Cell signaling regulates several physiological processes by receiving, processing, and transmitting signals between the extracellular and intracellular environments. In signal transduction, phosphorylation is a crucial effector as the most common posttranslational modification. Selectively recognizing specific phosphorylated motifs of target proteins and modulating their functions through binding interactions, the yeast 14-3-3 proteins Bmh1 and Bmh2 are involved in catabolite repression, carbon metabolism, endocytosis, and mitochondrial retrograde signaling, among other key cellular processes. These conserved scaffolding molecules also mediate crosstalk between ubiquitination and phosphorylation, the spatiotemporal control of meiosis, and the activity of ion transporters Trk1 and Nha1. In humans, deregulation of analogous processes triggers the development of serious diseases, such as diabetes, cancer, viral infections, microbial conditions and neuronal and age-related diseases. Accordingly, the aim of this review article is to provide a brief overview of the latest findings on the functions of yeast 14-3-3 proteins, focusing on their role in modulating the aforementioned processes.
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
Potassium is an essential intracellular ion, and a sufficient intracellular concentration of it is crucial for many processes; therefore it is fundamental for cells to precisely regulate K+ uptake and efflux through the plasma membrane. The uniporter Trk1 is a key player in K+ acquisition in yeasts. The TRK1 gene is expressed at a low and stable level; thus the activity of the transporter needs to be regulated at a posttranslational level. S. cerevisiae Trk1 changes its activity and affinity for potassium ion quickly and according to both internal and external concentrations of K+, as well as the membrane potential. The molecular basis of these changes has not been elucidated, though phosphorylation is thought to play an important role. In this study, we examined the role of the second, short, and highly conserved intracellular hydrophilic loop of Trk1 (IL2), and identified two phosphorylable residues (Ser882 and Thr900) as very important for 1) the structure of the loop and consequently for the targeting of Trk1 to the plasma membrane, and 2) the upregulation of the transporter's activity reaching maximal affinity under low external K+ conditions. Moreover, we identified three residues (Thr155, Ser414, and Thr900) within the Trk1 protein as strong candidates for interaction with 14-3-3 regulatory proteins, and showed, in an in vitro experiment, that phosphorylated Thr900 of the IL2 indeed binds to both isoforms of yeast 14-3-3 proteins, Bmh1 and Bmh2.
- Publikační typ
- časopisecké články MeSH
Transcription factor p53 protects cells against tumorigenesis when subjected to various cellular stresses. Under these conditions, p53 interacts with transcription factor Forkhead box O (FOXO) 4, thereby inducing cellular senescence by upregulating the transcription of senescence-associated protein p21. However, the structural details of this interaction remain unclear. Here, we characterize the interaction between p53 and FOXO4 by NMR, chemical cross-linking, and analytical ultracentrifugation. Our results reveal that the interaction between p53 TAD and the FOXO4 Forkhead domain is essential for the overall stability of the p53:FOXO4 complex. Furthermore, contacts involving the N-terminal segment of FOXO4, the C-terminal negative regulatory domain of p53 and the DNA-binding domains of both proteins stabilize the complex, whose formation blocks p53 binding to DNA but without affecting the DNA-binding properties of FOXO4. Therefore, our structural findings may help to understand the intertwined functions of p53 and FOXO4 in cellular homeostasis, longevity, and stress response.
Death-associated protein kinase 2 (DAPK2) is a CaM-regulated Ser/Thr protein kinase, involved in apoptosis, autophagy, granulocyte differentiation and motility regulation, whose activity is controlled by autoinhibition, autophosphorylation, dimerization and interaction with scaffolding proteins 14-3-3. However, the structural basis of 14-3-3-mediated DAPK2 regulation remains unclear. Here, we structurally and biochemically characterize the full-length human DAPK2:14-3-3 complex by combining several biophysical techniques. The results from our X-ray crystallographic analysis revealed that Thr369 phosphorylation at the DAPK2 C terminus creates a high-affinity canonical mode III 14-3-3-binding motif, further enhanced by the diterpene glycoside Fusicoccin A. Moreover, concentration-dependent DAPK2 dimerization is disrupted by Ca2+/CaM binding and stabilized by 14-3-3 binding in solution, thereby protecting the DAPK2 inhibitory autophosphorylation site Ser318 against dephosphorylation and preventing Ca2+/CaM binding. Overall, our findings provide mechanistic insights into 14-3-3-mediated DAPK2 inhibition and highlight the potential of the DAPK2:14-3-3 complex as a target for anti-inflammatory therapies.
Phosphorylation by kinases governs many key cellular and extracellular processes, such as transcription, cell cycle progression, differentiation, secretion and apoptosis. Unsurprisingly, tight and precise kinase regulation is a prerequisite for normal cell functioning, whereas kinase dysregulation often leads to disease. Moreover, the functions of many kinases are regulated through protein-protein interactions, which in turn are mediated by phosphorylated motifs and often involve associations with the scaffolding and chaperon protein 14-3-3. Therefore, the aim of this review article is to provide an overview of the state of the art on 14-3-3-mediated kinase regulation, focusing on the most recent mechanistic insights into these important protein-protein interactions and discussing in detail both their structural aspects and functional consequences.
- MeSH
- alosterická regulace genetika MeSH
- apoptóza genetika MeSH
- fosforylace genetika MeSH
- lidé MeSH
- mitogenem aktivované proteinkinasy p38 genetika MeSH
- proteinkinasy genetika MeSH
- proteiny 14-3-3 genetika MeSH
- signální transdukce genetika MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
Ca2+/calmodulin-dependent protein kinase kinase 2 (CaMKK2) regulates several key physiological and pathophysiological processes, and its dysregulation has been implicated in obesity, diabetes, and cancer. CaMKK2 is inhibited through phosphorylation in a process involving binding to the scaffolding 14-3-3 protein, which maintains CaMKK2 in the phosphorylation-mediated inhibited state. The previously reported structure of the N-terminal CaMKK2 14-3-3-binding motif bound to 14-3-3 suggested that the interaction between 14-3-3 and CaMKK2 could be stabilized by small-molecule compounds. Thus, we investigated the stabilization of interactions between CaMKK2 and 14-3-3γ by Fusicoccin A and other fusicoccanes-diterpene glycosides that bind at the interface between the 14-3-3 ligand binding groove and the 14-3-3 binding motif of the client protein. Our data reveal that two of five tested fusicoccanes considerably increase the binding of phosphopeptide representing the 14-3-3 binding motif of CaMKK2 to 14-3-3γ. Crystal structures of two ternary complexes suggest that the steric contacts between the C-terminal part of the CaMKK2 14-3-3 binding motif and the adjacent fusicoccane molecule are responsible for differences in stabilization potency between the study compounds. Moreover, our data also show that fusicoccanes enhance the binding affinity of phosphorylated full-length CaMKK2 to 14-3-3γ, which in turn slows down CaMKK2 dephosphorylation, thus keeping this protein in its phosphorylation-mediated inhibited state. Therefore, targeting the fusicoccin binding cavity of 14-3-3 by small-molecule compounds may offer an alternative strategy to suppress CaMKK2 activity by stabilizing its phosphorylation-mediated inhibited state.
- MeSH
- fosforylace účinky léků MeSH
- glykosidy chemie farmakologie MeSH
- kinasa proteinkinasy závislé na vápníku a kalmodulinu chemie metabolismus MeSH
- krystalografie rentgenová MeSH
- lidé MeSH
- mapy interakcí proteinů účinky léků MeSH
- proteiny 14-3-3 chemie metabolismus MeSH
- simulace molekulového dockingu MeSH
- vazba proteinů účinky léků MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Apoptosis signal-regulating kinase 1 (ASK1) is a ubiquitously expressed mitogen-activated protein kinase kinase kinase 5, which mediates various stress signals including oxidative stress. The catalytic activity of ASK1 is tightly controlled by oligomerization and binding of several cofactors. Among these cofactors, thioredoxin stands out as the most important ASK1 inhibitor, but only the reduced form of thioredoxin inhibits ASK1 by direct binding to its N-terminal domain. In addition, oxidation-driven thioredoxin dissociation is the key event in oxidative stress-mediated ASK1 activation. However, the structural mechanism of ASK1 regulation by thioredoxin remains unknown. Here, we report the characterization of the ASK1 domain responsible for thioredoxin binding and its complex using NMR spectroscopy and chemical cross-linking, thus providing the molecular basis for ASK1: thioredoxin complex dissociation under oxidative stress conditions. Our data reveal that the N-terminal domain of ASK1 adopts a fold resembling the thioredoxin structure while retaining substantial conformational plasticity at the thioredoxin-binding interface. Although oxidative stress induces relatively moderate structural changes in thioredoxin, the formation of intramolecular disulfide bridges leads to a considerable conformational rearrangement of the thioredoxin-binding interface on ASK1. Moreover, the cysteine residue at position 250 of ASK1 is the key element of this molecular switch. Finally, our results show that the redox-active site of thioredoxin is directly involved in ASK1 binding that is modulated by oxidative stress, thereby identifying a key target for the structure-based drug design.
- MeSH
- apoptóza * MeSH
- inhibitory proteinkinas farmakologie MeSH
- lidé MeSH
- magnetická rezonanční spektroskopie MeSH
- MAP kinasa-kinasa-kinasa 5 antagonisté a inhibitory metabolismus MeSH
- molekulární modely MeSH
- oxidace-redukce MeSH
- oxidační stres * MeSH
- thioredoxiny chemie metabolismus MeSH
- vazebná místa MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Steroidogenic acute regulatory protein (STARD1) is regulated by phosphorylation and 14-3-3 protein binding. STARD1 is a key player in cholesterol transport in mitochondria, and its regulation is not fully understood. Tugaeva et al. provide novel insights on the site-specific phosphorylation and subsequent 14-3-3-dependent regulation of STARD1 function. These results may help us understand the mechanism behind the regulation of steroidogenesis. Comment on: https://doi.org/10.1111/febs.15474.
Among all species, caspase-2 (C2) is the most evolutionarily conserved caspase required for effective initiation of apoptosis following death stimuli. C2 is activated through dimerization and autoproteolytic cleavage and inhibited through phosphorylation at Ser139 and Ser164 , within the linker between the caspase recruitment and p19 domains of the zymogen, followed by association with the adaptor protein 14-3-3, which maintains C2 in its immature form procaspase (proC2). However, the mechanism of 14-3-3-dependent inhibition of C2 activation remains unclear. Here, we report the structural characterization of the complex between proC2 and 14-3-3 by hydrogen/deuterium mass spectrometry and protein crystallography to determine the molecular basis for 14-3-3-mediated inhibition of C2 activation. Our data reveal that the 14-3-3 dimer interacts with proC2 not only through ligand-binding grooves but also through other regions outside the central channel, thus explaining the isoform-dependent specificity of 14-3-3 protein binding to proC2 and the substantially higher binding affinity of 14-3-3 protein to proC2 than to the doubly phosphorylated peptide. The formation of the complex between 14-3-3 protein and proC2 does not induce any large conformational change in proC2. Furthermore, 14-3-3 protein interacts with and masks both the nuclear localization sequence and the C-terminal region of the p12 domain of proC2 through transient interactions in which both the p19 and p12 domains of proC2 are not firmly docked onto the surface of 14-3-3. This masked region of p12 domain is involved in C2 dimerization. Therefore, 14-3-3 protein likely inhibits proC2 activation by blocking its dimerization surface. DATABASES: Structural data are available in the Protein Data Bank under the accession numbers 6SAD and 6S9K.
- MeSH
- fosforylace MeSH
- kaspasa 2 chemie genetika metabolismus MeSH
- konformace proteinů * MeSH
- krystalografie rentgenová MeSH
- lidé MeSH
- molekulární modely * MeSH
- multimerizace proteinu * MeSH
- mutace MeSH
- protein - isoformy genetika metabolismus MeSH
- proteinové prekurzory chemie genetika metabolismus MeSH
- proteiny 14-3-3 chemie genetika metabolismus MeSH
- rekombinantní proteiny chemie metabolismus MeSH
- vazba proteinů MeSH
- vazebná místa genetika MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
FOXO transcription factors are critical regulators of cell homeostasis and steer cell death, differentiation and longevity in mammalian cells. By combined pharmacophore-modeling-based in silico and fluorescence polarization-based screening we identified small molecules that physically interact with the DNA-binding domain (DBD) of FOXO3 and modulate the FOXO3 transcriptional program in human cells. The mode of interaction between compounds and the FOXO3-DBD was assessed via NMR spectroscopy and docking studies. We demonstrate that compounds S9 and its oxalate salt S9OX interfere with FOXO3 target promoter binding, gene transcription and modulate the physiologic program activated by FOXO3 in cancer cells. These small molecules prove the druggability of the FOXO-DBD and provide a structural basis for modulating these important homeostasis regulators in normal and malignant cells.
- MeSH
- DNA chemie genetika metabolismus MeSH
- genetická transkripce účinky léků MeSH
- genový knockdown MeSH
- HEK293 buňky MeSH
- knihovny malých molekul chemie metabolismus farmakologie MeSH
- konformace nukleové kyseliny MeSH
- lidé MeSH
- magnetická rezonanční spektroskopie MeSH
- molekulární modely MeSH
- nádorové buněčné linie MeSH
- promotorové oblasti (genetika) genetika MeSH
- protein FOXO3 chemie genetika metabolismus MeSH
- proteinové domény MeSH
- simulace molekulového dockingu MeSH
- stanovení celkové genové exprese metody MeSH
- vazba proteinů MeSH
- vazebná místa genetika MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
