host B. neritina.

  • evidence for the biosynthesis of Bryostatins by the bacterial symbiont candidatus endobugula sertula of the bryozoan bugula neritina
    Applied and Environmental Microbiology, 2001
    Co-Authors: Margo G Haygood, Seana K Davidson, Scott W Allen, Christine Anderson
    Abstract:

    The marine bryozoan, Bugula neritina, is the source of the Bryostatins, a family of macrocyclic lactones with anticancer activity. Bryostatins have long been suspected to be bacterial products. B. neritina harbors the uncultivated gamma proteobacterial symbiont “Candidatus Endobugula sertula.” In this work several lines of evidence are presented that show that the symbiont is the most likely source of Bryostatins. Bryostatins are complex polyketides similar to bacterial secondary metabolites synthesized by modular type I polyketide synthases (PKS-I). PKS-I gene fragments were cloned from DNA extracted from the B. neritina-“E. sertula” association, and then primers specific to one of these clones, KSa, were shown to amplify the KSa gene specifically and universally from total B. neritina DNA. In addition, a KSa RNA probe was shown to bind specifically to the symbiotic bacteria located in the pallial sinus of the larvae of B. neritina and not to B. neritina cells or to other bacteria. Finally, B. neritina colonies grown in the laboratory were treated with antibiotics to reduce the numbers of bacterial symbionts. Decreased symbiont levels resulted in the reduction of the KSa signal as well as the bryostatin content. These data provide evidence that the symbiont E. sertula has the genetic potential to make Bryostatins and is necessary in full complement for the host bryozoan to produce normal levels of Bryostatins. This study demonstrates that it may be possible to clone bryostatin genes from B. neritina directly and use these to produce Bryostatins in heterologous host bacteria.

  • identification of sibling species of the bryozoan bugula neritina that produce different anticancer Bryostatins and harbor distinct strains of the bacterial symbiont candidatus endobugula sertula
    The Biological Bulletin, 1999
    Co-Authors: Seana K Davidson, Margo G Haygood
    Abstract:

    Although the cosmopolitan marine bryozoan Buga chemotype M lacks Bryostatins with the octa-2,4- dienoate substituent. B. neritina contains a symbiotic y-pro- teobacterium "Cundidutus Endobugula sertula," and it has been proposed that Bryostatins may be synthesized by bac- terial symbionts. In this study, B. neritina populations along the California coast were sampled for genetic variation and bryostatin content. Colonies that differ in chemotype also differ genetically by 8% in the mitochondrial cytochrome c oxidase subunit 1 (CO I) gene; this difference is sufficient to suggest that the chemotypes represent different species. Each species contains a distinct strain of "E. sertula" that differs at four nucleotide sites in the small subunit ribo- somal RNA (SSU rRNA) gene. These results indicate that the chemotypes have a genetic basis rather than an environ- mental cause. Gene sequences from an Atlantic sample matched sequences from the California chemotype M col- onies, suggesting that this type may be cosmopolitan due to transport on boat hulls.

  • biology of the Bryostatins in the marine bryozoan bugula neritina symbiosis cryptic speciation and chemical defense
    California Sea Grant College Program, 1999
    Co-Authors: Seana K Davidson
    Abstract:

    Author(s): Davidson, Seana K. | Abstract: This dissertation investigates the identity and function of a bacterial symbiont described in the marine bryozoan Bugula neritina by R.M. Woollacott in 1981. B. neritina is the source of Bryostatins, unique cytotoxins suspected to have a bacterial source, and is considered a single species throughout its cosmopolitan temperate range. Bryostatins found from different collections of B. neritina vary, and only certain populations produce Bryostatins that possess an octa-2,4-dienoate substituent. In this dissertation the bacterial symbionts of the larvae are identified by small subunit ribosomal rRNA {SSU) gene sequences and named "Candidatus Endobugula sertula." The variable regions of these genes were used to design oligonucleotides specific to the symbiont. These specific oligonucleotides were used for in situ hybridization to the bacteria in the pallial sinus to confirm the origin of the sequence, and for specific amplification of symbiont SSU rRNA genes by PCR. Then the mitochondrial cytochrome c oxidase subunit I gene was used to identify two distinct species of B. neritina each harboring a different symbiont as determined by SSU rRNA sequence. Variation in the bryostatin profiles is associated with this genetic difference. Only one B. neritina/"E. sertula" association can produce Bryostatins with an octa-2,4-dienoate substituent (Bryostatins 1-3, 12 and 15). In order to elucidate the possible involvement of the symbiont in production of Bryostatins, experiments were conducted to eliminate "E. sertula" from R. neritina to determine whether B. neritina can continue to grow normally without the symbiont, and/or continue to produce equivalent levels of Bryostatins. Symbiont levels were estimated using a symbiont-specific PCR assay, then bryostatin activity levels were compared between control and treated B. neritina colonies. When symbiont levels were greatly reduced, bryostatin activity declined by approximately 50%. Genetic evidence was discovered that indicates "E. sertuld" has the potential to synthesize complex polyketides like bryostatin. Finally evidence was gathered to address the hypothesis that Bryostatins serve as defensive compounds for the bryozoan host. The distribution of Bryostatins in the colonies is suggestive of a defense, and it was found that predatory nudibranchs of B. neritina sequester Bryostatins and concentrate them in their egg ribbons. In summary, the symbiont's most likely function is to provide a chemical defense, Bryostatins, for the host.

  • Bacterial Symbionts of the Bryostatin-Producing Bryozoan Bugula Neritina
    New Developments in Marine Biotechnology, 1998
    Co-Authors: Margo G Haygood, Seana K Davidson
    Abstract:

    Bugula neritina (Cheilostomata, Cellularoidea) is an arborescent bryozoan with a cosmopolitan distribution in temperate marine waters. Bugula neritina is a subject of current research interest because it is the source of the Bryostatins (Pettit, 1991) a family of cytotoxic macrocyclic lactones, one of which, bryostatin 1, is currently in clinical trials for treatment of cancer (Jayson et al., 1995; Philip et al., 1993; Prendiville et al., 1993). Many bryozoans produce alkaloids (Anthoni et al., 1990) presumably as a chemical defense, but B. neritina is the only bryozoan currently known to produce complex polyketides. Polyketides are compounds typically produced by actinomycetes and fungi, and in at least one case by a proteobacterium (Schupp et al., 1995).

George R. Pettit - One of the best experts on this subject based on the ideXlab platform.

  • Neristatin 1 provides critical insight into bryostatin 1 structure-function relationships.
    Journal of Natural Products, 2015
    Co-Authors: Noemi Kedei, George R. Pettit, Cherry L. Herald, Matthew B. Kraft, Gary E. Keck, Noeleen Melody, Peter M. Blumberg
    Abstract:

    Bryostatin 1, a complex macrocyclic lactone isolated from Bugula neritina, has been the subject of multiple clinical trials for cancer. Although it functions as an activator of protein kinase C (PKC) in vitro, bryostatin 1 paradoxically antagonizes most responses to the prototypical PKC activator, the phorbol esters. The bottom half of the bryostatin 1 structure has been shown to be sufficient to confer binding to PKC. In contrast, we have previously shown that the top half of the bryostatin 1 structure is necessary for its unique biological behavior to antagonize phorbol ester responses. Neristatin 1 comprises a top half similar to that of bryostatin 1 together with a distinct bottom half that confers PKC binding. We report here that neristatin 1 is bryostatin 1-like, not phorbol ester-like, in its biological activity on U937 promyelocytic leukemia cells. We conclude that the top half of the bryostatin 1 structure is largely sufficient for bryostatin 1-like activity, provided the molecule also possesses ...

  • chapter 12 biosynthetic products for anticancer drug design and treatment the Bryostatins
    Anticancer Drug Development, 2002
    Co-Authors: George R. Pettit, Cherry L. Herald, Fiona Hogan
    Abstract:

    The chapter focuses on the use of Bryostatins for anticancer drug design and treatment. The field of anticancer drug discovery based on natural products is vast and covers many areas, including isolation, chemical identification, and synthesis, preclinical evaluation, both in vitro and in vivo, and clinical trials. The U.S. National Cancer Institute (NCI) research programs directed at discovery of new and clinically useful animal, plant, and microorganism anticancer constituents were implemented in September 1957, and quickly demonstrated that 2–4% of plant specimens produce a great variety of anticancer agents. Because of this vitally important NCI endeavor, new antineoplastic and/or cytotoxic biosynthetic products are now being discovered worldwide at an increasing rate, and the potential for discovery of new animal, plant, and microorganism biosynthetic products for treatment of human cancer is truly extraordinary, and offers great promise of many curative approaches to the cancer problem. The experiments conducted by Dr. Blumberg in the NCI showed that the potent anticancer activity of bryostatin and Bryostatins was primarily based on modulation of protein kinase C (PKC). Compared to various PKC interactive substances, bryostatin has proved to be a very potent antitumor-promoting agent, and a very promising anticancer drug. Bryostatin was also found to be an immune stimulant. Bryostatin was also found to stimulate the normal production of interleukin-2 (IL-2) and interferon, and it has provided curative levels of activity against a variety of murine experimental cancer systems.

  • The inhibitory effects of bryostatin 1 administration on the growth of rabbit papillomas
    Cancer Letters, 1999
    Co-Authors: Jason M. Bodily, George R. Pettit, Cherry L. Herald, David J Hoopes, Beverly L. Roeder, Sharon G Gilbert, Darin N Rollins, Richard A. Robison
    Abstract:

    Abstract Bryostatin 1 is a protein kinase C modulator that shows antineoplastic activity in a variety of tumor systems. This study examined the effects of bryostatin 1 administration on papilloma growth in rabbits. Investigations of optimal route, dose, and schedule were performed. Several groups of rabbits were inoculated with cottontail rabbit papillomavirus (CRPV) DNA. Bryostatin 1 was administered i.v., both daily and weekly, and intralesionally both weekly and bi-weekly. Intralesionally dosed papillomas were examined histologically for immune cell infiltration. In weekly and daily i.v. trials, 2.5 and 1.0 μg/kg, respectively, showed the greatest overall reduction in tumor size. Bryostatin 1 administered intralesionally also slowed papilloma growth. Treated lesions had significantly higher numbers of heterophils and eosinophils.

  • Bryostatin 1 Induces Biphasic Activation of Protein Kinase D in Intact Cells
    Journal of Biological Chemistry, 1997
    Co-Authors: Sharon A. Matthews, George R. Pettit, Enrique Rozengurt
    Abstract:

    Abstract Bryostatin 1 and phorbol esters are both potent activators of protein kinase C (PKC), although their specific biological effects can differ in many systems. Here, we report that bryostatin 1 activates protein kinase D (PKD), a novel serine/threonine protein kinase, in intact Swiss 3T3 cells and secondary mouse embryo fibroblasts and in COS-7 cells transiently transfected with a PKD expression construct. The dose response of PKD activation induced by bryostatin 1 follows a striking biphasic pattern with maximal activation achieved at a concentration of 10 nm. Higher concentrations of bryostatin 1 (100 nm) reduced PKD activation induced by phorbol 12,13-dibutyrate to levels stimulated by bryostatin 1 alone. Bryostatin 1-induced PKD activation was markedly attenuated by treatment of cells with the PKC inhibitors bisindolylmaleimide I and Ro 31-8220. However, these agents did not inhibit PKD activity when added directly to in vitro kinase assays, suggesting that bryostatin 1 stimulates PKD activation through a PKC-dependent pathway in intact cells. Our results raise the possibility that activated PKD in intact cells could mediate some of the multiple biphasic biological responses induced by bryostatin 1.

  • the Bryostatins inhibit growth of b16 f10 melanoma cells in vitro through a protein kinase c independent mechanism dissociation of activities using 26 epi bryostatin 1
    Cancer Research, 1996
    Co-Authors: Zoltan Szallasi, George R. Pettit, Nancy E. Lewin, Linh Du, Rachel Levine, Phi Nga Nguyen, Michael D Williams, Peter M. Blumberg
    Abstract:

    Bryostatin 1 is a potential cancer chemotherapeutic agent in Phase II clinical trials, with positive responses observed for malignant melanoma, among other tumors. The Bryostatins are known to be potent ligands for protein kinase C (PKC), functioning as partial antagonists. In the present study, we explore the mechanism by which the Bryostatins inhibit growth of B16/F10 mouse melanoma cells in vitro . Three experimental approaches suggest that the growth inhibition is independent of PKC. First, we characterized in detail the translocation and down-regulation of the PKC isozymes α, δ, and e in response to phorbol ester and bryostatin 1 in these cells. Although the dose-response curves obtained for the translocation-activation of PKC isozymes showed good correlation with the growthenhancing activity of phorbol 12-myristate 13-acetate, for no PKC isozyme was there a good correlation with the growth-inhibitory activity of bryostatin 1. Second, inhibition of PKC enzymatic activity by the specific PKC inhibitor bisindolyl-maleimide I did not block the inhibition of thymidine incorporation induced by bryostatin 1. Finally, 26-epi-bryostatin 1, a stereoisomer of the naturally occurring bryostatin 1 designed to have markedly reduced affinity for PKC, inhibited the growth of the B16/F10 melanoma cell lines with potency similar to that of bryostatin 1. We confirmed here that 26-epi-bryostatin 1 showed 60-fold reduced affinity for PKC and 30-60-fold reduced potency to translocate and downregulate PKC isozymes compared with bryostatin 1. We presume that the principal toxicity of bryostatin 1 reflects its interaction with PKC, and we would thus predict that epi-bryostatin 1 would be less toxic. Indeed, we found at least 10-fold reduced toxicity of 26-epi-bryostatin 1 in C57BL/6 mice compared with bryostatin 1. We conclude that the growth inhibition of the Bryostatins, at least in this system, does not result from interaction with PKC. As exemplified by 26-epi-bryostatin 1, this insight permits the design of analogues with comparable growth inhibition to bryostatin 1 but with reduced toxicity.