γ-Secretase cleaves multiple substrates within the transmembrane domain that include the amyloid precursor protein as well as the Notch family of receptors. These substrates are associated with ...Alzheimer disease and cancer. Despite extensive investigation of this protease, little is known regarding the regulation of γ-secretase specificity. To discover selective inhibitors for drug development and for probing the mechanisms of γ-secretase specificity, we screened chemical libraries and consequently developed a di-coumarin family of inhibitors that preferentially inhibit γ-secretase-mediated production of Aβ42 over other cleavage activities. These coumarin dimer-based compounds interact with γ-secretase by binding to an allosteric site. By developing a multiple photo-affinity probe approach, we demonstrate that this allosteric binding causes a conformational change within the active site of γ-secretase at the S2 and S1 sub-sites that leads to selective inhibition of Aβ42. In conclusion, by using these di-coumarin compounds, we reveal a mechanism by which γ-secretase specificity is regulated and provide insights into the molecular basis by which familial presenilin mutations may affect the active site and specificity of γ-secretase. Furthermore, this class of selective inhibitors provides the basis for development of Alzheimer disease therapeutic agents.
Wilms tumor protein (WT1) is a transcription factor selectively overexpressed in leukemias and cancers; clinical trials are underway that use altered WT1 peptide sequences as vaccines. Here we report ...a strategy to study peptide-MHC interactions by incorporating non-natural and photo-reactive amino acids into the sequence of WT1 peptides. Thirteen WT1 peptides sequences were synthesized with chemically modified amino acids (via fluorination and photo-reactive group additions) at MHC and T cell receptor binding positions. Certain new non-natural peptide analogs could stabilize MHC class I molecules better than the native sequences and were also able to elicit specific T-cell responses and sometimes cytotoxicity to leukemia cells. Two photo-reactive peptides, also modified with a biotin handle for pull-down studies, formed covalent interactions with MHC molecules on live cells and provided kinetic data showing the rapid clearance of the peptide-MHC complex. Despite "infinite affinity" provided by the covalent peptide bonding to the MHC, immunogenicity was not enhanced by these peptides because the peptide presentation on the surface was dominated by catabolism of the complex and only a small percentage of peptide molecules covalently bound to the MHC molecules. This study shows that non-natural amino acids can be successfully incorporated into T cell epitopes to provide novel immunological, biochemical and kinetic information.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
γ-secretase is an aspartyl protease that cleaves multiple substrates within their transmembrane domains. γ- secretase processes the amyloid precursor protein (APP) to generate β-amyloid (Aβ) peptides ...associated with Alzheimer's disease. Here, we show that APP possesses a substrate inhibitory domain (ASID) that negatively modulates γ-secretase activity for Aβ production by binding to an allosteric site within the γ-secretase complex. Alteration of this ASID by deletion or mutation, as is seen with the Flemish mutation (A21G), reduces its inhibitory potency and promotes Aβ production. Notably, peptides derived from ASID show selective inhibition of γ-secretase activity for Aβ production over Notch1 processing. Therefore, this mode of regulation represents an unprecedented mechanism for modulating γ-secretase, providing insight into the molecular basis of Alzheimer's disease pathogenesis and a potential strategy for the development of therapeutics.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
g-secretase is an aspartyl protease that cleaves multiple substrates within their transmembrane domains. g-secretase processes the amyloid precursor protein (APP) to generate g-amyloid (Ag) peptides ...associated with Alzheimer's disease. Here, we show that APP possesses a substrate inhibitory domain (ASID) that negatively modulates g-secretase activity for Ag production by binding to an allosteric site within the g-secretase complex. Alteration of this ASID by deletion or mutation, as is seen with the Flemish mutation (A21G), reduces its inhibitory potency and promotes Ag production. Notably, peptides derived from ASID show selective inhibition of g-secretase activity for Ag production over Notch1 processing. Therefore, this mode of regulation represents an unprecedented mechanism for modulating g-secretase, providing insight into the molecular basis of Alzheimer's disease pathogenesis and a potential strategy for the development of therapeutics.
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Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Gamma-secretase is an aspartyl protease that cleaves multiple substrates within their transmembrane domains. Gamma-secretase processes the amyloid precursor protein (APP) to generate gamma-amyloid ...(Agamma) peptides associated with Alzheimer's disease. Here, we show that APP possesses a substrate inhibitory domain (ASID) that negatively modulates gamma-secretase activity for Agamma production by binding to an allosteric site within the gamma-secretase complex. Alteration of this ASID by deletion or mutation, as is seen with the Flemish mutation (A21G), reduces its inhibitory potency and promotes Agamma production. Notably, peptides derived from ASID show selective inhibition of gamma-secretase activity for Agamma production over Notch1 processing. Therefore, this mode of regulation represents an unprecedented mechanism for modulating gamma-secretase, providing insight into the molecular basis of Alzheimer's disease pathogenesis and a potential strategy for the development of therapeutics. PUBLICATION ABSTRACT
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DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
6.
Griscelli syndrome Ariffin, H; Geikowski, A; Chin, T F ...
Medical journal of Malaysia
69, Številka:
4
Journal Article
We report a case of Griscelli Syndrome (GS). Our patient initially presented with a diagnosis of haemophagocytic lymphistiocytosis (HLH). Subsequent microscopic analysis of the patient's hair ...follicle revealed abnormal distribution of melanosomes in the shaft, which is a hallmark for GS. Analysis of RAB27A gene in this patient revealed a homozygous mutation in exon 6, c.550C>T, p.R184X . This nonsense mutation causes premature truncation of the protein resulting in a dysfunctional RAB27A. Recognition of GS allows appropriate institution of therapy namely chemotherapy for HLH and curative haemotopoeitic stem cell transplantation.
...-Secretase cleaves multiple substrates within the transmembrane domain that include the amyloid precursor protein as well as the Notch family of receptors. These substrates are associated with ...Alzheimer disease and cancer. Despite extensive investigation of this protease, little is known regarding the regulation of ...-secretase specificity. To discover selective inhibitors for drug development and for probing the mechanisms of ...-secretase specificity, we screened chemical libraries and consequently developed a di-coumarin family of inhibitors that preferentially inhibit ...-secretase-mediated production of Aβ42 over other cleavage activities. These coumarin dimer-based compounds interact with ...-secretase by binding to an allosteric site. By developing a multiple photo-affinity probe approach, we demonstrate that this allosteric binding causes a conformational change within the active site of ...-secretase at the S2 and Si sub-sites that leads to selective inhibition of Aβ42. In conclusion, by using these di-coumarin compounds, we reveal a mechanism by which ...-secretase specificity is regulated and provide insights into the molecular basis by which familial presenilin mutations may affect the active site and specificity of ...-secretase. Furthermore, this class of selective inhibitors provides the basis for development of Alzheimer disease therapeutic agents. (ProQuest: ... denotes formulae/symbols omitted.)
γ-Secretase cleaves multiple substrates within the transmembrane domain that include the amyloid precursor protein as well as the Notch family of receptors. These substrates are associated with ...Alzheimer disease and cancer. Despite extensive investigation of this protease, little is known regarding the regulation of γ-secretase specificity. To discover selective inhibitors for drug development and for probing the mechanisms of γ-secretase specificity, we screened chemical libraries and consequently developed a di-coumarin family of inhibitors that preferentially inhibit γ-secretase-mediated production of Aβ42 over other cleavage activities. These coumarin dimer-based compounds interact with γ-secretase by binding to an allosteric site. By developing a multiple photo-affinity probe approach, we demonstrate that this allosteric binding causes a conformational change within the active site of γ-secretase at the S2 and S1 sub-sites that leads to selective inhibition of Aβ42. In conclusion, by using these di-coumarin compounds, we reveal a mechanism by which γ-secretase specificity is regulated and provide insights into the molecular basis by which familial presenilin mutations may affect the active site and specificity of γ-secretase. Furthermore, this class of selective inhibitors provides the basis for development of Alzheimer disease therapeutic agents.
Wilms tumor protein (WT1) is a transcription factor selectively over expressed in several types of leukemia and solid tumors, making it a promising potential target antigen for immunotherapy. Several ...open clinical trials use native or altered peptide sequences derived from the WT1 protein in order to overcome the weak immunogenicity of the self-antigen. Here we report a new strategy to circumvent tolerance by designing peptides that incorporate non-natural amino acids into the native sequence of WT1 peptides. Starting from the nonamer sequences WT1 187–195 and WT1 235–243, eight peptides containing natural amino acids and nine peptides in which different chemical modifications (fluorination, photo-reactive azido groups or benzophenone groups) were introduced at major histocompatibility complex (MHC) and T cell receptor binding positions, were synthesized. The new non-natural peptides could stabilize MHC class I molecules better than the native sequences and were also able to elicit strong specific T-cell responses. Photo-reactive peptides were additionally modified with biotin handles to allow streptavidin-biotin pull down and western blot analysis of kinetics of binding and catabolism. Upon UV irradiation, these peptides covalently bound to MHC molecules on the live cells; clearance of the peptide-MHC covalent complex occurred over 24 hours, consistent with the T2 thermo-stabilization data for the same peptide. Further catabolic studies may elucidate the important or novel cellular proteins involved in antigenic peptide processing and cross presentation and should aid in vaccine development. We are investigating whether covalent interaction with the MHC may lead to alterations in immune responses as well. T cells stimulated with one of the synthetic peptides (WT1J-W4WF) cross-reacted with the native WT1J sequence and were able to kill WT1 positive HLA-A0201 matched acute lymphoblastic leukemia cell lines. In conclusion, this study shows that peptides with non-natural amino acids can be successfully incorporated into T cell epitopes to provide increased immunogenicity and novel biological information.
Gamma-secretase is an aspartyl protease that cleaves multiple substrates within their transmembrane domains. Gamma-secretase processes the amyloid precursor protein (APP) to generate gamma-amyloid ...(Agamma) peptides associated with Alzheimer's disease. Here, we show that APP possesses a substrate inhibitory domain (ASID) that negatively modulates gamma-secretase activity for Agamma production by binding to an allosteric site within the gamma-secretase complex. Alteration of this ASID by deletion or mutation, as is seen with the Flemish mutation (A21G), reduces its inhibitory potency and promotes Agamma production. Notably, peptides derived from ASID show selective inhibition of gamma-secretase activity for Agamma production over Notch1 processing. Therefore, this mode of regulation represents an unprecedented mechanism for modulating gamma-secretase, providing insight into the molecular basis of Alzheimer's disease pathogenesis and a potential strategy for the development of therapeutics.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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![Modulation of [gamma]-secre...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0027-8424/small "Modulation of [gamma]-secretase specificity using small molecule allosteric inhibitors")
