Published online before print August 3, 2007
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
1 Correspondence: E-mail: hrosenberg{at}niaid.nih.gov
The manuscript "Inhibition of MyD88 dimerization and recruitment of IRAK1 and IRAK4 for a novel peptidomimetic compound" was selected as a Pivotal Advance because it provides an initial characterization of ST2825, an intriguing heptapeptide analog specifically designed to inhibit MyD88 dimerization, and via this mechanism, to control TLR9 mediated inflammatory responses.
Dr. Sette, early on in the manuscript, you describe a process by which a series of molecules were synthesized and screened for anti-MyD88 activity, yielding ST2825. Can you tell us a bit more about how this came about? What exactly was this screening process? How many molecules underwent screening?
CS: This work originated with my long-standing collaboration with researchers from Sigma-Tau, S.p.A., an Italian pharmaceutical company. When I first began collaborating with this group, these scientists were deeply involved in studies aimed at interfering with MyD88 signaling. They were trying to tackle this signaling pathway by screening chemical libraries in search of potential inhibitors. A primary screening assay designed to evaluate potential MyD88 dimerization inhibitors set up by researchers from Tecnogen, a subsidiary of Sigma-Tau, was based on a yeast two-hybrid system. Positive hits were assayed by means of a secondary functional test which evaluated NF-
B inhibition in HeLa cells.
When I joined these teams, we decided to change direction a bit and to take a more direct approach by focusing on the subdomains of MyD88, specifically attempting to locate sites that were critical for MyD88 dimerization. In 2005, we published a first paper [1
] in which we identified a small region within the TIR domain of MyD88 that was required for dimerization. A cell-permeable heptapeptide containing this small region of the protein efficiently interfered with MyD88-dependent IL-1ß signaling in live cells. Beginning with the predicted structure of the heptapeptide, chemists at Sigma-Tau synthesized a series of analogs, which we then tested for functional activity. We used activation of NF-B by IL-1ß stimulation (a pathway strongly dependent on MyD88 signaling) as a read-out to test the activity of these synthetic compounds. ST2825 was selected from among more than one hundred molecules tested because, in addition to inhibiting NF-B activation, it also reproduced the effects on MyD88 dimerization that we had described previously for the original MyD88 heptapeptide.
In theory, blocking MyD88 homodimerization should have an impact on signaling through several TLRs—has this possibility been explored to any extent?
CS: So far, we have tested the effect of our molecule only on TLR9 signaling in B cells, because this pathway has been extensively characterized as MyD88-dependent. But additional TLRs may also be affected by ST2825. Indeed, with the exception of TLR3, all known TLRs depend entirely or partly (as TLR4) on MyD88 for intracellular signaling. We are currently investigating these possibilities.
In your manuscript, you refer to the work of Rebek and colleagues [2 ], who also developed an inhibitor of TLR signaling via a similar strategy. Have you (or anyone else) considered the possibility of additive or even synergistic effects from combining these inhibitors?
CS: The inhibitor described by Rebek and colleagues [2 ] is a low molecular weight mimic of three protruding residues within the BB-loop of the MyD88 TIR domain. In their study, they demonstrate that this molecule efficiently blocks the interaction between IL-1R and MyD88 TIR domains, rather than MyD88 dimerization, as shown by ST2825. Hence, ST2825 and Rebek's inhibitor are very likely to exert additive rather than synergistic effects, because they interact with different steps in the same signaling cascade. It will of course be important now to compare the effect of these inhibitors in vivo, because host-tolerance and efficiency of delivery may vary depending on the tissue or the cell type to be targeted.
Returning to your work specifically—in the experiments presented here, ST2825 was administered immediately before IL-1ß, thus providing blockade before the inflammatory stimulus. Do you have any experimental evidence suggesting that this compound might abrogate ongoing inflammation, such as that characteristic of ongoing chronic disease?
CS: We are currently investigating the effectiveness of ST2825 in several acute inflammation models, thus our strategy has focused on administration of ST2825 before the inflammatory challenge. Next, we plan to evaluate the pharmacokinetic properties of our inhibitor and test additional treatment regimens such as those you are suggesting. In particular, we are interested in testing ST2825 in experimental animal models of autoimmune and inflammatory diseases, such as lupus, inflammatory bowel disease, and multiple sclerosis. In particular, multiple sclerosis could represent an important target for MyD88 inhibition, given the recent findings of Prinz and colleagues [3 ] that indicate that MyD88–/– mice are completely resistant to developing experimental autoimmune encephalomyelitis (EAE), the most widely used animal model for the study of multiple sclerosis [4 ]. Roles for CpG/TLR9 and/or flagellin/TLR5, two pathways that rely heavily on MyD88 signaling have been demonstrated in models of lupus and inflammatory bowel diseases, suggesting that our inhibitor might be efficacious.
On a similar note, is there any evidence to suggest that changes to the basic structure of ST2825 might render it more effective as an anti-inflammatory agent?
CS: Yes, that is exactly what we are pursuing. We are trying to introduce small changes in the structure of ST2825 in order to circumvent a major problem we have encountered so far withthis inhibitor, namely, its poor solubility, which impairs administration in vivo.
On a more personal level, can you tell the readers of JLB a bit more about yourself, your career, and what else you enjoy in addition to your scientific pursuits?
CS: I graduated with a degree in Biology in 1992 from the University of Rome La Sapienza. Rather than enroll immediately in a Ph.D. program in Italy, I decided to go abroad to study in the US. My first stop was the laboratory of Professor Marco Conti at Stanford University, where I studied the role of cAMP phosphodiesterases in G-protein coupled receptor-mediated signal transduction. After almost three years, I returned to Italy to begin a Ph.D. program at the University of Rome "Tor Vergata." After graduating in 1998, I returned to California to work in the laboratory of Professor Jeremy Thorner at the University of California at Berkeley, where I continued my training in signal transduction, and then returned to Italy in 2001. I began as an Assistant Professor in the department of Public Health and Cell Biology at the University of Rome "Tor Vergata" in the laboratory of Professor Raffaele Geremia. Then, when I obtained my first grants, I had the opportunity to develop my own group and pursue my own independent research interests. However, I maintain important collaborations with my colleagues abroad on several aspects of our ongoing research.
My main interests are traveling, reading, and playing sports. Running and bicycling are currently my favorites. I also enjoy very much spending time with my friends and going out for a good dinner in the many fine restaurants that Rome has to offer.
Is there anything else that you would like to add to this interview?
I would like to stress the importance of the collaborative effort between my laboratory and Sigma-Tau, which is one of the few Italian pharmaceutical companies that continues to invest resources in basic science. This project could have not been accomplished without their scientific and financial support. To reinforce this collaboration, I have now moved part of my laboratory to the Institute of Experimental Neuroscience Fondazione Santa Lucia, where we can work more closely with other scientific groups that have expertise in the study of multiple sclerosis and other inflammatory diseases. In Italy, there is a dramatic need for both public and private support for basic research. Hence, the opportunity I have had to collaborate with Sigma-Tau was of great value for the development of my career.
 View larger version (147K): [in a new window] |
Figure 1. Dr. Claudio Sette studied Biology at the University of Rome "La Sapienza," spent three years as a predoctoral fellow at Stanford University, and received his Ph.D. at the University of Rome "Tor Vergata" in 1998. After a postdoctoral fellowship at University of California at Berkeley, he returned to Italy and the University of Rome "Tor Vergata" in 2001, where he currently holds the position of Associate Professor. His research interests focus on cross-talk between signal transduction and the regulation of gene expression at the post-transcriptional level in different experimental settings.
|
Related Article
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
