Development and characterization of potent and specific peptide inhibitors of p60c-src protein tyrosine kinase using
J R Kamath1, R Liu, A M Enstrom
1Division of Hematology and Oncology, Department of Internal Medicine, UC Davis Cancer Center, University of California Davis, 4501 X Street, Sacramento, CA 95817, USA.
Abstract:
The cytoplasmic protein p60c-src, an ubiquitous non-receptor protein tyrosine kinase (PTK) is a potential anticancer target as it is over-expressed and/or constitutively active in several cancer types. In addition, the phenotype of c-src knock-out mice is consistent with osteopetrosis, which suggests that inhibitors against this enzyme may also be therapeutic for osteoporosis. Using a known peptide substrate for c-src, MIYKYYF, as a template, we have developed a series of pseudosubstrate-based peptide inhibitors. Structure-activity relationship studies have been performed on one of these inhibitors, CIYKYYF. In a kinase assay using YIYGSFK as the substrate, CIYKYY has been demonstrated to inhibit p60c-src, with an IC50 of 0.6 microm. Further truncation has led to the determination that even the smaller peptide, CIYK, is a moderately potent inhibitor with IC50 of 15 microm. Some improvement in inhibitory potency (IC50 = 11.8 microm) has been observed with the replacement of Tyr3 in CIYK with beta-phenylalanine (beta-Phe). The tetrapeptide CI(beta-Phe)K will be used as a lead compound for future development of peptidomimetics and small molecule inhibitors that have the capacity to penetrate the plasma membrane of intact cells.
Insights
Researchers developed peptide inhibitors targeting the protein tyrosine kinase (PTK) p60c-src, a potential target for cancer and osteoporosis treatments. Lead compound CI(beta-Phe)K shows promise for developing new drugs.
Area of Science:
- Biochemistry
- Pharmacology
- Molecular Biology
Background:
- p60c-src, a cytoplasmic protein tyrosine kinase (PTK), is over-expressed in various cancers, indicating its potential as an anticancer target.
- The role of c-src in osteopetrosis suggests its inhibitors may also treat osteoporosis.
Purpose of the Study:
- To design and synthesize novel pseudosubstrate-based peptide inhibitors of p60c-src.
- To investigate structure-activity relationships of these inhibitors, focusing on CIYKYYF and its derivatives.
Main Methods:
- Peptide synthesis based on the known c-src substrate MIYKYYF.
- Kinase assays to determine inhibitory potency (IC50) of synthesized peptides against p60c-src.
- Structure-activity relationship studies involving peptide truncation and amino acid substitution.
Main Results:
- The peptide CIYKYY demonstrated significant inhibition of p60c-src with an IC50 of 0.6 microm.
- Truncated peptide CIYK retained moderate inhibitory activity (IC50 = 15 microm).
- Substitution of Tyr3 with beta-phenylalanine in CIYK yielded CI(beta-Phe)K with improved potency (IC50 = 11.8 microm).
Conclusions:
- Peptide inhibitors targeting p60c-src have been successfully developed.
- The lead compound CI(beta-Phe)K serves as a basis for future peptidomimetic and small molecule inhibitor development.
- These inhibitors hold potential for treating both cancer and osteoporosis.
