title: N-terminal carboxyl and tetrazole-containing amides as adjuvants to Grb2 SH2 domain ligand binding.
abstract: High affinity binding of peptides to Src homology 2 (SH2) domains, often requires the presence of phosphotyrosyl (pTyr) or pTyr-mimicking moieties in the N-terminal position of the binding ligand. Several reports have shown that N(alpha)-acylation of the critical pTyr residue can result in increased SH2 domain binding potency. For Grb2 SH2 domains which recognize pTyr-Xxx-Asn-NH(2) motifs, significant potency enhancement can be incurred by N(alpha)-(3-amino)Z derivatization of tripeptides such as pTyr-Ile-Asn-NH(2). Using ligands based on the high affinity pY-Ac(6)c-Asn-(naphthylpropylamide) motif, (where Ac(6)c=1-aminocyclohexanecarboxylic acid), additional reports have shown moderate potentiating effects of N(alpha)-oxalyl derivatization. The current study examined variations of the N(alpha)-oxalyl theme in the context of a Xxx-Ac(6)c-Asn-(naphthylpropylamide) platform, where Xxx=the hydrolytically stable pTyr mimetics phosphonomethyl phenylalanine (Pmp) or carboxymethyl phenylalanine (Cmf). The effects of N(alpha)-(3-amino)Z derivatization were also investigated for this platform, to ascertain whether the large binding enhancement reported for tripeptides such as pTyr-Ile-Asn-NH(2) could be observed. In ELISA-based extracellular Grb2 SH2 domain binding assays, it was found for the Pmp-based series, that extending the oxalyl carboxyl out by one methylene unit or replacing carboxyl functionality with a tetrazole isostere, resulted in binding potency greater than the parent N(alpha)-acetyl-containing compound, with enhancement approximating that observed for the N(alpha)-oxalyl derivative. When Cmf was used as the pTyr mimetic, only modest differences in IC(50) values were observed for the series. Examination of the N(alpha)-(3-amino)Z derivatized Pmp-Ac(6)c-Asn-(naphthylpropylamide), showed that binding affinity was reduced relative to the parent N(alpha)-acetyl analogue, in contrast to the reported significant enhancement of affinity observed with other peptide ligands. Treatment of MDA-453 tumor cells, which are mitogenically driven through erbB-2 tyrosine kinase-dependent pathways, with Pmp-containing inhibitors resulted in growth inhibition, with the N(alpha)-oxalyl and N(alpha)-malonyl-containing compounds exhibiting IC(50) values (4.3 and 4.6 microM, respectively) approximately five-fold lower than the parent N(alpha)-acetyl-containing compound. Tetrazole and N(alpha)-(3-amino)Z-containing inhibitors were from two- to four-fold less potent than these latter analogues in the growth inhibition assays.
authors.affiliation: Laboratory of Medicinal Chemistry, Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Building 376, FCRDC, Frederick, MD 21702-1201, USA. tburke@helix.nih.gov
authors.forename: T R
authors.initials: TR
authors.lastname: Burke
authors.forename: Z J
authors.initials: ZJ
authors.lastname: Yao
authors.forename: Y
authors.initials: Y
authors.lastname: Gao
authors.forename: J X
authors.initials: JX
authors.lastname: Wu
authors.forename: X
authors.initials: X
authors.lastname: Zhu
authors.forename: J H
authors.initials: JH
authors.lastname: Luo
authors.forename: R
authors.initials: R
authors.lastname: Guo
authors.forename: D
authors.initials: D
authors.lastname: Yang
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000577:Amides / Q000737:chemistry; D000970:Antineoplastic Agents / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D001665:Binding Sites; D004354:Drug Screening Assays, Antitumor / Q000379:methods; D004797:Enzyme-Linked Immunosorbent Assay; D051380:GRB2 Adaptor Protein; D006801:Humans; D020128:Inhibitory Concentration 50; D008024:Ligands; D009281:Naphthalenes / Q000737:chemistry* / Q000494:pharmacology*; D009842:Oligopeptides / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D011506:Proteins / Q000187:drug effects* / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013777:Tetrazoles / Q000737:chemistry; D014407:Tumor Cells, Cultured; D018909:src Homology Domains / Q000187:drug effects*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000577:Amides; D000970:Antineoplastic Agents; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; D008024:Ligands; D009281:Naphthalenes; D009842:Oligopeptides; D011506:Proteins; D013777:Tetrazoles; C045574:1H-tetrazole