Cytoplasmic dyneins are motor proteins in the AAA+ superfamily that transport cellular cargos toward microtubule minus-ends. Recently, ciliobrevins were reported as selective cell-permeable inhibitors of cytoplasmic dyneins. As is often true for first-in-class inhibitors, the use of ciliobrevins has in part been limited by low potency. Moreover, suboptimal chemical properties, such as the potential to isomerize, have hindered efforts to improve ciliobrevins. Here, we characterized the structure of ciliobrevins and designed conformationally constrained isosteres. These studies identified dynapyrazoles, inhibitors more potent than ciliobrevins. At single-digit micromolar concentrations dynapyrazoles block intraflagellar transport in the cilium and lysosome motility in the cytoplasm, processes that depend on cytoplasmic dyneins. Further, we find that while ciliobrevins inhibit both dynein's microtubule-stimulated and basal ATPase activity, dynapyrazoles strongly block only microtubule-stimulated activity. Together, our studies suggest that chemical-structure-based analyses can lead to inhibitors with improved properties and distinct modes of inhibition.DOI:
http://dx.doi.org/10.7554/eLife.25174.001
Cytoplasmic dyneins are motor proteins in the AAA+ superfamily that transport cellular cargos toward microtubule minus-ends. Recently, ciliobrevins were reported as selective cell-permeable inhibitors of cytoplasmic dyneins. As is often true for first-in-class inhibitors, the use of ciliobrevins has in part been limited by low potency. Moreover, suboptimal chemical properties, such as the potential to isomerize, have hindered efforts to improve ciliobrevins. Here, we characterized the structure of ciliobrevins and designed conformationally constrained isosteres. These studies identified dynapyrazoles, inhibitors more potent than ciliobrevins. At single-digit micromolar concentrations dynapyrazoles block intraflagellar transport in the cilium and lysosome motility in the cytoplasm, processes that depend on cytoplasmic dyneins. Further, we find that while ciliobrevins inhibit both dynein's microtubule-stimulated and basal ATPase activity, dynapyrazoles strongly block only microtubule-stimulated activity. Together, our studies suggest that chemical-structure-based analyses can lead to inhibitors with improved properties and distinct modes of inhibition.DOI:
http://dx.doi.org/10.7554/eLife.25174.001
“…(99, 100)] or compounds that show relative selectivity for S6K1 (101, 102). It was initially thought that the high degree of identity between the kinase domains of S6K1 and S6K2 would prevent the development of S6K2-selective kinase inhibitors.…”
Section: S6k2 As a Therapeutic Target For Cancermentioning
S6 kinase 2 (S6K2) is a member of the AGC kinases super-family. Its closest homolog, S6K1, has been extensively studied along the years. However, due to the belief in the community that the high degree of identity between these two isoforms would translate in essentially identical biological functions, S6K2 has been largely neglected. Nevertheless, recent research has clearly highlighted that these two proteins significantly differ in their roles in vitro as well as in vivo. These findings are significant to our understanding of S6 kinase signaling and the development of therapeutic strategies for several diseases including cancer. Here, we will focus on S6K2 and review the protein–protein interactions and specific substrates that determine the selective functions of this kinase.
“…F179 has a purine as the hinge-binding group, instead of the pyrazolopyrimidine in F108 and F109. Replacing the pyrazolopyrimidine moiety with purine resulted in a two-fold loss of activity [15], which might be relevant to the weaker binding of F179 as compared to those of F108 and F109. F176 and F177 form weaker interactions with the hinge region than the other inhibitors, which may be the reason for their relatively less robust binding activities.…”
Section: Resultsmentioning
confidence: 99%
“…The inhibitors include 4-(benzimidazol-2-yl)-1,2,5-oxadiazol-3-ylamine derivatives [11], a piperazinyl-pyrimidine analogue PF-4708671 [12], the 4-phenyl-1 H -pyrazole derivative AT7867 [13], thiophene urea-templated inhibitors [14], and pyrazolopyrimidines [15, 16]. The structure of S6K1KD complexed with the non-specific inhibitor staurosporine was the first to be reported [17].…”
Ribosomal protein S6 kinase 1 (S6K1) is a serine/threonine protein kinase that plays an important role in the PIK3/mTOR signaling pathway, and is implicated in diseases including diabetes, obesity, and cancer. The crystal structures of the S6K1 kinase domain in complexes with staurosporine and the S6K1-specific inhibitor PF-4708671 have been reported. In the present study, five compounds (F108, F109, F176, F177, and F179) were newly identified by in silico screening of a chemical library and kinase assay. The crystal structures of the five inhibitors in complexes with the S6K1 kinase domain were determined at resolutions between 1.85 and 2.10 Å. All of the inhibitors bound to the ATP binding site, lying along the P-loop, while the activation loop stayed in the inactive form. Compound F179, with a carbonyl group in the middle of the molecule, altered the αC helix conformation by interacting with the invariant Lys123. Compounds F176 and F177 bound slightly distant from the hinge region, and their sulfoamide groups formed polar interactions with the protein. The structural features required for the specific binding of inhibitors are discussed.
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