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Medicinal Chemistry Reviews - Online, Volume 2, No. 4, 2005
Contents
Bifunctional Penicillin-Binding Proteins as
an Antibacterial Target: Update on Enzymatic Properties and Cellular Functions Pp.265-275
Anne
Marie Di Guilmi
New Insights about the Potential Application
of the Association of Vitamins C (Sodium Ascorbate) and K3
(Menadione) as Auxiliary Therapy in Cancer Treatment Pp.277-282
J.
Verrax, S. Bollen, M. Delvaux, H. Taper and P. Buc Calderon
Regulating Cysteine Protease Activity: Essential
Role of Protease Inhibitors as Guardians and Regulators Pp.283-297
Boris
Turk, Dusan Turk and Guy S. Salvesen
Pandemic of Atopic Diseases – A Lack of
Microbial Exposure in Early Infancy? Pp.299-302
M.
Kalliomaki
Unnatural Protein Engineering: Producing
Proteins with Unnatural Amino Acids Pp.303-323
Thomas
J. Magliery
An Update on the Other Telomerase Inhibitors:
Non-G-Quadruplex Interactive Agent, Non-Antisense, Non-Reverse Transcriptase
Telomerase Inhibitors
Pp.325-343
L.A.
Beltz and K.P. Manfredi
Proteoglycan Involvement in Inflammatory
Diseases. New Developments in GAG-Based Therapies Pp.345-357
Maryse
Delehedde, Hugues Lortat-Jacob, John T. Gallagher, David Bonnaffe, Estelle
Adam, Olivier Querolle, Stephane Lequien, Stephane Degove, Philippe Lassalle
and David Bechard
Conformational Changes Preceding
Amyloid-Fibril Formation of Amyloid- Beta, Prion Protein and Stefin B;
Parallels in pH Dependence
Pp.359-367
Yoichi
Matsunaga , Eva Zerovnik, Tatsuo Yamada and Vito Turk
Abstracts
[Back to top] Bifunctional Penicillin-Binding Proteins as
an Antibacterial Target: Update on Enzymatic Properties and Cellular Functions
Anne
Marie Di Guilmi
Bifunctional Penicillin-Binding
Proteins (PBPs) catalyze bacterial peptidoglycan synthesis; their
glycosyltransferase (GT) activity carries out glycan chain polymerization and
the transpeptidase domain allows stem peptide cross-linking. The latter domain
is the target of b-lactam antibiotics,
while the glycosyltransfer region is a potential target for the design of novel
antibacterial drugs. This review aims at presenting recent advances related to
various aspects of bifunctional PBPs. The coordinated activity between the
different PBPs and the peptidoglycan hydrolases has been investigated by
genetic and immunofluorescence localization approaches, and the results offer
insight onto the cellular functionalities of these essential enzymes. Deletions
of all bifunctional PBPs in two Gram-positive organisms did not cause cell
death, suggesting the presence of a yet unidentified protein competent for the
polymerization of the glycan chains in the absence of the classical GT domain
of the PBPs. An important milestone in the study of the GT functionality has
been the chemical and enzymatic synthesis of the natural lipid II substrate.
This molecule has been employed in detailed study of the GT activity of
bifunctional Escherichia coli PBP1b and PBP2a from Streptococcus
pneumoniae. Mapping of the interaction between GT domains and inhibitors
(moenomycin, vancomycin) and between lipid II and various peptide antibiotics
(nisin, mersacidin, ramoplanin) may be useful in the design of new efficient
drugs inhibiting peptidoglycan bio- synthesis.
[Back to top] New Insights about the Potential Application
of the Association of Vitamins C (Sodium Ascorbate) and K3 (Menadione) as
Auxiliary Therapy in Cancer Treatment
J.
Verrax, S. Bollen, M. Delvaux, H. Taper and P. Buc Calderon
Cancer is
characterized by cell cycle deregulation, progressive loss of cell
differentiation and uncontrolled growth. Since cancer cells are particularly
sensitive to oxidative stress, we took advantage of this poor antioxidant
status to develop an experimental approach to selectively expose cancer cells
to an oxidant insult induced by the association of vitamins C and K3
(CK3). The results we obtained reinforce the major role of oxidative
stress as the main mechanism involved in cell killing by CK3, either
under in vivo or in vitro conditions. Such an antitumor activity
has been attributed to redox cycling of the vitamins and the possible
generation of peroxides and other reactive oxygen species. We report herein, on
the ability of the association of ascorbate with several quinone derivatives
(having different redox potentials) to cause cell death. Finally, we determined
that cell death by CK3 is not related to the activation of MAP
kinases pathways.
[Back to top] Regulating Cysteine Protease Activity:
Essential Role of Protease Inhibitors as Guardians and Regulators
Boris
Turk, Dusan Turk and Guy S. Salvesen
Cysteine proteases
are widespread in nature. Their implication in numerous vital processes and pathologies
make them highly attractive targets for drug design. The proper functioning and
regulation of activity of cysteine proteases is a delicate balance of many
factors, one of the most crucial being the protease
inhibitors. In this review the basic principles of physiological protease
inhibition by protein inhibitors are discussed with the focus on papain-like
cathepsins and the caspases, and their inhibitors.
[Back to top] Pandemic of Atopic Diseases – A Lack of
Microbial Exposure in Early Infancy?
M. Kalliomaki
An increase in the
frequency of allergic diseases during last several decades has been linked to
improved hygienic conditions. This review focuses on a few recent findings in
this extensive field. Accumulative data suggest that a spectrum of CD4+T
cells, including type 3 T helper cells, T regulatory 1 cells, CD25+T
cells, and natural killer T cells, has a crucial role in the regulation of
allergic inflammation. Farming environments, found protective against atopic
diseases, contain great amounts of microbial compounds, pathogen-associated
molecular patterns, which have been shown to induce activation of
immunomodulatory genes. These microbe-derived signals are mediated by
pattern-recognition receptors which activate different signal transduction
pathways in immune and non-myeloid cells. Both pathogens and commensals express
these immunomodulatory components. Better understanding of the mechanisms
operative in situ may result in new probiotic and other microbe-derived
therapies against allergic diseases.
[Back to top] Unnatural Protein Engineering: Producing
Proteins with Unnatural Amino Acids
Thomas
J. Magliery
Less than a decade
ago, the ability to generate proteins with unnatural modifications was a
Herculean task available only to specialty labs. Recent advances make it
possible to generate reasonable quantities of protein with unnatural amino
acids both in vitro and in vivo. The combination of solid-phase
peptide synthesis and enzymatic or chemoselective ligation now permits
construction of entirely-synthetic proteins as large as 25 kD. Incorporation of
recombinant fragments (expressed protein ligation) allows unnatural
modifications near protein termini in proteins of virtually any size.
Site-specific modification of small quantities of protein at any position can
be achieved using chemically-acylated tRNA. Microelectroporation now extends
this method to cells like mammalian neurons, and combination with RNA-display
makes unnatural proteins compatible with combinatorial methods. Widespread or
residue-specific methods of amino acid replacement are especially suitable for
the production of biomaterials, and bacteria have been engineered to expand the
repertoire of amino acids available for this technique. Excitingly, the
wholesale addition of engineered tRNAs and synthetases to bacteria and yeast
now makes site-specific incorporation of unnatural amino acids possible in
living cells with no chemical intervention. Methods of expanding the genetic
code at the nucleic acid level, including 4-base codons and unnatural base
pairs, are becoming useful for the addition of multiple amino acids to the
genetic code. These recent advances in unnatural protein engineering are
reviewed with an eye toward future challenges, including methods of creating
nonpeptidic molecules using templated synthesis.
[Back to top] An Update on the Other Telomerase Inhibitors:
Non-G-Quadruplex Interactive Agent, Non-Antisense, Non-Reverse Transcriptase
Telomerase Inhibitors
L.A.
Beltz and K.P. Manfredi
Human telomeres
are several kilobases of repeated (TTAGGG)n sequences at the ends of
chromosomes, a short fragment of which is lost with each cell division. This
shortening serves as a "mitotic clock", limiting the number of
divisions which normal somatic cells can undergo. Cells undergoing continuous
division need some method of bypassing this clock. One such method is the
expression of telomerase, a ribonucleoprotein that rebuilds the lost portion of
telomeres. Between 80-95% of tumors are telomerase-positive, including ovarian
and hepatocellular carcinoma, neuroblastoma, leukemia/lymphoma, and cancers of
the breast, prostate, lung, kidneys and bladder, and many immortalized cell
lines. While absent in most normal tissues, it’s expressed at higher levels in
germline tissues, bone marrow, and lymphocytes.
Due to telomerase
expression in most tumor cells and its absence in most normal tissues, telomerase
inhibitors are being investigated as anticancer agents. This review focuses on
non-reverse transcriptase inhibitor, non-oligonucleotide, non-G-quartet
interactive agent telomerase inhibitors. These agents include: differentiating
agents, kinases and phosphatases, cell cycle and apoptosis regulating agents,
immunotherapeutic agents, antibiotics, steroids, bisindole derivatives, and a
variety of other compounds, including herbal medical compounds and
cyclooxygenase inhibitors. These agents hold great promise for the future
treatment of malignancies.
[Back to top] Proteoglycan Involvement in Inflammatory
Diseases. New Developments in GAG-Based Therapies
Maryse
Delehedde, Hugues Lortat-Jacob, John T. Gallagher, David Bonnaffe, Estelle
Adam, Olivier Querolle, Stephane Lequien, Stephane Degove, Philippe Lassalle
and David Bechard
Proteoglycans (PG)
are complex macromolecules which consist structurally of a core protein and
associated glycosaminoglycan (GAG) chains. The different GAG chains of PG,
heparan sulfate/heparin, dermatan/chondroitin sulfate, keratan sulfate are
synthesized as polymers of repeating disaccharide units. The structures of GAG
chains are highly diverse and confer to them a variety of structures and
functions. Without covering PG complexity in structures and roles, the most
usual classification for PG is based on their localization: being at the cell
membrane or in the extracellular matrix, being intracellular or circulating in
the blood. By virtue of the multiplicity of protein binding partners (e.g.
growth factors, chemokines), PG have been shown to be involved in the
regulation of a large number of pathophysiological processes. They are strongly
implicated in the different stages of inflammation from the recruitment of
inflammatory cells to the release of mediators of inflammation by infiltrating
leukocytes and the turnover of extracellular matrix. The overarching theme of
PG in inflammation is the regulation of the inflammatory microenvironment,
which has to change continuously and dynamically during the progression of the
inflammatory response. These changes include the modulation of the activity of
GAG-binding cytokines, growth factors, proteases and protease inhibitors. The
interactions of regulatory proteins with GAGs provide much of the focus for
GAG-based therapeutic targets and the development of GAG mimetics could have in
the near future, clinical applications as modulators of cytokine or enzyme
functions in inflammatory diseases.
[Back to top] Conformational Changes Preceding
Amyloid-Fibril Formation of Amyloid- Beta, Prion Protein and Stefin B;
Parallels in pH Dependence
Yoichi
Matsunaga , Eva Zerovnik, Tatsuo Yamada and Vito Turk
Amyloid beta (Ab) protein in Alzheimer’s disease and scrapie
prion protein (PrPsc) in Scrapie is the key component of amyloid
plaques in brain whereas stefin B is an intracellular cysteine proteinase
inhibitor, broadly distributed in different tissue and recently reported to
form amyloid fibrils in vitro. By reducing the pH to around 4.6, the
native conformation of both polypeptides is changed into less ordered,
metastable intermediates that are stabilised by formation of the more stable
fibrils. In Ab, the Glu at position 11 was found to be responsible for the
conformational change at pH 4.6. Metal ions, including copper and zinc, could
also induce conformational changes of Ab at neutral pH. The acid modified Ab conformer exhibited protease K resistance,
preferential internalisation and accumulation in the human glial cells. In
N-terminally truncated PrP90-231, spanning PrP residues 94-112 and the central
region 146-154 incorporating Glu152 was identified as a significant participant
for the conformational changes in acidic pH. In stefin B, reducing the pH to pH
3.3 results in another intermediate of the molten-globule type which also leads
to amyloid fibril formation. Multiple sequence alignment revealed distinct
similarities of Ab (1-42) peptide, stefin B (13 to 61 residues) and prion fragment (90 to
144 residues).