title: Macrocyclization in the design of Grb2 SH2 domain-binding ligands exhibiting high potency in whole-cell systems.
abstract: While most SH2 domains bind phosphotyrosyl (pTyr) containing peptides in extended fashion, the growth factor receptor-bound protein 2 (Grb2) SH2 domain preferentially binds ligands in bend conformations. Accordingly, incorporation of bend-inducing functionality into synthetic ligands could potentially enhance their affinity for this SH2 domain. A macrocyclic tripeptide mimetic that contains a simplified pTyr surrogate lacking an alpha-nitrogen has recently been shown to exhibit high Grb2 SH2 domain-binding affinity in extracellular ELISA-based assays. However, the same compound is largely ineffective in whole-cell assays. It is known that acidic functionality originating from the alpha-nitrogen of pTyr residues or from the alpha-position of P0 pTyr mimetics not only increases binding affinity of peptides to Grb2 SH2 domains in extracellular assays but also enhances potency in cell-based systems. Such functionality is absent from the previously reported macrocycle. Therefore, the current study was undertaken to examine the effects of introducing carboxylic functionality at the pTyr mimetic alpha-position of macrocyclic ligands. It was found that such a modification not only enhanced Grb2 SH2 domain binding in extracellular assays but also conferred high efficacy in whole-cell systems. The most potent compound of the current study exhibited an IC(50) value of 0.002 microM in an extracellular ELISA-based assay, and in MDA-MB-453 cells, it both inhibited the association of Grb2 with p185(erbB-2) and exhibited antimitogenic effects with submicromolar IC50 values.
authors.affiliation: Laboratory of Medicinal Chemistry, Center for Cancer Research, National Cancer Institute-Frederick, National Institutes of Health, Frederick, Maryland 21702, USA.
authors.forename: Chang-Qing
authors.initials: CQ
authors.lastname: Wei
authors.forename: Yang
authors.initials: Y
authors.lastname: Gao
authors.forename: Kyeong
authors.initials: K
authors.lastname: Lee
authors.forename: Ribo
authors.initials: R
authors.lastname: Guo
authors.forename: Bihua
authors.initials: B
authors.lastname: Li
authors.forename: Manchao
authors.initials: M
authors.lastname: Zhang
authors.forename: Dajun
authors.initials: D
authors.lastname: Yang
authors.forename: Terrence R
authors.initials: TR
authors.lastname: Burke
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000970:Antineoplastic Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D002460:Cell Line; D003500:Cyclization; D015195:Drug Design; D004797:Enzyme-Linked Immunosorbent Assay; D051380:GRB2 Adaptor Protein; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D018716:Molecular Mimicry; D010455:Peptides / Q000737:chemistry*; D019000:Phosphotyrosine / Q000737:chemistry*; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*; D013329:Structure-Activity Relationship; D018909:src Homology Domains
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000970:Antineoplastic Agents; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; D008024:Ligands; D010455:Peptides; D011506:Proteins; D019000:Phosphotyrosine