NEAT IMAGE CHO PHOTOSHOP CC ZIP
These latter findings have suggested the concept of “chemical zip codes”, whereby the different patterns of substitution will optimize the ligands for microdomains within the membrane, driving the selectivity. Using combinatorial libraries of DAG-lactones, we have shown that modifications limited to the hydrophobic side chains can lead to marked differential activity for different biological endpoints. We have described compounds with substantial selectivity between the PKC and RasGRP families of DAG signaling proteins. We have been able to achieve nM binding affinities for PKC approaching those of the phorbol ester. These structures combine a rigid template, yielding enhanced affinity, with relative chemical simplicity, permitting synthetic exploration of chemical space.
As an alternative, we have developed DAG-lactones. Because of their structural complexity, however, these compounds have been problematic for detailed structure function studies.
Natural products such as bryostatin 1 or phorbol ester function as ultrapotent analogs of DAG, where their structural rigidity maintains their pharmacophoric groups in an optimal orientation for C1 domain interaction. The phospholipid headgroups have interactions with the DAG or DAG analog and the side chains of the DAG or DAG analog will insert into and interact with the hydrophobic core of the lipid bilayer. A complication is that the phospholipid surface itself contributes to the binding complex. The increased hydrophobicity of the ligand-C1 domain complex promotes membrane insertion of the C1 domain, both leading to a conformation change of the PKC accompanied by PKC activation and driving translocation of the PKC from the cytosol to the membrane. Ligand binding completes the hydrophobic surface and additional hydrophobicity is contributed by hydrophobic substituents on the ligand such as the fatty acid side chains of the DAG. It possesses a hydrophilic binding cleft surrounded by a hydrophobic surface. Our current understanding is that the C1 domain functions as a hydrophobic switch.
Īmong the agents in clinical trials targeting PKC, bryostatin 1 and ingenol 3-angelate (PEP005) both function as DAG analogs which bind to the C1 domain. RasGRP3 plays a central role in B cell receptor signaling and in solid tumors such as prostate cancer. PKC is a validated therapeutic target for cancer. Consistent with the central role of DAG in cellular signaling, these C1 domain containing families of proteins play critical roles in cellular function and dysfunction. DAG levels are translated into cellular signaling via interaction with C1 domains, which represent the DAG recognition motif in seven families of signaling proteins, including those of protein kinase C (PKC), RasGRP, chimaerin, and protein kinase D. DAG is generated downstream both of receptor tyrosine kinases and of G protein coupled receptors as a consequence of phospholipase C activation, which leads to breakdown of the signaling lipid phosphatidylinositol 4,5-bisphosphate. Our analysis shows that seemingly small structural modifications of the hydrophobic regions of these biomimetic PKC effectors contribute to pronounced modulation of membrane interactions of the ligandsĭiacylglycerol (DAG) signaling represents one of the basic signaling pathways within the cell. Specifically, we find that a slight change in the linkage to the indole ring resulted in significant differences in membrane binding and association of the DAG-indololactones with lipid bilayers. In parallel, the fluorescent properties of the ligands were employed for analysis of their membrane association profiles. Translocation and binding activity assays underline significant variations between the PKC translocation characteristics affected by the ligands as compared to their binding activities. We present a comprehensive analysis of membrane interactions and biological activities of several DAG-indololactones. N-methyl substituted diacylglycerol-indololactones (DAG-indololactones) are newly-synthesized effectors of protein kinase C (PKC) isoforms and exhibit substantial selectivity between RasGRP3 and PKC alpha.
0 kommentar(er)
