Establishment of a binding assay for protein kinase C isozymes using synthetic C1 peptides and development of new medicinal leads with protein kinase C isozyme and C1 domain selectivity.
Conventional and novel protein kinase C (PKC) isozymes contain two cysteine-rich C1 domains (C1A and C1B), both of which are candidate phorbol-12, 13-dibutyrate (PDBu)-binding sites. We synthesized C1 peptides of 50-70 residues corresponding to all PKC isozyme C1 domains using an Fmoc solid-phase strategy. These C1 peptides were successfully folded by zinc treatment, as monitored by electrospray ionization time-of-flight mass spectrometry. We measured the K(d)'s of [3H]PDBu for all PKC C1 peptides. Most of the C1 peptides, except for delta-C1A and theta-C1A, showed strong PDBu binding affinities with K(d)'s in the nanomolar range (0.45-7.4 nM) comparable with the respective whole PKC isozymes. The resultant C1 peptide library can be used to screen for new ligands with PKC isozyme and C1 domain selectivity. Non-tumor-promoting 1-oleoyl-2-acetyl-sn-glycerol and bryostatin 1 showed relatively strong binding to all CIA peptides of novel PKCs (delta, epsilon, and eta). In contrast, the tumor promoters (-)-indolactam-V, ingenol-3-benzoate, and PDBu bound selectively to all C1B peptides of novel PKCs. The preference of tumor promoters for the domain might be related to tumorigenesis since recent investigations proposed the involvement of novel PKCs in tumor promotion in vivo using transgenic or knockout mice. Moreover, we recently have found that a new lactone analogue of benzolactams (6) shows significant selectivity in PKCeta-C1B binding.
Irie
Kazuhiro
K
Laboratory of Organic Chemistry in Life Science, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Sakyo-ku, 606-8502, Kyoto, Japan. irie@kais.kyoto-u.ac.jp
Nakahara
Akifumi
A
Nakagawa
Yu
Y
Ohigashi
Hajime
H
Shindo
Mayumi
M
Fukuda
Hiroyuki
H
Konishi
Hiroaki
H
Kikkawa
Ushio
U
Kashiwagi
Kaori
K
Saito
Naoaki
N
D001665:Binding Sites; D007527:Isoenzymes / Q000138:chemical synthesis* / Q000378:metabolism / Q000494:pharmacology; D007769:Lactams / Q000138:chemical synthesis* / Q000378:metabolism / Q000494:pharmacology; D019151:Peptide Library; D015240:Phorbol 12,13-Dibutyrate / Q000378:metabolism*; D011493:Protein Kinase C / Q000138:chemical synthesis / Q000378:metabolism / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D015800:Protozoan Proteins
D007527:Isoenzymes; D007769:Lactams; D019151:Peptide Library; D015800:Protozoan Proteins; D015240:Phorbol 12,13-Dibutyrate; C438379:ZFK protein, Trypanosoma brucei; D017346:Protein Serine-Threonine Kinases; D011493:Protein Kinase C