RESUMO
GalNAc-glycopeptides derived from mucin MUC1 are an important class of tumor-associated antigens. α- O-glycosylation forces the peptide to adopt an extended conformation in solution, which is far from the structure observed in complexes with a model anti-MUC1 antibody. Herein, we propose a new strategy for designing potent antigen mimics based on modulating peptide/carbohydrate interactions by means of O â S/Se replacement at the glycosidic linkage. These minimal chemical modifications bring about two key structural changes to the glycopeptide. They increase the carbohydrate-peptide distance and change the orientation and dynamics of the glycosidic linkage. As a result, the peptide acquires a preorganized and optimal structure suited for antibody binding. Accordingly, these new glycopeptides display improved binding toward a representative anti-MUC1 antibody relative to the native antigens. To prove the potential of these glycopeptides as tumor-associated MUC1 antigen mimics, the derivative bearing the S-glycosidic linkage was conjugated to gold nanoparticles and tested as an immunogenic formulation in mice without any adjuvant, which resulted in a significant humoral immune response. Importantly, the mice antisera recognize cancer cells in biopsies of breast cancer patients with high selectivity. This finding demonstrates that the antibodies elicited against the mimetic antigen indeed recognize the naturally occurring antigen in its physiological context. Clinically, the exploitation of tumor-associated antigen mimics may contribute to the development of cancer vaccines and to the improvement of cancer diagnosis based on anti-MUC1 antibodies. The methodology presented here is of general interest for applications because it may be extended to modulate the affinity of biologically relevant glycopeptides toward their receptors.
Assuntos
Anticorpos Monoclonais/imunologia , Antígenos de Neoplasias/imunologia , Neoplasias da Mama/microbiologia , Carboidratos/imunologia , Glicopeptídeos/imunologia , Oxigênio/imunologia , Animais , Anticorpos Monoclonais/química , Neoplasias da Mama/patologia , Neoplasias da Mama/terapia , Carboidratos/química , Desenho de Fármacos , Feminino , Glicopeptídeos/química , Glicosídeos/química , Glicosídeos/imunologia , Glicosilação , Humanos , Neoplasias Mamárias Experimentais/imunologia , Neoplasias Mamárias Experimentais/patologia , Neoplasias Mamárias Experimentais/terapia , Camundongos , Camundongos Endogâmicos BALB C , Estrutura Molecular , Oxigênio/química , Selênio/química , Selênio/imunologia , Enxofre/química , Enxofre/imunologiaRESUMO
The ability of glycosyldiselenides to act as lectin ligands and their selective detection in plasma by (77)Se NMR is reported.
Assuntos
Lectinas/química , Compostos Organosselênicos/sangue , Humanos , Isótopos , Ligantes , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Estrutura Molecular , Selênio/químicaRESUMO
Cross-metathesis (CM) has recently emerged as a viable strategy for protein modification. Here, efficient protein CM has been demonstrated through biomimetic chemical access to Se-allyl-selenocysteine (Seac), a metathesis-reactive amino acid substrate, via dehydroalanine. On-protein reaction kinetics reveal a rapid reaction with rate constants of Seac-mediated-CM comparable or superior to off-protein rates of many current bioconjugations. This use of Se-relayed Seac CM on proteins has now enabled reactions with substrates (allyl GlcNAc, N-allyl acetamide) that were previously not possible for the corresponding sulfur analogue. This CM strategy was applied to histone proteins to install a mimic of acetylated lysine (KAc, an epigenetic marker). The resulting synthetic H3 was successfully recognized by antibody that binds natural H3-K9Ac. Moreover, Cope-type selenoxide elimination allowed this putative marker (and function) to be chemically expunged, regenerating an H3 that can be rewritten to complete a chemically enabled "write (CM)-erase (ox)-rewrite (CM)" cycle.
Assuntos
Alcenos/química , Processamento de Proteína Pós-Traducional , Proteínas/química , Selênio/química , Selenocisteína/química , Cinética , Modelos Moleculares , Conformação ProteicaRESUMO
Herein, we describe a mild and efficient Zn(II)-mediated electrophilic selenocyclization reaction of readily available and stable 3,4-O-isopropylidene-protected hydroxyalkenyl sulfides to 2-deoxy-2-phenylselenenyl-1-thio-glycosides. This material was transformed into a 2-phenylselenenyl glycal in a controlled manner using an activation-elimination sequence.
Assuntos
Selênio/química , Sulfetos/química , Tioglicosídeos/química , Espectroscopia de Ressonância Magnética , Estrutura MolecularRESUMO
Multiple, complementary methods are reported for the chemical conversion of cysteine to S-allyl cysteine on protein surfaces, a useful transformation for the exploration of olefin metathesis on proteins.